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Articles from 1999 In November


MPMN November '99 Cover Products

MPMN November '99 Cover Products



High-Voltage Capacitors

High-voltage, multi-layer capacitors from Spectrum Control Inc. (Fairview, PA) can be voltage conditioned up to 5000 Vdc. Capacitance ranges from 50 pF to 2.2 µF in 15 standard sizes.




PC Controller

Billed as an industry first, the MachineLogic PC logic controller from CTC Parker Automation (Milford, OH) combines PC-based open design with the reliability and cost-effectiveness of programmable logic controllers.




Cleanroon Assembly

The machining plant at Norman Noble Inc. (Highland Heights, OH) now includes a cleanroom, which allows the company to assemble and package medical devices in a low-particulate environment.




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Copyright ©1999 Medical Product Manufacturing News

Packaging equipment



Packaging equipment

Small-item packaging machine

The Smallpak Air 5 Deluxe packages small medical products. The unit's sealing, printing, and sizing functions are easily validated and repeatable. A touch panel features controls with English prompts. Programmable settings include sealing temperature, dwell time, seal pressure, and package length (adjustable to 5 in.). The unit also features built-in service records and problem-solving diagnostics. Odessa Packaging & Smallpak, 202 N. Bassett St., Clayton, DE 19938.


Microtiter plate packagers

Systems for microtiter plate packaging can handle bags on a roll or form pouches in a form-fill-seal fashion, inserting a zipper if necessary. Newly developed techniques allow the insertion of Tyvek or peelable pouch material for easy opening. The units are especially suitable for packages with very high profiles, such as styrofoam trays loaded with 15- or 50-ml conical diagnostic tubes. Vacuum is pulled on each package prior to sealing. Most systems applications are designed for in-line, but hand loading is also possible. Action Packaging Automation Inc., P.O. Box 190, Roosevelt, NJ 08555-0190.


Four-side seal machine

An automated electronic four-side seal machine provides high-speed sterile pouching of medical devices. Pouch dimensions up to 14 x 50 x 1 in. can be used. The machine is also available in a dual-lane configuration with a web width capability of up to 24 in. A slanted sealing head may be installed for liquid filling and packaging. The machine is accurate and repeatable, and its operation can be validated. Independent computer control of each of the five main drive modules (infeed, side seal, cross seal, cut, and print) ensures that any potential changes in one module do not invalidate the others. Doyen Medipharm Inc., 520 Speedwell Ave., Morris Plains, NJ 07950-2132.


Packaging system

An automatic bag opening, filling, sealing, and shrink packaging system is designed for wicketed printed or plain shrink bags and plain polyethylene bags. The system produces a final product with high resistance to leaks. It consists of an all-air-operated stainless-steel bag loader interfaced with a USDA-approved horizontal continuous band sealer. The loader accommodates bags up to 11-in. wide and can open bags at a rate of up to 36 bags/min. All Packaging Machinery Corp., 90 13th Ave., Ronkonkoma, NY 11779.


Hot-seal packager

An updated hot-seal packager provides advances in motion programming, including improved tension control, autotuning of web tension, the lowering of friction on the shingling conveyor system, and batch counting. Software interfaces allow for voice recognition, touch screen interfaces, and access to an on-line help system. Other features of the packager include the ability to remove seal rings while the machine is still warm, 1-in. separation of heat seal rolls without loss of registration, and optional load cells for heat seal loading readout. Delta Industrial Service Inc., 11501 Eagle St. N.W., Minneapolis, MN 55448-3062.


Precision heat sealers

Designed for the medical industry, precision pouch sealers produce perfect, validatable seals. The units' Res-Con controller, featuring a keypad and LCD readout, simplify operation. Time, temperature, and pressure are accurately controlled and monitored for quality control and FDA validation. A printout of each temperature cycle can be obtained. Optional features include a vacuum system to evacuate pouches before sealing, an adjustable stainless-steel stand, and a convenient worktable. Packworld USA, 539 S. Main St., Nazareth, PA 18064.


Medical tray sealer

A medical tray sealer features fully integrated network-compatible data acquisition (Windows NT) software capabilities. The BMPC tray sealer can do real-time monitoring and recording of time, temperature, and pressure for every seal cycle. A large touch screen display simplifies setup and seal monitoring, while a dual shuttle permits independent time and pressure setup, assuring packaging flexibility and maximum productivity. Belco Packaging Systems Inc., 910 S. Mountain Ave., Monrovia, CA 91016.


Pouch dispenser

The Sur-Pak pouch dispenser is a high-speed, low-maintenance system that inserts medium-sized pouched products (such as desiccants, oxygen absorbents, and overwrapped medical products) weighing up to 60 g into an outer package at a rate of 300 pouches/min. It complements the manufacturer's small-pouch dispensing unit and is capable of handling pouches up to 4 in. wide and 3/8 in. thick. A nonslip web-advance system handles a continuous web of slippery foil and Tyvek pouches without the crushing pressure associated with nip roll devices. AZCO Corp., 385 Falmouth Ave., Elmwood Park, NJ 07407.


UV printing system

Precisely positioned in-line marking on all types of web materials is possible with a UV printing system. The UV-Flexo Inprint operates in a rotary flexographic mode, offering simple handling and low cost. The anilox roller and doctor blade chamber guarantee even ink transfer, which provides high-quality printing for tiny details and solid areas. Special UV inks are used, and these cure in milliseconds when exposed to the UV dryer. With these inks, only minimal cleaning and setup are required. The printer can be integrated with continuous- or intermittent-motion packaging lines. Griffin-Rutgers Company, Inc., 25 Trade Zone Ct., Ronkonkoma, NY 11779.


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Copyright ©1999 Medical Product Manufacturing News

FEATURED PRODUCTS & SERVICESFrom the November issue of MPMN

FEATURED PRODUCTS & SERVICES
From the November issue of MPMN



LED Light Pipes

LPX series lightpipes transmit the light from a surface-mounted circuit board LED to a display panel. The light pipes can also blend the hues of new multi-color LEDs. The devices are available with three display lens shapes and produce up to a 160° viewing angle. Visual Communications Company, Inc., 7920-G Arjons Dr., San Diego, CA 92126.


Clad Molybdenum Wire

Metallurgically bonded platinum-clad or nickel-clad molybdenum wire is suitable for high-temperature applications in which oxidation or corrosion resistance is required. Featuring smooth, consistent surface finishes, the wire is available in sizes from 0.005 to 0.06 in. diam with typical claddings ranging from 10 to 30% by weight. Anomet Products Inc., 830 Boston Tpke., Shrewsbury, MA 01545.


Switching Power Supply

Designed to provide power to dc servomotors and other inductive loads, the ISP300-4 is a 75-V-dc switching power supply that delivers 6 A of continuous current and can drive up to three IM483 microstepping drivers. With built-in short-circuit, overtemperature, and overvoltage protection, the device minimizes the impact of inductive current surges and rapid changes in power. Intelligent Motion Systems Inc., P.O. Box 457, 370 N. Main St., Marlborough, CT 06447.


Quick-Disconnect Couplings

Sanitary Couplings are quick-disconnect couplings terminated with sanitary-style fittings. The couplings attach directly to popular 3/4-in. mini- and 1-in. maxi-size sanitary fittings, eliminating the need for cumbersome adapters or tubing assemblies. The couplings come with flow diameters of 0.29 and 0.5 in. Colder Products Co., 1001 Westgate Dr., St. Paul, MN 55114.


Connector Line

These electronic connectors are designed for mounting on PC boards, flow sensors, instrumentation, and other demanding applications. The 102, 103, and 1031 series are available with up to 7, 12, and 19 gold-plated contacts, respectively. The connectors are manufactured with chrome-plated, machined brass bodies that withstand heavy-duty use. Fischer Connectors, 115 Perimeter Center Pl., Atlanta, GA 30346.


