Medical Device Link.

Next-Generation Lithium-Ion Polymer Batteries Offer Improved Run Times, Increased Safety

New developments in lithium-based batteries have the potential to revolutionize the portable medical device industry. Lithium-ion (Li-ion) polymer batteries promise to vastly increase the run times of devices, are rechargeable, and weigh less and take up a smaller amount of space than conventional Ni-Cad and nickel-hydride batteries.

In addition, Li-ion polymer batteries, unlike standard Li-ion batteries, can be molded into any shape necessary since they use a gelatinous electrolyte in place of a liquid. Consequently there is no danger of leakage, the primary reason that traditional Li-ion batteries are flammable and prone to sparks. Finally, Li-ion batteries do not contain toxic heavy metals.

Lithium-ion polymer batteries such as the PowerPad 160 from Electro Fuel (Toronto) offer increased run times in a smaller package.

A number of companies have been working on these developments. Among these is Electrofuel (Toronto), which unveiled its Powerpad 160 Li-ion polymer battery in 1999. It offers an energy density of 470 W/L (183 Wh/kg), considerably higher than the 200–250 W/L common for conventional batteries. According to vice president of marketing David Murdoch, this marks the "biggest jump in energy density in the history of batteries."

The Powerpad 160 also has other advantages in comparison to standard batteries, Murdoch adds. First, it can function for 20,000 cycles (one cycle consists of a charge and discharge). Second, the battery's high density can help eliminate bulk.

Batteries achieve 16-hour run time in tests

Murdoch mentions that the battery powered an IBM 600-MHz laptop computer for 16 hours in tests, compared to the 2 hours of run time typical of conventional batteries. He indicated that hospitals have expressed interest in using the batteries with notebook computers used in bed-to-bed applications.

The company is interested in using the batteries in pacemakers, but is not focusing on medical possibilities in the near term because of obstacles in scale-up to mass production.

The Powerpad 160 comes in a standard A4 footprint and weighs 2.2 lb. Electrofuel is expecting to release a battery with an energy density of 225 Wh/kg (600 Wh/L) in 2001.

One company not experiencing difficulty in producing large quantities of batteries is Valence Technology (Henderson, NV). The company has been shipping its manganese Li-ion polymer batteries to customers for more than a year from its factory in Northern Ireland, which has the capacity to produce up to 15 million batteries a year.

Bill Battison, vice president of marketing for Valence, touts size flexibility as a main selling point. The company offers five sizes, including one that measures 8 x 12 in., and can also build the batteries to custom specifications.

An earlier problem involving low cycle life has been solved, according to Battison. The batteries now offer more than 1000 cycles at room temperature. The 4 x 4-in. battery has an energy density of 157 Wh/kg; the largest battery can provide 4.6 A/h of power.

Valence is focusing on applications with large footprints, including defibrillators and portable noninvasive medical devices, as well as cell phones and notebooks.

Illion Technology Corp. (Plymouth Meeting, PA), a product of a recent merger between Lithium Technology Corp. and Pacific Lithium Ltd. (Auckland, NZ), is planning to offer a Li-ion polymer battery based on Lithium Technology's proprietary fiber-web substrate technology.

The company will construct its batteries using Pacific Lithium's high-performance fibers and composite battery structures using continuous-flow fiber-web coating and handling methods. The company is ready to begin "large production [of the batteries] on a joint-venture basis," according to David Cade, chairman and chief executive officer of Illion Technology.

Toshiba America Electronics Inc. (Irvine, CA) recently began offering its Advanced Lithium Battery. Because it is devoid of liquid, the company plans to eliminate protection circuitry in this product by the end of this year. This should lower the cost and space required for the battery pack, giving "customers additional space to use a larger cell," says Ritch Russ.

Companies are taking different approaches

Toshiba America Electronics projects production to increase to 1 million cells a month by April, up from 500,000 cells in January.

Moltech Corp. (Tuscon, AZ) has taken a different approach through its development of a high-performance lithium-sulfur (Li-S) battery. Its technique creates a kind of 100-µm thin-film sandwich out of lithium and sulfur, which allows for a much lighter and thinner battery cell, according to David Williams, director of sales and marketing.

The company plans to offer the battery by the end of this year. The cells will have a voltage rating of 2.1 V per cell and an energy density of 200 Wh/kg (260–300 Wh/L), and will measure only a few millimeters thick, said Williams.

Also taking a different tack is Saft America (San Diego). It is offering what is described as the first medium prismatic batteries, according to product manager Andy Bartocci. Bartocci claims that the MP-series batteries provide the highest capacity on the market in a single cell, and that they can replace several cylindrical cells in a parallel arrangement.

The three versions of the batteries offer 1.8 Ah, 3.9 Ah, and 5.5 Ah, compared with 1.5–1.6 Ah for a conventional Li-ion battery. Using four MP 174865 batteries (with 3.9 Ah each) in a laptop computer allowed for 4 hours of run time.

