Soft Robots Finally Cut the Cord
Researchers found that flexible batteries can be stabilized by magnetic fields, allowing soft robots to operate without a tether.
If you dig deep enough, you will find that cutting-edge robots built in academic labs aren’t always all they are cracked up to be. Soft robots, in particular, often seem to be hiding some significant limitations behind flashy presentations and carefully produced videos. Sure, they may be incredibly flexible and able to squeeze their way into nearly any space that they might need to go, but… what are those barely-visible wires at the top of the frame?
As you might have guessed, they lead to a bulky power supply that is anything but soft and flexible. Because of these properties, power is often supplied to soft robots via a tether, which greatly limits their range and mobility. A soft battery would be a much better choice, but soft batteries built with today’s technologies degrade quickly and add extra rigidity to the robot’s body.
Fortunately, this trade-off may not exist in the future. A group led by researchers at Tsinghua University has found a way to stabilize soft batteries. Their technique is well-suited for use in soft robots, as existing actuators commonly used in soft robots are part of their solution.
The team’s solution involved rethinking the relationship between a robot’s actuation system and its battery. In many soft robots, magnetic fields are already used to induce movement via a method known as magnetic actuation. The researchers discovered that these very same fields can also improve the internal chemistry of flexible zinc–manganese dioxide batteries, dramatically extending their usable life.
Working with this insight, the researchers vertically stacked flexible batteries embedded throughout a manta ray-inspired robot body. Instead of lying flat and rigid, the soft silicone-encapsulated cells are arranged in a way that preserves the robot’s natural deformability while maximizing available surface area for energy storage.
Under the influence of the robot’s magnetic actuators, the batteries demonstrated significantly improved stability. The magnetic field guides the movement of ions inside the battery, suppressing dangerous dendrite growth — tiny metal spikes that can cause short circuits — and strengthening the structure of the cathode material. As a result, the enhanced batteries retained over 57% of their capacity after 200 charge cycles, nearly doubling the performance of identical batteries without magnetic exposure.
To demonstrate the technology, the team built a fully untethered soft robot capable of swimming, sensing, and communicating wirelessly. The manta ray robot navigates water using flapping fins, sends real-time inertial and temperature data to a computer, and even reroutes itself when encountering obstacles. The same magnetic fields that drive its movement also maintain the stability of its onboard power system.
Looking ahead, the researchers hope to integrate additional sensors and explore how magnetic enhancement might improve other battery chemistries and formats. By merging actuation, energy storage, and sensing within a single soft body, this work promises to make soft robots more practical for future real-world applications.
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