Argon Ion Lasers

The 177 series of high-power, air-cooled argon ion lasers offers output power of up to 500 mW, tube lifetimes exceeding 5000 hours, a true TEM00 output beam, and field-replaceable plasma tubes. The company's wavelength-selective mirror technology supports single-line operation at 458, 488, and 514 nm or multiline output for maximum power. Spectra-Physics, 1350 W. Middlefield Rd., Mountain View, CA 94043.


Design Software

Cadkey 99 design software offers solid-body healing and tolerant edge functionality that convert imprecise imported model geometries to precise, manufacturable Cadkey solid models. In addition, Cadkey 99 includes a new one-pass IGES translator for rapid import of IGES files and a Parasolid file translator for XT files. Cadkey Corp., 33 Boston Post Rd. W., Marlborough, MA 01752.


Magnetic Field Sensors

Miniature, low-cost analog magnetic field sensors offer multiple sensing axes in a single-chip device. Fabrication by photolithography ensures that the mutual orthogonality of the chip's sensitive axes is held to better than 0.1°. The sensors are available in SOIC-8 packaging or chip form. GMW Associates, P.O. Box 2578, Redwood City, CA 94064.


Nylon Compound

This elastomeric nylon compound offers excellent stiffness, resists collapsing, and doesn't soften at body temperature. These qualities are the result of cross-linking polymers rather than simply blending them. Formulations come in either clear form or a variety of transparent or opaque colors. Applications include catheters and valving. Foster Corp.,
P.O. Box 997, Dayville, CT 06241.


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Copyright ©1999 Medical Product Manufacturing News

Solid Imager Offers Near-Production-Quality Parts : Five-Phase Stepper Motors and Drivers Deliver High Speed and Torque : An Automated Programmer for Fine-Pitch Devices



Manufacturing Equipment

Solid Imager Offers Near-Production-Quality Parts

Comes integrated with software and high-speed resin

A FIFTH-GENERATION SOLID imaging system from 3D Systems Corp. (Valencia, CA) is capable of delivering near-production-quality parts approximately four times faster than the company's current high-end system. The SLA 7000 production solid imager is suitable for use in concept modeling, rapid prototyping, tooling, and near-production applications for the medical imaging industry. Richard Balanson, the company's president and chief operating officer, says that he believes the SLA 7000 system "sets a new industry standard for performance by being an order of magnitude faster than its nearest competitor."

A number of features have been introduced to give the user greater flexibility in setting speed and surface finish. The system is equipped to build ultrathin 0.001-in. layers, which is important for rapid tooling and other applications that require part precision and high surface resolution. The system also boasts a dual-spot, high-powered laser for enhanced throughput and efficiency. System stability has been increased through a self-contained, maintenance-free cooling system that controls the temperature of the laser. A maximum build area of 20 x 20 x 23.62 in. allows users to produce a very large part or multiple small parts simultaneously.

On the software side, the SLA 7000 includes 3-D part preparation and machine control software designed for the Windows NT operating environment. In comparison to previously used Unix-based software, the new software verifies files up to 150 times faster, renders parts up to six times faster, and prepares files more than twice as fast.

Included as well is a high-speed, multipurpose stereolithography resin developed in conjunction with Ciba Specialty Chemicals Corp. (East Lansing, MI). Features of the resin include fast photospeed and good mechanical properties.

For more information, contact 3D Systems Corp. at 888/337-9786.


Components

Five-Phase Stepper Motors and Drivers Deliver High Speed and Torque

Steppers and drivers come ready to use

A SERIES OF FIVE-PHASE STEPPER MOTORS and drivers from Nyden Corp. (Northport, NY) is designed for use in packaging and pick-and-place robotics, x-y stages, automatic blood sampling devices, and other medical equipment. PSU50-133 drivers are supplied with an onboard power supply and can be connected via a 115-V-ac bus or directly to a 115-V-ac line. Motor drive voltage is boosted internally to 140 V dc, achieving ultrahigh speed/torque performance in comparison to steppers and motors with fewer phases. The drivers are also equipped with an adjustable auto-current-cutback feature to save power and to prevent heat buildup when the motor is idle.

The drivers feature settings for full, half, and quarter steps, making them more accurate than two-phase microstepping motors. Providing a high drive current for higher speeds, the drivers also feature step-and-direction or CW/CCW command signals. Additionally, the drivers contain a drive-current-off command to turn off holding torque for easy manual positioning. The steppers and drivers come ready to install out of the box.

For more information, contact Nyden Corp. at 408/232-7700.


Electronics

An Automated Programmer for Fine-Pitch Devices

Offers throughput of up to 850 devices per hour

THE INCREASING USE of fine-pitch devices resulting from shrinking product sizes causes a number of problems for conventional manual programming systems. Because the devices are prone to electrostatic discharge and pin damage, they must be handled very carefully, which slows down the manufacturing process. The PP 100 automated programmer from Data I/O Corp. (Redmond, WA), a system aimed at medium- to high-volume manufacturing environments with medium to high device-mix requirements, addresses these concerns with such features as universal programming sites, an advanced pick-and-place system, and a throughput of up to 850 devices per hour.

Each of the PP 100's programming sites comes with up to 84-pin drivers. This, coupled with the use of socket adapters for different package types, allows the system to accommodate a wide range of device packages. Users can choose from 4 to 16 programming sites to scale device throughput to their requirements.

Each programming station has an independent controller. As soon as a device is inserted, the programmer begins programming it. This allows continuous operation of the pick-and-place head and higher throughput. The pick-and-place handler can place devices in programming sockets to within 0.005 in. accuracy. The PP 100 can use tray, tube, and tape-and-reel media to receive devices and measures 46 x 32 x 62 in.

The PP 100 is equipped with an Ethernet interface that allows the user to analyze the system's performance and establish a central database for downloading device program data files. The system supports more than 8000 fine-pitch and traditional device types and over 45 data file formats. A vision positioning system, which measures a device's size, shape, and alignment prior to placement in the programming socket, is available. Optional CO2 and YAG laser marking and labeling capabilities are also available.

For more information, contact Data I/O Corp. at 425/881-6444.


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Plastic Breathes Life into Respiration System



Plastic Breathes Life into Respiration System

An innovative plastic joint has patients breathing easier.

Made by Dubois Ltd. of Great Britain, a new disposable breathing system features a "Swivel Y" connector made of Carilon polymers, aliphatic polyketones from Shell Chemical Co. (Houston). Replacing a heavy metal and rubber joint, the Swivel Y is "a cost-effective disposable component with the functionality of a heavy reusable Y piece but at the cost of a disposable fixed Y," according to Anthony Fraser, sales and marketing director for Dubois.

A new disposable breathing system features a Y connector made of Carilon polymers from Shell Chemical Co.

Carilon polymers offer strength and stiffness over a broad temperature range; good toughness, wear, and friction characteristics; and low hydrocarbon permeability. These characteristics allowed Dubois to use the polymers as lips and undercuts for snap-fit assembly without damaging or distorting the finished product. Additionally, the high lubricity of the polymers lets the joint move easily while ensuring a tight fit and minimizing leakage. The polymers are also resistant to chemicals, which reduces stress-cracking problems, and can be sterilized by gamma rays.

For more information about Carilon polymers, visit Shell's Web site at http://www.shellchemicals.com.


Increased Demand Seen for Imaging Equipment, Fetal and Neonatal Monitors

Markets for diagnostic imaging equipment and fetal and neonatal monitors should grow over the next six years, according to two reports issued by Frost & Sullivan, a Mountain View, CA, healthcare marketing and consulting company.

