Meet the robot fish with battery fluid blood


Soft robotics development combines drive and power in a single liquid system. Andrew Masterson reports.


The robotic lionfish, with battery fluid blood clearly visible.

James Pikul; pikul@seas.upenn.edu

Scientists have created a robot lionfish that can swim against the current and has battery fluid for blood.

Such a description sounds slightly sinister, but in reality the robo-fish, outlined in a paper in the journal Nature, represents an important proof-of-concept that solves one of the critical challenges in mobile robotics – weight management.

In order to move and continue doing so over periods of time, all robots must have mechanics and a power source. Traditionally, these are two separate systems; movement might be provided by hydraulics, for example, while power is delivered by a charged battery.

Both systems represent weight that has to be carried, and mass that has to be incorporated into the build. And a brute relationship, common to all machines, remains in play: the more weight that must be moved, the greater the amount of power needed to move it.

In making the robotic lionfish, however, Robert Shepherd from Cornell University in the US, and colleagues, created an “electrolytic vascular system” in which battery fluid not only provides the energy to power onboard pumps and electronics, but also functions hydraulically to drive the machine.

The researchers claim it can swim strongly enough to battle against oncoming currents, fan its fins in a display of lionfish verisimilitude, and operate for 36 hours before it needs recharging.

“Modelled after redox flow batteries, this synthetic vascular system combines the functions of hydraulic force transmission, actuation and energy storage into a single integrated design that geometrically increases the energy density of the robot to enable operation for long durations,” they write.

The robo-fish represents a significant advance in the field of “soft” robotics, an approach that builds machines from flexible and deformable materials. It is, write Shepherd and colleagues, a step toward creating “the multifunctional interconnected systems found in living organisms” and the benefits that result.

“This use of electrochemical energy storage in hydraulic fluids could facilitate increased energy density, autonomy, efficiency and multifunctionality in future robot designs,” they conclude.

  1. https://doi.org/10.1038/s41586-019-1313-1
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