A soft electronic skin could allow people with prosthetics to sense pressure and temperature, helping them to more easily interact with their surroundings.

Thin and stretchable like regular skin, the electronic skin sticks to surfaces like a Band-Aid. It contains sensors to measure external temperature and pressure, which it sends to an implanted electrode in the brain in the form of electrical signals. These signals vary in frequency to help the brain tell the difference between sensations like a softer touch and a firm handshake, a strawberry and an apple, or hot and cold. 

It was created by a team of researchers from Stanford University, who implanted soft e-skin electrodes in the brains of rats and recorded electrical signals from the animals’ motor cortex, the region of the brain responsible for carrying out voluntary movements. The animals twitched their legs in response to different levels of pressure recorded by the brain, depending on the strength of the stimulation frequency, demonstrating that the e-skin was able to detect differing levels of pressure in the same way that animals and humans can do ordinarily. 

The team says the work could lead to better prosthetics and could help create robots that can feel human-like sensations. The research is published in a paper in Science today. 

“Our dream is to make a whole hand where we have multiple sensors that can sense pressure, strain, temperature, and vibration,” says Zhenan Bao, a chemical engineering professor at Stanford University, who worked on the project. “Then we will be able to provide a true kind of sensation.”

The lack of sensory feedback is one of the main reasons people stop wearing a prosthesis, as it can leave users feeling frustrated.

Although previous e-skins have used soft sensors to sense touch, they were forced to rely on rigid external components to convert them into measurable electronic signals. Such systems tend to restrict people from moving naturally. This new e-skin is entirely soft, which could help avoid that problem.

The fact that the e-skin is thin and soft, and uses little power, makes it an exciting prospect for people working in the prosthetics field, says Silvestro Micera, an associate professor of neural engineering at the Swiss Federal Institute of Technology, who did not work on the project. 

“We have to see it integrated in a real prosthesis,” he says. “That’s clearly the next step.”