U.S. Fetal and Neonatal Monitoring Equipment Markets analyzes the electronic fetal, neonatal multiparameter, and neonatal noninvasive blood gas monitoring markets. The report forecasts slow growth for sales of the monitors through 2005. It also describes the markets as "moderately to heavily saturated," with companies in the industry focusing on capturing new markets.

The other report, World Diagnostic Imaging Equipment Markets, evaluates the magnetic resonance imaging (MRI), ultrasound, computed tomography, x-ray, and nuclear medical imaging equipment segments of the diagnostic imaging marketplace. Overall, Frost & Sullivan expects industry revenues to exceed $14.6 billion by 2004. Sales of MRI equipment in particular are expected to increase due to improvements in technology. According to the report, the MRI industry will experience an 11% annual revenue increase through 2005, to more than $3.6 billion.

For more information on the reports, visit Frost & Sullivan's Web site at http://www.frost.com.


Medtronic, Xomed to Merge

Medtronic Inc. (Minneapolis) and Xomed Surgical Products Inc. (Jacksonville, FL) have signed a merger agreement under which Medtronic will acquire all shares of Xomed, a leading provider of surgical products used by ear, nose, and throat surgeons. The transaction is valued at approximately $800 million, with Xomed shareholders to receive $60 in Medtronic stock for each share of Xomed. The companies expect the transaction to be completed by the end of the year.

"Xomed's market leadership, strong clinical relationships, highly regarded management, and full range of products offer Medtronic a new platform for continuing growth beyond our current franchises," said William W. George, chairman and chief executive officer of Medtronic, which makes a wide variety of medical devices.


New Technology Aims to Slash Needle Sticks

BTG plc (London) has made available for licensing a new technology that could reduce the approximately one million needle-stick injuries reported in the United States each year. Developed by two experts in the field of hydrophilic polymers, the technology uses such polymers to cover the point of a needle and thereby render it harmless.

Once a needle is used, the polymers absorb moisture from the injected solution or surrounding fluid. This causes the polymers to expand and thereby blunt and block the needle, preventing its reuse and virtually eliminating the possibility of a needle-stick injury, according to BTG.

Since no special needle-retraction mechanism is needed, the technology can be used with a conventional syringe. This makes it easy and inexpensive to use and potentially adaptable for almost any needle, BTG claims.

For more information, visit BTG's Web site at http://www.btgplc.com.


Company to Develop Tools for Making 'Mesoscale' Electronic Devices

As part of a four-year, $7.5 million project, the Defense Advanced Research Projects Agency (DARPA) has awarded Potomac Photonics Inc. (Lanham, MD) a contract to develop and commercialize a laser-based tool for the fabrication of next-generation passive electronic devices. The award also grants Potomac full commercial rights to the tool.

The award is part of DARPA's Mesoscopic Integrated Conformal Electronics (MICE) program, the goal of which is development of a commercially available machine capable of producing "mesoscale" electronic devices in a conformal manner on virtually any substrate. Larger than silicon chips but smaller than printed circuit boards, mesoscale electronic circuits promise to allow further miniaturization of medical and other devices.

Approximately 40 µm wide, this conductive gold medal line was deposited using a laser technique being developed by Potomac Photonics Inc.

Potomac's MICE tool showcases the company's experience in laser microfabrication technology, as well as a proprietary deposition process developed at the Naval Research Laboratory in Washington, DC. This combination has already resulted in the fabrication of conductors, resistors, capacitors, and inductors.

For more information, call Potomac Photonics at 301/459-3031.

In Brief

Hill-Rom (Batesville, IN), a manufacturer of patient care systems, has acquired Amatech Corp. (Acton, MA), a manufacturer and distributor of surgical table accessories and patient positioning devices...Tekni-Films, Tri-Seal, Plastron/Natvar, and Colorite Polymers have combined to form Tekni-Plex Health Care Group (Somerville, NJ). The new company is a diversified manufacturer of packaging products and materials for the healthcare industry...The Health Industry Manufacturers Association (Washington, DC) announced its approval of the decision of the National Toxicological Program to reexamine the potential reproductive and developmental effects of seven phthalates. One phthalate, DEHP, is used in a variety of medical devices, including blood bags, intravenous tubing, and respiratory equipment...Colorado MEDtech Inc. (Boulder, CO) has acquired the assets of Creos Technologies LLC (Englewood, CO), a provider of x-ray generator subsystems for the medical imaging industry, for approximately $2 million...Tyco International Ltd. (Hamilton, Bermuda), a diversified manufacturing and service company, has agreed to acquire General Surgical Innovations Inc. (Cupertino, CA), a medical manufacturer and distributor of balloon dissection devices. The value of the transaction is approximately $100 million...GE Marquette Medical Systems (Milwaukee), a provider of medical diagnostic equipment, has signed a definitive agreement to acquire Prucka Engineering Inc. (Houston), a company that specializes in electrophysiologic research and development, for an undisclosed sum...Merit Medical Systems Inc. (South Jordan, UT) has acquired the catheter unit of Mallinckrodt Inc. (St. Louis). The catheter plant, located in Angelton, TX, manufactures diagnostic and interventional catheters for cardiology and radiology procedures...Norton Performance Plastics Corp. (Wayne, NJ), a manufacturer of specialty polymer products, has acquired Sanitary Couplers (Springboro, OH), a manufacturer of reusable couplers for hoses. The company will be a part of Norton's PPL Fluid Systems business...Guidant Corp. (Indianapolis), a manufacturer of products for the treatment of cardiovascular and vascular disease, will acquire CardioThoracic Systems Inc. (Cupertino, CA), a cardiac surgery instrument and systems company. The transaction will be a tax-free exchange valued at approximately $313 million...BD (Franklin Lakes, NJ), formerly Becton Dickinson and Co., has acquired Saf-T-Med Inc. (Chicago), the maker of a safety-engineered syringe and other needle-based medical devices...Biomet Inc. (Warsaw, IN), an orthopedic device manufacturer, has agreed to merge with dental implant manufacturer Implant Innovations Inc. (Palm Beach Gardens, FL). The transaction, to be completed by late November, is valued at approximately $175 million...MedSearch Technologies Inc. (New York City) has completed its acquisition of M&W Medical Supply LLC, a research and development company...Phillips Petroleum Co. (Bartlesville, OK) and Solvay Polymers Inc. (Houston) have agreed in principle to build and operate a high-density polyethylene manufacturing facility in the United States...St. Jude Medical Inc. (St. Paul, MN) has signed a definitive agreement to acquire Vascular Science Inc., a Minnesota-based developer of suture-free devices for coronary artery bypass graft anastomosis, for $80 million in cash and $20 million in milestone payments.



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Transmitter Signals a New Approach in Battle Against Incontinence



Transmitter Signals a New Approach in Battle Against Incontinence

Wireless technology may ease the suffering of many in nursing homes

Long-term care could be in for a big change, thanks in part to a tiny radio.

Pressed to improve care and reduce costs, long-term care (LTC) facilities are rethinking their methods of handling a variety of problems. One of the biggest of these is managing urinary incontinence. Total costs for dealing with the consequences of incontinence—including urinary tract infections and pressure sore infections caused by prolonged exposure to urine—have been estimated at over $28 billion annually.

In the past, treatment of the 1 million U.S. nursing home residents suffering from incontinence included diapers and periodic visits from nursing home staff to check for voiding episodes. Often, patients would go unattended for hours, which (in addition to personal discomfort) resulted in pressure sores and skin breakdown.

To alleviate the suffering of these people, Health Sense (Santa Margarita, CA) has unveiled a high-tech method of dealing with incontinence. Using wireless technology provided by World Wireless Communications (Salt Lake City), the Health Sense approach aims to reduce and eventually eliminate incontinence episodes.

