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Articles from 2001 In January


Reshaping the Medical Device Packaging Industry

The U.S. market for medical device packaging is expected to continue notable levels of growth over the next few years. Forecasts of annual growth rates have ranged from 4 to 5.5% among industry observers—growth spurred largely by increased volume rather than profit margins. In this month's article, Adapting Packaging Technology to Meet Device Industry Needs, a number of packaging professionals comment on issues that are influencing device packaging—including advances in technology, pressure to cut costs, and new testing strategies.

"Expect to see more development in film technology, combining different polymers in multilayer structures, to build in desired functional properties," says Carl D. Marotta, president, Tolas Health Care Packaging (Feasterville, PA). He adds that in addition to tear, puncture, and abrasion resistance, these properties will include selected barrier and peelability characteristics.

Industry observers have noted that some packaging concepts are overengineered. Marotta agrees that overengineering does occur at times, "particularly where a like material may be used for a wide range of product applications." He adds that "this can be somewhat lessened by selectively choosing materials that best satisfy specific package criteria, using lower-cost materials for commodity devices, and vice versa." Marotta explains that, "This may not always be most cost-effective, but will ensure that the higher-value product reaches its intended use safely, undamaged, with sterility maintained, and conveniently delivered to the patient."

Pressure to actively seek cost savings continues to exert a strong influence on many packaging decisions. Says Marotta, "Cost savings are an ever-present concern of both packaging manufacturers and device companies. However, we cannot ignore the overall value provided by high-performance, quality packaging, in terms of ease-of-use, security, shelf stability and general reliability."

Looking to the future, Marotta believes that the market "will continue to seek and respond to more-functional design and more-specialized packaging, both in flexible and rigid packaging."

In addition to new materials and production methods, package testing is also experiencing significant changes. Stephen Franks, executive vice president, T.M. Electronics Inc. (Worcester, MA), anticipates a greater reliance on nondestructive testing methods. Says Franks, "Pressure and vacuum decay testing will see an evolution into faster and more-automated forms for high-speed, in-line testing." These changes are expected to result partly from the development of more-defined requirements for physical versus microbiological testing for sterility. "In effect, sooner or later there will be an accepted standard for a leak size or leakage rate that will prove to be allowable and maintain a sterile barrier for the shelf life of the package," he adds.

The motivation for the use of nondestructive testing is fairly basic, says Franks. "I believe that, as usual, economics is the strongest force, right behind regulatory pressures. Nondestructive testing provides the opportunity to do on-line testing for high-volume manufacturers, and saves material loss and reprocessing time for lower-volume manufacturers who do sample audit testing using destructive techniques."

What are the hurdles to such testing? Franks suggests it may be that the medical package is both flexible and complex. "From a structural viewpoint, testing the medical device package is like trying to measure a rubber band. A lot depends on the state of the package when it is tested. From a materials viewpoint, there are multiple materials that will react to different measuring systems in different ways. The final hurdle is the peelable package, which puts the manufacturer of packages between the proverbial rock and a hard place. The package must simultaneously be strong and maintain its integrity for the claimed shelf life and be weak enough to open on demand. Not always an easy task."

Gregg Nighswonger is executive editor of MD&DI.


To the MDDI January 2001 table of contents | To the MDDI home page

Copyright ©2001 Medical Device & Diagnostic Industry

Design Considerations in Small-Diameter Medical Tubing

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

Originally Published January 2001

Cover Story

Ron Roth

With the development of new and revolutionary minimally invasive procedures, the corresponding requirements for small-diameter tubing have become more demanding and complex. Today's designers of medical devices are faced with demands for smaller, better, more-sophisticated, and more-cost-effective products. While the overall trend has been to minimize the cost of individual components, there still is a market for high-performance (and thus more-profitable) medical devices if either of two conditions can be met:

  • A significant decrease in clinical procedure time can be demonstrated, with equivalent or improved results.
  • The results from treatment using the device are new and are currently unattainable with any other method.

In many cases, achieving an efficient catheter-delivery system figures among the fundamental design requirements in developing a novel medical procedure. Examples of such device applications include angioplasty, stent-delivery, cryogenic, drug-delivery, and arthrectomy catheters, and various other retrievable catheter devices.

This article discusses a range of tubing design topics, including principles of geometric dimensioning and tolerancing, the use of Monte Carlo simulations, implementing the concept of design for manufacturability, modeling and optimization of catheter delivery systems, and future trends in the development of small-diameter tubing and catheter products.

GEOMETRIC DIMENSIONING AND TOLERANCING

Geometric dimensioning and tolerancing is a method for specifying design requirements with respect to the actual function and relationship of part features, and is a technique that can ensure their most economical and effective production. When developing small-diameter tubing, it is important for designers to specify the correct datums or features. Aids to successful design include making sure that:

  • The features chosen are clearly identified or recognized.
  • Corresponding features on mating parts are used to establish datums to ensure proper part assembly.
  • The datums on an actual part are accessible during manufacturing so that measurements can be readily made.

Typically, the inner diameter (ID), outside diameter (OD), or both are selected as datums. Additional attributes, such as wall concentricity or eccentricity and part straightness along the length of the tube, may also be specified.

For ultra-thin-wall tubing, it is common for the designer to specify the ID and wall thickness as design features and the OD as a reference, as shown in Figure 1. For thicker-wall versions, it is better for the designer to specify the tube ID and OD; the ID, OD, and wall minimum; or the ID, OD, and wall eccentricity. The use of established drawing standards guarantees that the designer's intentions are accurately communicated to the tubing supplier.

Figure 1. Basic specifications drawing for small-diameter tubing.

MONTE CARLO SIMULATIONS

The use of a technique known as a Monte Carlo simulation can be very useful in determining correct part tolerances. A Monte Carlo–determined tolerance is roughly two to three times larger than a tolerance determined by a worst-case analysis. This is particularly true under the following circumstances:

  • The required tolerance results obtained from a worst-case analysis are too tight.
  • The fit and attribute performance from two or more mating parts is complicated and the results thereof cannot easily be determined analytically.
  • A part attribute is critical and the designer wishes to understand the impact that tolerance variations will have on that attribute.

