Platinum hairs give added touch to artificial skin

As a mechanical sensor, human skin is uniquely versatile: It can detect not just the magnitude of a contact force but the particulars of how the force is applied. Thus, we know whether we're being poked or pinched, tapped or tugged. Now, researchers led by Kahp-Yang Suh (Seoul National University, South Korea) have engineered an electronic skin that can similarly discriminate between various kinds of touch. The skin consists of two thin polymer sheets, each lined with hair-like, platinum-coated nanofibers. When the sheets are sandwiched together, as illustrated at left, the nanofibers—each about a micron long and a tenth of a micron wide—interlock to form Pt–Pt contacts that close an electronic circuit. The total contact area, and therefore the resistance, changes when the sheet is subjected to mechanical stress. Pressure, shear, and torsion each produce distinct electronic signatures, so even when all three are applied at once, the detected stress can be resolved into its component parts. In laboratory tests, the artificial skin, pictured at right, proved sensitive enough to track the movement of crawling ladybugs and detect the impact of a falling water droplet. The researchers envision the thin, flexible sensors being used as prosthetic devices or medical monitors; worn like a bandage on the wrist, the device is easily sensitive enough to measure a human pulse. (C. Pang et al., Nat. Mat., in press.)—Ashley G. Smart