By some estimates, up to 70% of urinary incontinence is a result of difficulty in self-toileting, rather than bladder-related physical problems. Thus, proper nursing care can dramatically improve recovery rates. Targeted at LTC facilities that provide this care, the Redeem system from Health Sense is designed to help long-term caregivers set up a facility-wide automated incontinence management program.

How It Works

Redeem features a wireless transmitter that clips onto an electrically conductive disposable strip called Sense 'R Strip. When a nursing home resident voids, the strip instantly detects the episode and the radio transmits data on the incident to a central computer at a nursing station. The system promptly notifies caregivers of the episode and stores information about the event in a central database. When caregivers attend to the resident, the system sends the computer a second radio signal to document the time elapsed between the voiding event and the rendering of care.

The Redeem incontinence management system features a wireless transmitter that clips onto an electrically conductive disposable strip called Sense 'R Strip (left). The system also includes a PC and special software.

Over time, data on episodes and caregiving accumulates, creating a visual "fingerprint" of each resident's incontinence patterns. This fingerprint can be viewed on a computer screen or printed out to develop resident-specific care plans, establish bladder and bowel retraining programs, and institute preventive toileting procedures throughout the facility.

The nurse's workstation, a stand-alone PC running special Health Sense software, is the window that allows healthcare personnel to view information about which patient is having an episode, as well as the patient's room and voiding history. Connected to the PC is a receiver, which is linked by coaxial cable to an antenna fixed in position above the monitoring station. A reinforced fiberglass housing was chosen for the antenna because typical PVC material contains enough water to adversely affect the incoming signal.

The antenna receives data sent by the transmitter, which is located near the patient. This transmitter, the 900 Micropulse transceiver from World Wireless, uses a 9-V power source consisting of three stacked-coin cells. Designers chose ABS for the device's exterior because of the plastic's high impact tolerance, UL 94HB fire-retardancy rating, and ability to take on a bright color, which makes the transceiver stand out--and so helps keep it from being accidentally discarded.

Off and On Signal

The 900 Micropulse employs a pulse modulation scheme that turns the signal on and off in pulses. While the transceiver is in operation, the signal is on less than 10% of the time, according to Scott Christensen, an application engineer for World Wireless. Besides reducing power consumption, pulse modulation also extends the transceiver's range. Federal Communications Commission regulations governing unlicensed radio transmissions limit the power of such transmissions, but allow averaging of power output over time. "Since we're only on a tenth of the time, we can increase the power to 10 times the power" of a continuous signal, Christensen explains.

The small size of the 900 Micropulse transceiver makes it easy to wear.

This means the 900 Micropulse can put out a 10-mW, 900-MHz signal, which allows data transmission up to 300 feet. By contrast, other radios that were considered needed the help of antennas stationed every 25 feet to carry the signal the required distance. Earlier versions of the Redeem system, which included less powerful radios, also required multiple antennas, while the new system needs only one, according to Norman Roberts, Health Sense's director of new product development.

At some point, the transceiver may be called on to receive as well as transmit signals, thereby making Redeem a "smart system," Roberts says. Right now, since radio-frequency interference could prevent the nurse's workstation from receiving the transceiver signal, the device can be programmed to send the signal a number of times. But if the computer can send a message back to the transceiver saying that the signal has been received, the transceiver could stop transmitting at that point.

At present, Redeem is installed in just two facilities, where patients are developing fewer bedsores and enjoying a higher quality of life, according to Roberts. He expects the system to be operating in 95 facilities by the end of the year, and Health Sense has ordered 1200 transmitters from World Wireless to meet the anticipated demand.

The performance of wireless technology in the Redeem system may be a debut that leads to more medical roles. "It's a substitute for cables in many applications," Christensen says. "In any application where you're doing remote monitoring, [wireless technology] would be useful."


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Copyright ©1999 Medical Product Manufacturing News

Oil-free pumps



Pumps

Oil-free pumps

With pumping speeds from 170 to 900 L/min, a line of oil-free pumps for vacuum ovens and dryers contain pistons that are suitable for roughings and backing of turbo, cryo, and ion pumps. The piston-type pumps provide pressure of over 20 mTorr; do not need oil, diaphragms, or cooling water; and do not need maintenance for the first 20,000 hours. An optional soft-start speed control automatically slows the pumps when gas loads are small and increases speed if the pressure starts to rise. Vacuum Research Corp., 2419 Smallman St., Pittsburgh, PA 15222.




Dry vacuum pumps

High-flow dry vacuum pumps are available in pumping speeds of 3.1 and 7.1 cu ft/min and offer a vacuum level of up to 60 Torr, making them suitable for aspirating sticky and viscous substances. Two models are available, with the largest weighing 22.5 lb and having a footprint of 11 x 9 in. Both models are equipped with a dial vacuum gauge to verify that connections are leaktight. An attached inlet trap inhibits accidental ingestion of liquid into the oil-free pumping mechanism. Welch Vacuum Technology, a subsidiary of Thomas Industries, 7300 N. Linder Ave., Skokie, IL 60076-0183.




Miniature pump

Manufactured with a snap-and-clasp press-on head, a miniature diaphragm pump is suitable for use in gas analyzer, air monitoring systems, blood pressure monitoring devices, nebulizers, and anesthesia equipment. The measurements of the 3013 pump are 41.5 x 22.5 x 33.3 mm, making it smaller than the 3003, the pump's predecessor. The pump also runs more quietly than the 3003 and is capable of producing 450-mbar pressures and 10-in.Hg vacuums. ASF Thomas, 2100 Norcross Pky., Norcross, GA 30071-3669.




Diaphragm air pump

A single-head diaphragm air pump provides free flows to 35 L/min, pressures to 22 psi, and vacuums to 21 in.Hg. The T2-01 pump operates with a high-efficiency dynamic valve design that uses 20% less power than other units in its performance range, according to the manufacturer. The pump, which has no exposed moving parts, is suitable for use in portable air and gas applications. Multihead configurations that provide up to 120 L/min free flow and vacuums to 25 Torr are also available. T-Squared Manufacturing Corp., 1275 Bloomfield Ave., Unit 3-50A, Fairfield, NJ 07004.




Variable-volume pumps

Designed to be completely maintenance free, a line of pumps can be located wherever fluidic requirements dictate, regardless of maintenance accessibility. The pumps offer space and weight savings and up to 10 times the life cycle of conventional syringe pumps, according to the manufacturer. LPV-series pumps are available in custom and 50-, 250-, 750-µl configurations. The coefficient of variation is 0.04% at full stroke. The Lee Co., 2 Pettipaug Rd., Westbrook, CT 06498-0424.




Oil-free vacuum pump

Combining a structured, molded diaphragm; high-speed check valves; and a brushless dc motor, an oil-free vacuum pump eliminates EMI/RFI present in brush-type motors. The N813AN pump provides a 13 L/min flow rate with an end vacuum of less than 0.5 mbar. The low vacuum range makes the two-stage, dry diaphragm pump suitable for use in portable medical and roughing applications. Chemical-resistant versions and versions with different flow rates are also available. KNF Neuberger Inc., 2 Black Forest Rd., Trenton, NJ 08691-1810.




Dispensing system

A multichannel dispensing system uses a single motor drive to control multiple fluid channels. The Multiplex dispensing system is digitally programmable for dispense rate and volume and delivers a pulse-free linear profile with 40,000:1 resolution. The self-priming ceramic piston/cylinder pump modules use industry-standard fluid fittings and are interchangeable. Applications include diagnostic reagent striping, microtiter plate dispensing, form-fill-seal applications, and sterile bottle, vial, and syringe filling. IVEK Corp., Fairbanks Rd., North Springfield, VT 05150.




