Pick-and-Place Grippers with Tunable Adhesion from Capped Soft Hollow Pillar Structure

Abstract

Dynamically tunable dry adhesion has numerous applications in biological systems and industrial processes. Soft hollow pillars (SHPs) have demonstrated to have exceptional adhesion tunability under pneumatic actuation through sidewall buckling or bulging mechanisms. However, the adhesion strength of SHPs is significantly lower than that of solid elastomeric pillars, which can limit their practical use. In this study, mushroom-shaped SHPs with a mushroom cap, or capped SHPs (C-SHPs), are introduced to enhance the adhesion performance of soft grippers based on hollow pillar structures. Experiments and finite element modeling demonstrate that the cap significantly improves adhesion strength (1.8 to 2.9×) and adhesion tunability (∼1000×) by optimizing stress distribution and altering the crack initiation process at the contact interface. The effect of the cap size on the adhesion strength of C-SHPs under various pressures is systematically investigated. Miniaturized SHPs and C-SHPs are fabricated for pick-and-place manipulation of lightweight objects. An untethered device containing a C-SHP is designed and assembled to highlight the energy-efficient operation of C-SHPs, with a ∼139 mJ energy consumption per pick-and-place cycle, showcasing their potential for applications in precision handling tasks. This work establishes C-SHPs as a robust and adaptable solution for tunable dry adhesion systems.