The concerted response of thousands of nanoscale polymer hairs to pressure, shear or torsion can be exploited to build flexible touch sensors, reports a paper online this week in Nature Materials. Such sensors are one of the key elements in the development of electronic skin, which mimics the properties of human skin for applications in robotics or prosthetics.

Flexible sensors for the detection of mechanical loads are generally complex to fabricate. In contrast, the sensors created by Kahp-Yang Suh and colleagues can be assembled by simply interlocking two supported arrays of platinum-coated polymer hairs. The contact between the hairs allows electrical current to flow through the device, with an electrical resistance that depends on the degree of interconnection. Under external loads such as pressure, shear and torsion, the polymer hairs twist and bend, increasing the contact area and leading to a discernible decrease in resistance. The devices are extraordinarily sensitive to small loads and their utility has already been demonstrated in a number of applications including heart-rate monitoring.