A team of engineers and researchers at Caltech and ETH Zurich say they have developed an artificial skin capable of detecting temperature changes using a mechanism similar to the one used by the organ that allows pit vipers to sense their prey. The material could be grafted onto prosthetic limbs to restore temperature sensing in amputees, according to the scientists, who added that it could also be applied to first-aid bandages to alert health professionals of a temperature increase, a sign of infection, in wounds.

 

A paper about the new material will be published in Science Robotics on Wednesday.

 

While fabricating synthetic woods in a petri dish, a team led by Caltech’s Chiara Daraio, Ph.D., created a material that exhibited an electrical response to temperature changes in the lab. It turned out that the component responsible for the temperature sensitivity was pectin, a long-chain molecule present in plant cell walls.

 

“Pectin is widely used in the food industry as a jellifying agent; it’s what you use to make jam. So it’s easy to obtain and also very cheap,” says Dr. Daraio, professor of mechanical engineering and applied physics in the Division of Engineering and Applied Science.

 

The team shifted its attention to pectin and ultimately created a thin, transparent flexible film of pectin and water, which can be as little as 20 μm thick (equivalent to the diameter of a human hair). Pectin molecules in the film have a weakly bonded double-strand structure that contains calcium ions. As temperature increases, these bonds break down and the double strands “unzip,” releasing the positively charged calcium ions.

 

Either the increased concentration of free calcium ions or their increased mobility (likely both, the researchers speculate) results in a decrease in the electrical resistance throughout the material, which can be detected with a multimeter connected to electrodes embedded in the film.