Artificial leather bruises like the real thing


Researchers at the Chinese University of Hong Kong have developed artificial skin that can effectively indicate if damage has occurred, just like our bruises on the skin naturally. The new skin is made with an ionic hydrogel and demonstrates changes in electrical signaling when it deforms. It also produces a change in purple color, which provides a visual indicator. Technology can be useful in making prostheses more realistic and sensitive and alerting users to possible damage.

Prostheses are increasingly advanced, with various technologies that aim to allow users to feel and respond to their environment more easily and intuitively. Much of this is developing skin-like materials with improved functionality. Ionically conductive hydrogels represent a promising option for these materials, as they are extensible and biocompatible compared to some other electronically responsive skin materials.

The latter technology takes advantage of these properties to form an artificial skin that can provide an electronic signal when deformed. However, Hong Kong researchers went a step further by introducing a color-changing mechanism that mimics bruises. The hydrogel is impregnated with a molecule called spiropyran, which changes color from yellow to purple like a purple when mechanical stress is applied. The team describes the gel as a mechanochromic organohydrogel and contains a network of crosslinked micelles.

The “bruise” that appears after damaging the skin lasts about 2 to 5 hours, before disappearing. So far, researchers have tested the skin with volunteers, who recorded it on various parts of the body, including fingers, knees and hands. The skin successfully recorded normal movements in these appendages and joints and, when stretched during these movements, provided an electrical response, but without bruises. However, when the skin was whipped, pinched, or abused, a characteristic purple tinge occurred.

The technology could provide a simple visual indication to prosthesis users so they could suffer damage to the prostheses and help them identify and avoid sources of damage. It is also in line with the progression towards more realistic and functional rehabilitation devices.

Study a Materials and interfaces applied by ACS: Colorimetric ionic organohydrogels that mimic human skin for the detection of mechanical stimuli and the visualization of lesions

Via: ACS

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