Flexible actuator design lets the insect-sized bots navigate effectively in complex environments with improved movement control.
Researchers in China have developed a new actuation system for insect-sized soft robots that could improve mobility in confined or complex environments. The work, published in Nature Communications, uses a muscle-inspired elasto-electromagnetic mechanism rather than rigid miniature motors, which are prone to damage and friction at small scales.
Muscles function like actuators, moving body parts by contracting and relaxing their fibres. Linked to the body’s nervous and electrical systems, they enable a variety of movements, including those that produce forces far greater than the animal’s body mass.
The actuator combines a flexible silicone polymer (polydimethylsiloxane), a neodymium magnet, and an electrical coil embedded with soft magnetic iron spheres. Fabricated via a 2D moulding process. It operates at under 4 volts and is powered by onboard batteries.
The system can also undergo large deformations, with a contraction ratio of 60% and produces an output force of 210 newtons per kilogram. It does not require continuous power to hold a position, a method similar to energy-saving mechanisms found in mollusks.
The actuation relies on a balance of elastic and magnetic forces. When current flows through the coil, a Lorentz force interacts with the magnet, deforming the actuator as the iron spheres respond. The flexible polymer allows the structure to recover its shape once power is removed.
The team built several autonomous soft robots using the actuator, including a 16 × 10 × 10 mm inchworm-like crawler weighing 1.8 g and producing 0.41 N of force. The robot, powered by a 3.7 V lithium-ion battery and onboard control circuit.
The robots have been able to move across varied surfaces such as soil, stone, PVC, glass, and wood, and withstood drops from 30 m without damage, and can maneuver in inclined surface of 5 to 15 percent.
