Cambridge University scientists have created a new class of low-cost hydrogels that are 3D printable, biodegradable, and self-heal at room temperature, making them suitable for soft robotics applications.
Soft sensing technologies possess all the hallmarks to transform robotics, tactile interfaces and wearable devices, but if there’s anything holding them back from being commercialized it’s their non-durability and high energy consumption.
This hasn’t stopped Cambridge’s David Hardman and his colleagues from pursuing soft sensing, self-healing materials for robotic hands and arms.
They have now – as part of the EU-funded SHERO project – developed innovative materials that can detect when they are damaged, take the necessary steps to temporarily heal themselves and then resume work – all without the need for human interaction.
Unlike previous versions that needed heat to heal, the Cambridge team’s new materials heal at room temperature, making them more useful for real-world applications.
The scientists started with a stretchy, gelatin-based material which is cheap, biodegradable and biocompatible, and carried out different tests on how to incorporate sensors into it by adding in lots of conductive components.
They found that printing sensors containing sodium chloride (salt) instead of carbon ink resulted in a material with the properties they were looking for.
Hardman attributes this to salt’s soluble nature in the water-filled hydrogel which provides a uniform channel for ionic conduction or the movement of ions.
When measuring the electrical resistance of the printed materials, Hardman and his colleagues found that changes in strain resulted in a highly linear response.
Moreover, adding salt further enabled sensing of stretches of more than three times the sensor’s original length, validating that the material can be incorporated into flexible and stretchable robotic devices.
According to co-author Dr Thomas George-Thuruthel, the self-healing materials are cheap and easy to make either by 3D printing or casting.
They are also a better alternative to many existing methods as they show long-term strength and stability without drying out, and are made entirely from widely available, food-safe materials such as gelatin.
Image and content: University of Cambridge