The term simulation refers to any analytical method meant to imitate a real-life system, especially when other analyses are mathematically complex or difficult to reproduce. A Monte Carlo simulation is a method in which randomly produced numbers (typically from a computer) are generated for uncertain variables and analyzed to determine the model and/or assembly performance. As recently as 10 years ago, it was common for large companies to spend significant funds to purchase Monte Carlo simulation software; today, this function can be completed on a personal computer using common spreadsheet programs.

In some cases, it is permissible to specify tolerances for a part that may not be achievable all of the time. This situation is acceptable if a system is in place that eliminates the bad parts sometime during the manufacturing process. The process for eliminating "bad" parts is often as simple as adding an additional part requirement that is usually directly related to the actual part function. For example, suppose that the tubing designer has determined that a tight wall specification is necessary to meet a required pressure rating, and the tubing vendor has responded with a high quote, citing the tight tolerances. Working together with the tubing vendor, the designer could relax the tight wall tolerance and add a 100% pressure-testing inspection requirement.

The following example is provided to demonstrate actual results that can be obtained from using a Monte Carlo simulation in designing a catheter shaft. A designer wished to better understand the yield point of a 0.022-in.-ID x 0.028-in.-OD polyimide tube. (In this case, the term yield point is defined as the point at which the tube begins to elongate under a load, which generally is taken as an elongation of 2%.) For this example, both the ID and OD tolerances were ±0.00025 in. and the wall was assumed to be perfectly concentric. Based on pull-test data, the yield stress of polyimide was determined to be between 11,500 and 14,500 psi.

For purposes of the simulation, it was assumed that the minimum and maximum of the three variables (ID, OD, and yield stress) are three-sigma statistical limits. Using a Microsoft Excel spreadsheet, 10,000 tubes were modeled. For each tube, the computer randomly chose an ID, OD, and yield stress, with the variables following a standard Gaussian distribution. Based on each catheter design, the cross-sectional area of the tube was computed from the computer-generated ID and OD. This cross-sectional area was multiplied by the computer-generated yield stress, which resulted in the computed yield-point load.

A graph of frequency of occurrence versus predicted tubing yield load is shown in Figure 2. The distribution is Gaussian because the assumption was made that all of the variables involved in the computation were Gaussian distributed. For a Monte Carlo simulation model size of 10,000 samples, the predicted yield load varies from 2.50 to 3.60 lb. However, 98% of the time, the yield load varies from 2.75 to 3.40 lb. Thus, according to the Monte Carlo simulation, approximately 1% of the time the part had a yield load of 2.50 to 2.75 lb. A worst-case analysis might lead the designer to frequently expect low yield-load results. A Monte Carlo simulation states that the likelihood of such low yield loads is in fact very rare, and also guides the designer in focusing on identifying and minimizing variations in the overall assembly.

Figure 2. Predicted yield loads of 0.022 x 0.028-in. polyimide tube from Monte Carlo simulation.

A Monte Carlo simulation is typically not a tool used every day by catheter designers. However, it can play a useful role in determining part tolerances, forcing designers to analyze and determine which attributes are critical to the part specification. Such precision in the design process can often spell the difference between a successful product launch and one that is mired in manufacturing difficulties.

DESIGN FOR MANUFACTURABILITY

One of the pressing issues for any new product or process development project is the complexity of the required manufacturing process and its expected yields. Many manufacturers incorporate early manufacturing involvement teams into their design organization, with the objective of optimizing the manufacturability of the design from the beginning of the development process. The following sections summarize recent trends in catheter manufacturing, including assembly techniques, component outsourcing tactics, and sterilization methods.

Assembly Techniques. Until recently, epoxies were commonly used in catheter assemblies. These adhesives deliver very high performance but have the drawback of requiring long cure cycles or elevated cure temperatures. The use of epoxies thus requires additional manufacturing floor space for staging of subassemblies during the cure cycle, which results in higher overhead. As a result, the use of epoxies in catheter subassemblies has often been replaced by the following alternatives:

  • Adhesives that can be cured on demand through exposure to ultraviolet light.
  • Thermal welding of mating parts. This is accomplished via localized heating of certain materials (for example, Pebax and urethanes), which causes them to reflow and create a integral adhesive bond for the surrounding parts.
  • Elimination, in some cases, of the use of adhesives altogether through innovative processes. For example, variable-stiffness catheter products can be manufactured as a continuous process.
  • The alteration of certain plastics that require an adhesive bonding operation to produce more manufacturing-friendly materials. For example, a polyimide tube can be modified by overcoating the OD with a Tecoflex urethane layer in the region where a thermal welding operation (joining) is to occur.

Component Outsourcing. Many major medical device manufacturers are outsourcing more subassembly to component manufacturers. This trend requires the component manufacturers to assume more responsibility for delivering finished or nearly finished catheter components. Additional operations that are typically requested from component manufacturers include:

  • Cutting to exact length tolerances of nonbraided tubing products.
  • Cutting to length of braided components in which the tip is nondeformed and the braid wires are imbedded in the tubing product (nonfrayed).
  • Secondary operations such as flaring, tipping, hubbing, hole drilling/punching, curve forming, and ID/OD tube tapering.
  • Surface preparation of fluoropolymer materials for bonding.

Problems with outsourcing subassembly operations can often be minimized by requiring that the component manufacturer have a good quality system in place. ISO certification of quality systems is fast becoming a requirement for medical component suppliers.

Sterilization Methods. Another important issue concerns the terminal sterilization method used for the finished catheter device. Many catheter manufacturers are tending to favor the use of E-beam or gamma irradiation over ethylene oxide gas. The preference for high-energy sterilization has the result of eliminating the use of some fluoropolymer materials, such as fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE) in catheter assemblies. This can compromise the finished devices' performance, since equivalent substitutes have not been found that offer all of the performance attributes of these two materials.

MODELING AND OPTIMIZATION OF CATHETER DELIVERY SYSTEMS

In the design of any catheter delivery system, among the important design qualities that may come into play are the tubing's profile or form factor as well as its trackability, pushability, and torqueability. Trackability refers to the characteristic of a catheter that allows it to follow through tortuous paths to its ultimate destination. Trackability cannot be measured directly, but rather is a combination of factors such as:

  • Shaft flexibility.
  • The friction between a catheter and its surrounding environment.
  • Column strength, which is the ability of the catheter to withstand axial forces without compression or stretch.

