Realistic and efficient robotic limbs for the human body are a step closer following a breathtaking breakthrough in artificial structural materials that are not only 3-D printable and biodegradable but also self-healing.
The materials, which are low-cost, flexible and made from a jelly-like substance can also sense temperature, increasing or decreasing strain and variations in humidity.
Developed by researchers at the University of Cambridge, these materials also can partially repair themselves at room temperature.
It has long been recognised that soft sensing technologies could transform practical robotics with the development of tactile interfaces and wearable devices. However, those advances have been hampered because most soft sensing technologies simply aren’t durable enough for real-world applications and consume high amounts of energy.
“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,” says engineer David Hardman, one of the lead researchers on the project, from the United Kingdom’s Cambridge University.
Hardman and his colleagues are developing ground-breaking new materials for robotic hands and arms. These materials detect when they are damaged, can then temporarily heal themselves and resume their task – all without the need for human interjection.
Dr Thomas George-Thuruthel, also from the Cambridge Department of Engineering, says they have been working with self-healing materials for several years. However, their sights are now on coming up with faster and cheaper ways to make truly self-healing robots.
Self-healing robots have been around for a while, but previous incarnations required heating to promote the restoration process. The real breakthrough for the Cambridge researchers came when they realised the new material could heal at room temperature, which makes them much more useful in real-world applications.
The researchers began with a “stretchy, gelatine-based material” which is cheap, biodegradable and biocompatible. They then completed a variety of tests on how to incorporate sensors into the material by adding different conductive components, says Hardman.
One of these key ingredients is salt. The researchers found that producing printed sensors containing sodium chloride – common salt – instead of carbon ink created the properties they were looking for.
Since salt is soluble, it provides a uniform channel within the water-filled hydrogel for ionic conduction which, simply put is the movement of ions. This then allows the researchers to measure tension and deformations in the material arising from that strain.
The addition of salt also facilitated an ability to sense stretching more than three times the sensor’s original length, which means the material can be incorporated into flexible and stretchable robotic devices.
The self-healing materials are easy to make, either by 3D printing or casting and are superior to many existing options because they show long-term strength and stability. They are made entirely from widely available, food-safe, materials and, importantly, they do not dry out.
The self-healing hydrogels can be used in a variety of ways. For example, while the research is focused thus far on developing artificial hands this new technology may in the future also be incorporated into custom-made wearable and biodegradable sensors and even artificial skin.
“It’s a really good sensor considering how cheap and easy it is to make,” says Dr George-Thuruthel, who, in a nod to the future, adds that researchers may be able to “make a whole robot out of gelatine and print the sensors wherever we need them.”