Self-powered synthetic skin could be used to diagnose diseases.

A Stanford professor has developed solar-powered artificial skin, capable of detecting chemical and biological molecules, that could be used to diagnose patients.With artificial skin, we can basically incorporate any function we desire," said Zhenan Bao, a professor of chemical engineering, at the American Association for the Advancement of Science on 20 February. "That is why I call our skin 'super skin'. It is much more than what we think of as normal skin." Bao said that the skin, which is being developed for use in robotics and prosthetic limbs, could lead to the creation of diagnostic robots that detect disease simply by touching a patient's blood or urine and registering the levels of certain molecules. They could even monitor blood-alcohol levels in drunk drivers by touching a subject's sweat. The flexible polymer "skin" is coated with a layer of molecules (precisely which molecule changes according to what researchers are trying to detect) just a nanometre thick. On contact with certain chemical or biological molecules, this layer binds itself to the substance, thus signifying the detection. For any particular disease, there are usually one or more specific proteins associated with it -- called biomarkers -- that are akin to a 'smoking gun'," said Bao. "Detecting those protein biomarkers will allow us to diagnose the disease." The theory was put into practice and Bao's team managed to correctly identify a type of DNA. The addition of a solar cell that can generate, conduct and transmit signals from the sensors even when stretched to 30 percent its length allows for far more mobility -- without a battery that needs recharging, the subject can be lighter and have more freedom. It's able to do this by working on two axes, with a wave-like surface that conducts energy through a liquid metal. The durable nature of these solar cells affords infinite possibilities. They can not only be used on joints, as with artificial skin, but can be adapted to clothing, cars, lenses and even parts of buildings, said Darren Lipomi, a postdoctoral fellow on Bao's team. Bao was already well on her way to developing what she calls "super skin", having invented an integrated sensor in 2010 that is sensitive to touch and light pressure. Touch sensitivity was introduced by adding a very thin layer of rubber to the skin's surface. The rubber is made up of millions of tiny inverted pyramids which alter thickness when touched, affecting the flow of electricity through the skin. This change in energy flow is interpreted by sensors as touch. The skin can be made more sensitive by increasing the number of pyramids.