Researchers at the Adolphe Merkle Institute and Case Western Reserve University (Cleveland, USA) have developed a soft, worm-like robot that can wriggle itself through tiny spaces, and move in almost any direction on any surface.

Soft earthworm-like robots that exhibit mechanical compliance can, in principle, navigate through uneven terrains and constricted spaces that are inaccessible to other robots. Such devices are potentially useful for applications that include search and rescue operations, underground exploration, pipe inspection, and even biomedical procedures such as endoscopy or colonoscopy.

However, unlike the living species that they mimic, most of the previously reported worm-like robots contain rigid components that limit their mechanical compliance, such as motors and other actuators. To overcome this limitation, researchers from AMI’s Polymer Chemistry and Materials group and their US partners developed and investigated a highly flexible robot with a fully modular body that is almost entirely based on soft polymers.

Temperature control
The device contains segments that are assembled from bilayer actuators, which reversibly change their shape when heated and cooled, respectively. The possibility to individually activate the bilayer actuators through electrically powered heating elements allows one to control the robot’s movements with great precision. Mimicking the locomotion principle exploited by earthworms, the robot is propelled by the sequential contraction and expansion of the various segments. This operating principle also allows the robot to access spaces that are much smaller than its cross-section in the resting state.

Improvements needed
Limitations of the first embodiment of the new robot design are that its movements are quite slow, and that its motion requires a considerable amount of energy. The researchers believe, however, that the robot’s modular architecture will allow improving these performances by using faster and more energy-efficient bending actuators, without changing the overall design. Moreover, the current version is externally powered and controlled, but it could be become autonomous with the incorporation of soft batteries and independent control systems.

The results of this research project have been published in the leading scientific journal Advanced Materials. This work was carried out with joint funding from the US and Swiss National Science Foundations as part of the Partnerships for International Research and Education (PIRE) program Bio-inspired Materials and Systems.

Muff, L. F.; Mills, A. S.; Riddle, S.; Buclin, V.; Roulin, A.; Chiel, H. J.; Quinn, R. D.; Weder, C.; Daltorio, K. A. Modular Design of a Polymer-Bilayer-Based Mechanically Compliant Worm-like Robot. Advanced Materials 2023, 34, 2210409. https://doi.org/10.1002/adma.202210409.