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Articles from 2002 In March


Low-power microchip brings music to users' ears, rhythm to ailing hearts

Originally Published MPMN March 2002

SPECIAL

Low-power microchip brings music to users' ears, rhythm to ailing hearts
This behind-the-ear hearing aid uses the Babel 24 microchip from Zarlink Semiconductor and Cochlear Ltd. to process sounds at low power levels.

A mixed-signal microchip designed to minimize power loss may be the missing component needed to make smaller hearing aids and pacemakers with extended battery lives. Codesigned by Zarlink Semiconductor (San Diego; www.zarlink.com) and Cochlear Ltd. (Sydney, Australia; www.cochlear.com), the Babel 24 microchip is constructed in a special complementary metal-oxide semiconductor (CMOS) technology that is configured for power efficiency rather than speed. "About 90% of CMOS devices on the market are configured for speed, which is required for many applications but also demands a lot of power," says Zarlink director of medical product marketing François Pelletier. "Our chip is designed with low-leak transistors and special drain techniques for the remaining 10% of applications in which extending battery life is more important."

The Esprit 3G hearing aid is one of the first products to benefit from this novel technology. Marketed by Cochlear, the low power requirement for this device enabled all external components to be condensed into a single speech-processor box that is small enough to wear behind the ear, making it the world's first behind-the-ear speech processor for people with severe hearing impairments. "The Babel 24 microchip used in this device draws less than 2 mA at 3.7 V," says Pelletier. "That's about one-tenth the power requirement of other products on the market." Pelletier estimates that the chip extends the unit's battery life to 2 weeks. Despite low power requirements, however, the chip remains powerful enough to process signals from the aid's internal telecoil and plug-in FM receiver in addition to performing standard functions.

Pacemakers also stand to benefit significantly from this technology due to the difficulties incurred during battery replacement. "Speed is not really a concern for pacemakers, which run in frequencies of megahertz rather than kilohertz," says Pelletier. "Instead, it's more important that the batteries last as long as possible since replacement is impractical." The Zarlink and Cochlear pacemaker chip draws 5 mA at 3 V, allowing unit batteries to last for up to 8 years.

But pacemakers and hearing aids are not the only devices that can use this technology. "Right now we're developing these chips for brain stimulators, bladder control devices, and even a swallowable camera," notes Pelletier.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Biocompatible foam suitable for bone augmentation

Originally Published MPMN March 2002

SPECIAL

Biocompatible foam suitable for bone augmentation

A patented thermoplastic syntactic foam was developed by the R&D division of Boeing Phantom Works (St. Louis, MO; www.boeing.com) to eliminate electromagnetic interference in antenna units mounted in the wings of F/A-18E/F Super Hornet carrier-based aircraft. It soon became apparent, however, that the biocompatible material with strength, density, and porosity properties similar to natural bone may have other applications.

The foam consists of a solidified mixture of hollow 90-µm-diam silica spheres. A polymer such as polyethermide is used to wet and bind the microballoons into an array to create porosity. Researchers found that the material effectively conducts bone into the porous implant via its controlled interstitial porosity. The foam can be molded or machined into complex structural shapes, and its density and porosity can be engineered to closely mimic natural bone tissue.

Boeing has donated the patent covering the foam's medical applications to the University of Pennsylvania (Philadelphia; www.upenn.edu), where researchers will continue its development. "We concluded that the best way to complete the technology development and recognize its full potential was to donate it to the University of Pennsylvania, an institution with a top-notch orthopedic facility," says Boeing vice president of intellectual property business Gene Partlow. "The university's technology transfer office has an outstanding record of successfully commercializing medical technologies."

Currently, the foam is being rigorously tested at the university's Center for Technology Transfer. "The foam has already been shown to allow regrowth of cancellous bone tissue, which is a porous proto-bone tissue," says director of licensing Tom Fitzsimmons. "We are still conducting tests to determine whether the foam can replace cortical bone, which is the strong, load-bearing tissue, once the material has established a beachhead with the cancellous tissue ."

According to Boeing, more than one million patients a year require bone augmentation. Thermoplastic syntactic foam could be used to repair bone defects, provide prostheses for maxillofacial reconstruction, serve as intervertebral spacers, and be used to fabricate orthopedic and other implants.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Electroactive polymers flex their muscles

Originally Published MPMN March 2002

SPECIAL

Electroactive polymers flex their muscles
Polymers that lengthen and bend like natural muscles with the application of electrical current may be used to create robotic systems that are flexible and damage tolerant.

