US researchers have created a synthetic skin that promises to give robots the human sense of touch. The skin, or sensor array, developed at the University of Illinois, is a polymer containing thin film metal resistors and is just 25 microns thick.
To provide accurate information when replacing or assisting humans during surgery, space missions, or even handling fragile goods in factories, robots must have precise or superior sensory abilities. However, the sense of touch has so far proved difficult to mimic, particularly where the sensitive surface would have to be in contact with contaminants, as making a surface stronger generally causes it to be less sensitive.
Most attempts to construct a tactile surface have used silicon, but this is brittle and cannot stand up to impacts and deformation. The Illinois system consists of a polymer skin containing embedded metal film wiring and sensors, and is constructed using a specially treated surface mould. The team took a silicon wafer and created miniature recesses in it before coating it in layers of patterned polyamide, heat curing and oxidising it.
‘The silicon wafer is used like a cookie sheet,’ said Jonathan Engel, a member of the research team. ‘It is treated so that the skin can later be released after we have finished its construction. Essentially it is built from the bottom up using micro-machining techniques that keep production costs to a minimum.’
After heating nickel-chromium strain gauges are added followed by layers of gold-chromium composite wiring and polyamide. The sensor skin is then dipped into a chemical bath to release it from the mould. The result is a skin with raised tactile bumps that can be soldered to a flat or flexible surface that would feed data back to a computer.
A robot using the skin will be able to grip objects and construct an image of them based on their physical composition. Engel is also working on adding thermal sensors to the system.