Electronic 'Skin' Monitors Brain, Heart Activity
IRA FLATOW, host: This is SCIENCE FRIDAY. I'm Ira Flatow. Computer chips embedded into people is, you know, a mainstay of science fiction. Well, we may have come one step closer because this week, a team of researchers revealed a translucent, flexible circuit, a sort of electronic skin that you can apply to your own skin just like a temporary tattoo. And once the device is activated, it can monitor your heartbeat, the flexing of your muscles, your brainwaves. It can even detect speech.
And outfitted with a wireless transmitter, it could send all that data straight to your computer or maybe even to your doctor, or who knows, the limits of the imagination of things we might be able to do with this.
How soon, then, before you can find one of these at your pharmacy or have one fitted by your doctor? And other than monitoring vital signs, what could this be used for? As I say, the possibilities are limitless. What do you think?
Would you wear one, or how could you be sure that cyber-skin is not sending message you don't know about or maybe you don't want to send? Give us a call, our number 1-800-989-8255, 1-800-989-TALK. And if you're on Twitter, you can tweet us, @scifri, @-S-C-I-F-R-I, or go to our website at sciencefriday.com, where we actually have a video up there.
If you go to the website at SCIENCE FRIDAY, you can see an actual video playing of our segment and watch the tattoo with a pirate on it. It's kind of cute, interesting to look. John Rogers is a professor of materials science and engineering at the University of Illinois at Urbana-Champaign, and his study on electronic skin appears in the journal Science. Welcome back to SCIENCE FRIDAY, Dr. Rogers.
Dr. JOHN ROGERS: Yeah, hi. Thanks for having me.
FLATOW: Did I describe it correctly?
ROGERS: Pretty close, yeah. What we've tried to do here is to create a form of electronics that has its physical properties, in particular its elastic module, its bending, rigidity and thickness, matched to the upper layer of the skin, the epidermis. And in that form, it can integrate in a very natural way, you know, both mechanically and electrically to, you know, allow monitoring of physiological status and even do forms of stimulation.
FLATOW: How did you make this? How did you pack all that electronics into something so thin it feels like you're wearing just a tattoo?
ROGERS: Well, it's a good question. I mean, if you look at conventional silicon integrated circuits, they're built on the surfaces of silicon wafers. They're about a half a millimeter thick. And they have the properties of a plate of glass. It's flat, it's rigid, brittle. You drop it, it breaks. And so that's not a very good starting point, you know, if you want to build a class of electronics that looks like the body, you know, soft and curvilinear and elastic.
But it - you know, and so initially that looks like a gigantic gap, a chasm you'd have to cross, but it turns out it's not all that hard, you know, at least intuitively. You make silicon extremely thin. And elementary bending mechanics dictates that as things get thinner, they become more flexible because their bending rigidity goes down.
And then we structure those thin sheets of silicon into filamentary serpentine shapes, build devices in that kind of geometry, interconnect them with wires that have the same shape into almost a spider web type of open-mesh format in the electronics.
And if you take that kind of system, and you bond it to a thin sheet of a rubber like silicone, then you can make an overall circuit system that mimics the skin in terms of its mechanical properties.
FLATOW: And so it can feel anything or react to anything that goes through the skin, like a muscle reaction or anything.
ROGERS: Well, almost anything. I mean, we demonstrated a set of building blocks for, you know, a variety kind of circuits and sensors. So we did, you know, transistors is a sort of obvious one, LEDs. We also did diodes, resistors, inductors, antennas, and we also demonstrated some sensor functionality.
So we have electrophysiological sensors, basically electrode pads that can sense electrical activity in the body. You can also stimulate through the skin with those same pads. We have temperature sensors, strain sensors so we can measure motion of the skin, as well.
And we took some of those building blocks and put them together to make functional devices for measuring activity of the heart, the brain and the skeletal muscles.
FLATOW: So why is this better than the current technologies we have for measuring vital signs?
ROGERS: Well, I think in a variety of ways. I mean, if you look at the standard technologies, you're probably familiar with them. You see them in the hospital. They involve rigid point-contact electrodes you tape onto the skin, or you affix them there with a mechanical strap.
Then a bulk wire goes to a separately located box of rigid electronics, you know, and that's kind of the way it's done. And that's great for lots of applications clinically. It can be used for a research setting, as well. But it's not that comfortable. It's irritating to the skin. It constrains the motion.
The number of electrode interfaces that you can add, just from a practical standpoint, is limited by the bulk wiring. And so I think, you know, our approach maybe represents an advance over that more traditional interface in the sense that it brings all of the electronics and a multitude of electrodes into contact with the skin in a very non-invasive natural way that's mechanically invisible to the person who's wearing the device because it's not constraining the motion of the skin at all.
FLATOW: So you might envision a consumer use and a medical use, for example.
ROGERS: Potentially. You know, I think, you know, we have some ideas. I'm sure other folks come up with concepts, as well. Our main focus from a research standpoint is on healthcare related applications because I think that's the most impactful, you know, class of use of this kind of device. So we're spending our time mostly in that arena, physiological status monitoring, human-machine interfaces, devices to assist with physical rehabilitation, these kinds of things.
FLATOW: But there's no reason why you couldn't monitor your own heart rate if you're a runner or a pulse if, you know, if you have problems or how much you're doing of anything.
ROGERS: Well, sure. You know, all those kinds of things. I think, you know, the future, you know, would be one in which you would continuously measure your wellness and health status and use that information, you know, in conjunction with your doctor to try to improve your lifestyle and improve your health.
