Untethered robots suffer from a stamina problem.
A possible solution: a circulating liquid – “robot blood” – to store energy and power its applications for sophisticated, long-duration tasks.
Humans and other complex organisms manage life through integrated systems.
Humans store energy in fat reserves spread across the body, and an intricate circulatory system transports oxygen and nutrients to power trillions of cells.
But crack open the hood of an untethered robot and things are much more segmented: Over here is the solid battery and over there are the motors, with cooling systems and other components scattered throughout.
Researchers at Cornell University have created a system of circulating liquid — “robot blood” — within robotic structures, to store energy and power robotic applications for sophisticated, long-duration tasks.
The researchers have created a synthetic vascular system capable of pumping an energy-dense hydraulic liquid that stores energy, transmits force, operates appendages and provides structure, all in an integrated design.
“In nature we see how long organisms can operate while doing sophisticated tasks. Robots can’t perform similar feats for very long,” said Rob Shepherd, associate professor of mechanical and aerospace engineering at Cornell.
“Our bio-inspired approach can dramatically increase the system’s energy density while allowing soft robots to remain mobile for far longer.”
Shepherd, director of the Organic Robotics Lab, is senior author of “Electrolytic Vascular Systems for Energy Dense Robots,” which published in Nature. Doctoral student Cameron Aubin is lead author.
The researchers tested the concept by creating an aquatic soft robot inspired by a lionfish, designed by co-author James Pikul, a former postdoctoral researcher, now an assistant professor at the University of Pennsylvania. Lionfish use undulating fanlike fins to glide through coral-reef environments.
Silicone skin on the outside with flexible electrodes and an ion separator membrane within allows the robot to bend and flex.
Interconnected zinc-iodide flow cell batteries power onboard pumps and electronics through electrochemical reactions.
The researchers achieved energy density equal to about half that of a Tesla Model S lithium-ion battery.
The robot swims using power transmitted to the fins from the pumping of the flow cell battery. The initial design provided enough power to swim upstream for more than 36 hours.
Underwater soft robots offer tantalizing possibilities for research and exploration. Since aquatic soft robots are supported by buoyancy, they don’t require an exoskeleton or endoskeleton to maintain structure.
By designing power sources that give robots the ability to function for longer stretches of time, Shepherd thinks autonomous robots could soon be roaming Earth’s oceans on vital scientific missions and for delicate environmental tasks like sampling coral reefs.
These devices could also be sent to extraterrestrial worlds for underwater reconnaissance missions.
Written by Matt Hayes.
DOI: https://doi.org/10.1038/s41586-019-1313-1
