Today’s artificial limbs have improved greatly in recent years, but even the best replacements can’t substitute tactile sensation— what it feels like to touch something, to nearly touch and to be touched. New electronic skins could be a step toward touch-sensitive artificial limbs, and machinery like robots.
In one example, German researchers are building skin that doesn’t directly feel, but infers the presence of an object through close proximity. Researchers at Technical University Munich built hexagonal circuit boards, about three-quarters of an inch square, each equipped with four infrared sensors and six temperature sensors. The sensors can detect an object from a distance of about 1 centimeter, which equates roughly to the distance at which the fine hairs on human skin can sense an object, the researchers said. “We thus simulate light touch,” Philip Mittendorfer, a TUM scientist who developed the skin-circuits, said in a statement earlier this summer.
While this approach relies on rigid materials, other research groups in Europe and the US are working on tactile skin made of stretchable surfaces that can bend just like skin. Stéphanie Lacour at the University of Cambridge is building circuits on a substrate of clear elastic silicone, which can stretch and transform without breaking. The elastic materials can wrap around limbs or even fingers, an ideal option for future implants or even touchscreen interfaces (see the end of the gallery for more on this concept).
And in the US, researchers at various institutions in California have been building stretchable electronic skin that could bring touch sensitivity to machines. One skin, built by Stanford University scientists, is 1,000 times more sensitive than human skin, according to research published earlier this year.
It’s based on organic transistors, made of elastic material sandwiched between two electrodes. Another prototype developed at the University of California-Berkeley works in a similar manner, but is made of inorganic nanowire circuits.