Multichannel pump

Offering up to 32 channels on a single drive, a pump provides near pulseless flows at rates from 0.6 to 28 ml/min. The PumpPro MPL pump features an updated pump head that allows for greater flow rate control and improved tube life, according to the manufacturer. Additionally, a 30-turn occlusion knob allows for fine adjustment of flow rate on each channel and can be locked to maintain the setting and prevent accidental tampering. The occlusion adjustment is separated from the tube-loading lever and remains constant when tubes are changed. Watson-Marlow Inc., 220 Ballardvale St., Wilmington, MA 01887.




Metering pump

Specifically designed to handle highly corrosive liquids, a high-purity Teflon metering pump can handle liquids as hot as 250°F. The Model SV104, a self-contained unit, has a solid-state speed controller that provides variable flow adjustment from 100 to 800 ml. The pump is self-priming, maintains a constant flow within 2% under stable voltage and pressure, and has a maximum outlet pressure of 15 psi at a flow rate of 100 ml/min. Valcor Scientific, 2 Lawrence Rd., Springfield, NJ 07081.




Magnetic-coupled pump

A sealless, magnetic-coupled, corrosion-resistant centrifugal pump is designed for applications requiring both low flow and the development of pressure. The Model 320 can handle a flow of up to 3.3 gpm with pressures of up to 17.3 psi. The pump has the durability of a centrifugal pump, making it suitable for continuous duty, according to the manufacturer. March Manufacturing Company, Inc., 1819 Pickwick Ave., Glenview, IL 60025.




Micropumps

Miniature self-priming 5-µl micropumps are designed to handle programmed, precision-controlled microdispensing of high-purity or aggressive fluids. The pumps can be factory set to handle discrete fixed output flows at volumes of 3 to 8 µl per solenoid actuation. It provides an inert fluid path for precise, repeatable dispensing with an accuracy of 0.5 µl. The pump can also provide a continuous pulsating flow to replace maintenance-intensive peristaltic pumps. Bio-Chem Valve Inc., 85 Fulton St., Boonton, NJ 07005.




Dual-head pumps

Offering two pump heads that can by used in both series or parallel, 5-in.-long lightweight pumps can produce up to 20 L/min at free flow. The Dual Head C Micro Air pumps can attain a maximum pressure of 28 psi and a vacuum rate of 26 in.Hg in series performance. The pumps can attain a maximum pressure of 13 psi and a vacuum rate of 23 in.Hg in parallel performance. Sensidyne Inc., 16333 Bay Vista Dr., Clearwater, FL 33760.




Miniature diaphragm pumps

An oilless miniature diaphragm pump series provides pressures of up to 7.1 psi with open airflow of 1.18 L/min. The 3D-series pumps have a chemical-resistant valve, diaphragm, and head assembly and will mount on any plane. Stroke options are available for performance modification; dc voltage options are available in iron or ironless core motors. Suitable applications include air samplers, gas detection systems, blood pressure and respirator monitors, and portable aspirators. Gast Manufacturing Inc., P.O. Box 97, Benton Harbor, MI 49023-0097.




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Copyright ©1999 Medical Product Manufacturing News

Medical Technology for the Future: Ensuring Patient Access to Innovation

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI November 1999 Column

HIMA's current chairman reviews recent initiatives in regulation and reimbursement and discusses the importance of product development and patient access to new devices.

All of us in the medical device industry have an enormous stake in ensuring patient access to inno-vative medical technology in a de-manding, cost-conscious healthcare environment that is often unfriendly—or even downright hostile—to new ideas and inventions. Patient access to new medical technology is the cornerstone of our industry's marketplace. The key question for the device industry and for HIMA is, What can we do to ensure that the industry's latest and best technology is available to all who need it?

LETTING THE MARKET DEFINE VALUE

First and foremost, medical technology starts with investment in product development. I believe that HIMA and the industry can strongly impact—and perhaps greatly increase—the availability of investment dollars by promoting a reimbursement system based on customer-determined product value. Because investment in product development is the first step in patient access to medical technology, the process that determines the "value" of innovation is incredibly important. We in the industry are willing to stand or fall, to succeed or fail according to the conclusions of a consumer-driven, market-based decision process. Healthcare policymakers must allow the marketplace to make decisions about value, and the industry must be allowed to develop new products for the marketplace.

To help smooth the development of new products, HIMA has worked with FDA to secure an increasingly efficient approval process, and the FDA Modernization Act of 1997 (FDAMA) represents a giant stride in the direction we want to go—without sacrificing patient safety. The act requires a least-burdensome approach for product approvals. This is important, because an appropriate interpretation of "least burdensome" can significantly affect clinical development times. FDAMA also encourages the use of international standards and mandates the establishment of a dispute-resolution procedure. Throughout this past year, HIMA has devoted substantial attention to FDAMA implementation, and it's easy to see why we needed to do that. The way in which this landmark law is put into practice—encompassing as it does new FDA policies and procedures—is vital to our future and to securing the delivery of new technologies to patients more quickly.

When fully implemented, we can expect FDAMA (along with the agency's own internal reengineering efforts) to increase FDA efficiency. In addition to these gains, we can look forward to a reduction in regulatory redundancy and costs for both the industry and the agency as a result of the mutual recognition agreement (MRA), negotiated between the United States and the European Union (EU), with input from HIMA and the industry, in 1997. The MRA, which was formally signed in May 1998, is expected to be fully implemented by December 2001, by which time FDA plans to "normally endorse" inspections and reviews by EU third-party bodies.

CHANGING THE REIMBURSEMENT PROCESS

In order for patients to have access to innovative medical technology, we need to know if, when, and at what level reimbursement will be provided for new products and therapies. Again, we in industry believe that reimbursement decisions should be customer-driven and market-based. However, not every healthcare policymaker supports this concept. In this regard, our work is cut out for us. We must inform, educate, and persuade.

Our efforts in the reimbursement area already extend to the Health Care Financing Administration (HCFA), where we are encouraging a number of substantive changes to Medicare processes and policies. We have welcomed President Clinton's Medicare plan to improve patient access to new procedures and prescription drugs. But we have also expressed concern that the Clinton plan means robbing Peter to pay Paul by helping fund the drug benefit through a new round of provider payment cuts—cuts that could undermine patient access to medical technologies. Ideally, there should be a holistic approach to HCFA's coverage, coding, and payment decisions. HCFA's decision-making processes for new technologies should be transparent to all concerned, and we believe that the developer of the technology under consideration should be included in the process.

The need for change in this domain goes far beyond HCFA. The governments in Japan, France, and Germany are each working through complex healthcare system challenges. These governments clearly need our help in seeing new medical technologies as solutions rather than as cost drivers.

As we make the case for medical technology with policymakers, it is vital to recognize that there is political strength in numbers. We must not forget that, to a large degree, the general public supports our industry and our primary message—that patients should have access to new medical technology.

PUBLIC PERCEPTIONS OF MEDICAL TECHNOLOGY

Let me back up this last assertion with some numbers. In recent research into public perceptions of medical technology, HIMA found that 90% of those surveyed have a favorable impression of the device industry. Moreover, 98% believe that technology saves and improves lives. Between 60 and 65% of respondents say they oppose federal price controls, while 80% believe that price controls could lead to less R&D for medical technology. Any slowdown in innovation is opposed by 80% of those surveyed, and 89% want access to the latest technology when they get sick. Finally, 83% disagree with any plan to control costs by limiting technology, and 94% agree that insurers should pay for a product if FDA approves it.

These public perceptions are critical considerations as we chart our industry's path into the 21st century. We have a great story, and when it is told, patients and consumers are incredibly responsive. We must capture in words and quantify in numbers the benefits to patient outcomes that derive from new technologies. We must make the case that, in those situations when technology does contribute to an increase in expenditures, the investment is more than offset by gains for patients of longer, more productive lives. These are important points, and our responsibility is to ensure that they are never missing from future healthcare policy debates.

