Soft robot uses magnetic fields to power itself autonomously

Due to their agility and gentle touch, soft robots are ideal for traversing delicate or enclosed spaces to perform various tasks, such as inspecting industrial pipes in chemical plants. However, achieving embodied intelligence in such systems, where sensing, movement and power supply work together in an untethered configuration, remains a challenge.

Flexible materials can deform and adapt, but their power sources are unable to do so. Conventional batteries can stiffen the robot’s body, drain quickly or degrade under strain, leaving soft robots tethered or with a short lifespan.

Now, researchers from the National University of Singapore have found a way to turn this limitation into an advantage. Their research findings, published in Science Advances, demonstrate that the same magnetic fields used to control soft robots can also enhance the performance of the batteries inside them.

“Magnetic fields are typically used to stimulate motion in soft robots, in a process called ‘actuation’, but we realised they could also stabilise electrochemical reactions inside flexible batteries,” said Assistant Professor Wu Changsheng. “Allowing actuation and energy management to share the same physical principle enables us to make the robot truly self-contained and efficient.”

The team designed flexible zinc-manganese dioxide (Zn-MnO2) batteries encapsulated in soft silicone and vertically stacked within a robot body inspired by the manta ray. Unlike traditional lateral arrangements, this vertical integration maximises space and keeps the robot pliable.

“We took a page from the manta ray because its body embodies exactly what we want to achieve — a natural integration between movement, sensing and energy use,” Wu said. “Its form allows synergistic coordination of multifunctionalities in an efficient and compact way, making it a perfect biological model for embodied intelligence.”

Through tests, the researchers revealed that the magnetic field produced by the robot’s own ferromagnetic actuators stabilised the internal chemistry of the flexible batteries, reducing the risk of dendrite growth — needle-like metal deposits that can cause short circuits — and maintaining energy output under repeated stress and bending. Under magnetic enhancement, the batteries retained 57.3% of their capacity after 200 cycles, nearly double that of unenhanced samples.

“After further investigation, we found out how this enhancement works. The Lorentz force generated by the magnetic field acts on moving ions in the electrolyte and redirects zinc ion trajectories during plating, creating a more uniform ion flux that promotes even zinc deposition at the anode and effectively suppresses dendrite growth. Simultaneously, the magnetic field aligned electron spins within the manganese oxide lattice, reinforcing atomic bonds and preventing crystal degradation during charge and discharge,” added Xiao Xiao, a co-first author of the publication. “This dual magneto-electrochemical stabilisation, achieved in a fully flexible format, is an exciting step towards durable onboard power systems for soft robots operating in challenging, dynamic environments.”

To demonstrate the concept, the team built a magnetically actuated manta ray robot equipped with the flexible batteries, soft magnetic elastomer actuators and a lightweight hybrid circuit for sensing and wireless communication. The robot’s fins flap in response to external magnetic fields generated by a coil or electromagnet array, enabling it to stabilise the locomotion and adapt to different water surfaces.

As expected, the same magnetic fields that drive and steer the robot also enhance its energy stability — confirming the researchers’ vision to merge motion control with power management. The robot can perform basic swimming manoeuvres, such as linear propulsion, 90-degree turns, and complex trajectories, all while transmitting real-time data to a computer that visualises its movements in a digital twin environment.

Within this set-up, the robot exhibited autonomous decision-making abilities. For instance, when it encountered an obstacle, onboard inertial sensors detected sudden changes in acceleration, which in turn prompted the control system to adjust its orientation and reroute. The robot successfully navigated narrow passages through posture adjustments and executed U-turns when facing impassable obstacles. During perturbation tests, the feedback algorithm rapidly corrected deviations in yaw, pitch and roll angles caused by external forces like waves or physical contact, maintaining stable trajectory control. The integrated temperature sensors enabled environmental monitoring, mapping thermal gradients in aquatic environments.

Looking ahead, the researchers plan to expand the robot’s sensing capabilities by incorporating miniaturised sensors such as ultrasonic sensors for surrounding perception or chemical detectors for water-quality monitoring. They are also exploring how magnetic enhancement could improve other battery chemistries, such as lithium-ion, or other battery forms, such as wearable battery fibres, to enhance energy density and operational endurance.

“Our vision is to enable soft robots that can think and act autonomously in complex or inaccessible spaces — whether inspecting pipelines, monitoring marine habitats or supporting medical interventions in the operating theatre,” Wu said.

Top image caption: The magnetically actuated manta ray robot is equipped with flexible batteries, soft magnetic elastomer actuators and a lightweight hybrid circuit for sensing and wireless communication. Image credit: National University of Singapore.