FLATOW: On the video you helped us put on our website, you have - it is part of a pirate tattoo, so kind of interesting.
ROGERS: Yeah, that was a little bit of a fun demonstration. I mean, what we wanted to show there is that, you know, just a conventional, temporary transfer tattoo could also be used as a substrate for these devices. And, you know, as you know, that's a low-cost commodity item that's already, you know, proven in terms of, you know, its compatibility with skin.
And so the notion is just to add our electronics to that kind of system and laminate it up on the skin in the way you ordinarily would to build some active functionality there.
It turns out that tattoo is actually a custom-made cartoon generated by the post-doc who led this work. So you notice it has a U of I logo on the hat. Illinois has nothing to do with pirates. So I haven't really figured out the connection, but that's what it is.
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FLATOW: Well, you know, it's a popular kind of tattoo that people wear, so I would imagine. But I imagine also that it can't be permanent, this skin, because your skin sort of sloughs off after a while, does it not?
ROGERS: That's exactly right. So the sort of resonance time on the skin is going to be determined by two things. One is sort of engineering considerations of how well the devices are bonding to the skin, and, you know, how robust they are to skin deformations.
We think we have a pretty good handle on that aspect of things. But as you mentioned, there are natural biological processes going on that, you know, are going to be limiting ultimately. So I think two, three weeks is kind of a time scale for cells to move to the surface of the skin and exfoliate off. So beyond that, you're going to need to, you know, add additional functionality to the system to either passively or actively manage those biological processes so as to avoid an adverse consequence of long-term mounting.
So I think that's challenge that's a topic of future work.
FLATOW: One of the potential applications you mentioned in your paper is, quote, "covert communications." I hear the CIA in this.
ROGERS: Yeah, so, you know, we've been working on this topic for a while, you know, two-and-a-half years or so. And during the course of the work, there has been a variety of people who have suggested different modes of use.
And, you know, we wanted to, you know, highlight a couple of non-healthcare applications, and that one had actually been suggested to us. And it's somewhat related to this game-control demonstration that we did prove out in the paper, whereby a device on the throat is picking up electrical signals associated with contraction of muscles near the throat area as the wearer is speaking different words, and then, you know, a software pattern recognition algorithm to translate that data into a limited vocabulary of words that can then control a game.
Now you can imagine doing the same thing without actually vocalizing the words. So you could imagine a sub-vocal mode of communication, then, using that kind of approach. And I think of that covert communication sort of in that context.
FLATOW: I guess covertly, you might be able to attach it to somebody's skin, and maybe they might not even notice it.
ROGERS: Yeah, I don't know. I haven't thought too deeply about those kind of applications.
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FLATOW: So you're just an engineer making this stuff?
ROGERS: Pretty much, yeah, academic. You know, that's my main...
FLATOW: So you haven't got a price tag on this or, you know, how soon it might come?
ROGERS: Well, yeah, I mean, I'm not qualified to make those kind of estimates. I mean, I would point out a couple things. One is that we've tried to use, as much as possible, standard, established electronic materials like silicon. And so we're not trying to reinvent the wheel.
We also use, for the most part, just mildly adapted versions of the processing tools that are used in the conventional silicon industry. So those aspects, I think, bode well for reasonable cost. That's number one.
Number two is we have a start-up company in the Cambridge area, smart business folks there that are venture capitalists have taken a close look at the economics of it and have decided to invest because they think there are realistic commercial opportunities. And so that's kind of an indirect reflection on, you know, probably a cost structure that, you know, is a sensible one.
FLATOW: You know, whenever people get done with what they have, they're never happy with it.
FLATOW: Right? How are you going to upgrade it immediately? What do you say: Oh, we could have done this better, or we should try this?
ROGERS: Well, I think there's a lot of things. You know, this is a first step. I think it's our first - you know, it's the first paper kind of in this direction. So, you know, on the engineering side, I think power and communications, those are the two big, you know, functions that you would want to have embedded directly in this system.
We demonstrated a couple of ideas on power, inductive wireless powering coil that works pretty well. You can do solar cells. They're very tiny. They're not generating that much power. So in both cases, I think we'd like to be able to couple to a storage device, either storage capacitor or battery. We don't have those yet.
So that represents one topic that we're focusing on now. On the communications side, we demonstrated a lot of building blocks that have radio frequency operation capabilities, but we haven't wired them together to make a full radio. So I think that's something we'd like to do, as well.
That's on the engineering side. On the application side, we're just moving forward with devices that are wired up with very thin, lightweight ribbon cables so that we can evaluate different modes of use and physical rehabilitation, status monitoring which we mentioned before, this human-machine interface stuff. So kind of two thrusts to what we're doing.
FLATOW: All right, Dr. Rogers, thank you for taking time to talk to us.
ROGERS: Sure, my pleasure.
FLATOW: Fascinating, good luck to you.
ROGERS: OK, thank you.
FLATOW: John Rogers is a professor of materials science and engineering at the University of Illinois at Urbana-Champaign and is studying this electronic skin, and that study appears in the journal Science. And you can go to our website, you can see the electronic skin in action and that cute pirate tattoo, how it's applied and how the electronic skin stays there.
We're going to take a break. When we come back, we're going to talk about if climate models are right. May we be living in a drier, hotter world in the future? And what does that mean about crops, that crops are dying out there? You've seen it in the Southwest. You've seen them in Africa. Are we in for something much bigger, on a global community? Stay with us. We'll be right back after this break.
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FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.
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