At UC Berkeley, engineers have created a material out of semiconductor nanowires that is as touch sensitive as human skin. The so called “e-skin” is projected to be used in future robots to provide tactile feedback and perhaps even in prostheses to return a sense of touch to amputees. Because the inorganic single crystalline semiconductors making up the material are chemically stable, they have a promising future in medicine.
The UC Berkeley engineers utilized an innovative fabrication technique that works somewhat like a lint roller in reverse. Instead of picking up fibers, nanowire “hairs” are deposited.
The researchers started by growing the germanium/silicon nanowires on a cylindrical drum, which was then rolled onto a sticky substrate. The substrate used was a polyimide film, but the researchers said the technique can work with a variety of materials, including other plastics, paper or glass. As the drum rolled, the nanowires were deposited, or â€œprinted,â€ onto the substrate in an orderly fashion, forming the basis from which thin, flexible sheets of electronic materials could be built.
In another complementary approach utilized by the researchers, the nanowires were first grown on a flat source substrate, and then transferred to the polyimide film by a direction-rubbing process.
For the e-skin, the engineers printed the nanowires onto an 18-by-19 pixel square matrix measuring 7 centimeters on each side. Each pixel contained a transistor made up of hundreds of semiconductor nanowires. Nanowire transistors were then integrated with a pressure sensitive rubber on top to provide the sensing functionality. The matrix required less than 5 volts of power to operate and maintained its robustness after being subjected to more than 2,000 bending cycles.
The researchers demonstrated the ability of the e-skin to detect pressure from 0 to 15 kilopascals, a range comparable to the force used for such daily activities as typing on a keyboard or holding an object. In a nod to their home institution, the researchers successfully mapped out the letter C in Cal.
Link: Engineers make artificial skin out of nanowires…
Abstract in Nature Materials: Nanowire active-matrix circuitry for low-voltage macroscale artificial skin