(177o) Sliding Friction through Dislocation Glide in Shape Complementary Soft Interfaces.

We investigate microscale friction phenomena through the utilization of shape-complementary polymeric structures. These biomimetic structures, serve to enhance friction selectivity, with wide-ranging potential applications spanning eco-friendly rubber processing in tire manufacturing to efficient object handling in soft robotics. Specifically, we employ Polydimethylsiloxane (PDMS) patterned with microstructures approximately 16 μm in height and 10 μm in diameter, spaced roughly 20 μm apart. Friction between such fibrillar surfaces is measured using a custom-built tribometer. When brought into contact, these samples spontaneously generate arrays of interfacial dislocations, contingent upon misorientation and lattice spacing disparities. Orientation mismatches yield arrays of screw dislocations, while lattice mismatches produce arrays of edge dislocations, all on a micron scale, mirroring the structure of atomic-scale dislocations. Employing a camera and LabVIEW software, we visualize the interface and record dislocation motion. Relative sliding motion between the samples occurs through interfacial glide of these dislocation structures, resulting in periodic variations in friction due to the periodicity of dislocation misfit energy along the interface. These phenomena serve as micron-scale analogs of atomistic friction mechanisms. To elucidate the microscale behavior of each fibril, we fabricate larger (millimeter-scale) samples with identical aspect ratios to replicate microfibril motion at various diametric and length overlaps. We build a geometric model to calculate the energy dissipated by each pillar as it passes other fibrils and compare it with data obtained from microscale experiments. Additionally, we conduct comprehensive finite element analyses to explore the intricate interactions between individual fibrils.