Imagine an artificial muscle made of plastic that could defeat its human counterpart in an arm-wrestling match by flexing and stretching in response to an electrical stimulus. It might seem like an unusual application for a new kind of intelligent plastics called electroactive polymers (EAPs), but it is just one of many being developed at NASA's Jet Propulsion Laboratory (Pasadena, CA; www.jpl.nasa.gov). Based on work dating back to an 1880 experiment performed by Wilhelm Roentgen, EAPs may help designers simplify a range of mechanical tasks by emulating the qualities of biological muscles. "With these materials, it will someday be possible to produce biologically inspired robotic systems that are agile, resilient, damage tolerant, noiseless, and lightweight," says senior research scientist and group leader Yoseph Bar-Cohen.

EAPs are generally classified into two types by the movement they offer: bending or stretching. Bending plastics are constructed of flexible ribbons of carbon, fluorine, and oxygen molecules. When electricity is applied to the ribbon, charged particles in the polymer are pushed or pulled to either side depending on polarity, causing the material to bend. Stretching EAPs consist of thin plastic sheets that are wrapped into cigarlike cylinders. When a positive charge is applied to one end of the cylinder and a negative charge to the other, the sheets contract toward the center of the tube, forcing a lengthwise expansion of as much as 380%. Activation charges for these plastics range from one to several thousand volts.

With high actuation displacement and force, EAP materials should have many applications in the medical field in years to come. One of the most interesting is the replacement or augmentation of damaged human muscles. Other possible uses include catheter-steering mechanisms, miniature in vivo diagnostic and microsurgery robots, and interface devices used to connect neurons and electronic devices. And while many of these materials are not yet robust enough for commercial use, Bar-Cohen remains confident about their potential. "My hope is someday to see a handicapped person jogging to the grocery store using this technology," he says.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Resorbable implants advance craniofacial surgery

Originally Published MPMN March 2002

SPECIAL

Resorbable implants advance craniofacial surgery

Craniofacial surgery can greatly improve the lives of patients with abnormalities. The invention of a new product can not only ensure that these procedures achieve dramatic results in correcting deformities, but also solve problems than can arise when traditional methods are used.

Until now, surgeons have used metal implants to reconstruct and repair facial bones. Although the surgeries are generally successful, there are drawbacks to the use of metal. The most significant is that it must be removed after the bones have healed. This exposes the patient to another surgery, which always poses a risk. Additionally, scatter artifact of the metal plates obscures the surgical field in MRI and CT scans, and the presence of metal can complicate tumor treatment.

A product that is strong enough to hold bones together while they are mending, yet completely resorbs into the body when healing is complete, would be the answer to these problems. Realizing the promise of such a substance, two plastic surgeons in San Diego, Steven R. Cohen, MD, and Ralph E. Holmes, MD, and members of the craniomaxillofacial/neuro business unit of Macropore Biosurgery Inc. (San Diego; www.macropore.com), decided to team up. Their first project was to create a resorbable implant for a procedure used to correct the Crouzon's syndrome midface deformity in children.

Like many other craniofacial surgery procedures, the LeFort III distraction has required the use of titanium plates and screws to fix the facial structure. While this system has often worked, "patients spent long periods of time in external or internal metal devices," says Cohen. Additionally, according to Cohen, the plates and screws were difficult to remove after completion of the procedure.

The partnership came up with a resorbable distraction system that is manufactured from a medical-grade 100% amorphous polylactic acid copolymer 70:30 Poly(L-lactide-co-D, L-lactide), which retains approximately 70% of its initial strength after 9 months and 50% after 12 months. The implants metabolize into carbon dioxide and water following a process of bulk hydrolysis and resorb completely in approximately 18 to 36 months. This eliminates the need for removal procedures while avoiding long-term palpability and ambient-temperature sensitivity.

"The use of bioresorbable materials in medicine has great potential," says Cohen. "Some of the uses I anticipate include drug delivery, stem-cell container devices, ear shunts, soft-tissue reconstruction in ear and nasal passages, coronary artery stents, and treatment of burn victims."

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Guidewire material eliminates superelastic plateau

Originally Published MPMN March 2002

SPECIAL

Guidewire material eliminates superelastic plateau
A guidewire material combines stiffness and straightness with flexibility and kink resistance.

At its booth at the Medica show in Düsseldorf, Germany, the company Furukawa Electric Europe Ltd. (London; www.fitec.co.jp/ftm/nt-e) introduced visitors to a high-stiffness guidewire with no yield point and no superelastic plateau. The guidewire material, called FHP-NT, is unique in its combination of stiffness and straightness (the material is nearly as stiff as stainless steel) with flexibility and kink resistance. FHP-NT offers high torque transmission and is designed to allow medical manufacturers to produce guidewires without infringing on a well-known international patent. According to Andrew Proffitt, technical sales manager at Furukawa, this is a "tremendous opportunity."

