Cutting open a soft robotic hand

Jelly-like robots self-heal after being sliced with a blade

Image credit: Vijie Universeitat Brussel

A team of researchers at Vrije Universiteit Brussel have developed a material for soft robots which can completely stitch themselves back together after being damaged, with almost perfect function after recovery and no signs of scarring.

Robots with the human ability to self-heal, but at a staggering pace, are a common fixture of science fiction, from the malicious killer robot at the centre of the Terminator franchise to the benign Baymax of Big Hero 6.

The majority of the robots in operation today are coated in tough metal or plastic coats which resist damage. However, the emerging field of soft robotics – the development of robots covered with soft, flexible materials – could intensify the necessity of self-healing capabilities in robots.

Soft robots are generally considered more pleasant to interact with, especially for children and immobilised hospital patients. Their squishy coverings make them ideal for grasping delicate objects (such as when picking fruit), and capable of absorbing the shock of sudden impacts. However, these robots are more vulnerable to other forms of damage, such as being sliced by sharp metal edges.

Foreseeing these types of injuries as a potential stumbling block for field of soft robotics, the Belgian team, led by PhD student Seppe Terryn, have developed a new material made of recyclable, temperature-sensitive elastic material capable of self-healing.

It is composed of cross-linked “Diels-Alder” polymers, formed from large, heat-sensitive molecules. When exposed for 40 minutes to moderate heat – around the temperature of a freshly-made cup of tea, the material’s lattice breaks down, and knits back together during cooling. During this process – the Diels-Alder reaction – microscopic and macroscopic damage can be completely fixed.

The researchers tested their material on three different soft robotics applications which use pneumatics: a gripper, a hand, and artificial muscles. Pneumatic actuators such as these frequently suffer damage due to excessive pressures and wear, affecting their function.

Vrije Universiteit Brussel

According to the researchers' Science Robotics study, the material is capable of completely repairing itself from scalpel blade cuts within 24 hours of heat exposure. It leaves no discolouration, “scarring”, or weak spots, and after healing, function is estimated at 98-99 per cent.

Next, the Vrije Universiteit Brussel team will work towards developing sensors to monitor the health of soft robots.

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