The requirements for any delivery system have to take into account specific but often contradictory design parameters. For example, a small profile and flexible tip may meet the requirement for a nontraumatic design but also result in lower pushability and torqueability of the catheter shaft.

In order to minimize the number of iterations required to arrive at an optimal catheter system design, it is useful to develop an analytical model of a tubing shaft. The simplest approach is to develop a linear, lumped parameter model to estimate product qualities. The following section summarizes the governing equations that a designer can use to estimate catheter pushability, torqueability, and flexibility.

Figure 3. Axial force (F), or pushability, applied to length of tube.

Catheter pushability refers to the response of a tube when a longitudinal force is placed along its axis, as shown in Figure 3. For small deflections, the tubing properties can be considered to approximate a spring system, in which the longitudinal stiffness of the spring is determined by the equation

where klong is the longitudinal spring constant, E is the modulus of elasticity, A is the cross-sectional area, and L is the length of the catheter shaft. In order to maximize pushability, the designer needs to maximize the quantity klong. This can be achieved in various ways:

  • By maximizing the cross-sectional area of the tubing.
  • By maximizing the modulus of elasticity by using a stiffer material.
  • By decreasing the overall part length.

Catheter torqueability describes the behavior of a tube when a moment of torque is placed about its longitudinal axis (Figure 4). Once again, for small deflections, the tube's mechanical properties approximate a spring system, in which torsional stiffness is determined such that

where ktorq is the torsional spring constant, G is the shear modulus, J is the polar moment of inertia, and L is the length of the catheter shaft. Maximizing torqueability means maximizing the quantity ktorq, which can be accomplished:

  • By maximizing the polar moment of inertia. For a simple tube profile, the governing equation for J is as follows:

where do is the tube OD and di is the tube ID. In order to maximize J, the designer needs to maximize the outside diameter and the wall thickness:

  • By maximizing the shear modulus using a stiffer material.
  • By decreasing the overall part length.

Tube flexibility can be modeled as a clamped beam system subject to a downward force at the beam, as shown in Figure 5. For small deflections, the tubing approximates a spring system, with the flexural stiffness determined by

where kflexural is the flexural spring constant, E is the modulus of elasticity, I is the moment of inertia, and L is the length of the catheter shaft. In many cases, it is desirable to minimize the flexural stiffness of the catheter, which the designer does by minimizing the quantity kflexural through actions that can include:

  • Minimizing the moment of inertia. For a simple tube profile, the governing equation for I is as follows:

where do is the tube OD and di is the tube ID. In order to minimize I, the designer needs to minimize the OD and the wall thickness:

  • By minimizing the modulus of elasticity by using a soft material.
  • By increasing the overall part length.

 
Figure 4. Torque or moment (M) applied to a tube.

 
Figure 5. Flexibility (F) or bending force applied to end of tube.

Commonly, composite tubing designs are used for catheter delivery systems. These include designs consisting of one or more plastic materials as well as wire-reinforced (braid or coil) designs. The modeling concepts described previously can also be used to analyze and compare composite tubing designs. The stiffness properties of each separate and distinct layer can be computed and combined using principles of classical lamination theory.

To illustrate the effectiveness of the lumped parameter model previously described, six different small-diameter tubing designs were evaluated in terms of flexibility, pushability, and torqueability. A different material was used for each of the six tubes: Tecoflex 60D, PTFE, PeBax 72D, Hytrel 8238, polyimide, and braided polyimide.

For this example, it was assumed that the tubing featured an ID of 0.032 in., an OD of 0.040 in., and thus a wall thickness of 0.004 in. Results from this analysis are summarized in Table I. For simplicity, the catheter shaft length was considered to be the same for all six designs. To illustrate the range of tubing properties that can be obtained, the most flexible (the Tecoflex 60D tube) and the stiffest (the braided polyimide tube) can be compared in terms of push, torque, and flexural stiffness:

  • The braided polyimide tube has a longitudinal stiffness (EA) of 817, whereas the Tecoflex 60D tube has an EA of only 6. The braided polyimide tubing thus provides approximately 135 times more push than the Tecoflex 60D tubing.
  • Similarly, the braided polyimide tubing offers 281 times more torque than the Tecoflex 60D tubing.
  • Finally, the flexural stiffness of the braided polyimide tubing is approximately 133 times higher than the Tecoflex 60D tubing.

Given these results, it is obvious that the braided polyimide tubing design should be used on the proximal end of a delivery catheter system, where pushability is a requirement. The Tecoflex 60D design—because of its flexibility—should be used on the distal end of the catheter shaft.

Tubing Characteristics Tubing Material
Teco 60D PTFE PeBax 72D Hytrel 8238 Polyimide Braided Polyimide
ID (in.) 0.032 0.032 0.032 0.032 0.032 0.032
OD (in.) 0.040 0.040 0.040 0.040 0.040 0.040
Modulus of elasticity (psi) 13,200 50,000 63,000 135,000 500,000 1,800,000 (computed)
Wall thickness (mil) 4 4 4 4 4 Inner layer: 1.5 mil PI
Int. braid layer: 0.7x5-mil SS 304V, 16 wires, pick count = 60
Outer layer: 1.0-mil PI
Flexural stiffness (lb/in.2) 0.001 0.0037 0.0046 0.01 0.037 0.134
Longitudinal stiffness (lb) 6 22 29 61 226 817
Torsional stiffness (lb/in.2) 0.00075 0.0029 0.0036 0.008 0.028 0.212

Table I. Results of a lumped parameter modeling example.

The format shown in Table I allows the designer to make quick and simple comparisons between different tubing designs. This format is particularly useful in comparing composite tubing designs in which the number of variables—including materials, layer thicknesses, and reinforcement construction (wire material, number of braid wires, and braid angle)—increase significantly.

