Self-healing structural hydrogel is inspired by nature

It has been noted for several years that one area where humanoid robots are lacking is skin tone—most robots have a pasty white complexion, which is both disturbing and likely to lead to social problems once robots become mainstream.

Most artificial skin is not able to heal itself, which means that robots need skin replacement if it gets damaged or accidentally coloured in undesirable ways. There is also the issue of colours fading. When materials such as rubbers or plastics are coloured, it is generally done through the use of pigments, which, like clothes, tend to fade over time.

For that reason, robot scientists would like to use other types of colouring options, one of which is structural colours—materials that have their colour due to surface nanostructures rather than pigments.

As an example, animals such as birds and fish are immune to fading due to structural colouring on scales and feathers. The problem with using such colouring, the researchers note, has been figuring out how to make them strong enough to handle real-world problems like running into things. In this new effort, the researchers report that they looked to nature to overcome this problem.

The new hydrogel they developed is actually double layered—one layer holds the structural colours, the other offers self-healing. When the hydrogel is cut into two pieces, it can not only heal itself, it maintains the original colour while doing so.

The end result, the team reports, is a very tiny scar. The group has conducted extensive testing of the material and has found that it is capable of withstanding real-world conditions. It is not yet clear if the material could actually be used as a robot skin, but the researchers suggest it could be used for many different applications.