Caltech and ETH Zurich engineers have developed robots capable of moving on their own without using a motor, servos or some kind of power supply: instead, these devices move in the water thanks to the material from which they are made, changing in shape at temperature changes.
“Our examples show how we can use structured materials that are deformed by reacting to changes in the environment to control and move robots”,
says Chiara Daraio, professor of engineering and applied physics at Caltech’s Department of Mechanical and Applied Science.
The new propulsion system is based on strips of a flexible polymer that cycles when it is cold and stretches when it is hot. This polymer is positioned to activate a switch inside the robot body, which in turn is connected to a paddle that moves the device.
The switch is made of a material with two constant states (it can be fixed in two separate geometries). In particular, it is made of strips of elastic material which, when pressed by the polymer, passes from one position to the other. When the cold robot is placed in hot water, the polymer is stretched, activates the switch, and the resulting sudden release of energy moves the robot forward. The polymer strips can also be “regulated” to give specific reactions under different conditions, e.g. a thicker strip will need more to warm up and stretch than a thinner. This setting feature allows the design of robots capable of turning and moving at different speeds.
In the latest version of her plan, the team of Daraio and her associates managed to connect the polymer elements and the switches so that a four-oar robot moves forward on its own, leaving a small load and then returning.
“By combining simple moves, we were able to integrate programming into the material to perform a series of complex behaviors”,
said Osama Bilal, a postdoctoral student at Caltech, and one of the research participants.
In the future, it is estimated that more features and capabilities can be added – e.g. through polymers that react to other environmental conditions such as PH changes, salinity etc.
Future versions of these robots could be used to tackle chemical leakage, drug delivery, and so on.
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