DEVELOPMENT TRENDS

Composite Tubing. Composite tubing (tubing with two or more materials) is increasingly being used in medical devices. The reason is that composite tubing often offers significant product enhancement compared with a single-material tube design. For example, braided polyimide tubing with a PTFE inner liner is replacing plain polyimide tubing in many medical devices. The composite tubing design offers increased pushability and torqueability and improved lubricity on the ID compared with the unlined polyimide tube.

Safety Factors. Driven by the competition, manufacturers are striving to achieve further reductions in the wall thicknesses of small-diameter tubing products. However, designs offering the smallest profile sometimes result in a lowering of safety factors. For example, reducing the wall thickness of a tube that is pressurized during product use induces higher component stress levels. The techniques discussed in this article can assist the designer in better understanding the trade-offs involved.

Sensor Development. A prominent trend in catheter design is the development of systems that provide diagnostic as well as therapeutic capabilities. One method of approaching this objective is through the integration of sensors into the catheter shaft or tip.

In the case of tissue ablation, for example, the physician observes sensor-derived feedback and increases or decreases a control variable (typically, the voltage applied) to effect the degree of ablation required. For improved results, one or more thermocouples can be incorporated into the catheter shaft to provide useful information to the physician. For example, if it is known that the best tissue ablation occurs at a temperature of 42° to 47°C, either the physician can adjust the voltage required to obtain the correct set point or a microprocessor can be integrated into the supporting electronics to adjust the voltage using a PID or fuzzy-logic control system.

CONCLUSION

According to industry reports, the world market for minimally invasive medical devices was approximately $13 billion in 1999, and is growing at 15 to 20% annually. Based on these projections, the future for novel catheter-based product development appears to be bright.

Given the pressure to reduce device size and cost and improve performance, it is important for the product designer to completely understand the overall tubing system being developed. As part of this process, choices must be made that achieve optimization of materials, device geometry, and cost, while at the same time resulting in a simple product that is easy to manufacture. When finalized, these design choices must be documented in engineering drawings that communicate the requirements in a concise manner to the manufacturing department.

The models described in this article allow the designer to determine the proper part tolerances and catheter performance attributes. These models can be helpful in reducing the development cycle and producing a robust product design. When successful, the new catheter-based products can contribute to lower overall medical-systems cost, improved procedure outcomes, and enhanced quality of life for the patient.

BIBLIOGRAPHY

Jones, Robert. Mechanics of Composite Materials. Washington, DC, Scripta Book Co., 1975.

Shigley, Joseph Edward, and Mitchell, Larry D. Mechanical Engineering Design, 4th ed. New York: McGraw-Hill, 1983.

Ron Roth, PhD, is vice president of engineering at HV Technologies Inc. (Trenton, GA). The company manufactures polyimide tubing, high-performance composite tubing, and catheter subassemblies for the minimally invasive medical device market.



Return to the MDDI January 2001 table of contents | Return to the MDDI home page

Copyright ©2001 Medical Device & Diagnostic Industry

Molding Facility Adds Multishot Injection Molder


Molding Facility Adds Multishot Injection Molder

The new Arburg machine provides multishot injection molding services to Distinctive Plastics' customers.

A single-source supplier of high-precision injection molding and tooling services recently announced the addition of a new Arburg 110-tn multishot injection molding machine. The new machine offers a 4–6.8-oz shot size capacity and is capable of producing close-tolerance parts that require multiple resins or colors within a single mold. With a total of 19 new, modern, and real-time–process-monitored machines in its plant, Distinctive Plastics Inc. (Vista, CA) offers custom multishot molding and tooling. The company is ISO 9001 certified and QS 9000 compliant. —Katherine Sweeny

Demag Ergotech Unveils Customer-Support Center


Demag Ergotech Unveils Customer-Support Center

Demag Ergotech USA recently expanded into a new 26,000-sq-ft facility in Strongsville, OH, that will serve as its North American customer support headquarters. The company's injection molding machines feature 25–3000-tn clamping forces and have multicomponent and multicolor capabilities. "This new facility is set up not only to provide our customers with a state-of-the-art laboratory and machine preparation for on-time deliveries, but also to encourage employee interaction," says Rick Shaffer, vice president and general manager of Demag Ergotech USA.

Demag Ergotech's new Ohio facility showcases the company's products and provides global customer service.

The new facility is divided into several sections. The 6000 sq ft of office space is designed to allow engineering and process evaluation teams to interact with salespeople and to recommend the best equipment to fill a processor's needs.

The 7500-sq-ft showroom houses the latest Demag Ergotech equipment. At the recent open house, six machines were operating, including the new Elexis-E, Elexis-S, and a multicolor system. "Customers will have the opportunity to ship in molds for trial, compare machines, and evaluate variables to determine the best Ergotech solution for their processing requirements," says Adam Ferrell, product specialist.

Machine preparation and testing is conducted in a separate 12,500-sq-ft area which houses an extensive inventory of product lines for quick shipment. Water and electrical hookups are set up to accommodate simultaneous testing of four machines; all equipment is thoroughly tested before it is shipped from the facility. —Katherine Sweeny

Internet Update: "DotComs"


Internet Update: "DotComs"

Electronic Components Site Expanded

A company specializing in interconnect hardware and components has expanded its Web site to allow users to check distributor inventory and locate specs by catalog number on-line. By visiting the Standard Products page at http://www.keyelco.com, users can source Keystone Electronics products by entering a catalog number on-screen, clicking the Check Stock box, and scrolling down a list of more than 20 authorized global distributors.

Other features on the site include the Check Inventory box that allows users to find part specifications and drawings. Orders can be placed on-line by clicking the banner at the top of the page. Also posted on the Web site is Keystone Electronics' 104-page catalog, in PDF format, that lists the company's complete line of products that includes brackets, battery holders, IEEE sockets and plugs, and PCB terminals. A cross-referenced table of contents helps locate items of interest more quickly.

On-Line Supply Chain Collaboration Solution Announced

A Web-based application enables companies to conduct business on-line without the financial and organizational burdens associated with traditional supply chain management solutions. The application service provider (ASP)–based supply chain solution, located at http://www.castalink.com, provides a link to businesses, customers, and suppliers in one extended enterprise.

