Controllable Dry Adhesion due to Surface Micro-Defect Patterning

Abstract

Robotic automation continues to develop and is constantly in need for new gripping devices. Devices are needed to handle small delicate objects for pick and place applications. Traditional rigid grippers have difficulty adapting to varying objects, and pneumatic grippers require bulky pumps and compressed air. Dry adhesion devices can remove the need for rigid components or pneumatics by relying on adhesion as the main method to pick up and manipulate objects. Tunable dry adhesion refers to the ability of controlling adhesion, increasing and decreasing it as the task requires. Research continues to develop devices that offer the highest tunability ratio. Based on a subsurface stiffness modulating device proposed by Shan et al. a novel method for increase adhesion in the normal direction is proposed, using circular defects on the adhering surface of a PDMS (polydimethysiloxane) post. The fabrication process included photolithography and molding which produced high resolution defects with high placement accuracy. The proposed patterns resulted in an increased adhesion, and for certain patterns, an increase of roughly 40%, compared to a flat PDMS post. Simulations helped explain the point of failure observed in the experimental results and provided some clarification to the increase of adhesion. Contact splitting and other mechanics offer explanations for the increase of adhesion and work continues to be done to further identify the mechanics involved. Defect patterning can be paired with subsurface stiffness modulation, previously studied by the Shan Research Group to increase the tunability ratio and develop new devices for pick and place automation.