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Stretchy electronic device hugs the heart

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“Our electronics have a wavy mesh design so they can wrap around irregular and curved surfaces, like the beating heart. The device is thin, flexible, and stretchable and brings electronic circuits right to the tissue. More contact points mean better data,” says Yonggang Huang. The emerging technology may also be effective in the treatment of epilepsy, and the development of flexible sensors, transmitters, and photovoltaic devices. (Credit: Dae-Hyeong Kim, University of Illinois)

NORTHWESTERN/ U. ILLINOIS/ U. PENN (US)—A flexible, implantable medical device about the size of a nickel treats abnormal rhythms by wrapping around the heart to produce a high density map of electrical activity.

“The heart is dynamic and not flat, but electronics currently used for monitoring are flat and rigid,” says Yonggang Huang, the Joseph Cummings Professor of Civil and Environmental Engineering and Mechanical Engineering at Northwestern University.

“Our electronics have a wavy mesh design so they can wrap around irregular and curved surfaces, like the beating heart. The device is thin, flexible, and stretchable and brings electronic circuits right to the tissue. More contact points mean better data.”

Huang is senior author of a paper detailing the research, published as the cover story in the March 24 issue of the journal Science Translational Medicine.

The emerging technology may also be effective in the treatment of epilepsy, and the development of flexible sensors, transmitters, and photovoltaic and microfluidic devices.

The device, capable of directly sensing and controlling activity in animal tissue, is based on flexible electronics developed in 2008 by Huang and his collaborator John Rogers, the Flory-Founder Chair Professor of Materials Science and Engineering at the University of Illinois and one of the paper’s senior authors.

Brian Litt, also a senior author on the paper and associate professor of neurology and associate professor of bioengineering of the University of Pennsylvania, and his colleagues designed the medical experiments and tested the device in a large animal model.

The team demonstrated that the electronics continue to operate when immersed in the body’s fluids, and the mechanical design allows the device to conform to and wrap around the body’s irregularly shaped tissues.

The device uses 288 contact points and more than 2,000 transistors positioned closely together. Standard clinical systems usually have only five to 10 contact points. The new device is 14.4 millimeters by 12.8 millimeters, roughly the size of a nickel.

By bringing electronic circuits right to the tissue, rather than having them located remotely, the device can process signals right at the tissue and have  a much higher number of electrodes for sensing or stimulation than is currently possible in medical devices.

The device can collect large amounts of data from the body, at high speed. Researchers will be able to map the body’s complicated electrical networks in much more detail, with more effective implantable medical devices and treatments likely to emerge.

The current device is not wireless. The next big step in this new generation of implantable devices, say the researchers, will be to find a way to move the power source onto them. One solution could be to have the heart power the device.

Huang and Rogers created an array of tiny circuit elements connected by metal wire “pop-up bridges.” When the array is bent or stretched, the wires—not the circuits—pop up, allowing the circuits to be placed on a curved surface. (In the partnership, Huang focuses on theory and design, and Rogers focuses on the fabrication of the devices.)

The  “pop-up” technology allows circuits to bend, stretch and twist that  can be used in places where flat, unbending electronics would fail, like the heart, brain, or other places on the human body.

Any significant bending or stretching to circuits renders an electronic device useless, which is what limits current electronics for use on the body.

The U.S. Department of Energy and the National Institutes of Health, among others, supported the work.

Northwestern University news: www.northwestern.edu/newscenter/
University of Illinois news: http://news.illinois.edu/
University of Pennsylvania news: www.uphs.upenn.edu/news/

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