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Articles from 1999 In August


You Better Watch Out

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

EDITOR'S PAGE

The presence of a former U.S. Surgeon General adds some weight to a group discounting claims that plasticized PVCs are dangerous to your health.

In this column published around Christmas time last year, I quoted a member of a chemical manufacturers' group who was commenting on the decision of prominent toy stores to pull plasticized vinyl toys from the shelves. Although of the firm belief that the plasticizers were "completely harmless," the gentleman nevertheless predicted that the medical industry would inevitably succumb to public and legal pressures and "go the way toys go."

Well, Christmas may have come early in 1999 for the vinyl industry, for the manufacturers that depend on the availability of plasticized PVC to make a wide range of devices, and for the patients who use those products. And the ubiquitous, bewhiskered public figure bearing good cheer and a NOEL (no-observed-effect level) blessing is not Santa Claus but the former U.S. Surgeon General, C. Everett Koop.

Koop is the chairman of a panel of leading physicians and scientists that conducted a comprehensive review of the scientific literature concerning di(2-ethylhexyl) phthalate (DEHP) and diisononyl phthalate (DINP), two chemicals used as plasticizers in flexible vinyl products. The 17-member panel was convened by the American Council on Science and Health (ACSH; New York City) last February in response to ongoing questions about the safety of DEHP and DINP. The group examined a variety of data—including primary and secondary scientific literature; risk assessments prepared by regulators in the U.S., Canada, and Europe; and scientific manuscripts still in preparation—and issued a final report on its findings. (The full report, "A Scientific Evaluation of Health Effects of Two Plasticizers Used in Medical Devices and Toys," and a complete list of panel members can be found at http://www.medscape.com, with an executive summary available at http://www.drkoop.com.)

The conclusions in the report, according to Koop, are unambiguous: "Consumers can be confident that vinyl toys and medical devices are safe. The panel's findings confirm what the U.S. Food and Drug Administration and the Consumer Product Safety Commission have been saying about these products all along. There is no scientific evidence that they are harmful to children or adults."

The certainty expressed in Koop's pronouncement should come as no surprise. Serious scientists have long recognized, as the report states, that for DEHP—the phthalate used in medical devices—"results in rats and mice, in whom many of the [harmful] effects have been observed, are not appropriate for human risk assessment." In fact, the panel concludes, DEHP "is not harmful to even highly exposed people, those who undergo certain medical procedures such as regular hemodialysis or extracorporeal membrane oxygenation."

What is unusual, however, is the extent to which the panel emphasizes the beneficial characteristics of DEHP, and the forcefulness with which these sentiments are expressed in the report. For example, attributes imparted by DEHP to flexible tubing include "minimum interference to patient movement," the "strength to resist permanent deformation," the "ability to resist kinks that may impede or block fluid flow," and the "ability to withstand pressure infusion," among several others. These properties "are often critical in life-saving and medical intervention measures," and eliminating DEHP "could cause harm to some individuals." Any materials proposed as alternatives to DEHP or flexible PVC would have to be evaluated in terms of equivalent "patient safety, functional effectiveness, cost-efficiency, and regulatory compliance."

Such language represents an aggressive counterattack to the claims of "environmental groups" and others that their attempts to ban DEHP are in the interest of public safety. It appears as if Dr. Koop is making a list, checking it twice, and shouldering a sack of coal destined for the proponents of junk science.

Jon Katz

jon.katz@cancom.com


Copyright ©1999 Medical Device & Diagnostic Industry

Device Companies and Contracts: Don't Overlook the Regulatory Implications

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Manufacturers are certainly aware of the importance of FDA issues during the product approval process. However, according to a device attorney, companies often fail to consider regulatory factors when preparing routine commercial contracts.

Medical device manufacturers routinely enter into contracts. These contracts can take a wide variety of forms, covering areas such as contract manufacturing, clinical investigations, monitoring clinical studies, product development, or product distribution. When these contracts are drafted, the focus is generally on the commercial terms—for example, price, specifications, indemnification, duration of the agreement, termination, confidentiality, and other economically or legally significant elements. All of these factors are important and require careful attention.

DEFINING THE TERMS

Yet many contracts overlook—or at least give insufficient consideration to—another commercially significant aspect: terms relating to FDA. In fact, FDA issues often have sufficient commercial importance that they should be explicitly addressed in the contract. Indeed, under some circumstances, such as the shipment of devices for repackaging at another company's facility, FDA regulations require that there be an agreement addressing specified issues (21 CFR 801.150). Many companies, however, are not attentive enough to FDA-related issues when drafting contracts.

For example, many manufacturing contracts have a clause requiring the outside manufacturer to "comply with the quality system regulation (QSR)." However, contracts are less likely to address a related and important regulatory issue: the ability of the contract manufacturer to make product modifications. Under what circumstances, if any, can the manufacturer make a change in the product without the written approval of the purchaser? What about changes in component vendors or standard operating procedures, or the replacement of equipment?

Inappropriate changes can give rise to significant regulatory risks to the purchaser. Some changes could trigger the need for a PMA supplement or new 510(k) notice. Other changes could result in distributing a product that is adulterated for violating the requirements of the QSR. Even more worrisome, some changes could have adverse effects on the product, putting patients at risk. And yet, unnecessarily requiring prior written approval by the buyer, or imposing overly restrictive limitations, can unduly inhibit minor manufacturing changes or improvements.

There is no set solution to these problems. While there can be a regulatory need to prevent certain types of changes from being made without prior written consent, there are many contractual variations on this theme. For one thing, the degree of latitude given a manufacturer should be very different for a device approved through the PMA process as opposed to a Class I device that is largely exempt from the QSR. A contract to manufacture a QSR-exempt device can afford the manufacturer far more flexibility than a contract for a life-sustaining PMA device. A device purchaser must consider how its own needs should be addressed in this setting, and negotiate the terms accordingly.

CONTRACTING FOR COMPLIANCE

Even the familiar requirement that basically says the manufacturer "shall comply with all QSR requirements" should not be inserted blindly. From the manufacturer's perspective, this phrase is unrealistic. Complete compliance with the QSR may be the Holy Grail, but it is virtually unattainable: with enough searching, some QSR deviations can be found in any facility. However, the deviations can vary greatly in significance, from a calibration test performed a week late to an unvalidated manufacturing process.

The phrase "shall comply with QSR requirements" draws no distinction or gradations. The parties to a supply agreement should decide whether the standard phrase embodies their intent, or whether the commitment should be more qualified—for example, "substantial compliance" or "material compliance," or an explicit statement that a timely correction of any material deficiency will not result in breach of contract.

Moreover, even this modified language can be undercut by other contractual terms. For example, it is not uncommon for a contract manufacturer to warrant that the devices "are not adulterated within the meaning of the Federal Food, Drug, and Cosmetic Act." However, a device that does not conform to the QSR is technically adulterated, even if the nonconformance is trivial. Therefore, a promise to avoid adulteration, when combined with a commitment to be in "material compliance" with the QSR, creates, at a minimum, ambiguity as to what level of compliance is contractually mandated. Thus, if an agreement contains a "material compliance with QSR" clause, manufacturers should omit language warranting that no devices will be adulterated.

The lesson is simple. Even the most seemingly routine FDA-related clause—the commitment to comply—requires careful attention.

COMMON CONCERNS

Device companies may encounter a wide variety of contractual issues that involve regulatory implications. The following is a very truncated list of other FDA-related questions that may arise in commercial settings:

  • If there is an FDA audit of the contract manufacturer (or clinical investigator), will the other party (the purchaser or sponsor) automatically be notified? What if the audit results in the issuance of an FD-483? Does the second party have any opportunity to review the FD-483 response before it is sent back to FDA?
  • Companies frequently need to decide whether to initiate a recall or other corrective action. In the context of a distribution or manufacturing agreement, it may be helpful to address potential recall-related issues in the contract. For example, are the parties obligated to consult before initiating corrective action? Who decides whether to proceed in the event of a disagreement? Who has responsibility for conducting the recall? And who pays the recall-related costs?
  • Recently, FDA adopted a regulation relating to electronic records and electronic signatures, 21 CFR Part 11. It is a complicated, confusing regulation with which many companies are not yet in full compliance. Should a purchase agreement include an explicit commitment by the contract manufacturer that it will comply with the regulation? Part 11 issues can also occur in a variety of other commercial contexts, such as clinical data management or the generation of laboratory test records.
  • Many device companies have record retention/record destruction policies. Experience has shown that keeping old records tends to be more harmful than helpful; draft documents, interim reports, e-mails, and other informal documents are particularly likely to be problematic in any future litigation. However, the fact that a company has a record-destruction policy and conscientiously destroys certain documents will be of little help if the other party to a contract indefinitely retains copies of the same documents. The problems are compounded by the extraordinary ability of electronic records—once created—to defy complete annihilation. Thus, device companies may want to include record retention/destruction clauses in their agreements with companies with whom they share information.
  • Clinical study agreements need their own set of FDA-related contractual clauses. For example, a prudent sponsor will want a representation and warranty that the investigators have not been disqualified and are not facing disqualification. The sponsor may also want to be assured that the investigators have not received any warning letters. The agreement should also include clear audit rights.

FDA has issued a new regulation requiring financial information from clinical investigators. For perfectly understandable reasons, investigators may be reluctant to provide this information. Nevertheless, it is a regulatory requirement, and one that should be explicitly addressed in the clinical research agreement, regardless of whether the sponsor is contracting directly with the clinical investigator or through a third party.

CONCLUSION

There are innumerable permutations in contracts entered into by device manufacturers. Before signing these agreements, companies should take into account not only the standard types of commercial factors, but FDA considerations as well. The failure to do so could have an adverse regulatory effect and also result in surprisingly unpleasant financial consequences.

Jeffrey N. Gibbs is a partner in the law firm of Hyman, Phelps & McNamara, P.C. (Washington, DC). He was formerly associate chief counsel of enforcement for FDA.


Copyright ©1999 Medical Device & Diagnostic Industry

Third-Party Device Reviews Beat FDA's

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

WASHINGTON WRAP-UP

Private-sector reviews of 510(k) submissions average 33% faster than those conducted by the agency.

James G. Dickinson


  • Agency Will Audit Device Data for Y2K Compliance
  • FDA Guidance on Reporting Y2K Problems
  • Advisory Committee Questions Now on the Web
  • FDA Approves Bone-Density Test Device
  • Inspectors Going High-Tech
  • Withdrawn Flush Syringe Is Approved
  • Bladder Cancer Test Needs More Data for FDA Approval
  • Down-Classifying Shoulder Prostheses
  • Home Uterine Monitor 510(k) Draft Guidance

You always suspected it: private-sector device reviews for marketing approval just had to be faster than anything FDA could do. Although a full-scale third-party device review program isn't yet up and running (why pay for something FDA does for free?), limited experimentation with private device reviews bears out your canny instincts.

In May, FDA's Office of Device Evaluation (ODE) reported that the median review time of its pilot third-party review program for selected low- and moderate-risk devices that ended on November 21, 1998, was 29 days faster than the median review time of the agency staff for 510(k)s. Total elapsed time from the date of a third party's receipt of a 510(k) to the date of the final FDA decision was a median of 54 days (with an average of 78 days), while the median review time for all in-house 510(k)s was 83 days. More than 90% of all third-party reviews had less-than-90-day FDA cycles.

The ODE annual report for fiscal year 1998, posted on the agency Web site in May, reports that the 31 510(k)s that had been reviewed by third parties were received between August 1996 and July 1998. By the end of the fiscal year, ODE had issued final decisions on 30 of the 510(k)s, with one held for additional information. ODE's final decision matched the third-party reviewer's recommendation in 29 of 30 applications and was issued without the need for additional information in 55% of the submissions. Once the pilot review program ended on November 21, 1998, it was replaced by the Accredited Persons program established under FDAMA.

