A skin made with two layers of electrodes wrapped around an ion-infused sponge is better at detecting than human skin because it can sense nearby objects and what they’re made of.
25 January 2023
An artificial skin is even better than human skin at detecting objects, because it can detect and identify items it hasn’t touched yet.
“Human skin has to touch something to know what’s there,” says Yifan Wang of Nanyang Technological University in Singapore. “Human skin can only tell how soft or hard an object is. We wanted our artificial skin to have more features.”
Even without touching an object, Wang and his colleagues’ artificial skin can detect if it’s close and can also discern some clues about the type of material it’s made of. “We can tell if it’s a piece of metal, plastic…or some biological material,” she says.
The skin is made up of two outer layers of nickel-coated conductive fabric that serve as electrodes. These surround a porous sponge soaked in ionic liquid, which is a salt in a liquid state that acts as a conductor of electricity. The two layers act like a capacitor, storing electrical energy in an electric field.
The ions in the sponge increase the performance of the capacitor, which effectively measures how much the distance between the two electrode layers changes. That ability to detect small changes is behind how artificial skin can detect that it has touched something.
The detection performance of the capacitor, which Wang says is 10 to 100 times more sensitive than a standard capacitor, means it can also detect very small changes in the electric field around the skin, allowing it to detect nearby objects. Plus, those subtle changes can help you identify what kind of material a nearby object is made of.
In tests, the skin was able to successfully detect and classify a number of objects approaching it as polymers, metals, or fur, indicated by specific changes in capacitor measurements.
“The process is relatively simple. As the component approaches contact, it enters the electric field edges of the capacitive structure,” says Jonathan Aitken of the University of Sheffield, UK. “There are several interesting future pathways.” he says, but currently the skin relies on machine learning techniques to identify how the object it detects compares to known material data.
Wang thinks the skin could work on a robotic finger to allow factory robots to better understand which objects to pick up and which to put down without having to grab them, as well as being useful for prosthetics.
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