Regensburg 2025 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 44: Droplets, Wetting, Complex Fluids, and Soft Matter (joint session DY/CPP)

DY 44.11: Talk

Friday, March 21, 2025, 12:30–12:45, H47

Effect of geometrical confinement on friction in soft solids — •Aashna Chawla and Deepak Kumar — Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India

Soft and biological materials come in a variety of shapes and geometries. When two soft surfaces with mismatched Gaussian curvatures are forced to fit together, beautiful patterns emerge at the interface due to geometry-induced stress. In this study, we explore the effect of geometrically incompatible confinement of a thin sheet on a soft hydrogel substrate on friction. We use a novel experimental setup to measure the friction between a thin flat elastic sheet placed on a low-friction hydrogel substrate. We show that the frictional force at the interface strongly depends on the geometry and is significantly larger for the geometrically incompatible configuration of a flat sheet on a spherical substrate compared to the other two geometrically compatible configurations: flat sheet on a flat substrate and flat sheet on a cylindrical substrate. Furthermore, for the incompatible configuration of the flat sheet on a spherical substrate, we observe that the frictional force increases monotonically with the sheet radius, with a transition in the behavior at an intermediate radius. We show that these effects arise from the coupling of the stress developed in the sheet due to its geometrically incompatible confinement with the curvature of the interface, resulting in an increased normal force, thereby increasing friction. The insights gained from this study could have significant implications for our understanding of friction in various biological, nanoscale, and other soft systems.

Keywords: Geometrical incompatibility; Friction; Wetting; Thin sheets