A soft electroactive gel enables untethered robots to deform, grip, and move using only external electric fields, eliminating the need for internal wiring or circuitry.
(Nanowerk Spotlight) The flexibility of living tissue inspires efforts to build robots that are soft, adaptive, and capable of complex movements. Creating such machines is technically demanding, especially when they must operate without physical tethers. Soft robots need materials that deform easily, actuators that respond quickly, and control methods that are both precise and lightweight.
Most existing approaches fail to deliver on all three. Magnetic systems require bulky hardware. Light and heat actuation offer wireless control, but struggle with speed and complexity. Electric fields offer a promising alternative—but only if the materials can translate field stimuli into fast, large-scale movement without relying on wires or embedded circuitry.
Traditional electrically responsive gels deform slowly, limited by the movement of ions. Other systems, such as dielectric elastomer actuators, produce stronger and faster responses but rely on internal electrodes or onboard electronics that compromise their softness and range of motion. To make electric-field actuation practical for untethered soft robots, materials must respond quickly, deform extensively, and be controlled entirely from the outside. Advances in soft polymers and conductive nanomaterials have opened the door to this possibility.
A study published in Advanced Materials (“Electric Field Driven Soft Morphing Matter”) reports a material system that meets these criteria. Developed by researchers at the University of Bristol and Imperial College London, the material—called electro-morphing gel, or e-MG—combines a soft elastomer, a dielectric liquid, and paracrystalline carbon nanoparticles. When exposed to externally applied electric fields, e-MG exhibits fast, large, and reversible shape changes. These include stretching, twisting, bending, and locomotion. All movements are controlled wirelessly through low-cost external electrodes.
Demonstration of the deformability of e-MG robots. a) Illustration of the e-MG material structure and its principle of actuation under an electric field. b) Conceptual diagram showcasing the potential of e-MG robots in space applications. c) An e-MG gymnast swinging along a ceiling. d) An e-MG snail jumping over a gap. e) An e-MG robot delivering cargo through a channel. Demonstrations in (c–e) were performed in a dielectric liquid environment. Scale bars are 5 mm. (Image: Reprinted from DOI:10.1002/adma.202419077, CC BY)
At the heart of e-MG’s performance is its material composition. The elastomer provides structural flexibility, while the dielectric liquid softens the matrix and adjusts its electrical properties. The carbon particles, just tens of nanometers wide, introduce mobile charges. When the concentration of carbon exceeds a critical level—between 0.1 and 0.5 percent by weight—these particles form continuous paths for charge transport. The result is a percolated, electrically responsive gel that deforms rapidly in response to non-uniform electric fields.
The material responds to two physical mechanisms: electrostatic and dielectrophoretic forces. Electrostatic force acts on charges within the gel, pushing it in the direction of the field. Dielectrophoretic force acts on polarized material in a gradient field, pulling it toward stronger regions. When both forces align, the effect is amplified. By varying the carbon content, the researchers could tune which mechanism dominated. Low-carbon samples relied mainly on dielectrophoresis and showed slower actuation. Higher-carbon samples displayed rapid deformation driven by both forces. A carbon loading of 0.5 percent offered the best balance of speed, strength, and fabrication reliability.
The researchers demonstrated a range of complex behaviors enabled by this material. Robots built from e-MG could stretch by nearly three times their length, rotate in place, bend around corners, and spread out across surfaces. In one test, a snail-like robot jumped over a gap using a rapid sequence of stretch and release. In another, a humanoid-shaped robot swung along a ceiling by gripping and releasing electrodes. Because e-MG is soft, the robots can deform to anchor themselves against walls or climb vertical surfaces using only field stimuli.
Control is achieved through simple switching of external electrodes. In one setup, cylindrical electrodes arranged on a flat surface created localized electric fields. By energizing different electrode pairs in sequence, the team guided e-MG robots through figure-eight paths, across stepped platforms, and up inclined cones. The robots could roll, twist, or stretch depending on the local field configuration. In another setup using flat, planar electrodes behind a vertical surface, robots climbed upward by anchoring and pulling themselves from one energized region to the next. No wires, batteries, or on-board electronics were required.
Because electric fields can be tightly shaped, the system allows independent control of multiple robots in close proximity—something magnetic systems struggle to achieve. In one test, two e-MG robots moved independently across the same platform without interfering with each other. This localized control arises from the sharp spatial confinement of electric field gradients near each electrode. Field interactions are also affected by the robot’s shape and position, which modulates the field and adds further tuning capability.
To ensure practical utility, the researchers tested the material’s durability and environmental stability. After 10,000 actuation cycles, e-MG continued to perform reliably. Tests in both air and dielectric liquid confirmed consistent behavior across media. The system also remained functional in low-pressure environments designed to mimic space conditions. The use of mineral oil in some tests mimicked reduced gravity and surface friction, showing potential for extraterrestrial applications. The individual components of the material—silicone elastomer, silicone oil, and carbon nanoparticles—are all compatible with known aerospace standards.
The researchers also explored scalability. Miniature versions of the robot, over 4,000 times smaller in volume than their largest counterparts, still displayed the same range of actuation behaviors. This suggests that the material and actuation principles can be applied across different size scales. Potential uses could include navigating narrow spaces, manipulating fragile components, or performing soft contact tasks in confined environments.
This video showcases the versatility of electro-morphing gel (e-MG) robots without internal wiring and controlled by external electric fields. A jelly-like humanoid swings across a ceiling using agile limb movements. A snail-inspired robot jumps across a gap by stretching and contracting its soft body. Another robot navigates a narrow channel, anchoring itself to walls to push a cargo ball forward. These demonstrations highlight the adaptability and wireless control of e-MG systems in diverse tasks.
Although the robots cannot carry heavy loads, they can transport small objects by wrapping around them, embedding items within their body, or gripping via surface adhesion. The soft structure makes them particularly well suited for handling delicate or irregularly shaped items. Improvements in sensitivity could allow the same performance at lower voltages or longer distances from the electrodes, expanding their practical range.
The electrode systems themselves also offer flexibility. While most of the demonstrations used rigid copper or brass electrodes, there is no reason these could not be replaced with liquid, flexible, or even mobile systems. Drone-mounted or robotic-arm-carried electrodes could generate mobile electric fields, enabling remote navigation and manipulation in cluttered or unreachable environments. The team suggests that more complex electrode geometries could enable group coordination or programmable sequences of actions in future implementations.
By combining a soft, responsive material with remote electrical control, the e-MG system overcomes key limitations of previous wireless soft robotics. It removes the need for internal circuitry, expands the range of deformation patterns, and enables precise actuation using lightweight external components. Its demonstrated ability to morph, grip, and move through contactless stimulation provides a flexible foundation for new robotic platforms. These could be used in biomedical procedures, industrial inspection, or space exploration—where low weight, high adaptability, and remote control are essential.
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