Folding for Stiffening: A Novel Corrugated Electro-Adhesive Clutch

The compliance nature of soft robots permits them to effectively adapt to various challenging environments, but at the cost of poor payload carrying capabilities and lack of precision in motions. Electro-adhesive (EA) layer jamming clutches are an emerging type of active variable stiffness (VS) technique that features the advantages of structural simplicity, light-weight, rapid response speed, and low power consumption. However, current EA clutches mainly adopt a planar configuration, despite the large stiffness variations in tensional direction, they fail to exhibit effective stiffness variations in compression and bending directions due to the planar structures. To address this drawback, a novel corrugated EA clutch is proposed in this work to realize multi-directional VS. Its VS performances in tension, compression, and bending directions are benchmarked against a widely studied planar EA clutch and the effects of actuation voltage amplitude are investigated experimentally. The proposed corrugated EA clutch can effectively increase the brake forces when activated by 25, 23 and 8 folds in tension, compression and bending directions, respectively. To demonstrate its applications in soft robotics, a novel origami gripper with excellent adaptability is proposed by utilizing the corrugated EA clutch, and successful grasping on objects with various weights and morphologies is demonstrated.