Soft Shell Grippers with Highly Tunable Dry Adhesion through Low Negative Pressure for Universal Manipulation

Abstract Highly tunable dry adhesion has practical ramifications in robotic manipulation. While grippers based on mechanical interlocking and suction are adopted in various industries, soft grippers that can handle small and delicate objects reliably are yet to be invented. In this paper, it is reported that the presence of an adhesive substrate against a negatively pressurized soft hemispherical shell can significantly delay buckling of the shell. The net adhesion strength of such a depressurized shell can reach 60 times that of an open shell without any pressure difference. Simultaneous measurements of internal pressure, mechanical tension, contact area, and approach distance agree well with a semi‐analytical solid‐mechanics model. Introduction of defects at the polar region of the shells does not affect adhesion under the depressurized condition but significantly reduces adhesion under no pressure, leading to even higher tunability (almost infinity). The enhanced adhesion of a depressurized shell is found to be a combined effect of dry adhesion and suction. These shell grippers are shown to be effective in the universal manipulation of various objects with wide ranges of weight, shape, surface roughness, and mechanical compliance. The proposed depressurized soft shells provide a promising robotic gripping platform for industrial adoption.