The artificial skin sensitive to touch

The artificial skin sensitive to touch is emerging: we know now detect the landing of a butterfly! Two U.S. labs have developed two different technologies envisaged for prostheses or robots.

The prosthetic arm is becoming more realistic and efficient. Yet, they still lack the perception of touch, which would allow amputees to regain sensitivity of the world around them. The skin is in fact a body multisensory that responds reflexively to changes in temperature or pressure and felt the pain. These parameters are very difficult to transpose to hearing but there is novelty in the air, according to two independent publications published in the journal Nature Materials.

Zhenan Bao

The first concerns the work of Zhenan Bao and his colleagues at Stanford University in California. On an elastic polymer, polydimethylsiloxane (PDMS) structures pyramid are found at regular intervals. When subjected to pressure, crushed the pyramids were made up of PDMS, which changes the electrical properties of the material. Many organic transistors embedded in the polymer can detect these changes, corresponding to a change in pressure.

This structure is extremely sensitive: butterflies or blue flies placed on the structure have been detected, and it almost instantly. Unfortunately, the lack of flexibility is currently a barrier to its use. Bao believes, however, be able to improve it before the end of the year.

The artificial skin called e-skin is composed of pixels nanowires capable of detecting low pressures. Its flexibility could give him a good future. © Ali Javey and Kuniharu Takei / UC Berkeley
e-skin, sensitive and flexible

The other invention, called e-skin, brain is out of the University of California (Berkeley), including that of Ali Javey. It is based on the use of semiconductor nanowires made of germanium and silicon and forming a mesh mounted on a flexible rubber. When pressure is applied, the pixels that form each crossing nanowires are activated, indicating the position and intensity of pressure.

Not only the structure withstands extreme bending (less than 5 mm between the two ends of the structure) and even hundreds or thousands of consecutive folds, but the sensitivity is the height. The prototype is a square of 7 cm side, with 342 pixels can detect a pressure of 0-15 kPa, similar to that required to hold a pen or typing on a keyboard.

The flexibility of the artificial skin is necessary for their integration of robots or prosthetic hands. Moreover, their sensitivity appears to be adequately proven the daily lives of amputees, who may adjust their grip strength to hold such an egg without breaking it.

However, we are still far from integrating these materials into living tissue. They must first be biocompatible, that is to say, to be borne by the body without being attacked by the immune system and, moreover, they must be connected to the nervous system so that amputees can appropriate . These steps are still very distant, but it is not so bad for a start ...