A patch of artificial skin can convert signals from pressure or heat sensors into brain signals – touching this electronic skin after it was connected to a rat’s brain spurred the rat to kick its leg. This could be used to improve prosthetics for people who have skin damage.
Weichen Wang at Stanford University in California and his colleagues created a device called e-skin out of an electronic circuit and pressure and temperature sensors, all crafted out of a thin and stretchy rubbery material. The team merged these components into one patch that easily conforms to uneven surfaces, such as a human finger. E-skin works by imitating biological skin, where nerves detect pressure or warmth and then send sequences of electrical signals, or “pulse trains”, to the brain.
When it was heated or when pressure was applied to it, the e-skin’s sensors sent signals into the circuit, which converted them into pulse trains. To do all this, the e-skin needed up to 1/60th of the voltage used by older artificial skin devices. This could mean the e-skin won’t heat up as much, making it more comfortable for longer use, says Wang. Any artificial skin that could be used as a prosthetic for people with skin injuries needs to be comfortable enough to wear for a long time.
Skin sensations can trigger quick muscle movements, so the researchers connected the e-skin to the nervous system of a living rat to see whether it could do something similar. The team connected the electrodes in a patch of e-skin into the region of the brain that processes touch and temperature. They then put pressure on the device. The rat’s brain reacted by firing more signals between neurons in the region that controls movement. When the researchers routed those signals into the rat’s leg through an insertable artificial synapse device, it kicked.
“This is a clear demonstration: based on sensation, there were movements. And this is not a small thing, it’s quite challenging work to get the electronics to work well enough for this,” says Ravinder Dahiya at Northeastern University in Massachusetts. However, he says that the e-skin may need even more sophisticated circuity to be used in place of large areas of skin.
The device transmits all sensory data straight into the brain unfiltered, but human skin doesn’t handle sensory data this way. For instance, the pressure you exert on your fingertips as you hold a pen requires more attention from your brain than the sensations from skin on other parts of your hand, which are filtered out, says Dahiya.