The ODE report also indicates that the average review time for premarket approval (PMA) applications was cut by 25% compared with the previous year. During FY 1998, there were 46 PMAs approved, 7 under expedited review and 4 as humanitarian device exemptions. Of the 46 approved PMAs, 18 took 180 days or less, and 37 were completed in less than one year. Also approved were 427 PMA supplements, with 139 reviewed in real time. Average FDA review time for original PMAs reaching final action decreased from 207 days in FY 1997 to 154 days in FY 1998. The total average review time decreased to 6.4 months, marking the fourth consecutive year the total average review time has gone down.

Reversing an earlier stance, FDA now says it plans to audit the data of a sample of medical device manufacturers to ensure the devices will not malfunction in 2000 as a result of computer problems. Acting deputy commissioner for policy William Hubbard testified in May before a joint hearing of the House Commerce Committee's subcommittee on health and the environment and the House Oversight and Investigations Committee that the agency is seeking funding to audit data of manufacturers of 60 high-risk devices that could threaten patient health or safety if they malfunction on January 1, 2000.

FDA had said it saw no need to verify Y2K information provided by device manufacturers, but that position had been challenged by the General Accounting Office (GAO), Congress's investigating and research body. The GAO reported that some hospitals had tested devices shown on the FDA Web site as being Y2K compliant and found that they malfunctioned.

Even though the audit is to be done, Hubbard explained, the potential medical device problem is not as serious as some observers have claimed. "FDA believes that the information received to date confirms our original expectation that the year 2000 problems with medical devices will not be significant or wide-spread if facilities take appropriate actions to address this issue. There will be specific problems that need correction; however, the current assessment is that they are much more likely to disrupt patient care rather than be of direct danger to patients."

GAO Y2K expert Joel Willemssen testified that "organizations such as FDA can provide medical device users with a greater level of confidence that their equipment is Y2K compliant through independent reviews of manufacturers' compliance test results." He said that FDA-proposed audits would meet GAO's concerns.

The Center for Devices and Radiological Health (CDRH) has issued a guidance on reporting date-related medical device problems associated with Y2K or other date issues, such as 9/9/99 and 2/29/2000. Device manufacturers are required to report a death or serious injury, whether or not the event was a result of Y2K failure. They must also file a report when they become aware of information that reasonably suggests that a device has malfunctioned and would be likely to cause or contribute to a death or serious injury if the malfunction were to recur.

The guidance says that manufacturers need not report malfunctions such as failure of a device to change to the year 2000 in a recordkeeping function not likely to result in an adverse event or a device that performs properly but displays an error message such as "set clock." Similar requirements are set forth for user facilities and importers. The guidance reviews reporting exemptions available for recurring date events and says it intends to develop a separate exemption to cover Y2K events for which a manufacturer or importer takes no remedial action.

The guidance can be found at http://www.fda.gov/cdrh/postsurv/2299.html.

Device manufacturers now have another reason to visit FDA's Web site: to check out the questions the agency will ask device advisory committees in advance of panel meetings.

The innovative practice of providing such information was first seen in May, when CDRH posted two multipart questions for the Ear, Nose, and Throat Advisory Panel on its home page three weeks before for the panel met on June 18. The questions concerned "the significant issues of safety and effectiveness" of implantable middle-ear amplification devices and were part of the center's development of a guidance document for industry.

"I think it will become the norm," CDRH's Harry R. Sauberman said in commenting on the posting. "We wanted to do it to be more equitable for everyone." Device manufacturers and other interested parties can now know ahead of time what FDA's issues are and can be better informed if they want to call in for clarification before an advisory committee meets.

If the practice becomes widespread, it will go a long way toward eliminating persistent complaints that companies can be "blindsided" or "ambushed" by FDA at advisory committee meetings.

CompuMed Inc., of Manhattan Beach, CA, said in May that FDA had approved the marketing under a 510(k) of its OsteoGram 2000, an automated device to enable physicians to perform bone-density tests in their offices using their existing standard x-ray equipment. The system comprises a desktop scanner, a standard personal computer, and special software. According to company officials, the procedure involves taking an x-ray of the patient's hand and scanning it into the computer for automated analysis. Officials also reported that in a three-year study sponsored by Merck, the U.S. Public Health Service, and the Hawaii Osteoporosis Foundation, the OsteoGram outperformed competing devices in terms of osteoporosis prediction scores. It is also said to precisely measure changes in bone mass over time.

Every FDA inspector will be equipped with both a laptop computer and a portable scanner, if new FDA associate commissioner for regulatory affairs Dennis Baker has his way. Heading into his second month on the job, the former Texas state regulator remarked in May that the only thing holding him back in this objective was resources, but that he was hopeful of getting funds for such purchases in the next FDA budget, which so far is heading higher in Congress.

The laptops will enable investigators to begin each inspection with the current compliance profile of the firm, together with inspection reports not only on the facility to be inspected but on related company sites. And the scanners will save a lot of time by enabling investigators to enter product, equipment, and certain record information directly into the computers, Baker said.

Sabratek Corp. of Skokie, IL, announced in May that FDA had approved its 510(k) application for a normal saline IV flush syringe. Company officials said they had voluntarily stopped distribution of the product this past November pending 510(k) approval. The company reports that it is working with its suppliers in order to resume production and shipments to customers as quickly as possible.

DiagnoCure Inc. of Sainte-Foy, PQ, Canada, said in May it had been told that FDA needs additional information on the company's ImmunoCyt, a test for early diagnosis of bladder cancer, before the agency can act on the firm's application for approval to market the test in the United States. Company officials indicated the agency wants additional data on efficacy of the test among subjects of different races as well as on reproducibility of test results by different laboratories. They added that data on a clinical trial involving different races are being analyzed and can be submitted quickly and that laboratories have been selected for the interlab assessment. According to the company, the test has been approved in Canada and 12 other countries.

Ten voluntary standards from the American Society for Testing and Materials (ASTM) and five FDA guidance documents should together be enough to allow the reclassification of certain shoulder-joint prostheses, FDA has announced. In a May 29 Federal Register notice, FDA stated that it is reclassifying metal/polymer/metal nonconstrained or semiconstrained, porous-coated, uncemented prostheses into Class II from Class III. The agency sought public comment until last August 26 on an Orthopedic and Rehabilitation Devices Panel recommendation to down-classify these devices. The panel made its recommendation in January 1998, following review of a petition for reclassification submitted by the Orthopedic Surgical Manufacturers Association.

FDA-recommended special controls for Class II home uterine activity monitors can be found in CDRH's just-released draft guidance Home Uterine Activity Monitors: Guidance for the Submission of 510(k) Premarket Notifications. In the draft guidance, CDRH asks for results from a small clinical study showing that the device produces tracings at the receiving station that are readable. The guidance also elaborates on ways of providing a comparison with the predicate device and on cleaning and disinfecting, electrical safety testing, bench validation testing, and intended use.

The guidance can be found at http://www.fda.gov/cdrh/newpg.html.


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Copyright ©1999 Medical Device & Diagnostic Industry

New Polymers and Nanotubes Add Muscle to Prosthetic Limbs

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Research efforts are under way to use novel materials that can emulate the simplicity and function of human muscles.

At the University of New Mexico Artificial Muscle Research Institute (AMRI; Albuquerque), there is a full-scale plastic skeleton named Mr. Boney, who moves in a manner much like that of any human. Created by researchers at the university, Mr. Boney is powered by artificial muscles actuated by a chemical fluid that is pumped by a microprocessor-controlled heart. The AMRI Web site offers video clips of Mr. Boney riding a bicycle, a whimsical display of current efforts to apply advanced materials technology to the challenge of creating synthetic muscles.

The application of an electrical charge to single-walled carbon nanotubes produces a direct conversion of electrical energy to mechanical energy through a material response.

In the late 1940s, Israeli scientists found that bundles of fibers made from polymer gels would shrink when immersed in an acidic solution, then would swell significantly with the addition of a base to the immersion solution. Immersed in the acid solution, the negative ions of the polymer were attracted to the positive ions from the acid that permeated the gel, which resulted in the contraction. Immersed in the alkaline solution, the gel's negative ions were repulsed by the negative ions from the solution, causing the polymer to expand. The mechanical effect was similar to the action of natural muscle tissue.

In the 50 years that have passed since that initial discovery, little progress in the development of artificial muscle was made until recently. Research focused on the development of artificial muscles, particularly for robotic and prosthetic applications, has gained renewed interest largely as the result of advances in materials science.

In addition to exposing polymer gels to specific solutions to cause them to flex and contract, passing an electric current through a material can induce a similar effect. In simplest terms, the action is caused by electrical attraction and repulsion. Until recently, polymer-based materials were the foundation of most artificial muscle research. Most projects were focused on maximizing the polymer material's response in terms of reaction speed and strength.

ELECTRON BOMBARDMENT ENHANCES POLYMER RESPONSE

Much of the current research involving synthetic muscle technology is attempting to increase the degree to which the material responds to electrical or chemical stimulation. Qi-Ming Zhang, PhD, associate professor of electrical engineering at the Pennsylvania State University Materials Research Laboratory (University Park, PA), has conducted research to compare the use of piezoelectric and electrostrictive materials in a number of applications, including artificial muscles.

Zhang's research work has focused on poly(vinylidene fluoride-trifluoroethylene) copolymer, which was developed originally for thin-film blood-storage bags. Zhang notes that, although the material displays quite limited piezoelectric properties, its electrostrictive characteristics have been found to be pronounced.

In further studies, Zhang found that the material could be altered to increase movement in response to applied voltage. He found that bombarding the material with electrons altered its molecular conformation and created new chemical bonds. The electron bombardment inserts defects into the material, making it more compliant and flexible, according to Zhang. The process also increases the material's dielectric constant. He notes that most existing electrostrictive materials are brittle ceramics that break with excessive movement. The altered polymer material is capable of movement that is 40 times greater than some of the best known materials and is simpler and less expensive to manufacture.

ELECTRORHEOLOGICAL FLUIDS ALLOW MOVEMENT AT NEAR-HUMAN SPEED

Research at Rensselaer Polytechnic Institute (Troy, NY) has resulted in a method capable of reducing the time required for a polymer material to respond to the application of electric fields. The technique is a significant advance in the development of artificial muscle. The response time of polymeric gels and conducting polymers to electric fields has been quite limited until recently. Polymer-based "muscles" required at least three seconds and often longer to respond to electric impulses. Polymer "fingers" capable of lifting an egg, for example, required up to 20 minutes to perform the task.

By infusing polymer gel with electrorheological fluid (ERF), which stiffens to a solid in response to an electric field, Sonja Krause, PhD, professor of physical chemistry at Rensselaer, and Katherine Bohon, PhD, found that the polymer was capable of responding in 100 milliseconds. This approaches the time in which human muscles react to signals from the brain. The ERF contains cross-linked polyethylene oxide particles suspended in silicone oil. "We decided to mix an ERF with an elastic polymer to take advantage of the ERF's rapid response and the mechanical strength of the polymer," Bohon explained. After testing several combinations, the researchers mixed 40% commercial ERF with 60% poly(dimethyl siloxane). Flexible electrodes were placed in the composite gel. When subjected to a 1-Hz ac electric field of 3000 V/cm, the material began to compress with a response time well within the range of human muscle. Bohon explained that the method is based on the rapid response of "millions of tiny polymer particles in combination with the elasticity of a gel."

Although the system responds rapidly, its strength remains limited. An additional challenge is to develop ERFs that will respond to lower voltages than the initial version. More recently, Krause and Bohon created an electromechanical actuator using a commercially available ERF and cross-linked poly(dimethyl siloxane) surrounded by flexible polymeric electrodes. When a low-frequency ac field was applied, electrode movement was double the applied frequency, and the actuator was found to be capable of moving objects weighing 1 g.

AS FAST AS HUMAN MUSCLE AND TWICE AS STRONG

The challenge of making artificial muscle with strength equal to that of a human's is being addressed by Mo Shahinpoor, PhD, an engineering professor at the University of New Mexico and head of AMRI. Shahinpoor has succeeded in developing artificial fibers said to be twice as strong as human muscles.

