Stretchy ‘Super Skin’ Can Feel Pressure

October 26, 2011 Updated: September 29, 2015

Super-Stretchy Skin-Like Sensor (Stanford University)

Android-like robots with supple touch-sensitive skin are a possibility thanks to new research from Stanford University with the ultimate goal of restoring functionality to lost skin, for example in amputees and burn victims.

Scientists have developed a stretchy transparent skin-like film from Carbon Nanotubes (CNTs) that can accurately measure applied force.

The highly elastic material snaps back into place without any permanent deformation after being stretched to more than twice its length in any direction.

The technology could be used in making touch sensitive android-like robots, prosthetic limbs, computer touch screens, and for medical applications such as pressure sensitive bandages.

“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 study co-author Darren Lipomi in a media release.

At the heart of the film-like sensor are two layers of CNT-based “nano-springs" created by spraying CNTs in liquid form onto thin sheets of silicon.

Each layer is then stretched in one direction and released, causing the CNTs to buckle and develop their spring-like properties.

"After we have done this kind of pre-stretching to the nanotubes, they behave like springs and can be stretched again and again, without any permanent change in shape," said co-author Zhenan Bao in the release.

The layers of CNT nano-springs are placed face to face with their spring directions perpendicular to each other enabling the sensor to stretch in all directions.

Between the two nano-spring layers is a more deformable layer of silicon that stores an electrical charge. When pressure is exerted, the middle layer compresses, affecting the amount of charge it can store. This change enables the sensor to transmit what it is "feeling."

According to Bao, this artificial skin has the potential to sense pressure "well below the pressure exerted by a 20 milligram bluebottle fly carcass," based on previous research. However, the team focused on making the new sensor stretchy and transparent.

"We did not spend very much time trying to optimize the sensitivity aspect on this sensor," Bao said. "But the previous concept can be applied here. We just need to make some modifications to the surface of the electrode so that we can have that same sensitivity."

The findings were published online in the journal Nature Nanotechnology on Oct. 23.