Versatile microscale robots can bend into 3D shapes and crawl

Researchers at Cornell University have created microscopic robots less than a millimeter in size, printed as a 2D hexagonal “metasheet,” but which, with an electric discharge, transform into pre-programmed 3D shapes and crawl.

The robot’s versatility is due to an innovative design based on kirigami, a cousin of origami, in which slices in the material allow it to bend, expand and move.

The team’s paper, “Microscopic Robots with Electronically Configurable Metaleaves,” appears in Natural materials. The study’s co-lead authors are postdoctoral researchers Qingkun Liu and Wei Wang. The project was led by Itai Cohen, a professor of physics. His lab has previously produced microrobotic systems that can actuate their limbs, pump water through artificial cilia, and walk autonomously.

In a sense, the origins of the kirigami robot were inspired by “living organisms that can change shape,” Liu said. “But when people create a robot, once it’s made, it might be able to move some limbs, but its overall shape is usually static. So we created a metasheet robot. The ‘meta’ stands for metamaterial, which means they’re made of many building blocks that work together to give the material its mechanical behaviors.”

The robot is a hexagonal tile composed of about 100 silicon dioxide panels connected by more than 200 actuating hinges, each about 10 nanometers thick. When electrochemically activated via external wires, the hinges form mountain-and-valley-shaped folds and act to open and rotate the panels, allowing the robot to change its coverage area and expand and contract locally by up to 40 percent. Depending on which hinges are activated, the robot can take on different shapes and potentially wrap around other objects and then unfold to form a flat sheet.

Cohen’s team is already thinking about the next step in metasheet technology. It plans to combine its flexible mechanical structures with electronic controllers to create ultra-responsive “elastronic” materials with properties that would never be possible in nature. Applications could range from reconfigurable micromachines to miniaturized biomedical devices and materials that can respond to impact at nearly the speed of light, rather than the speed of sound.

“Because the electronics in every building block can harness the energy of light, it is possible to design a material that responds in a programmed way to various stimuli. When stressed, these materials, instead of deforming, could ‘leak’ or repel with a force greater than the one they were subjected to,” Cohen said. “We believe that these active metamaterials – these elastronic materials – could form the basis of a new type of intelligent matter governed by physical principles that transcend what is possible in the natural world.”