The fibers are each made up of several thousand individual strands and are created from polyacrylonitrile, which deforms in response to pH changes. According to Shahinpoor, the fibers are heated to 4500°F to form cross-links and boiled in sodium hydroxide to make them elastic, a process that binds the fiber within a gelatinous mass. The mass is then encapsulated in latex and bathed in water. The ionic-polymer fibers, encased within the latex shield, are bathed in a chemical solution and contract or expand in response to changes in the solution's pH.

Adding sodium hydroxide or another base causes the fibers to stretch to as much as twice their original length. Acid results in the fibers contracting nearly as fast as human muscles and with twice the strength, according to Shahinpoor. Use of computer-controlled pumps that regulate the flow of acid and base into the muscle make it possible to regulate and program the muscle's activity. The invention has been used to move a plastic skeleton's limbs, says Shahinpoor, who sees "tremendous possibilities" for the artificial muscle.

Shahinpoor believes that such artificial muscles can be "packaged into virtually any shape or size," and that muscle for use in human applications could become a reality within five to 10 years. Patents have already been filed on the technology, which could eventually have a number of medical uses. Among the potential applications are actuators for prosthetic limbs that could offer a smoother and more natural movement, artificial sphincters for treatment of incontinence, and a method for encasing the heart with synthetic muscle in lieu of transplant procedures.

NANOTUBES BROADEN POSSIBILITIES FOR ARTIFICIAL MUSCLES

One of the most recent advances in the development of synthetic muscle is based on use of a relatively new material, carbon nanotubes. The carbon nanotube is described as an extended buckminsterfullerene molecule, or "buckyball," the spherical molecule constructed solely from 60 carbon atoms that was synthesized in 1985 by Richard Smalley, PhD, and Sir Harold Kroto, PhD, who were 1996 Nobel laureates in chemistry for the discovery of fullerenes. Discovered in 1991 by Sumio Iijima, PhD, nanotubes are composed entirely of carbon atoms and, because of their molecule structure, provide exceptional strength.

Using carbon single-wall nanotube (SWNT) sheets, researchers at AlliedSignal Inc. (Morristown, NJ) are in the earliest stages of developing artificial muscle that they believe will be considerably stronger and more durable than human muscle tissue or currently available materials. The research, directed by Ray Baughman of AlliedSignal, is currently being funded by the Defense Advanced Research Projects Agency (DARPA). Key centers involved in the project include the University of Connecticut (Storrs, CT), University of Florida (Gainesville), Georgetown University (Washington, DC), Max Planck Institute (Stuttgart, Germany), University of Pisa (Italy), University of Utah (Salt Lake City), University of Washington (Seattle), and the University of Wollongong (Australia).

The research currently involves the use of a simple nanotube production technique that produces a nanotube "paper," based on processes developed by Smalley. Described as macroscopic actuators composed of billions of individual nanoscale actuators, these sheets function as a nanotube array in a fashion similar to natural muscle. According to the researchers, "Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide higher work densities per cycle than any previously known technology."

Describing nanotubes as being "actually seamless cylinders of graphite," Baughman says "the development of carbon nanotube muscles is in its earliest stages, but our recent demonstrations show us that this technology could be game changing for a host of key applications." He explains that, "In general, with any type of actuator, there are trade-offs between rate, modulus, and actuator response."

Baughman emphasizes that there are distinct performance advantages displayed by the use of carbon nanotubes. "With polymer-gel actuators, there are generally very-large volume and dimensional changes, but they are slow. They achieve high strokes, but low modulus." He adds that, "The nanotube actuators provide high work density per cycle."

While demonstrating a remarkable work capacity per cycle, the nanotube-based muscle requires far less electrical stimulation to function. "In terms of required application of power, the energy needed for the nanotube actuator is a full order of magnitude lower than that of polymer gel," says Baughman. He adds that, although most thin-film actuators require about 30 V to function, the nanotube material being developed requires approximately 1 V for actuation and about 4 V at most.

According to Baughman, there is a broad range of potential applications for the carbon nanotube material. Although a number of questions remain to be resolved, including biocompatibility issues, medical applications could eventually include improved actuators for prosthetic limbs and use in powering artificial hearts. He emphasizes, however, that the project is in its "very early stages." The nanotube actuators under study are the first prototypes and will require extensive testing before any of the potential advantages that the technology may provide for practical applications can be assessed.

CONCLUSION

The human muscle is a phenomenal example of engineering. The movement of blood within the body triggers the contraction of muscles to generate energy. As simple as this physical system may be, it has yet to be fully duplicated by artificial means. With the introduction of new materials—polymers that are more supple and responsive, or carbon nanotubes that offer tremendous performance yet require little energy—duplicating the function of muscles is likely to be achieved.

The technologies offer great promise for meeting a variety of medical challenges. Some researchers predict that powered prosthetic limbs will be made to move more naturally and with smaller energy requirements. Others suggest that layers of synthetic muscle tissue wrapped around a patient's heart may one day support the existing muscles sufficiently to serve either as a bridge to transplant or to obviate the need for a replacement organ.

Gregg Nighswonger is executive editor of MD&DI.


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Copyright ©1999 Medical Device & Diagnostic Industry

Understanding Wear and Friction in Medical-Grade Stainless Steels

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

A knowledge of the different types of wear and friction and of current test methods can lead to better-designed stainless-steel devices.

There has been little information—and a good deal of misunderstanding—regarding the subject of wear and friction of medical-grade stainless-steel materials. The following article was prepared on the premise that information addressing the basic behavior of stainless steels would greatly benefit both OEMs and process subcontractors in understanding these important topics.

Devices such as stainless-steel surgical drill bits can be susceptible to wear. The products depicted have been treated with a chromium composition coating (ME-92, from ME-92 Operations) to improve wear resistance.

The article begins with a brief survey of stainless steels—their various categories, uses, and physical and chemical properties. A section on wear introduces the types and causes of wear, reviewing galling, seizure, and abrasion. Several test methods for evaluating wear and galling are presented, along with factors affecting wear and an outline of design considerations for reducing wear and galling. The two classes of friction are then discussed, as are test methods for their measurement and design recommendations for friction applications.

CLASSIFICATION OF STAINLESS STEELS

Stainless steels are regularly used by the medical, chemical, and pharmaceutical industries because of their corrosion resistance, biocompatibility, and ability to withstand elevated temperatures. They offer superior corrosion resistance compared with other steels and aluminum, which is primarily due to the addition of chromium (at least 11% by weight) to the steel and the subsequent presence of chromium oxide on the outer surface. This passive surface layer superficially protects the base metal from further oxidation. Compared with titanium and cobalt alloys, stainless steels are readily available and relatively inexpensive. Some grades have been used for implantation and fixation because of their biocompatibility, while other types can be hardened for use as surgical cutting tools or pharmaceutical molds.

Chemical Analysis % (maximum unless noted)TS
(ksi)
Ys
(ksi)
EL
(%)
Hard
ness
(Rock-
well)
AISI C Mn P S Si Cr Ni Mo Other 
Austenitic Chromium-Nickel SteelAnnealed Condition
301 0.15 2 0.045 0.03 1.00 16.00-
18.00
6.00-
8.00
    110 40 60 Rb 85
303 0.15 2 0.2 0.15
min.
1.00 17.00-
19.00
8.00-
10.00
0.6   90 35 50
304 0.08 2 0.045 0.03 1.00 18.00-
20.00
8.00-
10.50
    8442 55 Rb 80
304L 0.03 2 0.045 0.03 1.00 18.00-
20.00
8.00-
12.00
    8139 55 Rb 79
310 0.25 2 0.045 0.03 1.5 24.00-
26.00
19.00-
22.00
    9545 45 Rb 85
310S 0.08 2 0.045 0.03 1.5 24.00-
26.00
19.00-
22.00
    9545 45 Rb 85
316 0.08 2 0.045 0.03 1.00 16.00-
18.00
10.00-
14.00
2.00-
3.00
  8442 50 Rb 79
316L 0.03 2 0.05 0.03 1.00 16.00-
18.00
10.00-
14.00
2.00-
3.00
  8142 50 Rb 79
317 0.08 2 0.045 0.03 1.00 18.00-
20.00
11.00-
15.00
3.00-
4.00
  9040 45 Rb 85
Ferritic Nonhardenable StainlessAnnealed Condition
430 0.12 1.00 0.04 0.03 1.00 16.00-
18.00
      7550 25 Rb 85
446 0.2 1.5 0.04 0.03 1.00 23.00-
27.00
    0.25 N 8050 20 Rb 83
Table I. Chemical and nominal mechanical properties of austenitic and ferritic stainless steels.


For medical applications, stainless steels can be classified into the following four categories: austenitic, ferritic, martensitic, and precipitation hardening. Tables I and II present the chemical and nominal mechanical properties for stainless-steel materials in each of these classifications.

Austenitic stainless-steel types include both 200- and 300-series materials. They have high concentrations of chromium and nickel and cannot be hardened by a quench-and-temper heat treatment. Hardness is generally in the Rockwell Rb 88 to Rb 95 range for annealed material and can be increased by cold-working. These are normally nonmagnetic grades, but some magnetism can be developed by cold-working. This category offers the highest degree of corrosion protection. Types 304 and 316—the first implanted stainless steels—are the most commonly used varieties from this classification. Both are available in a low-carbon grade that offers superior corrosion resistance in the welded condition.

Chemical Analysis % (maximum unless noted)TS
(ksi)
Ys
(ksi)
EL
(%)
Hard-
ness
(Rock-
well)
AISI C Mn P S Si Cr Ni Mo Other  
Martensitic Chromium SteelsAnnealed (Hardened)
410 0.15 1.00 0.04 0.03 1.00 11.50-
13.00
     704525Rb 80
420 0.15
min.
1.00 0.04 0.03 1.00 12.00-
14.00
     955025Rb 92
431 0.2 1.00 0.04 0.03 1.00 15.00-
17.00
1.25-
2.50
   1259520Rc 24
440A 0.60/
0.75
1.00 0.04 0.03 1.00 16.00-
18.00
 0.75 1056020Rb 95
440B 0.75/
0.95
1.00 0.04 0.03 1.00 16.00-
18.00
 0.75 1076218Rb 96
440C 0.95/
1.20
1.00 0.04 0.03 1.00 16.00-
18.00
 0.75 1106514Rb 97
Trim
Rite
0.15/ 1.00 0.04 0.03 1.00 13.50-
15.00
0.25-
1.00
0.40-
1.00
 88 54 28 Rb 88
Precipitation-Hardening Stainless SteelsSolution-Annealed
13-8 0.05 0.1 0.01 0.008 0.1 12.25-
13.25
7.50-
8.50
2.00-
2.50
0.9/1.35Al
0.010 N
16012017Rc 33
15-5 0.07 1.00 0.04 0.03 1.00 14.00-
15.50
3.50-
5.50
 2.5/4.5 Cu
0.15/0.45
CbTa
16014515Rc 35
17-4 0.07 1.00 0.04 0.03 1.00 15.50-
17.50
3.00-
5.00
 3.0/5.0 Cu
0.15/0.45
CbTa
16014515Rc 35
17-7 0.09 1.00 0.04 0.04 0.04 16.00-
18.00
6.50-
7.75
 0.75/1.50 Al1304010Rb 90
455 0.05 0.5 0.04 0.03 0.5 11.00-
12.50
7.50-
9.50
0.51.5/2.5 Cu
0.8/1.4 Ti
0.1/0.5
CbTa
145 115 14 Rc 31
a Carpenter Technology Corp.
Table II. Chemical and nominal mechanical properties of martensitic and precipitation-hardening stainless steels.


Ferritic types include some of the 400 series. These are nonhardenable steels, and are typically used for deep-drawn containers and some solenoids. Hardness of annealed material typically ranges from Rb 80 to Rb 100 (Rc 22.8), with only a moderate increase in hardness generally achievable by cold-working. Stainless steels in this classification are magnetic and provide less corrosion resistance than 300-series materials, but are especially resistant to stress corrosion cracking. They are seldom used for medical instrumentation involving contact with internal body fluids or tissues. Type 430 has been used for various medical applications, including operating tables, device cabinets, and trays.

