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Future of the electronic 'tattoo'

A new device thin enough to be laminated onto the skin could track heart, brain and muscle functions without bulky electrodes. It could also have military applications.

August 27, 2011|Amina Khan

Forget those old, bulky electrodes of the past. Researchers have created a device that can track your heart, brain and muscle activity as effectively as conventional monitoring systems -- and is thin enough to be laminated onto the skin like a temporary tattoo. Down the line, such electronic patches could be used to monitor vital functions, aid in physical rehabilitation or perhaps be deployed in covert military operations.

John Rogers, a materials scientist with the University of Illinois at Urbana-Champaign, discussed the research and its potential future uses.

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How did you make such a thin, flexible, stretchable electronic device?

It may seem like an impossible problem if you think about silicon as it exists today. In conventional integrated circuits, silicon comes in the form of a wafer. If you drop it, it shatters, just like a glass plate. But if you decrease the thickness by a factor of 1,000, then the bending stiffness decreases by a factor of a billion. So it's a huge, huge change. [And] it doesn't affect the performance of the transistors.

So we shave off a layer from the wafer -- it's floppy, it's flexible. But that's still not matching biological tissues, because the skin not only flexes, it stretches and it wraps curved surfaces.

So you have to go from thin membranes of silicon to thin, filamentary, serpentine noodles of silicon, essentially. And those wavy wires -- you can grasp them by the ends, you can sort of stretch them, elongate them, without fracturing the silicon.

So the circuit looks like an open spider web mesh of these wiggly lines.

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How long do they last?

We've kept them on for a few days. With transfer tattoo adhesives, they can stay on much longer without a problem.

They're manufacturable at low cost and they bond in ways that don't constrain the motion of the skin. [The device] has a lot of features that are appealing, so maybe it's a good starting point.

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How could these patches be useful?

Monitoring, for example, health and physiological status of a premature baby. This is a tiny fragile human, so you want something that's as noninvasive as possible.

Another is in sleep monitoring. Bulky devices tend to disrupt normal sleep patterns. So in studies for people who are suffering from sleep apnea, you'd be able to do that in a way that allows natural sleep.

Also, these devices don't just monitor processes in the body, but can stimulate them as well. So we are working with people at Johns Hopkins, using these devices to monitor and stimulate in the context of physical rehabilitation of atrophied muscles.

Current voice-recognition software needs to pick up audible sounds, but an electronic patch could pick up muscle contractions that happen without saying anything out loud. So it could be relevant for people who have speech problems or who suffer from diseases of the larynx.

And then there have been folks who've suggested covert communication capabilities -- subvocal modes for communicating between people.

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So this could have serious military applications.

That's the future. I don't know exactly when we're going to get there, but you can at least see the path to that endpoint.

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Sounds like you're blurring the line between man and machine.

Somewhat, yeah. Not at the level that many people think about it in terms of science fiction, but I think that's a step in that direction, at least.

From a mechanical standpoint, they really are well matched. But the challenge is going from circuits and semiconductor devices that are based on electrons and photons, to interacting with biology that's operating based on proteins, enzymes, antibodies and fluids. There's a difficult mismatch there.

[But] that's the grand vision of the direction we're going.

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This interview was edited for space and clarity.

amina.khan@latimes.com

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