Unraveling the Effects of Improved Cooling and Bias Force in the Actuation of a Shape‐Memory Soft Multimaterial Gripper

This study explores the enhancement of a soft actuator made from a NiTiCu6 Shape Memory Alloy (SMA) element embedded in a silicone rubber matrix functionalized with high aspect ratio graphene nanoparticles (GNPs). As a proof-of-concept we present the design, fabrication by stepwise molding, and testing of an operational soft gripper. Prototypes with the GNPs-enriched matrix are compared with plain elastomer ones with two different Shore hardness to assess thermal and mechanical effects on the actuation speed and energetics. They are tested in grasp-and-release cycles and during prolonged grip maintenance at constant force at 1.5 N and 1 N. Input electric currents are also varied between 5 and 9A. With GNPs-modified matrix, it is possible to speed up the release phase up to 40%, as the enhanced thermal diffusivity improves cooling rates, but it may also lead to increased energy consumption during low-current activations and prolonged gripping phases. In particular, for the grasp-and-release cycles, a stiffer matrix also requires higher input energies without comparable improvements in cooling times. Our findings underscore the potential for tailoring matrix properties to improve the overall functionality of SMA-based soft actuators, setting the stage for future work to refine performance through further material optimization and expanded testing scenarios.