"The idea is to have a material that functions like the human skin, which means incorporating the ability to feel and touch objects," said Ali Javey, associate professor of electrical engineering and computer sciences and head of the UC Berkeley research team developing the artificial skin."Humans generally know how to hold a fragile egg without breaking it.
But we'd also want the robot to be able to grip a stock pot without dropping it."Illustration of an artificial e-skin with nanowire active matrix circuitry covering a hand.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 "printed," 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."Inorganic materials, such as crystalline silicon, on the other hand, have excellent electrical properties and can operate on low power. But historically, they have been inflexible and easy to crack.In this regard, works by various groups, including ours, have recently shown that miniaturized strips or wires of inorganics can be made highly flexible – ideal for high performance, mechanically bendable electronics and sensors." The 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.
A fragile egg is held, illustrating the functionality of the e-skin device for prosthetic and robotic applications.
Credit: Ali Javey and Kuniharu Takei A longer term goal would be to use the e-skin to restore the sense of touch to patients with prosthetic limbs, which would require significant advances in the integration of electronic sensors with the human nervous system.
Previous attempts to develop an artificial skin relied upon organic materials because they are flexible and easier to process.
"The problem is that organic materials are poor semiconductors, which means electronic devices made out of them would often require high voltages to operate the circuitry," said Javey.