Nature powers up with a mechanical fish that runs off a circulating liquid power source:
The roughly 40-centimetre soft robot doesn’t have solid batteries — instead it is propelled by a dual-function fluid that stores energy and moves the fish’s fins. The approach allows the machine to store more energy in a smaller space and operate for longer periods without the need for heavy and cumbersome battery packs.
The innovation is a step towards creating autonomous robots — those that can perform tasks without human intervention or guidance, says Robert Shepherd, a roboticist at Cornell University in Ithaca, New York, who was part of the team that built the robot.
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Instead of using conventional hydraulic fluid, which typically circulates around machines to move their parts, Shepherd’s team used a battery fluid that powered the robot and also powered a pump to move the fins, making the fish swim.
The approach increased the amount of energy stored in the robot by 325%, compared with a machine that has a separate battery and hydraulic-fluid system, says Shepherd. The team calculated that the robot would be able to function for 37 hours without requiring recharging.
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You can read the research here.