Controllable Anisotropic Dry Adhesion in Vacuum: Gecko Inspired Wedged Surface Fabricated with Ultraprecision Diamond Cutting

Gecko adhesion has inspired the fabrication of various dry adhesive surfaces, most of which are developed to be used under atmospheric conditions. However, applications of gecko-inspired surfaces can be expanded to vacuum and even space environment due to the characteristics of van der Waals interactions, which are always present between materials regardless of the surrounding environment. In this paper, a controllable, anisotropic dry adhesion in vacuum is demonstrated with gecko-inspired wedged dry adhesive surfaces fabricated using an ultraprecision diamond cutting mold. The adhesion and friction properties of the wedge-structured surfaces are systematically characterized in loading-pulling mode and loading-dragging-pulling mode. The surfaces show significant anisotropic adhesion (P-ad approximate to 10.5 kPa vs P-ad approximate to 0.7 kPa) and friction (P-f approximate to 50 kPa vs P-f approximate to 30 kPa) when actuated in gripping and releasing direction, respectively. The wedge-structured surfaces in vacuum show comparable properties as exposed in atmosphere. A three-legged gripper is designed to pick up, hold, and release a patterned silicon wafer in vacuum. The study demonstrates a green, high-yield, and low-cost method to fabricate a reliable and durable mold for gecko inspired anisotropic dry adhesive surfaces and the potential application of dry adhesive surface in vacuum.