Piezoelectric skin could give robots ability to ‘feel’

Researchers at the Georgia Institute of Technology have created a new type of touch-reactive material that could give robots with the ability to 'feel'.

The material owes its heightened tactility to thousands of functioning piezotronic transistors, which each contain around 1,500 nanowires between 500 and 600nm in diameter.

Unlike other devices, the transistors are able to sense changes in their own polarity when pressure is applied. This is due to the nanowires' zinc oxide composition, which simultaneously gives them piezoelectric and semiconducting properties.

"Any mechanical motion, such as the movement of arms or the fingers of a robot, could be translated to control signals," explained Zhong Lin Wang, a Regents' professor and Hightower Chair in the School of Materials Science and Engineering at Georgia Tech. "This could make artificial skin smarter and more like the human skin. It would allow the skin to feel activity on the surface."

Over a period of three years, Wang and his colleagues used a chemical growth technique to fabricate arrays of 92 x 92 transistors. This allowed them to create arrays of strain-gated vertical piezotronic transistors on substrates suitable for microelectronics applications.

In the array devices, the active strain-gated vertical piezotronic transistors are sandwiched between top and bottom electrodes made of indium tin oxide aligned in orthogonal cross-bar configurations.

A thin layer of gold is deposited between the top and bottom surfaces of the zinc oxide nanowires and the top and bottom electrodes, forming Schottky contacts. A thin layer of the polymer Parylene is then coated onto the device as a moisture and corrosion barrier.

The resulting arrays have a density of 234 pixels per inch and can register pressures starting at 10kilopascals. According to the researchers, this makes them almost as sensitive as a human fingertip.

"This is a fundamentally new technology that allows us to control electronic devices directly using mechanical agitation," Wang added. "This could be used in a broad range of areas, including robotics, MEMS, human-computer interfaces and other areas that involve mechanical deformation."

Laura Hopperton

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