As a hosted application delivered over the Internet, the ASP is quick to implement, easy to use, and requires no additional hardware, software, or technical expertise. Castalink's product suite, eCASTM, enhances supply chain demand management, increases product visibility, and extends communication among users. —Katherine Sweeny

Angioplasty Balloon Samples Available On-Line

Ultrahigh-strength, thin-walled balloons used for PTCA, PTA, stent delivery, and other dilation procedures can be viewed on the Internet. The selection of 2–25-mm-diam samples in as many as a dozen different configurations can be ordered from Advanced Polymers Inc. (Salem, NH) at http://www.advpoly.com. Shapes include standard configurations, conical, offset, tapered, stepped, and square. Samples are available for immediate delivery by return mail and custom orders are processed in as quickly as three to four weeks.

The company features balloons with 5–50-µm wall thicknesses and 15–400-psi typical burst pressures. All sizes, shapes, and specifications are visually presented for selection on the Web site. Ultrathin PET heat-shrink tubing, custom catheter assemblies, and custom extruded tubing are also available.

In Brief


In Brief

GE Medical Systems (Milwaukee) announced that it has signed a definitive agreement to acquire Parallel Design (Phoenix), a supplier of transducers for medical ultrasound and other applications. GE also announced that it will establish a Global Transducer Technology Center of Excellence at Parallel Design's headquarters in Phoenix....Minnetronix Inc. (St. Paul, MN), a medical device outsourcing firm, has moved its corporate headquarters to the Snelling Office Park on Energy Park Drive....Southwest Mold Inc. (Tempe, AZ), a provider of engineering, precision tooling, and custom injection molding services, has received ISO 9002 certification from Underwriters Laboratories Inc. ...Intertech Development Co. (Skokie, IL) has acquired Camtech Automation (Elgin, IL). It plans to continue operation of Camtech in its present facilities as an Intertech Development Co. subsidiary. Both companies will gain expanded CAD-based design and engineering, manufacturing, technical support, and customer service capabilities....A supplier of enterprise-compliant management solutions for regulated industries, Qumas Inc. (Florham Park, NJ), has expanded and moved its U.S. headquarters from Summit, NJ, to a larger facility in nearby Florham Park....Coloplast (Marietta, GA) has joined the Global Healthcare Exchange LLC (Chicago), an Internet-based healthcare trading exchange with more than 35 members. Coloplast is a global leader in the therapeutic areas of ostomy, continence, and wound and skin care and maintains a focused effort on the acute-care, long-term-care, rehabilitation, and home-care markets.... Foster-Miller Inc. (Waltham, MA), a medical engineering design firm, has been approved by FDA as a registered medical device establishment.... AuctionMart.com (Bryan, TX) has formed a partnership with Medsite (New York City) to be the exclusive provider of previously owned medical equipment to Medsite members. The product selection available on AuctionMart.com is an extension of Medsite's core product offering of clinical tools and services.... A new plastic-to-metal joining technology has been developed through the cooperation of Coherent Inc. Semiconductor Group (Santa Clara, CA) and Gluco Ltd. (Leeds, UK). The technique centers around LaserBond, an interlayer material, that enables diode lasers to weld thermoplastic material, specifically polypropylene, to itself and to metals, including mild steel, stainless steel, and aluminum....Command Medical Products Inc. (Ormond Beach, FL) has purchased Micro Med Inc. (Portsmouth, NH), the contract manufacturing division of Disetronic Medical Systems. With the ISO 9002– and EN 46002–registered Micro Med division, Command Medical Products will offer expanded custom manufacturing and production capabilities.—Katherine Sweeny

Simplicity, Reliability, and Functionality Drive R&D in Marking Technologies

Originally Published January/February 2001

PRODUCT UPDATE

Simplicity, Reliability, and Functionality Drive R&D in Marking Technologies

Suppliers of pad, transfer, ink-jet, and laser printing equipment offer insights on recent innovations.

The suitability of one printing or marking method over another is often dictated by the application, the material that is being marked, and the size of the production run. Printing technologies that require plates, for example, are cost-effective for print runs in which parts are marked identically, but they would not be feasible for serialized or individual marking operations. In addition, the use of ink may be undesirable for certain applications.

Pad, transfer, ink-jet, and laser printing technologies do share one trait, however: R&D that has resulted in advances with the potential to benefit device manufacturers. In this section, key equipment suppliers share recent developments within their companies as well as in their industries as a whole. For an exhaustive list of equipment manufacturers and complete contact information, see the accompanying Buyers Guide on page 92.

Smart labels support read-and-write operations

One recent development in transfer printing is the introduction of radio-frequency identification (RFID) labels, or so-called "smart labels." Manufacturers can encode data in RFID labels, which appear and function like standard labels, explains Matt Ream, senior product manager for RFID systems at Zebra (Vernon Hills, IL). The encoded data can be read with a handheld or fixed-position RFID reader and writer.

Radio-frequency identification (RFID) labels do not require direct contact or line-of-sight visibility to be read. Zebra has developed a transfer printer for the production of RFID labels.

"One of the advantages of the smart label is that radio frequency is used to read the data on the label," says Ream. "This means it does not require direct contact or line of sight. Unlike a bar code, you don't have to see it to read it, which makes it very suitable for harsh environments. If you scratch the label or get dirt on it, you can still read the tag. One of the other advantages is that it's a read-and-write technology. After you print and program the label, you can actually update the information as needed." For example, label data can be changed when it is necessary to reship an item to a different location, or quantity numbers can be modified to maintain up-to-the-minute inventory tracking.

Zebra has just released the R-140 transfer printer for the production of smart labels. The R-140 has been designed to work like Zebra's direct thermal and thermal-transfer printers: "Operators can print and encode in one step without having to learn anything new," he says.

Ream contends that RFID represents a major innovation for medical labeling not only for its usefulness in tracking and traceability, but also because it has the potential to introduce substantial clinical improvements. For example, Zebra has been working with a company called En-Vision America (Normal, IL), which has developed a product called ScriptTalk that reads RFID drug labels aloud to patients who are unable to read the labels themselves. Ream also notes that critical applications such as blood storage can benefit from this technology. In France, for example, a major effort is under way to standardize the labeling of blood bags using RFID labels to ensure traceability. As blood tests are performed, the label can be updated to reflect the most recent results, thus reinforcing quality assurance.

