An artificial 'super skin' for androids

Stanford researchers have developed a stretchable, transparent skin-like sensor that could have applications in prosthetic limbs, robotics, and touch displays.

Credit: Steve Fyffe, Stanford News Service

Credit: Steve Fyffe, Stanford News Service

The wrinkle-smoothing wonder of Botox could some day be a thing of the past.

Stanford researchers have built a new transparent skin-like sensor that can stretch out to more than twice its normal length in any direction and bounce back to its original shape.

The sensor uses a transparent film of single-walled carbon nanotubes that are bent to act as tiny springs. The springs help the sensor to accurately measure almost any force applied on it--from a firm pinch to thousands of pounds.

"This sensor can register pressure ranging from a firm pinch between your thumb and forefinger to twice the pressure exerted by an elephant standing on one foot," said Darren Lipomi, a postdoctoral researcher in Bao's lab, who is part of the research team. "None of it causes any permanent deformation," he added.

According to Lipomi and his team, the sensor could be used in making touch-sensitive prosthetic limbs or robots, for various medical applications such as pressure-sensitive bandages or in touch screens on computers.

Key to the skin-like sensor are the carbon "nano springs." They are airbrushed onto a thin layer of silicone to form a transparent film of randomly oriented little clumps the researchers like to describe as "conductive spaghetti."

When the silicone is stretched, some of the clumps get pulled into alignment in the direction of the stretching. When released, the sensor rebounds back to its original dimensions while the nanotubes buckle and form little nanostructures that look like springs.

Stretching the sensor in the perpendicular direction yields additional clumps that transform into nano springs when released. Afterwards, stretched or un-stretched, the sensor maintains its total rebounding and conductivity properties.

The artificial skin is built using two layers of the nanotube-coated silicone, oriented so that the coatings are face-to-face, with a layer of easily deformable silicone in the middle. The silicone stores an electrical charge, much like a battery.

When pressure is exerted on the sensor, the silicone compresses, which alters the amount of electrical charge it can store. That change is detected by the two films of carbon nanotubes, which act like the positive and negative terminals on a typical automobile or flashlight battery. The change in electrical is charge is how the sensor transmits what it is "feeling."

"One of the long term applications is to use a stretchable, conformable, skin-like device in artificial intelligence systems. If you have a robot or android like Data from Star Trek, its skin can potentially be made out of something like this," said Lipomi in a video.

The research team published a paper describing the sensor in the latest issue of Nature Nanotechnology.


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