Temporary tattoos may soon be more than simple novelties. Equipped with ultrathin, self-adhesive electronics, an interim tramp stamp could also monitor heart rates, brain waves, and muscle activity without bulky equipment, conductive fluids, or messy glues, according to research published in the August 12, 2011 issue of Science. A collaboration among scientists from the University of Illinois at Urbana-Champaign, Northwestern University, Tufts University, the Institute of High Performance Computing in Singapore, and Dalian University of Technology in China, the “epidermal electronic system” (EES) incorporates miniature sensors, LEDs, teeny transmitters and receivers, and networks of wire filaments to create a new class of microelectronics that is not only virtually weightless but also requires little to no power.
SENSORS TO GO
Because of its negligible energy needs, the device can draw power from stray (or transmitted) electromagnetic radiation or miniature solar collectors. And at less than 50 microns thick—thinner than the diameter of a human hair—the EES is able to harness close-contact van der Waals forces, similar to electrostatic attraction, to stay on skin for up to 24 hours without any adhesives.
Regions of the body that previously proved too challenging for sensor application may now be monitored, such as the throat.
“Our goal was to develop an electronic technology that could integrate with the skin in a way that is mechanically and physiologically invisible to the user,” says corresponding author John Rogers, a professor in materials science and engineering department at the University of Illinois at Urbana-Champaign. “We found a solution that involves devices we designed to achieve physical properties that match to the epidermis itself. It’s a technology that blurs the distinction between electronics and biology.”
Although certain body areas, such as the elbow, are incompatible with adhesive electronics, most regions targeted for medical and experimental studies are ideal, including the forehead, extremities, and chest. Plus, regions of the body that previously proved too challenging for sensor application may now be monitored, such as the throat. In fact, on observing muscle activity during speech, researchers were able to differentiate words and even control a voice-activated video game interface with more than 90 percent accuracy.
“This type of device might provide utility for those who suffer from certain diseases of the larynx,” says Rogers. “It could also form the basis of a sub-vocal communication capability, suitable for covert or other uses.”