PHOTO CAPTION: An artificial skin attached to a person’s knee develops a purple “bruise” when hit forcefully against a metal cabinet. (Image Adapted from ACS Applied Materials & Interfaces 2021)
Researchers have developed an artificial skin that senses force through ionic signals and also changes color from yellow to a bruise-like purple, providing a visual cue that damage has occurred, they report in ACS Applied Materials & Interfaces.
Scientists have developed many different types of electronic skins, or e-skins, that can sense stimuli through electron transmission. However, these electrical conductors are not always biocompatible, which could limit their use in some types of prosthetics. In contrast, ionic skins, or I-skins, use ions as charge carriers, similar to human skin. These ionically conductive hydrogels have superior transparency, stretchability and biocompatibility compared with e-skins.
Mimics Human Bruising
Qi Zhang, Shiping Zhu and colleagues wanted to develop an I-skin that, in addition to registering changes in electrical signal with an applied force, could also change color to mimic human bruising, a media release from the American Chemical Society explains.
The researchers made an ionic organohydrogel that contained a molecule, called spiropyran, that changes color from pale yellow to bluish-purple under mechanical stress. In testing, the gel showed changes in color and electrical conductivity when stretched or compressed, and the purple color remained for 2-5 hours before fading back to yellow.
Then, the team taped the I-skin to different body parts of volunteers, such as the finger, hand and knee. Bending or stretching caused a change in the electrical signal but not bruising, just like human skin. However, forceful and repeated pressing, hitting and pinching produced a color change.
The I-skin, which responds like human skin in terms of electrical and optical signaling, opens up new opportunities for detecting damage in prosthetic devices and robotics, the researchers suggest, in the release.
[Source(s): American Chemical Society, EurekAlert]
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