A new electronic skin—a rubbery plastic-and-graphene film mimicking the structure of human skin—can detect texture, temperature, pressure and sound, reported Hyunhyub Ko, a materials scientist at the Ulsan National Institute of Science and Technology in South Korea.
This marks the first time anyone demonstrated an e-skin to sense so many different kinds of stimuli, which makes this incredibly impressive and innovative, said Alex Chortos, materials scientist, Stanford University.
Ko and colleagues designed the e-skin to identify many types of signals by mimicking the ultrasensitive skin of human fingertips. The researchers placed a soft ridged film over bumpy plastic-and-graphene sheets about the thickness of a few layers of plastic wrap. Touching the e-skin pressed electrodes on the bumpy sheets together caused current to flow through the device, which was hooked up to an electrical signal measuring machine. The amount of current depended on how much the bumps squished together, giving the researchers a sensitive way to gauge pressure.
Heating the e-skin also generated a current, showing how it senses temperature as well. A strip of the e-skin placed on a person’s wrist lets the researchers simultaneously measure skin temperature and blood pressure.
The e-skin’s ridges help it detect texture. When researchers skimmed the skin over glass or sandpaper, the ridges vibrated in different patterns detectable by the skin’s sensors. Sound waves also made the e-skin vibrate so it could “hear” noise from a speaker, playing one of Richard Feynman’s physics lectures, “There’s Plenty of Room at the Bottom.” The e-skin converted his words into electrical signals and sent them to a machine, which let researchers judge how well the e-skin sensed sounds.
According to Ko, this trial worked even better than an iPhone’s microphone. Cheng thinks the e-skin could serve in soft, wearable hearing aids. Unlike conventional aids, soft devices are comfortable because they mold to human skin, he added.
E-Skin Sending Brain Signals
Chortos and colleagues also developed a pressure-detecting e-skin, which sends signals directly to mouse brain cells. According to Chortos’s team, the cells dialed activity up or down depending on how hard researchers pushed on the skin and then how the brain receive the sent message.
This type of work offers a blueprint for scientists to utilize a system connecting biology with electronics, said Wenlong Cheng, chemical engineer, Monash University in Australia.
Merging E-Skin Technologies
“In the future, we could combine these techniques for real, operational electronic skin,” said Ko.
A combination of these e-skins could cover prosthetic limbs and plug directly into people’s nerve cells, helping users recognize whether they are touching something hot, rough or sharp like real skin does, added Ko. Additionally, the artificial skin could form the basis for soft, wearable medical devices.
The last number of years, scientists invented an assortment of e-skin elements, from different soft materials to new kinds of sensors. Some sensors can recognize more than one type of stimuli depending on the conditions and while e-skins still have a long way to go to reach human skin capabilities, the new work brings this technology so much closer, said Cheng.