Earthworms creep along the ground by alternately squeezing and stretching muscles along the length of their bodies, inching forward with each wave of contractions in a process called peristalsis. Now researchers at MIT, Harvard University, and Seoul National University have engineered a soft autonomous robot that moves via peristalsis, crawling across surfaces by contracting segments of its body, much like an earthworm. The robot, made almost entirely of soft materials, is remarkably resilient. Even when stepped upon or bludgeoned with a hammer, the robot is able to inch away, unscathed.
The robot is named “Meshworm” for the flexible, mesh-like tube that makes up its body. Researchers created “artificial muscle” from wire made of nickel and titanium — a shape-memory alloy that stretches and contracts with heat. They wound the wire around the tube, creating segments along its length, much like the segments of an earthworm. They then applied a small current to the segments of wire, squeezing the mesh tube and propelling the robot forward.
In the past few decades, many roboticists have looked for ways to engineer soft robotic systems. Without bulky, breakable hardware, soft robots might be able to explore hard-to-reach spaces and traverse bumpy terrain. Their pliable exteriors also make them safe for human interaction. A significant challenge has been in designing soft actuators, or motors, to power such robots. One solution has been to use compressed air, carefully pumped through a robot to move it. But air-powered, or pneumatic, robots require bulky pumps.
Instead, the team looked to the earthworm for design guidance. They noted that the creepy crawler is made up of two main muscle groups: circular muscle fibers that wrap around the worm’s tube-like body, and longitudinal muscle fibers that run along its length. Both muscle groups work together to inch the worm along.
The group also outfitted the robot with wires running along its length, similar to an earthworm’s longitudinal muscle fibers. When heated, an individual wire will contract, pulling the worm left or right.
Robots like the Meshworm may have many useful applications, such as next-generation endoscopes, implants, and prosthetics.
