Described in NGP Asia Materials, the biodegradable, jelly-like substance is also able to sense strain, temperature and humidity. The material can detect when it is damaged and partially repair itself at room temperatures. According to the team behind the work, embedding the material into soft robotics is the ultimate goal.
“Incorporating soft sensors into robotics allows us to get a lot more information from them, like how strain on our muscles allows our brains to get information about the state of our bodies,” said first author David Hardman from Cambridge’s Department of Engineering.
Earlier versions of the self-healing robots needed to be heated to heal, but the Cambridge researchers are now developing materials that can heal at room temperature, making them much more suited to real-world applications.
“We started with a stretchy, gelatine-based material which is cheap, biodegradable and biocompatible and carried out different tests on how to incorporate sensors into the material by adding in lots of conductive components,” said Hardman.
The researchers found that printing sensors containing table salt (sodium chloride) instead of carbon ink resulted in a material with the properties they were looking for. Since salt is soluble in the water-filled hydrogel, it provides a uniform channel for ionic conduction.
When measuring the electrical resistance of the printed materials, it was found that changes in strain resulted in a highly linear response, which they could use to calculate the deformations of the material. Adding salt also enabled sensing of stretches of more than three times the sensor’s original length, so that the material can be incorporated into flexible and stretchable robotic devices.
“It’s a really good sensor considering how cheap and easy it is to make,” said co-author Dr Thomas George-Thuruthel, also from Cambridge’s Department of Engineering. “We could make a whole robot out of gelatine and print the sensors wherever we need them.”
According to the researchers, the material could be developed further to be incorporated into artificial skins and custom-made wearable and biodegradable sensors.