It’s truly touching news... no sooner do we hear about the pressure-sensitive artificial skin created at UC Berkeley, than fellow Californians at Stanford University announce that they have also created such a material. While Berkeley’s skin relies on carbon nanotubes to detect pressure, however, Stanford’s skin utilizes a thin rubber sheet made up of tiny pyramids. It is reportedly so sensitive that it can “feel” the weight of a butterfly.
According to the research team, previous attempts at touch-sensitive skins made from thin rubber films have had at least one major problem – the material doesn’t have enough room to expand when pressed, so the molecules are forced into one another, become entangled, and can’t return to their original orientation. By molding the rubber into a matrix of microscopic pyramids, however, it becomes springier and its molecules don’t get messed up. It’s important that the material is able to spring back quickly, as that allows it to distinguish between separate touches that occur in quick succession.
The rubber film is sandwiched between two parallel electrodes, which register its compressions and rebounds as electrical signals of various strengths. The film and electrodes together are less than one millimeter in width, so the material should easily be flexible enough to wrap around objects such as a human hand, or a robotic arm. So far, the largest sheet of the skin is about seven square centimeters (1.08 square inches) in size.
The sensitivity of the material can be tweaked by altering the shape and density of the pyramids – existing samples have anywhere from several hundred thousand to 25 million pyramids per square centimeter. This allows to the material to more closely mimic real skin, which has differing sensitivities on different parts of the body.
Besides its use in artificial hands and robotic devices, the Stanford team see other potential uses for the material. If it were incorporated into bandages, for instance, doctors could tell exactly how tightly those bandages were being applied to their patients’ wounds. In a car, it could detect when an intoxicated or fatigued driver passed out and let go of the steering wheel.
The research was recently published in the journal Nature Materials.