Sound-Powered, Mini Medical Device Developed By Stanford Engineers

By Chuck Seegert, Ph.D.

Imagine a wireless implant that electronically performs its function, but requires no batteries. This reality was recently developed by Stanford engineers in a medical device that converts energy from ultrasonic waves and then wirelessly reports back when its tasks are complete.

Electronic implants have been successful in a limited number of applications. One notable example is cardiac pacemakers, which have helped many people deal with various cardiac conditions. While there have been some successes, implanting battery packs to run an electronic device often makes the implant too big for certain applications, and using wires to deliver power from a distant battery is also unwieldy.

These concerns may no longer be an issue with new “smart chips” from Stanford University engineers, according to a recent press release. The new device is designed to be powered by ultrasound, a form of energy that can be delivered through tissues safely and efficiently. Its functions are three-fold, and they include conversion of ultrasound into electricity, performing a medical function using the electricity, and reporting back with a radio signal when its function is complete. The applications may be far reaching.

"We think this will enable researchers to develop a new generation of tiny implants designed for a wide array of medical applications," said Amin Arbabian, an assistant professor of electrical engineering at Stanford, in the press release.

The team’s proof of concept device is composed of a 2.5 mm² off-chip antenna and a 1 mm x 2 mm chip designed in 65 nm CMOS, according to a paper presented by the team at the 2014 IEEE Custom Integrated Circuits Conference in San Jose, CA. The device can support a DC load power of 100 micro-watts and can run through three centimeters of chicken meat — the material used to simulate human tissue in the experiment, according to the paper.

The device is powered by the piezoelectric effect. The current version of the device is similar in size to the tip of a ballpoint pen, but the team plans to shrink it even more. This would lend the technology to many uses in the neurological space, where networks of electrodes could be used to study the brain.

"U.S. and European brain initiatives are pushing for a more complete understanding of the central nervous system," said Florian Solzbacher, a professor of electrical and computer engineering at the University of Utah and director of its Center for Engineering Innovation, in the press release. "This requires being able to interface with cells using arrays of micro implants across the entire 3D structure of the brain."

Implementing technologies that require no wires for communication or power transfer promises to take implant technology to a new level. In addition to remotely powered devices like this one, other researchers are developing wireless pressure sensors that may be used in prosthetic applications.

Image Credit: Arbabian Lab / Stanford School of Engineering