One final point must be kept in mind. Whatever health policy challenges the future brings us—as the pace of technological advance becomes ever more rapid and demanding—we must always look to what is best for patients and their doctors. In any future policy debate, this should be the ultimate standard and the deciding factor.

Ronald W. Dollens is president and CEO of Guidant Corp. (Indianapolis) and current chairman of the board of the Health Industry Manufacturers Association (HIMA).


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Copyright ©1999 Medical Device & Diagnostic Industry

A Scholarly Article You Can't Promote : Harmonization Power Grab? : FDA to Appeal Free-Speech Defeat : Y2K Won't Bother Many Devices : FDA's "Least Burdensome" Guidance

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI November 1999 Column

WASHINGTON WRAP-UP

James G. Dickinson

Also:

  • Harmonization power grab?
  • FDA to appeal free-speech defeat
  • Y2K won't bother many devices
  • FDA's "least burdensome" guidance

Your device is approved, and locked in fierce competition with a rival. A scholarly professional journal, peer-reviewed, publishes an article comparing your device favorably with its competitor—but there's a catch. The use described in the article has not been approved by FDA for your competitor's device—although it has been for yours.

The marketplace is volatile, the article's credentials are impeccable, and if you don't strike while the iron is hot you could come under stockholder criticism. So, at the next available professional meeting, you flood the place with reprints and promotional materials, including a video presentation of your product in use. The result: you receive a warning letter from FDA calling your device both "misbranded" and "adulterated." This is official correspondence your competitor can use against you in retaliation. In fact, your competitor is probably the means by which FDA found out about your promotion.

This is what happened in August to Thoratec Laboratories Corp. (Pleasanton, CA). According to an agency warning letter, Thoratec's promotions took parts of two articles in the Annals of Thoracic Surgery out of context in claiming that its ventricular-assist device (VAD) had an 88.5% patient survival rate compared with 50% for the BVS-5000 VAD from Abiomed Inc. (Danvers, MA) when both were used as a bridge to heart transplantation.

Notwithstanding the fact that the articles were circulated in a respected journal for the medical profession to assess as it saw fit, it has been FDA's long-held policy that such publications cannot be used in device manufacturers' commercial promotions, even when presented as "educational" communications. Although this policy has been dealt a serious legal blow in recent litigation (Washington Legal Foundation (WLF) v. FDA, see related item on page 36), FDA is not yielding easily—as its eight-page letter to Thoratec on August 12 illustrates.

There were several problems with Thoratec's use of the articles, the letter said. Beyond the fact that the comparator device had not been approved by FDA for "bridging" use, the articles in question were not based on "a controlled clinical trial conducted by either Thoratec or Abiomed," but instead reflected European clinical experience with circulatory support devices.

"The portions of the articles are taken out of context and provide only the briefest statements of comparison between devices," the letter continued. "Although such presentations may encapsulate the appearances of superiority for the Thoratec device that Thoratec apparently wishes to create, they are misleading presentations of clinical experience and conclusions."

Even the clinical experience of survival rates of the two devices, although correctly reported by Thoratec from the articles, was faulted as "misleading"—because the Abiomed device was not approved by FDA for bridging and because the study in question had not been conducted by either company. Moreover, the letter said, it was "not clear" that the comparisons of the survival rates were based on "statistically significant differences, and it is misleading for the company to imply that the differences are meaningful if they are not and if the devices have not been directly compared with each other for a specific outcome."

It thus becomes apparent that, despite the recently changed legal landscape—which includes explicit permission under both the WLF legal decision and the FDA Modernization Act (FDAMA) for manufacturers to disseminate unapproved-use information in published studies—FDA intends to continue to control the content of what manufacturers provide to health professionals. In other words, in FDA's view, the mere publication of an unapproved use in a peer-reviewed journal does not confer on the manufacturers of the studied devices the right to extract from the publication favorable mentions or recommendations that FDA might feel need contextual balancing, much less the right to amplify selective findings.

Though highly unlikely, it is conceivable that a truly objective manufacturer might extract such mentions so carefully—with relevant balancing information both intact and given all due emphasis—that FDA would not object to the finished promotional piece. The safer course is either to present the proposed promotion with all its scientific backup for voluntary FDA preclearance before use (and FDA does not afford such offerings its highest priority) or to file a supplemental application with the agency seeking to have the unapproved use approved and added to the product labeling.

Is FDA helping other government representatives seize control of the multilateral Global Harmonization Task Force (GHTF) that has been set up to bring consistency and equivalence to all the various regulations that govern the medical device industry?

Robert Britain, of the National Electrical Manufacturers Association, represents U.S. industry on an ad hoc group established recently to develop a consensus procedural document to be considered next year by GHTF. In August, Britain commented that an FDA-drafted version of the document looked to some like an attempt to tilt power to government and away from the concept of government and industry as equal partners. "For example," he said, "industry was excluded in a procedure written for final signoffs. We've always had consensus in the past because all sides had done so much homework. And there was acknowledgment of industry as an equal partner. But a document prepared by FDA would have excluded manufacturers from having any approval say-so."

Britain explained that "there are pros and cons to such a position. Those who favor it say that if guidances are approved only by the governments, there can't be any suspicion of industry contamination. Some U.S. companies think the decisions may carry more weight if they come only from government, so they were not as upset as the Europeans were. But some manufacturers, especially in Europe, don't like being left out of the process now after having been so fully involved for so long." Britain said that he shared the Europeans' concern, which led to his involvement in the ad hoc group being established with representatives from government and industry to "come up with a procedural document we all can live with."

CDRH deputy director for science Elizabeth Jacobson, who chaired the task force until September, admits that the draft she introduced to the ad hoc group "caused quite a stir." But she said that the task force has matured to the point where it needs a formal structure for resolving membership and other issues that are being raised. "I think it's normal for an organization to have this kind of operational struggle," said Jacobson. "I don't think this needs to be half as controversial as some people say."

FDA has decided to appeal its July 28 defeat in the Washington Legal Foundation (WLF) First Amendment case. Although an appeal risks being reviewed by the same hostile panel of judges that sweepingly ruled against FDA in the Durk, Pearson et al. dietary-supplement-labeling case earlier this year, the agency is gambling that this time it could draw different judges—especially someone other than Reagan appointee Laurence Silberman, who wrote the Pearson decision.

In its appeal, which the court has agreed to expedite, FDA plans to argue that "quirky" District Judge Royce G. Lamberth (another Reagan appointee) overstepped Supreme Court policy when he ruled that portions of FDAMA were unconstitutional. Not only did Lamberth fail to defer to FDA's judgment, but he also failed to defer to Congress. The agency plans to cite Supreme Court precedents establishing that both the administrative and legislative branches of government are entitled to more deference than Lamberth gave them in this case.

FDA also plans to cite the investigational history of the drugs encainide and flecainide, in which many patients received incorrect doses and had fatal reactions. FDA will argue that this was a vivid example of a case in which even more deaths could have occurred had the sponsor been able to promote unapproved uses. The agency is also considering introducing studies showing that even highly educated physicians are not immune to subtle promotional influences that can induce dangerous prescribing patterns, and that commercial incentives can increase this phenomenon.

FDA believes it can present a much stronger case to the appellate judges on WLF than it did in Durk, Pearson. According to one source, even Silberman has acknowledged that dietary-supplement issues are not as serious as drug issues.

In a statement updating its activities involving the Y2K computer problem, FDA says that the "vast majority of computer-controlled medical devices used and marketed in the United States will not be significantly affected by the Y2K date problem." However, according to the agency, "there are a few products, primarily in hospitals and laboratories, in which correct processing of date information is critical to the device's functioning."

