2, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Soft elastomeric surfaces with dynamically tunable dry adhesion have ample applications in transfer printing, pick-and-place handling processes, as well as climbing robots, among others. Polydimethylsiloxane (PDMS) is one of the most commonly used elastomers in soft robotics due to its manufacturability and desirable mechanical properties. Previous studies have shown that by inserting a rigid core into cylindrical PDMS posts, the dry adhesion strength of the PDMS surface to an opposing rigid surface can be significantly enhanced. In this talk, first as a natural extension to previous work, we demonstrate a strategy to dynamically tune the dry adhesion of a PDMS post by inserting a core whose rigidity can be tuned on demand. We achieve this by the use of Conductive Propylene-Based Elastomers (CPBE), a class of elastomers that can be laser patterned and whose rigidity can be dynamically tuned by resistive heating. As the core rigidity of the composite core-shell structure is altered, so does the stress distribution at the interface and hence the adhesion strength. We then propose a novel method that directly manipulates the stress distribution at the interface by embedding subsurface microfluidic channels of Low Melting Point Alloy (LMPA), whose rigidity can also be quickly tuned by resistive heating. The multi-step fabrication methods for these soft structures will be discussed. Adhesion experiments show that the adhesion change ratios can be easily above two times for both methods. We have also conducted FEA simulations to model interface crack propagation and predict adhesion strength for the composites with various geometries. Our experimental and simulation results are in good quantitative agreement.