Engineers and scientists from Caltech and ETH Zurich were able to construct a new material that can feel temperature differences, which could possibly be used in prosthetic limbs to act as a sensitive artificial skin.

The material, as reported in Science Robotics, uses a mechanism that is akin to the pit organ in vipers. The researchers were studying synthetic wood when they discovered that a molecule, pectin, played a role in generating an electrical impulse when exposed to changes in temperature.

The team subsequently developed a flexible film of pectin and water that is thin and transparent. The material can be made as thin as 20 microns (about the diameter of a human hair) and is sensitive to changes in temperature that fall between 10 and 55°C (50 and 131°F).

"Pectin is widely used in the food industry as a jellifying agent; it's what you use to make jam," senior author Chiara Daraio, professor of mechanical engineering and applied physics at Caltech, said in a statement. "So it's easy to obtain and also very cheap."

Pectin molecules are long chains weakly bonded together and they contain calcium ions. When temperatures increase, the chain breaks and the ions are free to move. Either the higher number of free ions or their newfound freedom (the researchers suspect both) allow for the material to have a reduced electrical resistance.

The material can detect changes as subtle as 0.01°C (0.018°F) over the temperature range – almost 10 times more sensitive than previously developed electronic skin and 100 times more responsive.

And it’s not just for artificial skin. The material could also be used as a smart dress wound. Since infections raise temperatures in the body, the material can be used as a signal to medical practitioners that something is affecting the wound.

The researchers are also looking into extending its capabilities to higher temperatures, not just for direct human application but for use in industry, consumer electronics, and even in robots.