Variable stiffness electroadhesion and compliant electroadhesive grippers

Soft adhesion is capable of attaching and bonding to rough surfaces and gripping non-planar materials. It is preferable for material handling applications where safe interactions with external environments and enhanced adaptability to changing conditions are required. Soft electroadhesion is an emerging controllable adhesion technology that is especially suited to soft adhesion applications, but is prone to contact peeling that causes unwanted de-adhesion and cannot lift heavy objects unless the lifting force is applied parallel to the surface. Variable stiffness electroadhesion (VSEA) can overcome these issues. Here a VSEA solution is developed by integrating electrostatic layer jamming and soft electroadhesion into a monolithic electrically-controllable structure. The VSEA pad can achieve rapid response (within 1 s) and significant stiffness change (2,200%), resist over four times the peeling force under a weight of 70 g, and generate 24.2 %, 34.8 % and 49.3 % greater adhesive forces on flat, convex and concave surfaces, respectively. The promising gripping performance of the VSEA gripper was demonstrated by lifting and moving curved and flat objects. The VSEA concept and solution shown in this work may pave the way for the ready integration of electroadhesion into soft robotic systems and promote the broad application of electroadhesion technologies.