Soft Autonomous Robot Crawls Like an Earthworm

MIT, Seoul National University, and Harvard University and researchers have designed a soft, highly flexible autonomous robot that performs peristalsis movement similar to that of an earthworm.

Dubbed "Meshworm", the robot features a versatile meshlike tube. An "artificial muscle" was made from contractible nickel and titanium wire wound around in a segment like fashion. The segments were treated with current by compressing the mesh tube, making the robot move forward. Demonstration on this design was presented in the journal IEEE/ASME Transactions on Mechatronics.

Engineering soft actuators, or motors for driving robots remained a challenge. However, robot can be set in motion by pumping compressed air through it.

Earthworms have two main muscle groups such as circular muscle fibers and longitudinal muscle fibers, enabling the worm to move in inches.

The team also focused on earthworm-like soft, peristalsis-driven system. By winding and heat-sealing a sheet of polymer mesh, scientists created a long, flexible spring-like tubular body. A nickel-titanium alloy was used for creating artificial muscle.

Based on the ratio of nickel to titanium, the alloy can fluctuate with heat. The alloy remains in austenite phase beyond a specific temperature, while shifting to a martensite phase when the temperature becomes low.

A tightly coiled nickel-titanium wire was wrapped around the mesh tube, imitating the earthworm’s circular muscle fibers. A small battery and circuit board was equipped to the tube, through which the wire gets heated by the current at certain segments along the body, thereby making the robot move forward. The algorithms formulated by the researchers control the wire's heating and cooling patterns.

Direction of the robot can be controlled by equipping it with wires coiled along its length.

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