Layer-jamming soft gripper for improved stiffness control and underwater adhesion

Abstract

Soft robotic grippers have attracted significant attention due to their lightweight, simple structures, and versatile applications. Especially, soft suction cups (SSCs) are generally used for their low energy consumption and a high lifting ratio. However, they encounter challenges for mitigating a trade-off between conformability and adhesion performance and applications for the wet conditions. This paper introduces the layer-jamming soft gripper (LJSG), a novel design that significantly enhances adhesion while maintaining adaptive conformability and demonstrates effective underwater adhesion. Notably, the LJSG is resistant to hydraulic leakage due to a protective membrane attached to its body. Additionally, our design concurrently enhances adhesion capability with layer-jamming mechanism compared to conventional SSCs and mitigates the impact of unjammed layers on conformability by incorporating an interval to reduce required preload for interfacial adaptation. These features collectively enable the LJSG to demonstrate reliable performance in grasping diverse objects underwater. We elucidate the layer-jamming mechanism and demonstrate how jammed layers enhance maximum pull-off force by analytical method, numerical method, and experiments. The LJSG shows 300 % adhesion improvement than previous SSCs via the experiments, while 290 % from the analytical method and 245 % from the numerical method. The experiments also demonstrate that LJSG has an enhanced capability for gripping curved objects. This design can be applicable for grasping objects regardless of their curvatures and sizes. Hence, these findings underscore LJSG’s potential for diverse applications, particularly in challenging underwater environments, and position it as a viable solution for adaptive, high-performance soft robotic adhesion.