Cold-marking laser process lessens material degradation

Medical device manufacturers are benefiting from improvements in the precision and control afforded by laser marking equipment. Coherent Laser Division (Santa Clara, CA) offers a laser marking process that it calls "cold marking," in which a UV laser creates a color change on the surface of plastic components to produce high-resolution marks without degrading the component material.

"Typically when you use laser marking, you melt the surface of a part by creating pits or decomposition materials," says Paul Crosby, vice president of Coherent. "With cold marking, the reaction takes place underneath the surface or right at the surface, so the component is not degraded. This can be very useful from a regulatory standpoint and can be done in a sterile environment." Crosby notes that this technology, which has actually been available for five or six years, is still just starting to be deployed for the medical manufacturing industry.

Laser technology is suited for marking very small components and fitting a large amount of information in a small area, and suppliers such as Coherent are constantly seeking ways to increase this precision. Subjected to increasing regulatory and quality control pressures, device manufacturers need to code more information at higher resolutions in small spaces so that the information can be readily retrieved later, says Crosby. As laser marking continues to make gains in precision, device manufacturers can also improve their product-tracking efforts.

Pad printers draw from a better inkwell

Device manufacturers who use pad printing can benefit from several recent advances in inks, plates, and prepress operations.

"Inks have improved so much," says Doug Parker, vice president of sales at Imtran Inc., a Foilmark Corp. company (Newburyport, MA). "The use of faster drying inks, improved control over inks, and greater opacity" are among the advances he cites.

One innovation of acute interest to the device industry, Parker says, is the introduction of radiopaque inks for catheter markings that block x-rays, enabling doctors to see the position of catheters. Unlike the previous generation of radiopaque inks that were not suited for invasive procedures, these new inks meet medical requirements for use in the body.

Parker also points out that printing plates have undergone significant changes. Improvements have been introduced in the types of polymers that are used to fabricate plates, says Parker, and the availability of very thin steel plates have made medium-sized production runs more economical than ever before.

Improving prepress operations continues to be a focus for the pad printing industry as a whole, adds Parker. "Prepress is going to be the future of pad printing," he says. "The simpler we can make the process, the more usable pad printing will be." To improve prepress operations, Imtran has developed a pinning system for aligning printing plates. Imtran produces plates that are designed to fit subplate pins to ensure precise and easy alignment. "When the customer buys the plates, they are already punched and they fit right onto the subplates," says Parker.

Ink-jet printers focus on ease of use

"We strive to make ink-jet printers that are ever more simple and reliable," says Andy Millar, product support manager at Willett America (Ft. Worth, TX). "We are continually working to develop systems that you could basically take off the shelf, put on your line, and be ready to use without any special training."

One of the major improvements developed by Willett is the incorporation of a self-cleaning feature on its printers. When an operator stops a self-cleaning Willett printer, the machine automatically flushes out any excess ink from its printheads, so that it is ready to print when it is restarted. Not only does self-cleaning make printer operation easier, says Millar, but it also reduces mess and the possibility of contamination, a major concern for medical manufacturers. Millar notes that Willett printers with this self-cleaning function can remain on the production line for several weeks without requiring attention. —Leslie Laine

Photo Courtesy of Wilden Engineering- Und Vertriebsgesellschaft mbH



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Innovative Molding and Screw Machining Enable Development of Microvascular Coupling System

Originally Published January/February 2001

Innovative Molding and Screw Machining Enable Development of Microvascular Coupling System

The device replaces conventional suturing to save operating time and cost.

A microvascular coupling device makes it possible to reattach nerves, veins, and arteries severed during surgery in as little as two minutes, 10 times faster than with conventional suturing.

The microvascular anastomotic system saves "my patients and myself one hour per day on the operating table, and the success rate, about 99%, is equal to conventional suturing," says James R. Urbaniak, MD, of Duke University Medical Center. He has performed 1400 of these procedures.

Medical Companies Alliance (MCA) of Bessemer, AL, which currently markets the device, outsources its manufacturing to two other companies. The coupling devices are as small as 1.0 mm diam, yet contain numerous high-precision machined and injection-molded components. The most challenging parts—six pins with a shaft diameter of 0.16 mm—are produced by American Laubscher Corp. (Farmingdale, NY) on Swiss screw machines at 10 times the speed and accuracy that could be achieved on conventional CNC lathes. McKechnie Plastic Components (Minneapolis) provides the molded parts and packages the completed device.

How It Works

The microvascular anastomotic system is a mechanical method for coupling small vessels ranging in size from 0.8 to 3.6 mm. The device contains two polyethylene rings that each have six sharp pins embedded in them. To perform an end-to-end anastomosis, the end of each vessel is brought through the center of an appropriately sized ring, turned over, and then impaled on the pins. The vessel is thus perforated from the outer surface to the inner surface. Closing the coupling device brings the two rings into opposition. Further closure allows each set of pins to become seated in perforations on the opposite ring, and in this way the vessels are coupled with lumen-to-lumen contact. The two halves of the device are then pinched with forceps to ensure proper seating of the pins. Final tightening of the device forces a drive pin to release the reattached vessels and the polyethylene rings from the holder. The temporary vessel clips are then released and flow is reestablished.

Polyethylene rings with embedded pins that have an overall length of 1.71 mm and a head diameter of 0.35 mm are used to couple small vessels during anastomotic procedures.

A Challenge for the Molder and Manufacturer...

Originally developed by 3M Medical Systems, the microvascular anastomotic system was sold to PrimeSource Surgical, a parent company of MCA. PrimeSource performed a worldwide search for a contract manufacturer before selecting McKechnie Plastic Components. "It was the one company that we knew had the expertise to insert-mold micromachined components and perform the required packaging and assembly operations," says Mark Breauninger, operations manager for PrimeSource. "The single-source manufacturing services provided by McKechnie allow us to focus on our core competency of device design and marketing."

