Stanford chemical engineering professor Zhenan Bao imagines a robot with super-human powers, a robot that can touch a person and say, “Oh, this person has that disease.” “Or,” she said, “the robot might touch the sweat from somebody and be able to say, ‘Oh, this person is drunk.’”
This vision isn’t science-fiction, folks. According to Stanford, Bao has developed an electronic artificial skin that can sense chemicals or biological material – and is powered by integrated stretchable solar cells.
A flexible organic transistor, made with flexible polymers and carbon-based materials, is the key to the skin. The transistor has a thin, highly elastic rubber layer, molded into a grid of tiny inverted pyramids. When pressure is applied, the layer changes thickness. That, in turn, changes the current flow through the transistor. The level of sensitivity is determined by the density of pyramids – from several hundred thousand to 25 million per square centimeter.
Adjusting exactly what the skin is sensing is then just a matter of coating the surface of the transistor with an extremely thin layer of certain binding molecules.
Of course, any information gathered has to be transmitted somewhere to be useful – to a brain, or a computer, for instance – and that’s where the solar power really comes in. “The cells have a wavy microstructure that extends like an accordion when stretched,” Stanford says. “A liquid metal electrode conforms to the wavy surface of the device in both its relaxed and stretched states.” The result is they can be stretched up to 30 percent beyond their original length and snap back without any damage or loss of power.