Stanford researchers develop ‘super skin’

Oct. 25, 2011, 2:02 a.m.

Stanford researchers have developed a stretchable, skin-like sensor as the latest accomplishment in associate professor of chemical engineering Zhenan Bao’s quest to create a “super skin.”

The transparent skin-like pressure sensor employs pioneering elastic that can stretch to twice its normal length in any direction and return to its normal length without suffering any deformation. The sensor may have far-reaching applications in the fields of touch-sensitive computer displays, robotics and prosthetic limbs. A large variety of medical applications may also be possible.

Darren Lipomi, a postdoctoral researcher, and Benjamin Tee and Michael Vosgueritchian, both graduate students in electrical engineering, are the lead authors of the paper published online by “Nature Nanotechnology” on Oct. 23. Bao is a coauthor.

The sensor can measure pressure on it, ranging from a pinch to the weight of an elephant, according to Lipomi. The device uses a clear film of single-walled carbon nanotubes acting as tiny springs, which protect the sensor from damage when stretched.

Researchers created the carbon “nanosprings” by spraying nanotubes in a liquid suspension onto a thin layer of silicone.

Stretching the silicone and returning it to its original shape forms the nanotubes into tiny springs, which can then detect pressure, while limiting damage from future stretching. Researchers “pre-stretched” the silicone in both perpendicular directions to lend the material the ability to rebound when stretched from any direction.

The nanostructures act as electrodes in measuring the force applied to them, made possible by the fact that the stretching to create the springs does not alter the electrical conductivity of the material.

The sensor itself consists of three layers of silicone-one layer of standard, easily deformed silicone surrounded by two layers of the nanotube-coated silicone. The two nanotube-coated layers sense the change in electrical charge stored in the middle layer when force is exerted on the device.

– Margaret Rawson

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