Proffitt explains that Furukawa melts the nitinol alloy in-house, which provides the company with a high degree of control over the material. "We are a raw material supplier, but we have expertise in the medical industry. This allows us to develop different grades of alloy for specific applications," he says, noting that the company supplies nitinol in coil springs, tube, and wires. Proffitt adds that visitors at the show expressed high interest in Furukawa's FHP material.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Antimicrobial systems multiply

Originally Published MPMN March 2002

SPECIAL

Antimicrobial systems multiply
A plastic compound incorporating an antimicrobial agent prevents the growth and migration of microorganisms on medical devices.

While basic hygiene procedures are the major factor in controlling bacterial infections, the use of antimicrobial systems in plastics can offer added protection at the product level. Two new silver-ion products from plastics suppliers promise to give medical devices antimicrobial qualities.

"Antimicrobial systems are no longer used only to protect a plastic material itself from degradation by microorganisms, but also to affect microbe populations found at the surface," says Julie Simmons, chemist at Wells Plastics Ltd. (Stone, Staffs, UK; www.wellsplastics.com). Wells is a compounder of additive master batches. The company has developed a technology that encapsulates silver-ion antimicrobial systems within a soluble matrix. According to Wells, use of the silver-ion formulations in wound dressings, urinary catheters, and other medical products can help to reduce infection.

Tests conducted by the company on polymeric tubing and fibers have shown the efficacy of the antimicrobial systems. Plastic tubing containing 2% of a silver-ion master batch was tested against Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. Against initial inoculum concentrations of 10,000 to 80,000 bacteria, the tubing achieved reductions of log 3, or 99.9%, reducing each of the three bacteria populations to <100 colony-forming units.

Meanwhile, another plastics company, Ensinger GmbH (Nufringen, Germany; www.ensinger-online.com) has joined forces with a firm offering antimicrobial technology to produce plastics that contain their own disinfectants. The firm recently signed an agreement with AgION Technologies (Beverly, MA; www.agion-tech.com) allowing it to offer plastic incorporating AgION's antimicrobial compound.

The AgION material is based on a silver-ion delivery system that prevents the growth and migration of bacteria, yeast, mold, and fungus on any product to which it is applied. The plastics offered by Ensinger constitute new antimicrobial compounds that combine the inorganic silver ions with a patented delivery structure.

Ensinger medical marketing specialist Fran Alder says that the company has an exclusive license to add AgION to nylons, and a nonexclusive license to compound it with other plastics. "This material addresses a critical issue with plastics," he says. "Are you really sterilizing plastics when you follow autoclaving procedures?"

Applications of the new compounds thus far have included surgical instrument handles and thermoformed trays.

The antimicrobial agent is able to withstand pH levels from 3 to 10 and temperatures up to 800°C, which makes it compatible with virtually any manufacturing and operating environment. In an acute oral toxicity study, the AgION agent was shown to be less toxic than ordinary table salt. The material has passed the ISO 10993-1 biocompatibility test for medical implants.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Company develops viable method for fabrication of LCP flexible circuits

Originally Published MPMN March 2002

SPECIAL

Company develops viable method for fabrication of LCP flexible circuits
Flexible circuits based on liquid-crystal polymer dielectric film feature low moisture absorption.

Flexible circuits based on liquid-crystal polymer (LCP) dielectric film feature properties superior to more commonly used polyimide-based components, but they have had limited acceptance. LCP is difficult to process, which has precluded its use as an alternative material in many cases. Now 3M Microinterconnect Systems Div. (Austin, TX; www.3m.com/microflex) has developed a fabrication process that will make LCP-based flexible circuits a feasible technology for a number of applications, according to the firm.

The LCP substrate has some uniquely desirable properties, according to marketing manager Bill Balliette. "The primary benefit is its low moisture-absorption and gas-transmission rates," he says. LCP has a water absorption rate of 0.1%, whereas polyimide has a 1 to 3% rate. Consequently, LCP flexible circuits are suited for applications where device electronics are in close proximity to a fluid or gas, raising concern about cross-contamination. "Bioanalytical equipment as well as electronic devices that undergo frequent sterilization with some kind of fluid or gas" are among key applications, says Balliette.

LCP offers dimensional stability with respect to changes in humidity and temperature, a property that benefits circuits to which numerous small elements are bonded. "As more and more elements are added to electronic components and they are made smaller and smaller, you end up with a potential manufacturing problem," says Balliette, who cites the example of multielement transducers used in ultrasound equipment. "When you're ready to bond that sensor element, the leads may not line up properly. The more dimensional stability you have in the material, the greater your ability to make that sensor array larger to cover more ground and capture more data."

3M processes its LCP flexible circuits in a manner similar to its polyimide-based components. "We build up the metal in a vacuumization process," says Balliette. This presents a number of advantages compared with laminating a copper foil over a substrate, which is how competing products are often fabricated. "When you etch away the laminated copper foil from the surface, it leaves the surface a lot rougher and you can't really get down to a fine pitch. The copper has a tendency to peel off," he says. "Vacuum metallization, on the other hand, lets you get to a very fine pitch and the copper traces still adhere to the substrate," Balliette adds. The chemical etching process, which is unique to 3M, and an absence of adhesives add value to the product.

