Caltech and ETH Zurich engineers have devised a new class of robots that propel themselves without using any motors, servos, or power supply.
According to the researchers, the robots paddle through water when the machine-like functioning material they are constructed from deforms with temperature changes.
“Our examples show that we can use structured materials that deform in response to environmental cues, to control and propel robots,” contends Professor Daraio, a team lead and corresponding author of the paper.
The new propulsion system relies on strips of a flexible polymer that is curled when cold and stretches out when warm.
According to the researchers, the polymer is positioned to activate a switch inside the robot’s body, that is in turn attached to a paddle that rows it forward like a rowboat.
The switch is made from a bistable element, which is a component that can be stable in two distinct geometries. In this case, it is built from strips of an elastic material that, when pushed on by the polymer, snaps from one position to another.
When the cold robot is placed in warm water, the polymer stretches out, activates the switch, and the resulting sudden release of energy paddles the robot forward.
According to the researchers, the polymer strips can also be tuned to give specific responses at different times. For example, a thicker strip will take longer to warm up, stretch out, and ultimately activate its paddle than a thinner strip.
The researchers contend that this tunability allows manufacturers to design robots capable of turning and moving at different speeds.
The current research builds on previous work by Daraio and Dennis Kochmann, professor of aerospace at Caltech. They used chains of bistable elements to transmit signals and build computer-like logic gates.
The team is now exploring ways to redesign the bistable elements so that they are self-resetting when water temperature shifts again.
According to the researchers, this makes them capable of swimming on indefinitely, so long as water temperature keeps fluctuating.
Image, video and content: Tian Chen and Osama R. Bilal/Caltech