Devices that could potentially be affected by the Y2K problem include those that use dates in a calculation or algorithm or for critical recordkeeping, such as radiation-therapy planning systems, hemo-dialysis machines, some clinical-laboratory systems, some blood-product devices, and some ultrasound systems.

FDA says most manufacturers of such machines have already identified solutions, provided upgrades for them, and notified their customers of the availability of those upgrades. FDA's statement describes steps the agency has taken and notes that inspectors are checking during regular inspections of manufacturing facilities to see what firms have done to ensure that their products, manufacturing processes, and distribution systems are Y2K compliant. The agency says it does not believe that Y2K date problems will lead to device failures of a type that would warrant mandatory recalls.

At the end of August, CDRH released its much-awaited draft entitled Guidance for Industry and FDA Reviewers on Evidence Models for the Least Burdensome Means to Market. The document addresses the first of several issues in determining the "least burdensome" means to allow appropriate premarket development and review of a product without unnecessary delays and expense to manufacturers. The "least burdensome" standard was imposed on the agency by FDAMA, with strong industry backing.

Tools that could be used by sponsors and reviewers to facilitate the process of determining the least burdensome means to market, the document says, include:

  • A decision algorithm to determine the need for clinical data.
  • A checklist for the contents of a submission.
  • Submission templates for some common situations.
  • Rapid access to data in the public domain via a Web page.
  • Rapid access via the Web page to current guidances for clinical data and study-design options.

The agency said it decided to address the clinical data issue first because it emerged in discussions with stakeholders as their greatest concern. The remaining tools will be evaluated, prioritized, and developed as appropriate.

FDA proposes a consistent process approach—rather than a table or hierarchy—that focuses on two key questions. First, does available valid scientific evidence provide reasonable assurance that the subject device is safe and effective, or establish substantial equivalence to a predicate device, when used as indicated in the target population? And second, what is the most appropriate and reasonable way to obtain such evidence?

The guidance lists points that should be considered in answering each question. For example, factors to be considered in determining whether available data meet the need would include the device and the use environment, the indication and the claim, current knowledge of the interaction of the disease or condition and the product, the relevance and applicability of the clinical data, and specific questions about the data.

If the existing data—including available clinical data—are not sufficient to answer "yes" to the first question, then implications raised by answering the second must be considered. FDA says stakeholders tend to focus their concerns on the least burdensome approach related to the need for a randomized, controlled trial—assuming that this would be the most costly approach in terms of time and money. The guidance says that FDA's experience is that such a trial is not always the most costly approach. Although the agency does not say what its real-world experience of trial costs is (probably little or none), this document shows that FDA is trying to be realistic about "least burdensome" requirements.


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Copyright ©1999 Medical Device & Diagnostic Industry

Silicone Rubber for Medical Device Applications

Medical Device & Diagnostic Industry Magazine
MDDI Article Index

An MD&DI November 1999 Column

A review of material properties and processing characteristics highlights silicone's enduring popularity for fabricating a range of medical products.

For those involved in medical product development, selecting a high-quality elastomer for critical applications can be a challenge. Designers, engineers, and managers must carefully evaluate a wide array of material properties and processing possibilities in order to meet demanding performance specifications and budget requirements. With so many materials and fabrication methods available today, it is often difficult to recognize the optimum solution, and the consequences of selecting an inferior material can range from lost time and money to total project failure.

To make the most informed decision, product developers should gather as many facts as they can about each material. This article is intended to provide a general overview of silicone rubber elastomers, including physical properties, fabrication methods, and potential advantages for device manufacturing.

CHEMICAL STRUCTURE AND CURE MECHANISMS

Since the 1960s, silicone rubber has found widespread use in medical, aerospace, electrical, construction, and industrial applications. Flexibility over wide temperature ranges, good resistance to compression set, a wide range of durometers, and inert and stable compounds are among the reasons for its popularity. Common silicone medical components and assemblies include airways; balloon catheters; tubing for feeding, drainage, and use with peristaltic pumps; compression bars; electrosurgical handpieces; infusion sleeves and test chambers; introducer tips and flexible sheaths; wire/fluid-path coextrusions; ear plugs and hearing aids; shunts and septums; and a variety of seals, stoppers, valves, and clips.

The unique properties of silicones enable them to be used for a variety of devices and components. Photo courtesy of Vesta Inc.

Silicone rubbers are synthetic polymers with an unusual molecular structure—a giant backbone of alternating silicon and oxygen atoms. This structural linkage is similar to that found, for example, in a mineral such as quartz, and silicones have superior heat resistance compared with other elastomers. There are two popular catalyst systems used to cross-link silicone polymers: peroxide (free-radical) systems and platinum (addition-cure) systems.

Early-generation silicones used peroxide as the catalyst to initiate curing of the silicone. However, the peroxide reaction leaves an acid residue in the rubber that can deposit a powder or "bloom" on the part surface if not removed through a postcure oven baking process. Though peroxide is still used, addition-cured, platinum-catalyzed silicones have gained wide acceptance among fabricators because of their faster cure rates, lack of peroxide bloom, and availability in an injectable, liquid form.

Platinum-catalyzed (addition-cured) silicone is supplied to fabricators in a kit containing two components, which are mixed in a fixed ratio such as 10:1 or 1:1. The kit contains a catalyst, a filler, and polydimethyl siloxane polymer. Blending of these components forms a compound ready for the vulcanization process. Besides high-consistency (gumstock) silicone rubber—which is also the form taken by peroxide-cured material—fabricators can purchase addition-cured silicone as liquid silicone rubber (LSR).

PROPERTIES

The strong silicon-oxygen chemical structure of silicone gives the elastomer its unique performance properties, including biocompatibility, superior temperature and chemical resistance, good mechanical and electrical properties, and natural clarity or translucence.

Biocompatibility. In extensive testing, silicone rubbers have exhibited superior compatibility with human tissue and body fluids and an extremely low tissue response when implanted, compared with other elastomers. Odorless and tasteless, silicones do not support bacteria growth and will not stain or corrode other materials. They are often formulated to comply with FDA, ISO, and Tripartite biocompatibility guidelines for medical products.

Temperature Resistance. Silicones can withstand a wider range of temperature extremes than nearly all other elastomers, remaining stable through temperature variations from –75° to 500°F. They can be sterilized via EtO gas, gamma or E-beam irradiation, steam autoclaving, and various other methods.

Chemical Resistance. Silicones resist water and many chemicals, including some acids, oxidizing chemicals, ammonia, and isopropyl alcohol. Concentrated acids, alkalines, and solvents should not be used with silicones.

Mechanical Properties. Silicone rubbers have high tear (to 250 ppi) and tensile (to 1500 psi) strength, good elongation (to 1250%) and flexibility, low compression set, and a durometer range of 5 to 80 Shore A. The softer forms of silicone have the ability to retain their softness indefinitely, with the softest durometers available in the form of reinforced gels.

Electrical Properties. Silicones exceed all comparable materials in their insulating properties as well as in their versatility for electrical applications. They are nonconductive and can maintain dielectric strength in temperature extremes far higher or lower than those in which conventional insulating materials are able to perform.

PROCESSING

Molding. Silicone elastomers are typically molded by three main methods: liquid injection molding (LIM), transfer molding, or compression molding. The LIM process, often chosen for high-volume applications, employs lower pressures and higher temperatures than the other molding methods—250 to 2000 psi injection pressure and temperatures of 245° to 485°F. By contrast, transfer and compression molding operate at pressures of 2000 to 8000 psi and temperatures of 200° to 370°F. In designing for the molding process, designers should take into account the material shrinkage rate, which can range from 2 to 4% depending on the type of silicone.

During molding, the three variables that must be controlled are temperature, pressure, and time. The temperature must be high enough to minimize cure times, yet low enough to prevent scorching of the elastomer. The pressure selected must allow for complete mold filling while permitting the escape of all the air, and must be optimized to prevent voids and flash. As in most molding, precise timing of all functions is critical for the production of consistently high-quality, fully cured parts.