Martensitic steels make up the remainder of the 400 series. These may be hardened via a quench-and-temper process, with hardness after heat treatment ranging from Rc 48 to Rc 56 for type 420 and Rc 52 to Rc 60+ for type 440C. Magnetic in the annealed and hardened conditions, these materials are not as corrosion resistant as the other categories of stainless steels. Types 420 and 440C are often used for surgical cutting instruments, drills, and reamers.

Precipitation-hardening (PH) stainless steels have properties between those of the martensitic and austenitic types. Hardness is developed by a solution heat treatment followed by an aging treatment, through which a second, hardening phase is formed. Hardness for 17-4 PH ranges from Rc 29 to Rc 44. These types have higher corrosion resistance than the martensitic varieties and offer higher bulk hardness than do 200- and 300-series materials. Contrary to what one might expect, this increase in hardness does not provide greater wear or galling resistance. These grades are magnetic and are widely used in orthopedic instruments.

CLASSIFICATION AND DESCRIPTION OF WEAR

When metal mechanical parts or assemblies fail, it is usually the result of fracture, corrosion, or wear. Wear certainly seems to be the least understood of these three factors; however, its importance in medical applications should not be overlooked. It is often assumed that wear and friction are very much the same thing, but lowering friction does not necessarily lower wear. Limited experience has caused some to maintain that a direct relationship exists between higher hardness and lower wear. The fact is that large-scale testing on a variety of materials shows that these are two distinct properties. Wear and friction are quite different.

Wear can be defined as both material loss and deformation at contact surfaces. Wear results in particle generation and surface degradation. Therefore, reducing the wear of surgical instruments lowers the production of wear particles and thus the possibility of introducing foreign matter into the body. Extended instrument life and consistent performance are other reasons for instrument designers to consider means of minimizing wear. Many types of wear have been observed and classified, as discussed below.1,2

Adhesive Wear. Adhesive wear is a common form of metal loss. In surgical instrument applications, adhesive wear and galling are the most frequently occurring forms of wear. Adhesive wear takes place when no outside abrasives are present between two wear surfaces. At low loads, an oxide film usually forms on the contact surfaces. This prevents metallic bonding between the mating materials but results in a low rate of wear referred to as oxidative or mild wear.

As loads are increased, a transition is reached: the oxide film breaks down and metallic bonding (cold welding) takes place between the two surfaces. This is referred to as severe metallic wear, and causes rapid material loss and high wear-particle generation.

Galling is a special case of severe adhesive wear. The wear particles can no longer be accommodated by the surface roughness and contact clearances. At this point, the contact surfaces become cold welded. Further movement causes the surface metal to de-form and tear. In extreme cases, metal seizure occurs. When contact pressures are high, galling and seizure can transpire with minimal amounts of sliding (less than one revolution or fractions of an inch).

Abrasive Wear. Abrasive wear occurs when a hard material scratches or gouges the surface of a softer material. The abrasive material can be either of the sliding surfaces or particles between the two surfaces. When the contact stress is too low to crush the abrasive particles, the cutting action is defined as low-stress scratching abrasion. This usually results in surface scratches with little subsurface deformation. In high-stress grinding abrasion, however, the loads are great enough to crush the abrasive material. This action usually causes permanent plastic deformation of the base metal, along with material removal. Gouging abrasion occurs when high stresses create significantly large grooves on the contact surfaces.

Erosion. Erosion is material loss from the abrasive action of moving fluids on a component. Erosion can be intentional, as when high-pressure liquid streams are used to perform rapid machining operations.

Components that experience large pressure changes and turbulent flow can wear due to cavitation erosion. Cavitation is the formation and collapse of numerous small bubbles during turbulent flow. The ultrasonic shock of the collapsing bubbles scrubs the metal surface, which can cause long-term surface loss. Fluid valves and pumps are examples of applications in which cavitation may occur. Surface destruction is accelerated by the presence of solid particles within a fluid stream.

Wear caused by suspended solid particles is referred to as impingement erosion. A material's resistance to impingement erosion varies with the angle of particle impingement and material hardness.1

Fretting. Fretting wear is material loss that takes place between tight-fitting surfaces that are subject to vibrational movements (such as riveted or otherwise-fastened joints and electrical connections). Material loss is from a combination of oxidative and abrasive wear. The oscillation of the two surfaces causes the formation of oxide films that are then abraded away by oxidized wear debris. The affected surfaces sometimes look as if they were mechanically deformed, so this wear is sometimes called false brinelling. It is also referred to as fretting corrosion, friction oxidation, chafing fatigue, or wear oxidation.3

WEAR TESTING

Tests are constantly being developed to measure the properties of materials. Some tests are designed to simulate actual use. These often use a large number of variables, such as speeds, loads, and times. For example, one could make a surgical bone cutter using all of the available material options. Each cutter could then be evaluated with a series of simulated-performance tests. This would certainly determine which of the materials was best suited for the particular application—but most likely at a substantial cost. In addition, the results of such tests would only be applicable to selecting materials for devices of similar design and use.

More general tests that measure characteristic properties tend to apply to a larger number of engineering design problems. Their use often allows a designer to rapidly narrow the selection to a few materials. One must use caution when applying general results to a specific design problem—unless the intended use is similar to the test configuration. Even greater caution must be used in applying results from simulated tests to different engineering problems.

Several tests have been used by industry for measuring the wear and galling resistance of materials. Three popular ones—for which much data exist—are ASTM G 83 "Standard Test Method for Wear Testing with a Crossed-Cylinder Apparatus," ASTM G 99 "Standard Test Method for Galling Resistance of Materials," and ASTM G 99 "Standard Test Method for Pin-on-Disk Wear Testing."4–6 Brief descriptions of each of these tests are provided in the following sections.

Crossed-Cylinder Wear Test. For the crossed-cylinder test (ASTM G 83), two cylindrical specimens are positioned perpendicular to each other in the test machine. (Some commercially available machines have an optional force-measuring system for determining coefficients of friction.) The test equipment allows one specimen to rotate at speeds of up to 400 rpm. The second, nonrotating specimen is pressed against the moving specimen at a specified load by means of an arm and attached weights. Sample surfaces are typically ground to a finish of 16 µin. AA or less. The test duration and rotational speed are varied depending on which of three test procedures is specified. The amount of wear is determined by weighing the specimens before and after the test. Results have been reported as weight loss, but are typically converted to volume loss.

Figure 1. Schematic of a "button and block" galling test arrangement.

Threshold Galling Stress Test. In the threshold galling or "button and block" test (ASTM G 98), a small button and a large block sample are machined to provided two flat surfaces with a 10- to 45-µin. AA finish. The couple is then compressed together at constant load with a hydraulic or screw-feed press. The test arrangement is presented in Figure 1. One specimen is slowly rotated one revolution relative to the other specimen. Sliding surfaces are then examined for the appearance of torn metal, which indicates that galling has occurred. If the specimens have not galled, new samples are tested at higher loads until galling occurs. Couples with higher-threshold galling stresses have greater resistance to galling.

Figure 2. A top view of a test arrangement (ISC-200 PC tribometer) used for a pin-on-disk wear test.

Pin-on-Disk Test. For the pin-on-disk wear test (ASTM G 99), two specimens are required. A pin with a radius tip is positioned perpendicular to a flat disk. A ball, rigidly held, is often used as the pin specimen. The test machine rotates the disk at 60 to 600 rpm. The wear path is a circle on the disk surface. Surface finishes of 32 µin. AA or less are typically used. Test results are usually reported as volume loss per cubic millimeter for the pin and disk separately. The results can be plotted as wear volume versus sliding distance or as friction versus sliding distance. A top view of the test arrangement is shown in Figure 2.

FACTORS AFFECTING WEAR

Wear is generally affected by several factors, among them materials selection, friction, surface load, sliding distance, surface hardness, surface finish, and lubrication. Controlling these factors can contribute to a successful application by helping to prevent wear and premature product failure.

Materials Selection. Wear varies greatly depending on the materials selected. For critical applications, it is crucial that the person responsible for materials and process selection is sufficiently experienced and has adequate information available to make a sound engineering decision. Carelessness in this area can result in poor instrument performance and even field failures. The time and money spent in proper materials and process selection can be vastly less expensive than field failures and product recalls.

Friction. Researchers have not observed a consistent relationship between friction and wear. Materials with low coefficients of friction may have high wear rates (Teflon, PTFE), and some high-friction materials, such as cast iron, have low rates of wear. Again, one must remember that friction and wear are different.

Surface Load. Increasing the surface load between sliding surfaces has been found to cause a proportional increase in material wear rates.

Sliding Distance. Increasing the sliding distance of an assembly will cause a roughly proportional increase in material loss.

Surface Hardness. Wear resistance generally increases proportionally with increasing surface hardness (which may be very different from bulk hardness). Surface deformation during wear causes a localized increase in surface hardness on work-hardened metals. This explains why high-strain-hardening, austenitic stainless steels are more wear resistant than harder precipitation-hardened stainless steels.

Surface Finish. Surface finishes between 10 and 70 µin. AA have been found to offer similar wear resistance for many stainless steels.7 Very smooth surfaces promote cold welding (galling) because of high molecular interaction. High finishes also lack adequate clearance to store wear debris. Overly rough finishes increase wear by allowing surface asperities (irregularities) to become interlocked, resulting in what is known as a "stick-slip" phenomenon as these surface irregularities are subsequently worn off when sliding occurs.

Lubrication. Lubrication can be used to prevent or reduce metal-to-metal contact and cold welding. Contact stresses may also be effectively reduced with lubricants. The type of lubrication and delivery system are important considerations for reducing wear and galling.

Many surface modifications and coatings are designed to perform as a "dry" lubricant. These can be used when wet lubrication is not practical.

Comparing Tensile and Inflation Seal-Strength Tests for Medical Pouches

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Clarifying the relationship between tensile and burst testing for the evaluation of package seals can help manufacturers establish more effective process control.

A frequently used analytic tool, seal-strength testing provides quantitative seal-strength data for the medical package manufacturer. Such testing has become more prominent with the release of AAMI/ANSI/ISO 11607, "Packaging for Terminally Sterilized Medical Devices," and its adoption by FDA as an "FDA-recognized consensus standard."1 Two readily available seal-strength testing methods are indicated for use in the ISO standard: tensile seal-strength testing and inflation seal-strength testing.

Tensile seal-strength testing uses a defined-width sample of a package perimeter seal. A moving jaw pulls the sample apart at a constant speed while measuring the resistance force during the seal separation. The inflation seal-strength test can be represented by either the "burst" or the "creep" test. The burst test—a method in which a whole package is inflated at a uniform rate until it ruptures—measures the peak pressure at rupture in order to determine seal strength and is the most commonly used inflation seal-strength test. Similarly, the creep test inflates a package to a constant pressure and holds the pressure either for a fixed time (a creep test) or until rupture occurs and the time to failure is measured (a creep-to-failure test). The creep test is similar to attaching a dead weight to a seal and waiting for the seal to shear or peel apart.

In cooperation with ASTM Committee F2.6 on flexible medical packaging methods, the authors have set out to investigate the nature of the relationship between the two seal-strength testing methods. Investigation of the relationship may shed light on the possibility of a universal correlation. Many device manufacturers as well as suppliers of medical pouches, package lids, trays, and materials have sought a universal correlation between the two methods—although none exists at this time.

A series of screening tests has been designed and run to determine whether the two methods can be compared, and, if so, on what basis. At issue is whether the inflation seal-strength tests can be configured to provide results that compare to the lowest tensile seal-strength area found in a medical package. An additional question is whether inflation seal-strength tests will provide the same level of sensitivity to process-change effects on seal strength as that seen with tensile testing.

