The development could propel a new class of medical devices that can be implanted or injected to the body without the need for bulky batteries or power cables.
"Such devices could revolutionize medical technology," said Ada Poon, an assistant professor of electrical engineering who presented her work at the International Solid-State Circuits Conference in San Francisco. "Applications include everything from diagnostics to minimally invasive surgeries."
The devices that could be made possible with this technology include stationary ones such as heart probes, chemical and pressure sensors, cochlear implants, pacemakers and drug pumps. Mobile devices could deliver drugs, perform analyses and maybe even dissolve blood clots or clear plaque from sclerotic arteries.
How it works
The device has antenna of coiled wire that picks up a signal from a radio transmitter outside the body.
As Stanford News Service explains:
The transmitter and the antennae are magnetically coupled such that any change in current flow in the transmitter produces a voltage in the other wire –- or, more accurately, it induces a voltage.
By transmitting power wirelessly like this, the transmitter can run electronics on the device and propel it through the bloodstream.
Solving an old problem
For 50 years, scientists have attempted to run implantable devices with wireless electromagnetic power but models showed that high-frequency radio waves would dissipate quickly in human tissue and fade exponentially the deeper they went.
Poon realized the assumption was incorrect. She found that while human tissue conducts electricity poorly, radio waves move easily through tissue and that little of the signal gets lost along the way.
That meant that antennae inside the body could be 100 times smaller than what was previously thought. The device she demonstrated at the conference is two millimeters square. Stanford News reports:
She has developed two types of self-propelled devices. One drives electrical current directly through the fluid to create a directional force that pushes the device forward. This type of device is capable of moving at just over half-a-centimeter per second. The second type switches current back-and-forth through a wire loop to produce a swishing motion similar to the motion a kayaker makes to paddle upstream.
"There is considerable room for improvement and much work remains before such devices are ready for medical applications," said Poon. "But for the first time in decades the possibility seems closer than ever."
Learn more about the advance in the video below:
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photo: Steve Fyffe