CMU scientists have developed a self-healing electrically conductive gel for soft robots

In order to reach their full potential, soft robotic devices cannot consist only of rigid electronic components encased in soft rubber. This can be helped by a new material that is soft, self-healing and electrically conductive.

Developed by a group of scientists from Carnegie Mellon University, the material consists of a gelatin base of polyvinyl alcohol and sodium borate, in which silver microparticles and gallium-based liquid metal droplets are embedded. In addition, ethylene glycol is added to it to prevent drying.

The material is not only capable of conducting electric current, but can also be stretched by 400% without breaking. In addition, if a piece of material is cut into two parts, it can be mechanically and electrically connected back.

During the tests, a strip of material was used to connect the battery to the motor on the outside of the soft body of the snail robot. When the strip was cut to the end (with the two cut ends still touching each other), the snail's speed dropped by more than 50%. After the ends "healed", the speed increased to 68% of the original.

In another test, two strips of gel were first used to transmit electric current to the engine of a toy car. The scientists then cut parts from the middle of both strips, connected the cut ends of the strips together to resume powering the motor, and used the two cut parts to power the LED on the roof of the car.

Finally, small pieces of material were used instead of traditional rigid electrodes to obtain electromyography (EMG) readings from various parts of the volunteer's body.

"Instead of connecting biomonitoring electrodes to equipment mounted on a trolley, our gel can be used as a bioelectrode that directly interacts with electronics mounted on the body and can collect information and transmit it wirelessly," says lead scientist, Professor Carmel Majidi. “It would be interesting to see soft-bodied robots used to monitor hard-to-reach places-whether it's a snail that can monitor water quality, or a slug that can crawl around our homes in search of mold.”