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Re-defining soft robotics with self-healing, conductive gel

Out There | April 10, 2023 | By:

An external strip of the gel connects the battery to the motor on this soft robotic snail. Photo: Carnegie Mellon University College of Engineering.

A new material could help produce self-healing and conductive robotic devices that are also soft. Developed by a team of scientists at Carnegie Mellon University, the substance consists of a gelatinous polyvinyl alcohol-sodium borate base, embedded in which are silver microflakes and gallium-based liquid metal droplets. It’s also infused with ethylene glycol, to keep it from drying out.

Not only is the material fully capable of conducting a robust electrical current, but it can be stretched up to 400 percent of its relaxed length without breaking. Additionally, if a piece of the material is sliced in two, it can both mechanically and electrically heal itself back into one piece.

In a test of the gel, a strip of it was used to connect a battery to a motor along the outside of a soft-bodied robotic snail. When that strip was sliced all the way through (with the two severed ends still touching one another), the snail’s speed dropped by over 50 percent. Once the ends had healed together, the speed increased up to 68 percent of the original velocity.

In another test, small pieces of the material were used in place of traditional rigid electrodes to obtain electromyography (EMG) readings from different locations on a volunteer’s body.

“Instead of being wired up with biomonitoring electrodes connecting you to bio-measurement hardware mounted on a cart, our gel can be used as a bioelectrode that directly interfaces with body-mounted electronics that can collect information and transmit it wirelessly,” says the lead scientist, Prof. Carmel Majidi. “It would be interesting to see soft-bodied robots used for monitoring hard-to-reach places, whether that would be a snail that could monitor water quality, or a slug that could crawl around houses looking for mold,” he adds.

A paper on the research was recently published in the journal Nature Electronics

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