Figure 1. The LIM process comprises meter mixing followed by mold forming/vulcanization.

Liquid Injection Molding. LIM offers many benefits in the fabrication of silicone rubber, including cleanliness and speed. In the LIM process, pumping systems deliver the two-part liquid silicone (catalyst and crosslinker) directly into a mixer for homogenization and then directly into the mold cavity, in a completely closed process (Figure 1). Molding and vulcanization (curing) occur rapidly within the mold cavity at a high temperature.

Overall, injection can take as little as 3 to 10 seconds, whereas molding and vulcanization take from 10 to 90 seconds or more, depending upon shot weight and ultimate section thickness of the part.

LIM minimizes contamination due to its closed process. Additionally, because it employs a single automated step, it provides consistent part quality with less chance for variation or human error. Other potential benefits of LIM include little material preparation labor, lower injection pressures, faster cycle rates, and the availability of fully automated systems.

Transfer and Compression Molding. Both transfer and compression molding of silicones are widely accepted and often used for medical products. Unlike the LIM process, transfer and compression molding are more labor intensive and require separate premixing of the rubber on a two-roll mill. Also, because these processes must be operated at lower temperatures, operating cycles are longer. Given the slower curing times, it is not uncommon to see large molds with 100 cavities or more for diaphragms, bottle closures, O-ring seals, and other applications.

In transfer molding, a hydraulic ram displaces rubber through the gates and sprues into the cavities. Compression molding differs in that the rubber is physically placed into the cavities and it is the closing action of the mold that completes the fill.



Figure 2. Extrusion steps include (left to right) mill blending, extrusion feed, pin and die profile forming, and vulcanization.

Extrusion. High-consistency silicone rubbers can be extruded to yield a broad range of tubing and profiles (extrusion is not generally feasible with liquid silicones). The extrusion process begins with the two-part gumstock (catalyst and crosslinker) being blended on a two-roll mill (Figure 2). The blending yields a homogeneous compound, which is formed into strips and fed continuously into the extruder. A variable-speed screw feed is used to maintain proper pressure at the pin and die. Once extruded, the tubing passes through hot-air vulcanization ovens, in which heated air or radiant heat cures the product. During the extrusion process, laser micrometer checks are often performed to help ensure proper dimensional control.

The extrusion process is able to produce single-lumen, multilumen, and coextruded tubing in a variety of diameters. Profiles or nonround cross sections can also be made from silicone for such applications as instrument stands, clips, gaskets, seals, ties, and markers. Specialized properties include x-ray opacity in stripe or opaque form, to enhance product visualization, and reinforcing to provide added strength, electrical conductivity, and kink or stretch resistance.

Examples of extruded silicone products include catheters, drain and fluid-path tubes, gaskets, ribbon, sheathing, balloon cuffs, and coextruded electrical conductors with integrated fluid-path lumens.



Figure 3. An example of a multicomponent silicone assembly, the catheter pictured above was produced using molding, wire encapsulation, bonding, tip beveling and coating, and hole drilling.

Assembly. There is almost no limit to the configurations in which two or more silicone rubber components can be joined to create assemblies for particular functions (Figure 3). The most common assembly methods for joining multiple silicone subcomponents include insert molding and bonding. The insert molding process involves injection molding around an existing part or parts. Bonding normally entails joining one or more silicone components together with silicone adhesives. Other assembly methods include tipping, reinforcing, dipping, and cuffing.

Silicone tubing can accommodate a range of lumen configurations to conform to application requirements.

Some silicone fabricators can provide subcomponent assembly in special environments—for example, cleanrooms and HEPA-filtered facilities—to meet OEM cleanliness requirements.

Secondary Operations. Full-service silicone fabricators can offer a range of secondary operations to satisfy specialized product requirements. Among such processes are silk-screening, slitting, punching, beveling, bundling, and functional testing.

MATERIAL COMPARISONS

Silicone rubber compares favorably with a number of other materials that might be considered for similar device applications—especially in the critical area of biocompatibility, but also regarding a variety of physical characteristics. For example, silicone offers greater clarity, better electrical-insulation properties, and superior lot-to-lot consistency than latex—not to mention the concerns regarding allergic reactions in latex-sensitive individuals. Silicone is more inert than PVC and contains no additives (such as plasticizers) that can leach out of the material. In general, silicone is clearer, more stable over a broad temperature range, and has a lower compression set than polyurethane, besides being provided in softer grades. And compared with most thermoplastic elastomers, silicone provides enhanced chemical resistance as well as more options for sterilization.

VENDOR CONSIDERATIONS

When evaluating silicone rubber as a potential material for a medical component or product, manufacturers should examine their possible need for design assistance, prototyping, material and part testing, and determination of cost-effectiveness. Whereas silicone rubber may have a higher cost per pound than other common elastomers, the potential for tooling, prototyping, and manufacturing efficiencies with silicone can often help manufacturers realize substantial savings.

Precision inspection capabilities are among the qualifications that manufacturers should expect in a silicone fabricator. Photo courtesy of Vesta Inc. (Franklin, WI)

Once a device company has determined that silicone rubber is the right material for a part and has selected a fabrication process, the firm should consider diverse qualifications when choosing a silicone fabricator.

Engineering and Design. A potential fabricator should be well staffed with experienced engineers who can help a company refine its concepts and design the custom tools to produce them. The fabricator should offer a choice of prototyping methods and be able to provide the required secondary operations.

Materials Expertise. Does the fabricator have the expertise and experience to aid in selecting the proper silicone compound for a particular application, and can it supply that grade? Engineers should also be available to help evaluate the physical specifications of the product and determine the optimum process parameters.

Manufacturing Capabilities. An important qualification is whether the fabricator maintains manufacturing facilities compliant with the quality system regulation. Depending on the project, it may be required for the vendor to be capable of both short and long runs and both low and high volumes. Does the vendor have advanced molding and extrusion equipment, including LIM equipment? Does it offer assembly, wash, and packaging operations? If cleanliness is an important specification for a part, does the vendor have a controlled environment in its manufacturing area?

Quality. With quality demands becoming more stringent throughout the device industry, a preferred fabricator should practice audited quality control production in its facility. Other important capabilities include the availability of advanced inspection equipment such as video microscopes and laser micrometers and the experience in raw-material testing, in-process inspection, statistical process control, and end-product testing. The vendor should also be able to perform 100% inspection or testing, when specified.

CONCLUSION

Silicone offers a range of well-established benefits for the production of medical products, including superior biocompatibility, good mechanical characteristics, chemical and temperature resistance, and processing flexibility. With its long history of successful use in the industry and unique combination of properties, silicone is well positioned to meet the ever more demanding material requirements of device manufacturers.

BIBLIOGRAPHY

Johnson, Virgil J. "Injection Molding with Liquid Silicone Rubbers: Using Process Design to Maximize Results." Medical Plastics and Biomaterials 4, no. 6 (1997): 26–33.

Lynch, Wilfred. Handbook of Silicone Rubber Fabrication. New York: Van Nostrand Reinhold, 1978.

Winn, Alastair. "Factors in Selecting Medical Silicones." Medical Plastics and Biomaterials 3, no. 2 (1996): 16–19.

Wolf, Byron E. "Comparing Liquid and High Consistency Silicone Rubber Elastomers: Which Is Right for You?" Medical Plastics and Biomaterials 4, no. 4 (1997): 34–40.

Charles Heide is market development manager at Vesta Inc. (Franklin, WI). The company manufactures silicone products through extrusion, liquid injection molding, and transfer molding.


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Copyright ©1999 Medical Device & Diagnostic Industry