BACKGROUND

When two packaging materials or webs are bonded together, the result is a seal. This seal can be either peelable or nonpeelable. Peelable seals are designed to separate upon application of a required separating force. Nonpeelable seals are intended to be stronger than the tensile or shear strength of the original materials. For medical packaging, peelable seals are designed to remain closed during processing and distribution, yet to be capable of being opened upon application of a reasonable separation force by the product user.

ANSI/AAMI/ISO 11607, "Packaging for Terminally Sterilized Medical Devices," states that "various methods can be used to determine seal strength, e.g., tensile strength testing and burst/creep pressure testing."1 The standard goes on to state that "there is no general correlation between tensile strength and burst/creep testing. They are separate tests and the results obtained have entirely different implications regarding package seal strength."

Package validation is, among other things, a methodology for ensuring that the sealing process is under control, is consistent, and meets the design requirements established for the process and materials. An effective method for establishing design requirements is by using seal-strength measurements. The primary issue for the selection of a test method is its sensitivity. Does the test method have the capability to discriminate between minor variations in the process? Both tensile tests and the newer burst/creep tests are sufficiently sensitive. The tensile seal-strength test is sensitive to 0.01 lbf and the burst/ creep tests have sensitivity to 0.02 psi.

Figure 1. Tensile testing machine used in ASTM F 88 test method.

The American Society for Testing and Materials (ASTM) has a test method designated as ASTM F 88, "Standard Test Method for Seal Strength for Flexible Barrier Materials."2 This method is designed around using a tensile testing machine to measure the force required to separate the seal of a 1-in.-wide sealed sample (Figure 1). The rate of separation is usually fixed at 12 in./min, with output measurement in pounds of force per inch of seal width. However, the value chosen from a typical force plot can be peak value, average value, or force deformation. Though the current standard only discusses "peak values" of seal strength, a revision to the test method under review at ASTM includes the use of the force-deformation curve and average seal strength.

Because medical packages have seals all around the perimeter of the package, using F 88 requires sectioning the perimeter seal into 1-in.-wide samples at random locations or continuously around the seal. In the majority of cases, a perimeter seal is only sampled at several locations, leaving areas of the perimeter untested.

Figure 2. Open-package test fixture.

The inflation seal-strength tests—burst and creep—are discussed in ASTM standard method F 1140.3 This method describes the apparatus and process used to automatically inflate a whole package and capture the peak rupture pressure (the burst pressure) or measure the hold pressure (creep pressure) over a defined time period. The measuring equipment is used along with either a clamp to seal an open-ended pouch (an open-package fixture, as in Figure 2) or a device for penetration of a completely closed package (a closed-package fixture, as in Figure 3).

Figure 3. Closed-package test fixture.

Because inflation tests use the whole package instead of a perimeter sample, they are well-suited for finding the weakest seal area. By monitoring this pressure-related value, the package supplier or device manufacturer can set minimum strength values and/or monitor the process of seal manufacture.

Each method has its inherent advantages. Inflation testing is obviously faster to execute since it requires little sample preparation and handling. Tensile testing offers a complete strength profile of the seal perimeter. Both provide a quantitative measure of the mechanical strength of the seal.

Figure 4. Failure mechanisms in seals: (top) normal opening; (middle) cohesive failure; (bottom) adhesive failure.

Output data of the tensile seal-strength test can be better understood by examining peelable-seal failure mechanisms. Peelable seals are designed to fail adhesively or cohesively (Figure 4).4 The applicable failure mechanism can be readily seen using the force-deformation-curve approach to tensile testing.5,6

Figure 5. Typical force-deformation curve shown on a seal failure profile.

Originally, the value used to determine the tensile strength of a seal was the maximum force required to separate the sealed webs. Although still in use, this concept is being replaced by the force-deformation-curve approach. Upon examining a seal failure profile, one generally sees peaks at the start and at the end of the curve (Figure 5). The starting peak, which is usually the maximum force, occurs for two reasons. First, the force required to start the peel separation or to overcome the static condition is greater that the force required to maintain motion. (This is similar to the physics of a static versus rolling coefficient of friction.) The second reason is that the edges of a seal are usually the result of higher seal pressures during the sealing process—which most likely also explains the second peak that occurs at the end of the curve.

The force-deformation curve makes it possible to determine the average separation force, either by averaging the forces along the curve or by integrating the area under the curve. The visual characteristics or shape of the curve can be used to identify the sealing adhesive and sealing conditions, similar to a "fingerprint" identification of the materials and process.

Figure 6. Test sample fixturing using (left) free-tail and (right) supported-tail methods.

Consistent methodology in holding the test sample is required to ensure the best test results. There are several ways to fixture the test sample. For flexible samples, the choice is between the "free-tail" and "supported-tail" methods (shown in Figure 6). Both methods are acceptable, but it should be noted that the resultant force-deformation curves or results are not equivalent. In the free-tail method, the angle of peel is constantly varying from 90° to greater than 90°. In the supported-tail method, the sample tail is restrained by the use of a fixture to keep the angle of peel at 180°. While the choice of fixturing method is one of individual preference, many believe that the free-tail alternative more closely emulates real-world conditions. It is important to note that use of the supported-tail method will result in higher numerical values of seal strength.

Historically, attempts have been made to calculate the relationship between tensile seal-strength and inflation burst tests based on a force balance. As noted by Wachala, an empirical relationship is the preferred means of relating the outcomes of the two tests.7 An analytical correlation can be derived, but—because of the complex nature of stresses applied to medical-pouch seals—usually results in errors that can exceed 30%. Futhermore, in today's market, the wide variety of sealing substrate materials adds more variables to the reaction of seal bonds to applied forces.

Chevron-style medical pouches were used to look at the relationship between tensile and inflation tests. This product geometry is very familiar to both suppliers and manufacturers, and can be used to examine both porous and nonporous package configurations as well as the effect of various length-to-width ratios on the burst pressure of a pouch. (The width dimension is the distance across the chevron feature of the pouch.) For example, limitations of unrestrained burst testing have been noted for packages with large length-to-width ratios. One limitation is finding the weakest seal area. Packages usually show a consistent rupture along the longest seal feature. In fact, this burst area may not always be the weakest seal in the pouch perimeter related to tensile seal-strength data.

Figure 7. Pouch-restraining fixture.

Properly conducted, unrestrained burst-strength testing of a pouch will result in a consistent burst-pressure value and a consistent burst area. This fact allows the unrestrained method to be useful as a process control tool. However, correlating tensile and inflation seal-strength testing requires additional control of the stresses on the package seals during the burst test. By restraining the pouch along its walls, the effect of material membrane stresses (so-called hoop stresses) can be minimized (Figure 7). In this way, the nature and direction of the forces needed to separate the seal can be examined, and it might be possible to develop equations to relate these forces.

The experience of some users indicates that under controlled conditions with the use of restraining plates, a predictable relationship can be developed between tensile and burst test results on a particular package.8 Accordingly, a screening experiment was developed to examine the nature of the variables that may affect burst pressure. An additional experiment was proposed in which the sealing parameters of temperature, pressure, and dwell time were varied for a specific pouch, and the change in burst pressure related to the change in average tensile strength. If this relationship can be established, then the restrained burst test would have the added advantage of not only relating the lowest seal-strength area to tensile seal strength but also of setting up a numeric relationship between the two tests.

Figure 8. Force-deformation curves showing relationship of different process settings.

One of the significant advantages of the tensile seal-strength method is its sensitivity, in that the force-deformation curve can discriminate changes in processing parameters. The graph in Figure 8 is an example of the differing results when the same materials were sealed at different processing parameters. These effects can be further enhanced depending on the type of peelable adhesive used. In this case, the adhesive was from a coextruded blend. The graph clearly shows that tensile seal strength and time increase directly as the sealing heat energy increases.

By relating burst and tensile tests, the faster burst-test technique will be available to provide tensile-related information directly to production or quality control personnel. In this way, corrective action can be taken almost immediately to prevent out-of-specification products from being manufactured.

EXPERIMENTAL DESIGN

The purpose of the initial experiments was to perform a screening of the possible relationships of variables in the inflation burst test. The initial tests were not meant to provide a rigorous statistical analysis, but only to indicate trends of the relationship. Statistical methods were applied to segregate significant differences.

Test Factor Level 1 Level 2 Level 3 Level 4 Level 5
Restraining condition Unrestrained 1/4 in. 1/2 in. 3/4 in. 1 in.
Geometry (L/W)a A (2:1) B (1:1) C (1:2)    
Flow rate (time to burst) Low Medium High    
Pouch type Open Closed      
Materials Nonporous Porous      
Package size Small Medium Large    
Package style Pouch Tray Strip bag    
Adhesive material Peelable Heat weld      
a Area is approximately the same.
Table I. Test factors for burst tests with medical packages.


The screening tests were designed to determine the effect on burst pressure (Pb) of an limited number of variables. Table I shows the possible test factors. Some factors were excluded from the initial test in order to provide the most effective test control. For example, the test materials were limited to nonporous films to exclude the variation in porosity of porous barrier films. As mentioned previously, package types were limited to peelable pouches, and package sizes kept to a common area while the length-to-width ratio was varied. The package bonding system was configured as a peelable, coextruded material to provide a more consistent medical peel pouch.

The screening tests were primarily designed to examine burst pressure with respect to restrained plate gap, to examine the effect of various length-to-width ratios, to discover if the burst area in restrained testing was in the lowest seal-strength area of the pouch, and to determine whether a significant difference in consistency exists between restrained and unrestrained burst tests. It should be noted that care in the design of the restraining plate fixture is required for both safety and fixture rigidity. Fixtures should be made of metals having a sufficient strength to resist the applied loads.9

A second test was designed to determine whether the restrained burst test would be sensitive enough to detect process changes in the seal manufacture. The pouch seals would be prepared at different conditions of temperature, pressure, or dwell time and then measured by both tensile and burst seal-strength test procedures.

The apparatus used for the tests was as follows:

  • Automatic package tester (T.M. Electronics Model BT-1000).
  • Open and closed package fixtures (T.M. Electronics).
  • Variable-gap restrained plate fixture (T.M. Electronics).
  • Pouches of coextruded film (#PLK-201 from Rexam Medical Packaging).
  • Motorized test stand (Chatillon) with force gauge (Mark-10) and analysis software.

TEST RESULTS

The primary effect on burst pressure (Pb) found in these tests was the influence of gap distance between the restraining plates. Significant differences (P>0.05) were seen at gaps of 1/4, 1/2, 3/4, and 1 in. These data are shown in Figure 9. The influence of length-to-width ratio is shown in Figure 10. When pouches were tested in an open-ended or totally closed configuration at different gaps, no significant differences were noted.

Figure 9. Average burst pressure versus plate gap size. Bags were nonporous B-bags (Rexam PLK-201) with a time-to-burst of 2.5 seconds. Correlation coefficient (R2) = 0.9971.

Figure 10. Effect of package length-to-width ratio (A, B, or C) on burst pressure (UR = unrestrained).

Figure 11. Tensile seal strength of pouches (separation speed = 12 in./min).

An examination of the burst area was conducted to distinguish between chevron- and side-seal rupture. Tests of tensile seal strength on all pouches showed that the chevron seal of the pouch contained the lowest tensile seal strength compared with the side seals (Figure 11). The data in Table II show that, depending on the length-to-width ratio, a plate gap could be found at which consistent bursting takes place in the lowest seal-strength area, which was identified as the chevron.

Test MethodChevron SealSide Seal
L/W=2:1 L/W=1:1 L/W=1:2 L/W=2:1 L/W=1:1 L/W=1:2
1/4-in. gap 8 37 5 0 0 0
1/2-in. gap 9 45 15 19 0 0
3/4-in. gap 0 21 5 5 0 0
1-in. gap 0 119 5 10 4 0
Unrestrained 0 35 5 12 11 0
Table II. Bag burst locations, showing relation to package length-to-width ratios.


