What's the News: Keeping track of what's happening inside the body often requires a great deal of equipment outside it: Just think of the tangle of sensors in any hospital room. Now, though, engineers have developed an ultra-thin electrical circuit that can be pasted onto the skin just like a temporary tattoo. Once it's served its purpose, you can simply peel it off. These patches could be provide a simpler, less restrictive way to monitor a patient's vital signs, or even let wearers command a computer with speech or other slight movements. How the Heck:
The researchers designed the circuit to match the mechanical properties of skin, meaning it can stretch, scrunch, and bend just like skin does. That's no easy task, given that electronics aren't usually elastic.
To do this, the researchers bent the circuit's wires into a squiggly shape (see the photo above) that can expand and shrink along with the skin. They also shrank various circuit components to the minute size of the natural bumps and grooves of human skin. Since they wanted to prove that the circuit could have a range of applications, the team included all sorts of different components, from sensors and transistors to wireless antennas.
The circuit is made on silicon wafers, then transferred to a sheet of water-soluble plastic, totaling about 40 micrometers thick. It's then transferred to the skin like a temporary tattoo: dab with water, let it dry, and you're good to go. (For people who feel the circuit doesn't match their style, it can be embedded in another temporary tattoo, as the video below demonstrates.) It can stay attached for a few days, and be peeled off at any time.
To test out the muscle-monitoring capabilities of the circuit, the researchers tested out how well it could recognize words when pasted on the throat, based on the electrical activity of nearby muscles. The circuit was sensitive enough, they found, that people wearing it could play a voice-controlled computer game---speaking the commands "left," "right," "up," and "down"---with 90% accuracy.
The Future Holds:
Now that the researchers have shown the various circuit components work individually, they're developing a more complex circuit where the components work together. They're also working to add piezoelectric components, which can harvest energy from the body's movements, and on making the device totally wireless, getting rid of the wires it now needs to download information.
By replacing bulky systems, the patches could make continuous monitoring of heart rate, muscle movement, or brain activity much easier and less obtrusive, the researchers hope.
Reference: Dae-Hyeong Kim et al. "Epidermal Electronics." Science, August 12, 2011. DOI: 10.1126/science.120615Image courtesy John A. Rogers