McKechnie originally purchased the equipment used by 3M to manufacture the device, but it has since developed new methods. The coupling device is insert molded under a 10-power microscope that is used to place the tiny pins into position by hand prior to molding. The pins must be located to very tight tolerances in order to meet up with molded holes. It is a process that engineers at McKechnie equate to "molding Velcro." The injection molding process is carefully controlled so as not to disengage the pins within the tool. If the pins were to move out of the hole, it would fill up with resin and damage the tool.

... And a Challenge for the Machinists

American Laubscher had been supplying 3M with the tiny pins used in the coupler, but when McKechnie began producing the product, they needed to validate American Laubscher's continued ability to provide them. It is critical that the tolerance of these pins is held to a few thousandths of an inch. They are made of stainless steel and have an overall length of just 1.71 mm and a head diameter of only 0.35 mm.

"The pins could have been produced on a conventional CNC lathe, but it would have been difficult and expensive. CNC lathes are inefficient and not very accurate in making the tiny moves required to produce parts of this size," says Mark Schaefer, vice president of business development for McKechnie. "Fortunately, we found that American Laubscher owns and operates something like 80 of the 100 microsized Swiss screw machines that exist in the world. These machines are far more efficient at producing specialized microcomponents, such as small cylindrical parts, in high volumes because the cams that drive their axes provide higher speed and greater accuracy for very small moves. The company produces 100,000 of these components per year for us at a very reasonable price while maintaining the most exacting quality standards," explains Schaefer.

Benefits for Both Surgeons and Patients

In a related clinical study, the microvascular anastomotic system proved highly successful in 100 free-tissue transfers on humans. The average time per procedure was 4 minutes, and the success rate was 98.4%. Mean follow-up was 8.6 months and flap survival rate was 100%. Countless hours of surgery time and its attendant costs have been saved with the microvascular anastomotic system.

Less Is More for Maker of LED Display

Woven fiber-optic technology fosters development of low-power display.

A dental curing unit that was voted new product of the year by Reality, a magazine distributed to dentists worldwide, uses a backlit LED display to show curing times, power output, and remaining bulb life. The Demetron division of SDS/Kerr (Orange, CA), which developed the Optilux 501, required a display that would siphon minimal current. "It's important to keep the power demand inside the curing light as low as possible," says Raymond Knox, senior project engineer at Demetron. "The halogen lamp is 80 W and the whole unit is 100 W, so there's not a lot left for the display backlight. We tried an off-the-shelf LED backlighting display," Knox says, "but it had 20 die and it sucked 1/4 A of current, much more than the 501 could tolerate." Demetron then turned to Lumitex (Strongsville, OH), a supplier of backlighting systems for a variety of applications, which was able to provide a blue backlight that required less than 20 mA of power.

Lumitex's patented woven fiber-optic technology made this low-power, cool-operating backlight possible. Thin, light-emitting, EMI-free panels are woven from plastic optical fibers. Light enters the panels via highly polished fiber ends. Computer controlled "microbends" cause the transmitted light to be emitted from the sides of the fibers through the cladding. Layers of fiber-optic weave are assembled together with double-sided adhesive, adding additional brightness with each layer. A Mylar reflector is laminated to the back and a clear vinyl top layer is added for extra durability. The optical fibers extend from the panel in cable form and are bundled into a brass ferrule and are highly polished. These ferrules are then connected to a remote light source, such as a single LED. This technology allows a standard 2 x 16 LCD (assuming a viewing area of 16 mm x <_ 200 mm) to be backlit using just one LED, with a brightness output of about 30 fL at just 30 mA. "In the case of the Optilux 501, we're backlighting a viewing area of 45 x 20 mm with a single LED at less than 20 mA," says Dave Page, product manager at Lumitex.

The Optilux 501 cures all commercially available composites and does so with an average cure time of only 10–20 seconds (depending on mode), prevents shrinkage of the material inside the tooth, and costs significantly less than rapid-cure lamps.





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Components for Implantables

Originally Published January/February 2001

SPOTLIGHT

Components for Implantables

Custom microconductor coils and helices

Microconductor coils and helices are produced as components for implantable pacing, defibrillation, and stimulation leads in cardiac, brain, and spinal cord therapeutic applications. Windable coil forms include unifilar to 12 filars—tapered, multiple pitch, stripped and dropped, and dogleg, with as small as 0.002-in. inner diam and tolerances to 0.0002 in. Medical-grade wire types that can be coiled include clad wire, DFT, braided, standard, and coated. Coils and helices can be coated with a variety of polymers and metal plating. Jerneen Micro Medical Technology, 475 Apollo Dr., Lino Lakes, MN 55014.


Stainless-steel electropolishing services

A provider of electropolishing services offers an alternative to buffing and machine tumbling, which can produce surface damage or distortion. Electropolishing passivates stainless-steel parts, removes burrs, and creates a bright, reflective surface finish that retards corrosion and resists the bacteria impregnation.It is a reverse plating process that selectively removes the high points on stainless steel with 0.0001-in. precision and deposits a clear, chemically bonded oxide. Electropolishing is a stress-free electrochemical process that involves immersing parts in an electrolytic bath and applying electrical current at a controlled rate. New England Electropolishing Company, Inc., 220 Shove St., Fall River, MA 02724.


Miniature electronic modules

Specializing in miniature electronic modules for medical applications, a supplier has developed a component that provides greater functionality and reduced power consumption in a smaller package size than was previously available. The 3D-CSP module incorporates the company's flip-chip and flexible-circuit assembly technologies. The surface area of the two- or three-die component is approximately 1 mm more than a single traditional integrated circuit. The module, which was recently used in a hearing aid, is suited for any medical application where high density is desirable. Valtronic USA, 6168 Cochran Rd., Solon, OH 44139.


Custom-manufactured implantable components

A company produces implantable components such as plates for reconstructive bone surgery, surgical tools, and catheter tipping molds, as well as hub molds for multilumen tubing. Prototyping and development, introductory quantities, and small-lot production quantities are provided. The company employs only craftsmen, toolmakers, die makers, mold makers, and precision machinists, and it is equipped with state-of-the-art CNC machine tools, including Wire and Sinker electric discharge machines. V & M Tool Co., Inc., 1303 North 5th St., Perkasie, PA 18944.