A test for significance was conducted to examine the hypothesis that restrained-plate burst tests were more consistent—that is, less variable—than unrestrained tests. The F test on variance from the tests at different gaps versus unrestrained testing is shown in Table III. These tests generally show no significant difference in variation between the unrestrained and restrained methods (p<0.05).

Gap n Variance (s2) Unrestrained/Restrained
s2 Ratio
Fcrit (0.05) Fcrit (0.01)
Unrestrained 5 0.0016      
1/4 in. 5 0.0064 4.0 6.39 15.98
1/2 in. 5 0.0004 4.0 6.39 15.98
3/4 in. 5 0.0016 1.0 6.39 15.98
1 in. 5 0.0016 1.0 6.39 15.98
Table III. Variance analysis of tests at different plate gaps versus unrestrained tests.


Figure 12. Linear regression of changes in burst and tensile seal strength related to changes in temperature. Correlation coefficient (R2) = 0.9422.

The test to relate burst-test sensitivity to process variation was conducted by manufacturing the fourth seal on the premade pouches at various temperatures and dwell times. The two seal-strength test methods compared by producing the fourth seal of the open-ended pouch at higher and lower tensile seal strengths than the chevron and side seals. To affect the tensile seal strength for the selected material, a temperature range of ±10°F and dwell time of 1.5 seconds was required. Pressure was held constant. These variations produced seals with the tensile and burst seal strengths shown in Table IV, with a linear regression of the results shown in Figure 12. The results clearly show a direct relationship between the two tests and a comparable level of sensitivity in monitoring process changes for this material.

Temp./Dwell/Press. Tss @ End
Seal (lb-in.)
Burst
Pressure (psi)
Area of Burst @
1/2-in. Gap
260/2.5/40 1.283 6.42 Chevron
250/1.5/40 1.156 6.15 End
235/1.5/40 0.929 5.62 End
Table IV. Values for temperature tests.

Economies of Scale: Electronics Manufacturing Services Bring Balance

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Outsourcing electronics manufacturing reduces operating costs and enables companies to focus resources on designing and marketing devices.

The evolution of electronics manufacturing services (EMS) from only high-volume applications such as board stuffing to more diverse service-oriented manufacturing has made this alternative viable for more medical device companies. Whether OEMs are redirecting internal support structures for specific product lines or eliminating redundancies between contracted and internal resources, moving some or all manufacturing outside can strengthen a company's competitive advantage by bringing focus to its core competencies of designing and marketing devices. Reengineering, limits on human and capital resources, and financial constraints are leading OEMs to analyze these core competencies and look outside for electronics manufacturing.

A multichambered convection oven is used for soldering memory PC boards during the final step in the SMT assembly process. Photo courtesy of DA-Tech Corp.

Evaluating outsourcing options and deciding when—and then which—electronics manufacturing service to use begins with an examination of the company's own internal strengths. Each device company must determine what criteria to use to identify a contract manufacturer that can become a seamless extension of the OEM. This article explores the options available from EMS providers and examines how an OEM can determine whether a service provider can respond to its specific needs.

"Contract manufacturers can develop economies of scale that device manufacturers can't, and can therefore provide cost savings that the OEM can't achieve on its own," says Phil DiVita, cofounder and director of Da-Tech Corp. (Ivyland, PA). "Because contract manufacturers buy more electronic materials [than OEMs], they have more power with suppliers. Because they have many electronics customers, they simply have more purchasing power. They function in a way that device manufacturers can't, such as having five or six surface mount lines that run continuously. They reduce risk to the manufacturer because they take on the risk of managing materials and work-in-progress or finished goods and can therefore schedule the flow of subassemblies and finished goods to take just-in-time orders," he explains.

According to DiVita, there are several reasons why it is economical for device companies to outsource electronics manufacturing. "They reduce risk and increase cash available to focus on their core competencies of designing and marketing rather than investing in training staff and developing new operations. Given all the forces—environmental, regulatory, economic, social, and industrial (the power of the buyers and suppliers)—that act on management, outsourcing provides a way to build competitive advantages related to costs and quality," DiVita says.

Reasons Why Companies OutsourceFactors in Vendor SelectionFactors for Successful Outsourcing
Reduce and control operating costs Commitment to quality Understanding company goals and objectives
Improve business focus toward core competencies Price (tactical outsourcing) Having a strategic vision and plan
Gain access to world-class capabilities References/reputation Selecting the right vendor
Free internal resources from noncore activities Flexible contract terms Ongoing management of relationships
Access resources not available internally Scope of resources A properly structured contract
Accelerate organizational change Additional value-added capability Open communication with affected individuals/groups
Allocate difficult to manage functions Cultural match Senior executive support and involvement
Make capital funds available Existing relationship Careful attention to personnel issues
Share risks Location Near-term financial justification
Gain a cash infusion OtherUse of outside experts
Table I. Top 10 reasons for outsourcing and factors in vendor selection and successful outsourcing. (Source: The Outsourcing Institute)


Medical manufacturers that hit a fork in the road must define their strengths and decide where to focus their resources. "Many device companies choose an EMS because manufacturing is our core competency," says Brian Tracey, vice president of corporate development for EFTC (Denver). Outsourcing frees up internal resources for more critical projects or activities. As a company's product line expands, outsourcing curbs the need to continually expand product development and manufacturing capabilities. Moving manufacturing to an EMS provider reduces operating costs and provides more flexibility (Table I).

Most device companies outsource electronics manufacturing to bring their products to market more quickly and cost-effectively. OEMs sometimes have small product development staffs that are at capacity, so outsourcing is necessary. Manufacturing capacity is also often the driver. The OEM either has no manufacturing capability or its production floor is at capacity. Says Russ Gray, vice president of operations and product development for UMM Electronics (Indianapolis), "In the case of start-up companies, an EMS can be well into the first phases of the project before the customer could hire and bring up to speed their first engineer."

"Because surface mount technology (SMT) manufacturing requires intensive capital investment, OEMs may get a product to market more cost-effectively by going outside. An EMS supplier can run multiple products down the same line, thereby achieving a higher rate of equipment utilization and a lower overall cost per assembly produced. In this example the cost to the OEM is based on its use of the production line. If OEMs choose to keep the manufacture in-house with only partial utilization of their production assets, they incur significant costs associated with equipment underutilization," says Frank Mokry, vice president of sales and marketing at K*Tec Electronics (Sugarland, TX).

An EMS supplier's primary function is to make electronics products. Device manufacturers design and market devices, but aren't always experts in manufacturing. And today's electronics products are integrating many advanced technologies such as new, smaller package types to achieve higher-speed data transmission. "In order for OEMs to make [electronics], they must invest in sophisticated equipment and infrastructure. The overhead for an EMS is much lower because it can use the same machines for multiple customers, says Manny Lee, president and chief executive officer of Excelsior Manufacturing (San Jose).

Many EMS providers are now set up to manufacture functionally tested, finished devices. If an EMS can assume that operational responsibility, says DiVita, device companies can better leverage assets through the use of conceptual engineering, cost-reduction analysis, design for manufacturability and testability (DFM/DFT), or even product launch programs.

To help determine whether an EMS pro-vider is a good match, it is recommended that OEMs develop a matrix that includes not only cost, but also process technology capabilities, quality requirements, engineering capabilities, project team structure, and other services. "It is particularly important to know whether an EMS provider focuses on high-mix, low-volume production or low-mix, high-volume programs," adds Ty Griffin, senior manager of quote services at EFTC.

"Be prepared. Conduct a thorough survey of potential EMS suppliers. Let them know expectations up front. It is also critical to understand their fundamental philosophy. The best way to do this is to meet the head of the organization," says Lee. "Device manufacturers must find an EMS that will manufacture a product that meets the intention of the design by the manufacturer, not only in quality but also in delivery. Not every company is identical."

PROJECT MANAGEMENT: WHO HAS CONTROL?

System development involves the EMS from the initial concept stage through to development and commercialization of the product. Turnkey production enables the EMS to assume responsibility for building a product that has already been designed and is ready for production. Stepping in at this stage enables them to assume production of end-of-life products as well, freeing manufacturing capacity at the OEM for a next-generation product. Even for device companies that have the resources to design a product in-house, EMS providers can offer advice early in the design stages that can reduce manufacturing costs. And, in many cases, the device company retains rights to technology developed jointly with the EMS. "Device companies must look for an EMS with an active and documented risk management process, covering project management plus product and process design," says UMM Electronics' Gray.

Device manufacturers outsource many next-generation products at UMM, for example. However, the company also works with customers to provide manufacturing and minor design changes on end-of-life products. This frees the customer's production area for new product launches and maintains the cash inflow from the mature product. "They are able to take advantage of both their cash cow and their shooting star revenues," explains Gray.

Prototype development by the UMM Electronics model shop.

Although outsourcing to an EMS means sharing the responsibility of a key element of product development, device companies can maintain manufacturing control. Many EMS providers use manufacturing resources planning (MRP) to enable them to track the manufacturing process. Some offer an intranet that the device company can access 24 hours a day. It is important to determine the level of contact necessary.

Type of ChangeCompany Approval Required Prior to ImplementationUMM Must Notify Company Prior to Implementation Approval or Notification Not Required
Changes to PCB layout or design X    
Changes to key electronic component values or part substitution of key active components X    
Changes to electronic component values or part substitution of nonkey active components   X  
Substitutions of passive electronic components     X
Changes to standard mechanical components     X
Changes to major purchased components (PC, keyboard, monitor, printer, or power supply) X    
Changes to proprietary software X    
Table II. UMM change notification protocol for products in manufacture.


UMM uses a change notification protocol process to ensure that OEMs retain control of the manufacturing process (Table II). This process requires that the OEM is informed of and approves all significant changes prior to their implementation. Some companies, such as Sparton Electronics (Brooksville, FL), use an enterprise resource planning (ERP) system that provides real-time shop-floor tracking to monitor quality yields and generates customized systems reports. Da-Tech has also recently implemented a new information management system. "The manufacturing resource planning system allows access to what is being manufactured and tracks a job from beginning to end. We are planning to allow customers to access this information directly," says DiVita.

With the advent of the Internet, EMS companies are able to use this technology to develop a more seamless, real-time connection with customers. Says K*Tec's Mokry, "We track the manufacturing process down to the component level—and provide our customers unfiltered access to this data, so that we and the OEM can more closely and accurately monitor the manufacturing process. Using K*Tec's proprietary intranet software, with access through the Internet, we provide our customers detailed visibility into how we manufacture their PCBA and box-build products—from detailed work instructions down to specific AVL information at the component level. This access is password protected (and outside the system firewall for security reasons), allowing visibility to the information by the customers from the convenience of their offices." Also available through the company's intranet are its DFM/DFT guidelines and company quality manual. "This allows customers immediate access to information that enables them to make design decisions in an informed manner that will help ensure the product is manufacturable, testable, and at the highest quality levels possible when released for production within our factory," says Mokry.

The intranet, he adds, makes the manufacturing process visible to the OEM and ensures a high degree of product traceability and accountability. "OEMs can view from their desktop any history that may exist on a PCBA or box-build assembly K*Tec produced for them. This access to real-time information empowers the customers with the ability to get an answer when they need it—24 hours a day, 7 days a week. There's no longer the need to call a manufacturing engineer or program manager to obtain manufacturing data. We have provided the means for the OEMs to obtain the information they need—when they need it," explains Mokry.

K*Tec also tailors the intranet site with any customer-specific needs or requests. For example, data can be output in whatever format a customer requires for internal use—Pareto reports, bar charts, pie charts, or any other report formats they specify. Information is updated in real time. "If an OEM's field salesperson needs to be able to commit to a number of assemblies to secure a sale, the salesperson can log onto the intranet site, see what is in process and finished goods, and provide the customer with a firm commitment to secure an order on the spot. We are able to provide virtual manufacturing capabilities to an OEM partner that has no internal manufacturing capabilities," Mokry says.

