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Monday, 25 August 2014

Wireless Power for Minuscule Medical Implants

Comment: And the wider applications?



Medical implants like pacemakers, deep brain stimulators, and cochlear implants could someday be joined by still more bioelectronic gadgets—devices that regulate insulin levels, control appetite, lower blood sugar, or treat brain injuries (see “Nerve-Stimulating Implant Could Lower Blood Pressure”).

But before we’re all riddled with electronics, researchers have to figure out how to power it all. Pacemaker batteries are too clunky for tiny devices saddled up to nerves, and existing wireless methods, such as those used for cochlear implants, won’t work with devices buried deep in the body.

That’s where electrical engineer Ada Poon and her team at Stanford University say they might be able to help. The group has developed a new method of sending magnetic fields well below skin level to power devices that would otherwise need batteries.

Wireless systems like the one used in cochlear implants sit permanently on the skin and derive power from electromagnetic induction, in which a current running through a coil of wire generates a magnetic field that then induces a current in a nearby device. The problem is that a field generated this way decays exponentially with distance from the generating coil, so it only works with devices close to the skin’s surface.

Poon and her team found a way to use electromagnetic induction through biological tissue without that exponential decay. They call the technique midfield wireless powering (as opposed to near-field, which refers to the exponentially decaying radiation, and far-field, which refers to the kind of radiation emitted from a cell tower).

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