Cambridge University researchers have developed self-healing, biodegradable, 3D-printed materials that can be used to create realistic artificial hands and other soft robotics applications.
Described as cheap and jelly-like, the materials can sense stress, temperature and humidity and can also partially self-repair at room temperature. The teams Results are reported in NPG Asia Materials†
Soft sensing technologies can transform robotics, tactile interfaces and wearable devices, among others. However, most soft sensing technologies are not sustainable and consume a lot of energy.
“By incorporating soft sensors into robotics, we can extract a lot more information from them, such as how our muscles enable our brains to get information about the state of our bodies,” said first author David Hardman of Cambridge’s Department of Engineering.
As part of the EU-funded SHERO project, Hardman and his colleagues have developed soft sensing, self-healing materials for robotic hands and arms. These materials can detect when damaged, take the necessary steps to heal themselves temporarily, and then resume work without human intervention.
“We’ve been working with self-healing materials for several years, but now we’re looking at faster and cheaper ways to make self-healing robots,” said study co-author Dr Thomas George-Thuruthel, also of the Department of Engineering. †
Previous versions of the self-healing robots had to be heated to heal, but the Cambridge researchers are now developing materials that can heal at room temperature, which would make them more useful for real-world applications.
“We started with a stretchable, gelatin-based material that is inexpensive, biodegradable and biocompatible and conducted several tests to integrate sensors into the material by adding many conductive components,” Hardman said.
The researchers found that printing sensors containing table salt (sodium chloride) instead of carbon ink produced a material with the properties they were looking for. Because salt is soluble in the water-filled hydrogel, it provides a uniform channel for ion conduction, the team said.
When measuring the electrical resistance of the printed materials, the researchers found that changes in voltage resulted in a highly linear response, which they could use to calculate the material’s deformations. Adding salt also allowed the detection of stretches more than three times the original length of the sensor, allowing the material to be processed in flexible and stretchable robotic devices.
The self-healing materials are cheap and easy to make, both by 3D printing and by casting. They are preferred over many existing alternatives because they are strong and stable over the long term without drying out, and they are made entirely from commonly available, food grade materials.
“It’s a really good sensor considering how cheap and easy it is to make,” says George-Thuruthel. “We could make a whole robot out of gelatin and print the sensors where we need them.”
The material is a proof-of-concept, but could be further developed for use in artificial skins and custom wearable and biodegradable sensors.
This work was supported by the Self-healing soft RObotics (SHERO) project, funded under the Future and Emerging Technologies (FET) program of the European Commission.