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nanotimes Research

10-09 :: September 2010

Robotics // Engineers Make Artificial Skin Out of Nanowires

E

ngineers at UC Berkeley, USA, have developed a pressure-sensitive electronic material from

semiconductor nanowires that could one day give new meaning to the term “thin-skinned.” The UC Berkeley researchers present in Nature Materials a nanowire active-matrix circuitry for low-voltage macroscale artificial skin.

“The idea is to have a material that functions like the human skin, which means incorporating the ability to feel and touch objects,” said Prof. Ali Javey, associ- ate professor of electrical engineering and computer sciences and head of the UC Berkeley research team developing the artificial skin.

Ali Javey and his team demonstrate macroscale (7x7 cm2

) integration of parallel nanowires arrays as

the active-matrix backplane of a flexible pressure- sensor array (18x19 pixels). The integrated sensor array effectively functions as an artificial electronic skin, capable of monitoring applied pressure pro- files with high spatial resolution. The active-matrix circuitry operates at a low operating voltage of less than 5 V and exhibits superb mechanical robustness and reliability, without performance degradation on bending to small radii of curvature (2.5 mm) for over 2,000 bending cycles. It is the first such material made out of inorganic single crystalline semiconduc- tors.

“Humans generally know how to hold a fragile egg without breaking it,” said Javey, who is also a mem- ber of the Berkeley Sensor and Actuator Center and a faculty scientist at the Lawrence Berkeley National Laboratory Materials Sciences Division. “If we ever wanted a robot that could unload the dishes, for in- stance, we’d want to make sure it doesn’t break the wine glasses in the process. But we’d also want the robot to be able to grip a stock pot without dropping it.”

Previous attempts to develop an artificial skin relied upon organic materials because they are flexible and easier to process.

“The problem is that organic materials are poor se- miconductors, which means electronic devices made out of them would often require high voltages to operate the circuitry,” said Javey. “Inorganic mate- rials, such as crystalline silicon, on the other hand, have excellent electrical properties and can operate on low power. They are also more chemically stable. But historically, they have been inflexible and easy to crack. In this regard, works by various groups, including ours, have recently shown that miniatu- rized strips or wires of inorganics can be made highly flexible – ideal for high performance, mechanically bendable electronics and sensors.”