Originally Published MPMN March 2003

SPECIAL

Advances in power sources improve the lifetimes of implantable devices

Power sources for medical devices are becoming smaller, longer lasting, and more environmentally friendly. Two such technologies may soon help propel the development of implantable medical devices.

Thermo Life Energy Corp. (Palm Beach, FL; www.adsx.com) offers thin-film, solid-state batteries that are rechargeable up to 50,000 times. Compared with NiMH, NiCad, or Li-ion cells, they use less material and are less costly to manufacture. Because the batteries are solid state with no liquid components, they pose no environmental hazards in manufacturing and they can be crushed with no adverse affect.

They operate in temperatures ranging from –45° to 140°C and can last for 20 years or more. The units measure 0.1 mm thick by about 2.5 cm square. They have an ultrahigh energy density of 200 Wh/kg and can be charged to 80% of rated capacity in 3–5 minutes.

Another device may also some day power implantable medical devices. A small battery being developed by researchers at Cornell University (Ithaca, NY; www.cornell.edu), converts energy from a radioactive isotope into motion, which could then be used to power a tiny machine or generate electricity for small devices.

The batteries contain a copper strip that measures 1 mm wide, 2 cm long, and 60 µm thick. The strip is cantilevered above a thin film of radioactive nickel 63, an isotope of nickel. As the isotope decays, it emits electrons that are collected on the copper strip, building up a negative charge. The isotope film becomes gradually positively charged as it loses electrons. The attraction between the positive and negative charges causes the strip to bend down. When the strip is sufficiently close to the isotope, current flows and equalizes the charge. The strip springs up again and the cycle is repeated.

The moving cantilever can actuate another device or move a cam or wheel to generate rotary motion. If a magnetized material were attached to the strip, it could generate electricity as it moved through a coil.

According to the researchers at Cornell, the devices will work in a wide range of temperatures. Because the nickel isotope has a half-life of more than 100 years, a system using a battery based on this technology could be powered for up to 50 years.

Norbert Sparrow, Susan Wallace, and Zachary Turke

Copyright ©2003 Medical Product Manufacturing News