New bioinspired earthworm robot for future underground exploration

Author : D. Farina. Credit: Italian Institute of Technology – © IIT, all rights reserved

Researchers at the Istituto Italiano di Tecnologia (IIT-Italian Institute of Technology) in Genova have realized a new soft robot inspired by the biology of earthworms, which is able to crawl thanks to a soft actuator that extends or squeezes, when air is passed over it or pulled. pulled out. The prototype has been described in the international journal Nature Portfolio Scientific Reports, and it is the starting point for developing devices for underground exploration, but also search and rescue operations in confined spaces and exploration of other planets.

Nature offers many examples of animals, such as snakes, earthworms, slugs, and caterpillars, that use the flexibility of their bodies and the ability to generate waves of physical travel along their bodies to move around and explore different environments. Some of its movements are also similar to plant roots.

Taking inspiration from nature and, at the same time, uncovering new biological phenomena while developing new technologies is the main goal of the robotics lab BioInspired Soft coordinated by Barbara Mazzolai, and this earthworm-like robot is the latest invention to come from the group.

The creation of earthworm-like robots is made possible by thoroughly understanding and applying the mechanics of earthworm motion. They use alternating contractions of their muscular layers to propel themselves both below and above the ground by generating retrograde peristaltic waves. Individual segments of their bodies (metamere) possess a certain amount of fluid that controls internal pressure to exert force, and perform independent, localized, and varied movement patterns.

IIT researchers have studied the morphology of earthworms and have devised a way to mimic their muscular movements, their constant volume coelomic chambers and the function of their bristle-like hairs (setae) by creating soft robotic solutions.

The team developed a peristaltic soft actuator (PSA) that implements the movements of the earthworm’s antagonistic muscles; from a neutral position it lengthens when air is pumped into it and compresses when air is expelled from it. The entire body of the robotic earthworm is made up of five PSA modules in series, connected by interlinks. The current prototype is 45 cm long and weighs 605 grams.

Each actuator has an elastomeric shell that encloses a known amount of fluid, thereby mimicking the constant volume of internal coelomic fluid in earthworms. Earthworm segments become shorter longitudinally and wider circularly and exert a radial force as the longitudinal muscles of the individual constant-volume chambers contract. Antagonistically, the segments become longer along the anterior-posterior axis and circumferentially thinner by contraction of the circumferential muscles, generating a penetrating force along the axis.

Each single actuator exhibits a maximum elongation of 10.97 mm at a positive pressure of 1 bar and a maximum compression of 11.13 mm at a negative pressure of 0.5 bar, unique in its ability to generate both longitudinal and radial forces within a single actuator module.

To propel the robot on the planar surfaces, tiny passive friction pads inspired by earthworm bristles are attached to the robot’s ventral surface. The robot demonstrated better maneuverability at 1.35mm/s.

This study not only proposes a new method for developing soft robots such as peristaltic earthworms but also provides a deeper understanding of locomotion from a bioinspired perspective in different environments. The potential applications for this technology are extensive, including underground exploration, excavation, search and rescue operations in underground environments and exploration of other planets. This bioinspired digging soft robot is a significant step forward in the field of soft robotics and opens the door for further advances in the future.

Italian Institute of Technology

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