"If a customer needs a product by a certain date, but encounters delays in design, we will try to condense our process to make up for the loss of time. When we make a product, we always manufacture a prototype. We provide all DFM and DFT reports to the OEM and use the information to come as close as possible to the ideal manufacturing situation. We look at the prototypes to jointly develop documents to use for full production. Finally, we conduct tests upon completion of the product to determine how the product is behaving compared to the specifications, says Excelsior's Lee.

CONCURRENT ENGINEERING

Working with the EMS provider from the conceptual design stage is one way to reduce manufacturing costs. Concurrent engineering is essential to meet today's product quality and cost targets, says UMM's Gray. "The manufacturing process for the product must be designed concurrently with the product. The issue here is the successful transition of a product from design and development to the production flow. Without concurrent engineering, this transition period can add costly delays to a customer's product launch."

Involving the EMS early in design review allows for analysis of the interconnect technologies and manufacturing processes required to produce a product compared to the manufacturing options available from the EMS. This enables the EMS to optimize the design to reduce time-to-market constraints associated with the manufacturing of the product. Concurrent engineering methods, as opposed to sequential design and development, says Mokry, enable the OEM to get the maximum benefit from the contract manufacturer. "If the EMS is working DFM/DFT issues at the earliest possible design stage with the OEM, the contract manufacturer will be in a much better position to offer valuable suggestions to positively impact cost and delivery than if it were involved after the design is completed," Mokry says.

"It is difficult to go backwards from a design that has ignored manufacturability. The medical device marketer may not be familiar with the tools and standards for, say, surface-mount technology. Concurrent engineering and implementing DFM concepts enable definition of the product that ties in issues you would only see down the road," says DiVita.

DESIGN FOR MANUFACTURABILITY AND TESTABILITY

DFM and DFT concepts are designed to address manufacturing and testing issues when the product is being designed to achieve the most cost-effective production. Plexus, for example, focuses technical resources to analyze product designs and recommend revisions that will improve manufacturability and testability. According to the company, these design- for-excellence techniques include solutions as early in the design phase as possible, often as part of the prototype analysis. When used in the manufacturing phase, such techniques can improve performance, reduce costs, or provide information for future designs.

When implemented at the design stage, DFM and DFT can help OEMs design out costs that might otherwise be incurred during manufacturing. DFM ensures quick time to market and more robust, manufacturable designs. "It's a standardized approach tailored to the parameters of the manufacturing equipment utilized to produce the assemblies," says Mokry. "DFM/DFT is an important activity that can result in significantly improved yields and quality of new products or product redesigns. This can shave weeks or even months off the time it takes to get a product through the new product introduction stage."

"These techniques allow an EMS to offer additional value by providing recommendations for designs to improve manufacturability and testability. It enables the OEM to change the design to align with the overall test platform. Bringing it more in line with the infrastructure of the EMS ultimately takes costs out of the process," says Tracey of EFTC. "For medical device companies, the criticality of such devices often means that if a part fails, it is a big problem."

"Early in the process," says Gray, "the OEM must specify the required product quality, reliability, and cost targets for the EMS. Knowing up front the expectations of the OEM enables a competent EMS to create a design that is manufacturable."

"DFM means that we review the design and make recommendations in order to develop a product that is more manufacturable. With DFM, the very reliability of the product quality level reduces costs to the OEM," says DiVita.

Medical Design Excellence Awards Recognize Form and Function

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Twelve companies recognized for outstanding achievements in medical device development received gold awards during the presentation ceremony for the Medical Design Excellence Awards of 1999.

This year's Medical Design Excellence Awards again underscore the unique nature of medical device development. Each device recognized for its design excellence was the fulfillment of a vision. Many resulted from the focused efforts of design teams that had been formed specifically to meet a carefully defined technical challenge. Other products were developed by persistent individuals who were struck by sudden inspiration or who looked at conventional technology from a new perspective and saw the potential to make a significant improvement.

It is clear that the need for improved or new medical products continually drives the pursuit of innovation in novel device designs and advanced manufacturing technologies. The emergence of new clinical applications and the availability of new technologies also spark the development of new medical products. These processes, however, are seldom bound by any rigid timetable. Most often, the process is long and arduous, involving years filled with numerous redesigns and prototypes, as well as continuous product and market testing. In rare instances, when all factors are in perfect accord, an innovation will burst quickly onto the market—sometimes within months.

This is the remarkable nature of the process of invention and innovation that leads ultimately to the introduction of new or advanced medical devices. The development of new products clearly requires a knowledge of the general process of technological improvement and an awareness of the many generations of incremental changes that often make predicting a device's ultimate use and design so difficult. Developers must recognize the value of product feedback rendered by users in real-life settings and of the critical role played by entrepreneurs and small companies in the creation of some of the most innovative products. They also must remain aware that the ability to correctly assess future trends and needs is of the utmost importance in the development of products that will succeed in the marketplace.

In developing new devices, designers must also strike a precarious balance between form and function. Does the device perform the tasks necessary to provide the desired medical treatment? Does it offer any advantages over conventional methods? Is use of the product cost-effective? Is the device simple to operate and easy to learn? Will it be readily accepted by end-users?

Form and function, cost-effectiveness, user acceptance, ease of use, and simplicity of training were among the factors considered by this year's panel of eight MDEA judges. The following 1999 gold-award winners were selected for having achieved excellence in their pursuit of innovation and invention.

THE On3: ENABLING HEALTHCARE WORKERS TO MOVE A PATIENT—WITHOUT BECOMING ONE

According to the U.S. Department of Labor, each year 56% of all healthcare workers injure their backs on the job, and back injuries account for up to 80% of total injury costs among this group. Thomas W. Votel, MD, inventor of the On3 lateral transfer device, had witnessed his fair share of back injuries when he decided to design a system that would remedy the situation. "We developed an easy-to-use device that allows one person to do what it used to take six to do. And, better yet, it reduces the risk of a back injury to a respectable level—like zero," the inventor explains.

The On3 allows a single healthcare worker to move a patient by wrapping the patient's draw sheet around the On3's transfer rod, clamping a belt to the rod, and clicking a retract-able, handheld control. The device smoothly transfers the patient from bed to cart in about 20 seconds.

From his initial concept for a one-person transfer device, Votel developed a crude mock-up. Because the common denominator between a hospital bed and a cart is the bed rail, he decided to use a mechanism attached to the bed rail to pull the patient. He took the hand crank off his tennis court net and fashioned it into a 25-lb unit that attached to the bed rail, yet was strong enough to pull a patient when a caregiver simply turned the crank.

At this point, Ergodyne (St. Paul, MN), distributor and manufacturer of the On3, approached redgroup (Minneapolis) to oversee R&D for the device, says the inventor's son, Thomas F. Votel, Ergodyne president and CEO. When the design team took this early, nonfunctional concept to three Minnesota hospitals for validation, the staff members told them they would not want to pick up and carry a device that heavy, and that they had no place to store it. They suggested the design team mount the device on a rolling cart, a commonly accepted way to transport heavy equipment in hospitals.

The R&D program soon changed dramatically, says Lars Runquist, a principal with redgroup. "Real estate is scarce in hospitals. The pushcart idea allowed the device to be moved easily and stored conveniently, even in hallways."

Reliability and strength were other important factors in the On3's design. "We needed a unit that could safely transfer a 500-lb patient, and that would last for years and be reliable to the end-user. If they (healthcare workers) didn't trust the machine, they wouldn't use it on a daily basis," Runquist explains. Extensive life and strength testing of the product were conducted at redgroup to ensure heavy-lifting capability and durability.

"Once we had a workable prototype, we tested it in about half a dozen hospitals," Votel says. In particular, Ergodyne hired the market research firm Marquette Research (Minneapolis) to conduct focus groups at two area hospitals. "We wanted to capture the end-user response to the device before we started the manufacturing process," he says. The focus groups were asked to fill out sophisticated questionnaires and were interviewed extensively for their input.

This research helped designers fine-tune the product's appearance as well as function. "We didn't want a heavy-duty industrial look, like a winch, but one that was simple and accessible, not only for the hospital workers, but also something that looked comforting to the patient," Runquist emphasizes.

"From an interface standpoint, we kept it very simple," Runquist says. "It's battery operated, and the transfer rod folds in half to fit right in the unit for storage. Also, while standing on one side of the bed, the operator can adjust [bed] height with foot pedals, align the patient, and begin transferring by clicking the remote control without walking around the bed several times. Even the remote control has just two buttons, one to adjust for skew [if the patient is off-center] and one to begin transfer."

The name also reflects the device's accessible nature. "We didn't want a name like XJ-2000. The name needed to convey how simple this product is to use," Runquist says. On3 is a reference to a physician's directive to move a patient on the count of three, Runquist explains.

Overall, Runquist thinks the feedback from end-users was the most crucial decision-making tool in the design process. "The users dictated where things should go as opposed to the client," he explains. "We got their input, and every milestone was validated by the hospital staff. The end result exceeded their expectations."

THE ORAL-B CROSSACTION: A NEW ANGLE ON THE TOOTHBRUSH

In April 1996, Brad Baker assembled Team Discovery at Oral-B Laboratories (Belmont, CA). Its mission: to develop a breakthrough product—a toothbrush that could clean teeth more effectively while offering an innovative ergonomic design. After three years of R&D, 26 patent filings, and a $70 million investment in new manufacturing processes, Oral-B has succeeded by delivering the most thoroughly researched product in its history: the CrossAction toothbrush.

One of the first challenges after assembling the design team was to rapidly develop prototypes, Baker explains. "Generally, it takes four to six months from the time we have an idea for a brush to when we can try it out on a consumer," Baker says. "With our dedicated focus on the product (the CrossAction) and a clear objective, we were able to reduce that to five weeks." Ultimately, consumers tested and gave feedback on more than 50 prototypes Team Discovery had designed based on the consumers' input.

Data were obtained from 72 tests involving more than 4000 consumers to determine desirable features, including a head that is tapered to reach back teeth, bristles that can reach around back teeth, high and low bristles to fit tooth shapes and crevices, and a rubber handle for a better grip. Experts then observed brushing and gripping behavior both in laboratory settings and in consumers' homes. Using the data, ergonomists, kinesiologists, and design research experts defined optimal cross sections for the toothbrush bristles, center of gravity location, elastomeric grip zones, and handle-head geometry. The bristles are also microtextured, making the entire bristle—not just the tips—more effective. Blue indicator bristles fade when it's time to replace the brush. Drawing on the expertise of a diversified design team was vital to the product's success, Baker says.

One of the CrossAction's most innovative features is the CrissCross bristle design. High-speed video cameras and computer imaging analysis of people brushing their teeth revealed that bristles are most effective the moment the brush changes direction because that's when they are angled enough to penetrate between teeth. The CrissCross bristles fill the space between the teeth longer than standard vertical bristles. After spending more than $2 million on independent clinical studies, the company determined that the bristle design removes 25% more plaque than today's top-selling toothbrush.

A second notable innovation is the brush's handle design. Research revealed five basic toothbrush grips: precision, power, spoon, oblique, and, the most common, the distal oblique. The CrossAction handle addresses all five grips and various hand sizes by using a unique combination of flat and curved surfaces, and rubber gripping areas.

THE HEMATYPE SEGMENT DEVICE: ENSURING USER SAFETY

Protecting blood samples—and healthcare workers—from contamination, especially in the age of HIV, is a serious problem in blood banks and hospital laboratories where lab technicians routinely draw samples for typing and cross-matching. Typically, a technician obtains a sample by cutting a flexible segment of tubing filled with blood with scissors, then squeezing the sample into a glass test tube. This results in a number of problems, such as blood spraying onto the healthcare worker or work surfaces, sharps injuries from cleaning scissors between cuttings, and the improper cleaning of scissors blades between cuttings, resulting in cross-contamination.

To address this problem, there is the Hematype, a small, disposable plastic device designed to eliminate virtually all problems associated with scissors. The Hematype houses a tiny steel needle that never comes in contact with the healthcare worker's skin. To use the Hematype, a technician places it atop an upright empty test tube in a rack and pushes one end of a blood-filled tube into the device until it is pierced by the needle. The technician then gently squeezes the tube to obtain a blood sample. Because the tubing stays inside the device, once a few drops of blood have been squeezed into the test tube, the remaining sample and Hematype can be discarded in a biohazard medical waste container, reducing a worker's exposure to blood.

