<p>Cephalopods exhibit high-performance manipulation abilities thanks to the unique structure of their tentacles. Characterized by the absence of a rigid skeletal support, cephalopods tentacles rely only on muscles and soft tissues to perform fine and complex motion. This type of biological structure is known as muscular hydrostat and in the past years has strongly inspired the scientific community toward the development of lightweight soft robots, capable to provide a large number of degrees of freedom and fine motion.</p><p>In this work, we take inspiration from the biological structure of the loliginid squid’s tentacles to develop novel muscular hydrostats. Squid’s tentacles are characterized by several thin layers of muscles, arranged along different directions (e.g., longitudinal, transverse, helically arranged), and embedded into a soft tissue. The assembly of these layers allows squids to achieve several degrees of freedom and smooth motion. We reproduced the different layers of squid’s tentacles by embedding low-cost and lightweight polymer Twisted and Coiled Artificial Muscles (TCAMs) inside elastomeric thin films to reproduce thin-walled muscular hydrostats. TCAMs are manufactured from inexpensive nylon monofilaments and can provide a contraction up to 35% when electrothermally actuated using a voltage of only 0.2V/cm. An optimized manufacturing process has been developed to fabricate TCAMs with tailored geometry in order to achieve the best compromise between maximum contraction and stiffness. The actuation of TCAMs inside the soft elastomer layer is controlled by means of a robust and adaptive controller in order to achieve a predefined actuation and avoid overheating of the final device. Each muscular hydrostat has been tested underwater to demonstrate waterproof abilities. The different muscular hydrostats have been finally assembled to reproduce a soft robotic tentacle, able to provide several degrees of freedom and emulate the actuation mechanism of squid’s tentacles.</p>

Squid-Inspired Muscular Hydrostats From Twisted and Coiled Artificial Muscles (Tcams)

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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