Highly tunable dry adhesion of soft hollow pillars through sidewall buckling under low pressure

Abstract

An approach to achieve highly tunable adhesion using low pressure by inducing sidewall buckling in soft hollow pillars (SHPs). Dry adhesion of these SHPs can be changed by two orders of magnitude (up to 145×) using low activating pressure (˜−10 kPa or ˜20 kPa). Negative pressure triggers sidewall buckling while positive pressure induces sidewall bulging, both of which can significantly change stress distribution at the bottom surface to facilitate crack initiation and reduce adhesion therein. A single SHP can be activated by a micropump to manipulate various lightweight objects with different curvature and surface texture. An array of SHPs can realize selective pick-and-place of an array of objects. Minor modifications to the SHPs in terms of geometry and material (with or without cap, circular or noncircular cross section) can further enhance the adhesion tuning performance of these SHPs.