This soft robot runs on a battery fluid that circulates around its body. Source: James PikulA team of researchers from Cornell University and the University of Pennsylvania has developed a robotic fish powered by battery fluid that the research team calls “robot blood.”

The 40 cm long soft robotic fish is not powered by standard solid batteries, but by a dual-function fluid that stores energy and enables the pectoral fins to propel the fish. Built to resemble a lionfish, the robotic fish can store more energy in smaller spaces while operating for extended periods of time — all without bulky battery packs.

Such a development, according to the researchers, could have implications for the future of autonomous robots, enabling them to be autonomous for extended periods of time, which until now has been a key obstacle in robotics, according to the research team. This is due in part to the fact that powering a robot to perform tasks without recharging requires disparate components, most of which are bulky, adding weight to the robot, and consequently, increasing energy use, which affects the dexterity, flexibility and autonomy of the robot.

To address that challenge, the team used battery fluid in lieu of bulk batteries to power the robot as well as a pump that enabled the robotic fish to move its pectoral fins, propelling it to swim. Working much more like an animal than a robot where animal parts are multifunctional versus the separate components that power a robot, the technique reportedly increased energy storage in the robot by 325% compared with a robot powered by a separate battery and hydraulic fluid system. Likewise, according to the team’s calculations, the robotic fish was able to operate for 37 hours without recharging.

“We realized that the operation time of most robots is very short before they have to recharge, on the order of tens of minutes, yet humans can operate for days without eating,” explained James Pikul, a co-author of the study and a researcher at the University of Pennsylvania’s Department of Mechanical Engineering and Applied Mechanics. “We wanted to solve this problem by finding ways to store energy in all the components of a robot. This robot blood is our first demonstration of storing energy in a fluid that is normally only used for actuation.”

For more on their results, go to the journal Nature.