Inchworm Robot Crawls Without Rigid Parts, Inspired by Nature

Researchers have developed a soft robot that mimics the inchworm's crawling motion, eliminating the need for rigid parts. This innovation draws inspiration from nature, specifically the flexing action of a muscle, and is detailed in research published on the arXiv preprint server. The field of soft robotics focuses on using pliable materials to replicate biological properties, offering an alternative to traditional robotic designs.

The robot's design involves alternating layers of carbon electrodes with a polymer material. When a low voltage is applied to the carbon surfaces, the polymer expands, creating a muscle-like flexing action. A five-layer configuration, approximately as thick as a strand of hair, was fabricated into a cylindrical artificial muscle by rolling the sheet. This design allows the robot to mimic inchworm movements through rhythmic voltage application.

The artificial muscle expands by about 10% when powered and returns to its original size when the power is off. By attaching a flexible plastic arch between the ends of the muscle, the robot can move forward on ribbed surfaces by gripping the grooves. Experiments showed the robot consistently moved perpendicular to the grooves, regardless of the angle. Future iterations could be tailored to specific surfaces.

This soft robot's locomotion requires no multiple actuators, making it suitable for demanding tasks in remote locations, such as inspecting sewer pipes or exploring Mars. The prototype operated for over four months, four hours a day, without performance degradation. The robot is also protected by a carbon nanotube coating, rendering it resistant to damage; even when punctured by needles, the nanotubes allowed the robot to continue functioning by bypassing the damaged areas. This resilience suggests it could withstand harsh conditions, including the cosmic radiation on Mars.