"There are other products that improve user safety, but to take it to the next level, we needed to minimize the breaking of the test tube and make a product that is intuitive—one you can understand just by looking at it," says Alan Wanderer, MD, medical director of Medical Safety Products Inc. (MSPI; Englewood, CO).

After a prototype was developed, MSPI conducted a clinical trial with several hospitals and one blood bank. Each facility was given the Hematype and several other devices and asked to compare features and performance. They were not told which product was being tested and were asked to choose the one they believed was the safest and easiest to use. Users' comments confirmed that the Hematype's inventors had created an easy-to-use solution.

To reduce test tube breakage, MSPI designed the Hematype so that its force is vertical and directed at the top, or rim, of the test tube, the strongest part. This design requires less downward vertical force to puncture the tubing segment than do other devices created for this purpose. Most such devices are situated inside the test tube and radial forces can cause the sides of the test tube to break when pressure is applied.

Another challenge in designing the Hematype was in accounting for different blood tubing manufacturers. Each brand of tubing has a slightly different thickness, width, and flexibility, and there are various methods of heat-sealing the segment ends. The Hematype accounts for all types of tubing. The inside of the device is ringed with alternating ribs and slots that are intended to help guide various-sized segments toward the needle.

Getting the healthcare community to accept new safety products can be difficult because of the intense cost-consciousness of most healthcare organizations, a reluctance to change procedures, and regulatory controls that hamper new product development, Wanderer notes. "Because [the Hematype] is disposable, the price was extremely important," he says. "We needed to be able to mass manufacture multimillion units cost-effectively. The mission was to be able to manufacture a product at a low enough cost that permitted acceptable pricing in a price-conscious market. This was accomplished using thoughtful design development both for the product and the multicavity tooling, cost-conscious materials selection, and efficient assembly techniques. The end result has been our ability to market a product at a reasonable price with an acceptable profit margin."

THE HI & DRI ISOLATOR: SIMPLIFYING DENTAL VISITS

The Hi & Dri, a 67-cent plastic oral isolation and protection device, keeps a patient's tongue and cheek out of harm's way while the dentist is at work. The Hi & Dri attaches to a piece of flexible tubing on the dental station's vacuum line, providing the dentist with access to the teeth while simultaneously protecting the patient's tongue and cheek from the drill and keeping the patient's mouth open. The vacuum suction keeps the patient's mouth clean and dry, removing saliva and aerosol mists from the dental drill and particulate material such as stray pieces of filling material. This single device replaces an arsenal of dental helpers including cotton rolls, saliva ejector tubes, tongue depressors, cheek retractors—and, sometimes, even the dental assistant. The device is so effective that it enables a dentist to perform most procedures single-handedly, freeing the dental assistant for other important tasks.

From its inception, the Hi & Dri was on the fast track. DriDent, the developer of the Hi & Dri system, initially approached the industrial designer Microplas Inc. (Clinton, MA) with a breadboard model of the device and with the desire to get molded parts to a dental show in October, which was only five months away.

One of the first issues for the design team to tackle was to determine the appropriate size and form for the device. Although DriDent wanted a shape that would work for 95% of the adult population, two sizes were eventually designed after the company was convinced that a "one size fits all" approach would not work. By using anatomical models and plaster castings of patients' mouths, a series of hand-fabricated models was created. The device shape also had to maximize the working area for the dentist. This meant keeping the material thickness and size of the vacuum chamber to a minimum. After experimenting with several shapes and sizes, a final form was selected and a functional model was created for testing.

"We came up with the concept and designed the best way to manufacture it first," says Steven Callahan, Microplas president. "Then we engineered the device and came up with the final aesthetic form." Pro/Engineer software was used to create the 3-D database that was created during the engineering process. "This would have been impossible with the old 2-D process," says Christopher Reinke, senior product designer at Microplas.

Determining the best and most cost-effective manufacturing process was the most significant factor in the design process, says Callahan. "The downstream people were involved the whole way," he adds. "The collaborative effort between design and manufacturing is the reason for this product's success. Manufacturing an amorphic form required a tricky process—it's not easy to mold." Because of the tight cost restriction, and because the device had to be hollow and airtight to work with the vacuum line, a polypropylene injection molding process was eventually chosen to produce the final two-part design. A secondary ultrasonic welding operation is used to assemble the two halves. Multicavity tooling is being used along with semiautomated assembly equipment to achieve pricing goals and first-year volumes of 4–6 million units.

THE INTUITIVE SYSTEM: MAKING SURGERY EASIER FOR BOTH PHYSICIAN AND PATIENT

Until recently, cardiac patients had to choose between two types of surgery: traditional open surgery and minimally invasive surgery (MIS). Traditional open surgery allows surgeons direct access to the organs but requires a large incision and results in trauma and lengthy recovery times for the patient. MIS minimizes incisions and accelerates recovery time. Such procedures require surgeons to use awkward, long-handled instruments, however, and the surgeon's movements are guided in a counterintuitive way via a CRT monitor. The Intuitive Surgical System eliminates the problem, combining the natural hand movements of open surgery with the less-traumatic benefits of MIS.

A government-funded research project by SRI, a Menlo Park, CA, think tank, served as inspiration for the Intuitive system. SRI's research involved the development of robotic ambulances in which surgery could be performed on wounded soldiers on the battlefield. When the founders of Intuitive Surgical Inc. (Mountain View, CA) came across the project, they realized it held potential for a novel form of MIS and formed a partnership with SRI to use the project as a launching point. Intuitive Surgical made several iterations of the design, resulting in the first product developed by the company, which was a privately held start-up.

Intuitive Surgical also consulted with several local surgeons who used MIS, particularly those with extensive cardiac and endoscopic surgery experience. Based on suggestions from the surgeons, they took the project to the dry-lab stage and worked with animals.

Spearheading a revolutionary product was a daunting task, says Steve Holmes, senior mechanical engineer for Intuitive Surgical. "There was no precedent," he explains. "The details of how it would work mechanically were difficult, and the hardware and software were tricky, but most challenging was envisioning how this would fit into the operating-room environment." The current system is the fifth generation, he estimates. "This [device] has undergone radical revisions as we learned more and more about the surgeon's environment."

The Intuitive system consists of two primary components: the viewing and control console and the remote surgical arm. Surgeons perform procedures seated at a console while viewing a high-resolution 3-D image of the surgical field. Highly specialized visual technology simultaneously transfers the surgeon's exact hand movements to precise microsurgical movements at the operative site, which requires only a 1-cm incision. Pencil-sized instruments incorporating the company's EndoWrist technology function like tiny computer-enhanced mechanical wrists, mimicking the dexterity of a surgeon's hand.

To create an immersive environment akin to open surgery, Intuitive Surgical developed its own proprietary 3-D viewing display system, used advanced robotics, replicated surgical instruments in the console, and created the EndoWrist technology that enhances performance by motion scaling, eliminating hand tremor, and providing sensory feedback. Because the surgeon's movements are counterintuitive in most traditional MIS systems—moving the hand to the left displays as rightward movement on the monitor—the firm addressed the problem by using a more straightforward viewing system.

Ergonomics was another challenge because the designers needed to strike a balance between the working position of a surgeon, who is usually standing up and looking down while operating, and the new position, in which the surgeon sits with arms at a 90° angle and looks at a monitor. Following numerous wood and foam model evaluations and clinical studies, the design team responded by moving some controls, such as camera movement, focus, and cauterizing, to a foot pedal. Hand instruments were modeled after actual instruments but were enlarged slightly, and a comfortable armrest was provided. The stereovision system was improved as well.

Integrating nine subsystems into the design while keeping it simple posed other problems. "We wanted everything to combine to make a surgeon feel that he's working in a minimally invasive environment," Holmes says. "We needed a coherent product that was not intimidating—that surgeons would want to interact with." The design team also needed to keep costs down to make surgery with the Intuitive system competitive with an open-surgery procedure. The entire business model was developed with the goal of not increasing costs for a procedure. Several of the tools are "reposable," meaning they can be used multiple times before disposal, and the cosmetic covers over the console are cast urethane for cost savings. The system "opens up the possibility of doing almost any surgery in a minimally invasive environment," Holmes says.

A Welcome Change

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI August 1999 Column

Creative Thinker Succeeds by Adapting to New Environments

In search of an outlet for his creative talents, John Redmond, vice president and general manager of medical devices for Gliatech (Cleveland), used to dream of becoming a writer. With this goal in mind, he earned his BA degree in English. But after interviewing for several newspaper positions, his practical side forced him to reconsider his choice and undergo a reality check. "I had to eat," he states bluntly. In light of this statement, it seems fitting that Redmond found a job as a sales representative in the food industry. But while this may have kept him well fed, it didn't nourish his desire for creativity.

It was only in 1976 when Redmond started working as a sales representative for Codman (Randolph, MA), a market leader in neurosurgery, that he found the outlet he was seeking. "I fell in love with the surgery side of the business," he says. "And as I began to develop my career in the medical device industry, I was able to satisfy my creative side by helping surgeons develop instruments." Redmond would observe surgery so that he could determine what problems the surgeons were having. He would then attempt to develop an instrument that would help them solve a particular problem.

In 1980, Redmond started working for V. Mueller (Niles, IL), where he continued to design neurosurgical products. As product manager for neurosurgery, he developed and introduced the Collis spinal set, which generated sales of more than $1 million per year. It was during this time that Redmond began to gain the knowledge and experience that would eventually help him to start his own business. Craig Moore, Mueller's vice president of marketing, served as a mentor to Redmond in this regard by allowing him to manage the neurosurgical product line as if it were his own company. "Craig really allowed me to grow and experience many things at a product manager level," says Redmond.

After five years with V. Mueller, Redmond continued his work in neurosurgery as business development manager for Aesculap (Burlingame, CA). In 1989, he and his former wife Jill started Redmond NeuroTechnologies Corp. in their basement. "I founded my own company because I was frustrated with the fact that large companies didn't really listen to the customer," Redmond explains. "Too many would discontinue products if the market wasn't large enough. Their decisions were based on internal economics and not on customers' needs." Redmond decided that his company would focus on one specialty—neurosurgery. The company operated for eight years, until the consolidation that was taking place in the industry started to dry up Redmond's distribution channels and he decided to sell the business.

After selling the company to NeuroCare Group (Pleasant Prairie, WI) in 1997, Redmond stayed on as vice president of marketing and business development until he was recruited by Gliatech, a company that researches, develops, and commercializes therapeutic products based on understanding the properties of glial cells, a major component of the nervous system. Redmond's primary responsibility is the commercialization of the Adcon product line, a series of proprietary, resorbable gels and liquids designed to inhibit postsurgical scarring and adhesions that occur when tissues and organs bind together. The product is applied directly to the surgical site, providing a barrier between tissues and organs. After approximately four weeks, the gels and liquids are absorbed naturally by the body.

For Redmond, one of the greatest challenges has been taking what was essentially a biotechnology company and building a medical device business. "It's a different world for some of the people involved in the company," he says. "One of the challenges management faces is changing and adapting the culture of the organization to a more commercialized type of business. We are currently going through a strategic planning process to address these issues and create a unique vision for what we see as a hybrid type of company."

Redmond believes that companies must be willing to adapt if they are going to succeed. "I think one of the mistakes that a lot of companies and managers make is that they don't stay open to change. This industry is changing so rapidly that you really need to be able to evaluate your position and adapt frequently." He also recommends managers surround themselves with a diverse group of employees who not only buy into the direction that the company is taking, but challenge them on issues as well. "The key is people," Redmond stresses, "not only employees, but customers as well. This product has so many applications, and customers are saying, 'We can use this product here, we can use it there.' We really need to listen to them."

Kassandra S. Kania is associate editor of MD&DI.


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