Initial plans for the batteries include use in cell phones, laptop computers, and related equipment. Bartocci adds that the batteries are being considered for several medical applications, including defibrillators, artificial hearts, laptop oxygenators, diagnostic equipment, instrumentation, and blood and infusion pumps.—David Bowen

Device-Related Testing and Laser Marking Systems Displayed at Electronics Show

Medical device engineers attending NEPCON West 2000 held February 29–March 2 in Anaheim, CA, were met by nearly a thousand exhibitors serving the electronics manufacturing industry. The range and diversity of products and services featured at the show—the largest of its kind in North America—is too great to capture in one article. Featured below are some of the most innovative products that caught our eye.

Fischer Technology (Windsor, CT) displayed the Fischerscope XDVM, an instrument that measures the coating thickness and alloy composition of nearly any metal coating system, including single, binary, and ternary alloy coatings; double coatings; double coatings with one alloy layer; and triple coatings. The technology involves bombarding the sample with x-rays, causing its coating to fluoresce. The instrument can then distinguish various coatings because they flouresce differently.

The system uses a microfocus x-ray tube, Ni and Be primary filters, a xenon-filled proportional counter tube (with internal 4096-channel ADC spectrum processing with compression to 256 channels for external display), and four focal planes for measuring close to steps and inside recesses with height differences up to 90 mm.

Despite the Fischerscope's high-tech capabilities, it has been designed with ease of use in mind. When the company representatives demonstrated several tests, the results were immediately available. The instrument is suited for high-volume coating thickness measurements on electronic components such as screws, connector contacts, contact strips, and PC boards. Specific medical applications include checking coatings on heart valves, hip joints, and medical tools and instruments.

AlphaGary Introduces Economical Silicone Replacement

Thermoplastic elastomer compounds for molding and extrusion applications have been launched in North America as a cost-effective replacement for silicone in disposable medical devices. The Evoprene Super G compounds reportedly allow users to benefit from the materials' elasticity and processing ease without sacrificing the critical properties of silicone.

Evoprene compounds combine elasticity and processing ease.

"Evoprene compounds will provide customers in the disposable medical device market with a new, innovative replacement in areas where thermoset silicone typically has been the only available material," announced Robert Gingue, managing director, worldwide, for AlphaGary Corp. (Leominster, MA).

Desirable properties of the styrenic-based TPE materials include their compression set characteristics, temperature resistance, and tensile strength. The compounds, which have been used in Europe for several years in a variety of industrial and consumer applications as well as in regulated industries, can be processed using standard thermoplastic equipment. They generally do not require predrying and are free of halogens.—Norbert Sparrow

Material Mimics Blood Vessel Lining to Prevent Thrombosis

By binding heparin to an artificial surface and promoting sustained anticoagulation, a coating process reportedly yields highly thromboresistant surfaces. The Carmeda BioActive Surface (CBAS) is the only commercially available material and technology able to achieve these results for a sustained period of time, according to Carmeda (San Antonio, TX).

A coating technology that prevents blood clotting is routinely used on ventricular assist devices and other critical medical equipment.

CBAS works by mimicking the endothelial lining of blood vessels with which invasive devices come into contact. The natural vessel wall carries molecules similar to heparin that prevent blood from clotting in blood vessels. More than 200 scientific papers and clinical studies have demonstrated the safety and efficacy of the blood-compatible material, reports the firm.

"There are several thromboresistant technologies on the market," says director of business development Andrew Jacobson, "but what makes CBAS unique is its sustained activity. CBAS has been proven in research and clinical settings to retain substantial bioactivity for periods lasting several months, possibly longer," Jacobson stresses.

The process has been licensed to Johnson & Johnson, Gore, Medtronic, and other device firms for use in specific applications. CBAS is suited for use on coronary stents, heart bypass equipment, implantable sensors, vascular grafts, circulatory devices, venous catheters, and related medical devices.—Norbert Sparrow

Material Matters and Devices a Focus of NPE Conference

The spirited debate on the use of PVC that has rocked the medical device industry moves to NPE 2000 in June. A discussion of the material's current status and its prospects for continued applications in healthcare is the topic of one of five conference sessions devoted to the use of polymers in the device industry. Titled Medical Productivity Through Innovation, the conference runs concurrently with the triennial plastics show that is held at Chicago's McCormick Place from June 19 to 23.

Scheduled to be moderated by Robert Portnoy of Exxon Chemical Co., the conference also includes a session on the use of polymers in advanced medical device and biomaterial applications presented by Jon Katz, editor of MPMN's sister publication Medical Device & Diagnostic Industry. "Recent breakthroughs in biotechnology and medicine have been said to herald the dawning of an entirely new era, and plastics are playing a critical role in many of the emerging technologies," says Katz. Areas under development range from drug delivery and artificial organs to tissue engineering and bioactive surface modification, adds Katz, and include advances in cardiovascular, ophthalmic, and orthopedic biomaterials.

A number of issues related to the use of polymers in medical equipment will be discussed at this year's NPE show.

Other sessions include an overview of current and emerging sterilization methods presented by William Young of Griffith Microscience, a look at regulatory and liability issues spearheaded by John Luedke of Covington and Burling, and a paper on developments in plastics biocompatibility testing and international standards from Paul Upman of North American Science Associates Inc. Len Czuba from Herbst Lazar Bell Inc. will address the PVC issue. Numerous other conference sessions devoted to horizontal plastics-related processes, equipment, and materials are also scheduled. Conference sessions focusing on the medical market are scheduled for June 22; admission is free to registered show visitors.

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