LCP flexible circuits are designed to meet the needs of sophisticated electronic assemblies used in digital hearing aids, ultrasound transponders, and similar devices. The firm will present technical data on the product's reliability at the International Conference on Advanced Packaging and Systems (www.imaps.org) in Reno, Nevada, on March 10–13.

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Emerging Technologies

Originally Published MPMN March 2002

SPECIAL

Emerging Technologies

A survey of new products and processes that will affect medical device design

Light-emitting polymers have glowing future

Constructed of light-emitting polymers, this 2.8-in. full-color display was jointly developed by Cambridge Display Technology and Seiko Epson Corp.

Special plastics that emit light when subjected to electrical current will provide the basis for developing thin, inexpensive color displays in the near future, predict researchers at Cambridge Display Technology (Cambridge, UK; www.cdtltd.co.uk). Discovered in 1989 by the company founder, light-emitting polymers (LEPs) could revolutionize sonography and other video display equipment by offering a durable technology that can be powered by two AA batteries. "With low power requirements and a thin-film design, these materials hold great promise for the medical device industry," says vice president of business development Stewart Hough.

LEP displays are constructed by applying a layer of the conjugated polymer material onto a glass or plastic substrate that has been coated with a transparent electrode. After the metal electrode has been sputtered or evaporated onto the top of the LEP, the application of electricity causes the polymer to emit light. Capable of providing the full RGB color spectrum, these displays have typical activation currents of 2–5 V and can be manufactured in a variety of sizes. "We've constructed units that measure 15 in. diagonally in the lab, but there are no theoretical size limitations with this technology," says Hough. "In the long term, I expect that production of 1 x 1-m displays will not be uncommon."

As LEP displays can be fabricated on a single sheet of glass or plastic, they offer manufacturers reduced production costs when compared with some liquid-crystal, field-emission, or plasma units. Submicrosecond response times that are unaffected by temperature and wide viewing angles are also cited as benefits. "Because the LEP film used is so thin, light is emitted very near the surface of the display, resulting in an image that can be viewed from almost any angle without color shifting," explains Hough. These features should prove attractive to manufacturers, and Hough expects to see commercialization of LEP products by the second quarter of 2002.

More:
Company develops viable method for fabrication of LCP flexible circuits
Antimicrobial systems multiply
Guidewire material eliminates superelastic plateau
Resorbable implants advance craniofacial surgery
Electroactive polymers flex their muscles
Biocompatible foam suitable for bone augmentation
Low-power microchip brings music to users' ears, rhythm to ailing hearts

Benjamin Lichtman, Norbert Sparrow, Katherine Sweeny, Zachary Turke, and Susan Wallace

Copyright ©2002 Medical Product Manufacturing News

Light-Curing System Site Upgraded

Originally Published MPMN March 2002

E-NEWS

Light-Curing System Site Upgraded
www.efos.com (click to enlarge)

To reflect Efos's name change to Exfo Photonic Solutions Inc., an updated Web site has been launched at www.efos.com. The site incorporates functional features that provide information on the company's light-based solutions. "The objective of the new site is to allow our existing and future customers to educate themselves on the capabilities of our light curing systems," says market development manager Ken Davis. A download section gives access to product specification sheets, application notes, industry papers, and animations of optical solutions. A virtual-reality tour of the company's facility is also available.

In the customer support section, a locator allows users to find the closest representative and distributor by rolling a mouse over a map. A comprehensive news section is updated daily to inform users of trade show and seminar locations, as well as any activity from the Exfo group of companies.

Katherine Sweeny

Copyright ©2002 Medical Product Manufacturing News

Downloadable Program Allows Product Experimentation

Originally Published MPMN March 2002

E-NEWS

Downloadable Program Allows Product Experimentation
ftp://ftp.ascension-tech.com (click to enlarge)

Manufacturer of motion-tracking devices Ascension Technology Corp. has released a software program that allows experimentation with its products in a standard Windows environment. Available for free download at ftp://ftp.ascension-tech.com/pub/ascension-tech.com/winBIRD/, WinBird helps users to learn about their tracking system and its capabilities.

Usable with single- and multisensor or multitransmitter configurations, the program enables users to change major device and system options to monitor how the changes affect returned data. On devices that support distortion detection, WinBird helps measure the amount of metal and noise interference in the environment. For multiple-transmitter systems, easy switching is achieved; for multisensor systems, sensors are separately displayed.

Download instructions and a Windows installer are available on the company's ftp site.

Katherine Sweeny

Copyright ©2002 Medical Product Manufacturing News