Robots that are soft in nature have come along in leaps and bounds of late, forming the basis for machines that are safer to work with, can grasp different objects and better handle rugged terrain. But the need to pack things like power sources and actuators inside has generally meant that miniaturization is out of the question. Researchers may have now opened the door to tiny, millimeter-scale soft robots, by developing a robotic caterpillar that is powered and controlled purely by external light.

Liquid crystal elastomers (LCE) are materials consisting of polymer networks that respond to changes in light, a property we have seen recently put to use in the development of stretchable laser-emitting rubber. Scientists at the University of Warsaw have been exploring how the material can be used to create three-dimensional shapes that, when stimulated by light, mimic certain types of movement found in nature.

This work has now culminated in the creation of a 15 mm (0.6 in) long robotic caterpillar made from LCE that is powered by green light and can be controlled by a modulated laser beam. The researchers say by altering the light patterns, the caterpillar can be made to take on different gaits and walk up slopes, squeeze through narrow spaces and even push objects as much as 10 times its own weight.

"Designing soft robots calls for a completely new paradigm in their mechanics, power supply and control," says Piotr Wasylczyk, head of the Photonic Nanostructure Facility at the Faculty of Physics of the University of Warsaw. "We are only beginning to learn from nature and shift our design approaches towards these that emerged in natural evolution."

The research was published in the journal Advanced Optical Materials.