Tubular metal alloy drilling services

A drilling process can be applied to metal alloys in tubular form to produce close-tolerance, uniform-wall-thickness medical implants and devices. Materials such as nobium, molybdenum, and nickel and titanium alloys, and other hard-to-machine materials can be processed. Wall variations of 0.25 to 0.38 mm TIR can be maintained throughout a length of 400 to 500 mm. The devices produced feature a finished OD size—no finish turning is necessary to correct concentricity. Dearborn Precision Tubular Products Inc., 80 Portland St., Fryeburg, ME 04037.


Shape-memory alloy components

Stents, filters, baskets, couplers, and related parts are manufactured from shape-memory alloys by a company with extensive experience processing nickel titanium. Manufacturing processes that were developed in-house ensure that the material's functional properties are fully exploited in devices as small as 0.4 mm diam. Complex shapes and patterns are routinely manufactured from tubing and sheet with typical slot widths of 0.02 mm and strut widths of 0.1 mm. The company's capabilities include laser cutting and welding, thermal expansion treatment, design and material optimization, electropolishing, and radiopacity. Stainless steel, titanium, and tantalum are also processed. EUROflex Schüssler GmbH, Kaiser-Friedrich-Str. 7, Pforzheim D-75172, Germany.


Polytetrafluoroethylene components

Expanded polytetrafluoroethylene (PTFE) is a soft, flexible, hydrophobic material with a porous microstructure that is air permeable yet tight under low pressures. Properties of PTFE include chemical resistance, high-temperature stability, and good dielectric and nonstick properties. PTFE components can be custom made to meet diameter, porosity, and wall thickness requirements. Impra Inc., P.O. Box 1740, Tempe, AZ 85280.


Antiadhesion biomaterial

A new biomaterial is a combination of hyaluronic acid and carboxymethylcellulose deposited on a polypropylene mesh. The Sepramesh biosurgical composite separates tissue surfaces, while an adhesion-resistant cell layer develops over the surface of the mesh. Without the antiadhesion cell layer, adhesions typically form within seven days following surgery. Also available are synthetic absorbable polymer sutures. Genzyme Surgical Products, One Kendall Sq., Cambridge, MA 02139.


Injection-molded ceramic components

A ceramic component provider offers tubes of various lengths with up to 0.125-in. outer diam and as small as 0.01-in. walls. Highly shaped 2 x 1-in. lids with 0.01-in. walls can be used for hybrid electronic circuits. Ceramic components can be used as end effectors in laparoscopic, endoscopic, and other surgical procedures. The company also supplies zirconia cochlea implant cases. Quest Technology LP, 6750 Nancy Ridge Dr., San Diego, CA 92121.


Radiopaque coatings and surface-texturing services

A company offers radiopaque coating deposition and ion beam surface-texturing services. Radiopaque materials stop x-rays, making a treated device visible on an x-ray or fluoroscopic image. Various radiopaque materials can be deposited as dense, well-adhered thin-film coatings in a variety of patterns such as marker bands and stripes. Both radiopaque coating application and ion beam surface texturing can be applied to metals and polymers. Ion beam texturing produces specific morphologies on metal and polymer surfaces, and a variety of uniformly or randomly spaced structure types can be produced. Ion beam–textured surfaces are durable and cannot delaminate because they are an intrinsic part of the underlying surface. Implant Sciences Corp., 107 Audubon Rd., #5, Wakefield, MA 01880.



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Is This Any Way to Spend the Holidays?

Originally Published January/February 2001

EDITOR'S PAGE

Is This Any Way to Spend the Holidays?

It was the day after Thanksgiving, and I joined hundreds of other people massed at the entrance waiting for the doors to swing open. As we trickled through the turnstiles, the jostling and elbowing began in earnest. But this wasn't Macy's, and the commotion had nothing to do with a cache of PlayStation 2 consoles. The main event was an endless array of medical products, from the simplest disposables to next-generation digital imaging equipment. You may have guessed by now that I spent my Thanksgiving holiday at the Medica trade show in Düsseldorf, Germany.

On some years, the four-day show coincides with Thanksgiving week. This causes some understandable grumbling from the U.S. contingent, which is none too pleased to be abroad on the one day of the year when, as Art Buchwald puts it, Americans eat almost as well as the French do. Nevertheless, if you're involved in the medical industry, Medica is hard to pass up. For me, the show represents one of the best opportunities of the year to develop article ideas and generally take the pulse of industry, which brings me to the subject of the wireless stethoscope.

I noticed the sleek device at the booth of PDD Product Innovation Consultants, a UK-based design firm. The company developed the product in part to get the attention of Medica visitors (mission accomplished, if I'm any indication), and partly to illustrate the company's capabilities, according to Alun Wilcox, head of medical projects.

"You know how long it takes to bring a medical product from concept to market," says Wilcox, who adds that by the time PDD has received approval to display an instrument they helped to develop, it's already old news. "So we decided to identify a medical device that could be improved upon and to display it at Medica to demonstrate what we can do." The venerable stethoscope was an ideal candidate, he adds.

The general design of the stethoscope has changed little over the years, yet it has limitations that modern technology could eliminate. For one thing, the doctor is tethered to the instrument and must get annoyingly close to the patient to use the device. While this may be of little concern to most of us, it can have a disturbing effect on the youngest patients, notes Wilcox. Children who are already skittish about seeing the doctor may be frightened by this large head bearing down upon them to eavesdrop on their organs. PDD conducted research among medical professionals and compiled a number of other drawbacks: the single-user design, a loss of sound quality caused by deteriorating tubing, and the fragile nature of the device, especially the diaphragm membrane. Clearly, it was time to build a better stethoscope.

The Radius incorporates remote communication technology to free the physician from old-technology shackles. About the size of a small mobile phone, Radius can transmit sound to a number of receivers, allowing medical personnel to listen in, and the transmitter can be left on the patient for ongoing monitoring.

The product has numerous other features and enhancements, according to Wilcox, but what it doesn't have is market clearance. PDD is currently seeking partners who would be interested in helping to bring the product from the concept to the trial stage. If you are interested in finding out more about Radius, contact Alun Wilcox by fax at +44 20 87351122 or e-mail him at [email protected].

Norbert Sparrow
[email protected]



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