Sound-powered tiny implantable chip to act as medical device

Stanford scientists are working on gen-next medical devices that would be implanted deep inside the body to monitor illness, deliver therapies and relieve pain by using ultrasound to supply power wirelessly.
Providing electric power to medical implants has been one stumbling block. Using wires or batteries to deliver power tends to make implants too big, too clumsy - or both.
Now, engineers are developing a way to send power - safely and wirelessly - to "smart chips" programmed to perform medical tasks and report back the results.
Their approach involves beaming ultrasound at a tiny device inside the body designed to do three things: convert the incoming sound waves into electricity; process and execute medical commands; and report the completed activity via a tiny built-in radio antenna.

"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 University.
Arbabian's team recently presented a working prototype of this wireless medical implant system at the IEEE Custom Integrated Circuits Conference in San Jose.

Researchers chose ultrasound to deliver wireless power to their medical implants because it has been safely used in many applications, such as foetal imaging, and can provide sufficient power to implants a millimetre or less in size.
Now Arbabian and his colleagues are collaborating with other researchers to develop sound-powered implants for a variety of medical applications, from studying the nervous system to treating the symptoms of Parkinson's disease.

"Tiny, wireless nodes such as these have the potential to become a key tool for addressing neurological disorders," said Florian Solzbacher, a professor of electrical and computer engineering at the University of Utah and director of its Centre for Engineering Innovation.
The Stanford medical implant chip is powered by "piezoelectricity," electricity caused by pressure.
In a piezoelectric material, pressure compresses its molecular structure much like a child jumping on a bed compresses the mattress. When the pressure abates, the piezoelectric material's molecular structure, like the mattress, springs back into shape.
Every time a piezoelectric structure is compressed and decompressed a small electrical charge is created. The team created pressure by aiming ultrasound waves at a tiny piece of piezoelectric material mounted on the device.

"The implant is like an electrical spring that compresses and decompresses a million times a second, providing electrical charge to the chip," said researcher Marcus Weber.
In the future, the team plans to extend the capabilities of the implant chip to perform medical tasks, such as running sensors or delivering therapeutic jolts of electricity right where a patient feels pain.