Originally Published MPMN October 2009

BREAKTHROUGHS

Firm Severs Ties with Electronic Devices

Bob Michaels

Imagine a high-wire act without the use of a wire, as a memorable New Yorker cartoon once did. Impossible, you'd say, and you'd be right. But imagine powering a host of electronic devices—including medical implants and handhelds—without wires, cords, or batteries. Impossible, you'd say, but you'd be wrong. WiTricity Corp. knows better.

The company will soon be marketing a family of components that can power devices without resorting to an ac power source or batteries. “Our technology is based on a phenomenon known as highly resonant magnetic coupling,” explains David Schatz, WiTricity’s director of business development and marketing.
The invention is based on a pair of structures called resonators, or coils, that resonate at the same matched frequencies and exchange energy via a magnetic field. “The idea is that you excite a power-source coil with a high-frequency alternating current, and that alternating current then induces a magnetic field,” remarks Schatz. “If you bring one of the matched resonators into range, the resonating magnetic field that’s created by the source induces an alternating-current flow on the power-capture device, which you can then tap into and use to power devices directly or convert to direct current and charge batteries.”
Conventional transformers do not exhibit this coupling characteristic, according to Schatz. If transformer coils are pulled apart from each other, they cannot exchange energy. “What we figured out is how to design and operate two coils in such a way that you can pull them apart from each other, and they will still couple quite efficiently at distances of even several times the diameter of the coils.”
For energy exchange to take place, oscillating magnetic fields are crucial. “We’re not moving electricity through the air using electric fields,” Schatz notes. “All the electricity per se is held in these coils. And the medium that’s being used to transfer energy from one coil to the other is an oscillating magnetic field.”
In the medical device realm, the company hopes to develop power sources for transcutaneous energy-transfer systems, which could replace traditional induction for transferring energy to implanted devices such as neurostimulators, pacemakers, and heart pumps. Currently, such implanted devices incorporate batteries, and patients have to wear an external power source. If WiTricity’s technology catches on, OEMs may be able to relax the requirements for positional alignment between the implanted capture device and the external power source.
A host of instruments and devices used in hospitals may also benefit from the company’s wireless technology. “If completely sealed devices can be built that prevent the entry of bacteria but can be charged or powered at a distance, that could be a really good enhancement of mobile powered instruments and devices,” Schatz adds.

WiTricity Corp.
Watertown, MA
www.witricity.com
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