Dynamically Tunable Dry Adhesion via Subsurface Stiffness Modulation

Tunable dry adhesion has a range of applications, including transfer printing, climbing robots, and gripping in automated manufacturing processes. Here, a novel concept to achieve dynamically tunable dry adhesion via modulation of the stiffness of subsurface mechanical elements is introduced and demonstrated. A composite post structure, consisting of an elastomer shell and a core with a stiffness that can be tuned via application of electrical voltage, is fabricated. In the nonactivated state, the core is stiff and the effective adhesion strength between the composite post and contact surface is high. Activation of the core via application of electrical voltage reduces the stiffness of the core, resulting in a change in the stress distribution and driving force for delamination at the interface and, thus a reduction in the effective adhesion strength. The adhesion of composite posts with a range of dimensions is characterized and activation of the core is shown to reduce the adhesion by as much as a factor of 6. The experimentally observed reduction in adhesion is primarily due to the change in stiffness of the core. However, the activation of the core also results in heating of the interface and this plays a secondary role in the adhesion change.