Description:

Establishing an adhesive contact between two materials requires two things: that surface energies favor the creation of an interface, and that it be possible to form a contact area given the material geometry and properties. While elasticity has long been understood to be important in determining the relative “stickiness” between non-conformal surfaces, in recent years capillary forces have emerged as playing key roles in adhesion with highly compliant materials. For example, recent studies have demonstrated that solid surface tension can compete with or dominate over bulk elasticity in governing contact mechanics on small length scales, and mounting evidence suggests that the internal free fluid phase of compliant polymer gels also contributes significantly to mechanical response via both poroelasticity and classic capillary wetting. In this work, we experimentally investigate the adhesion between polydimethylsiloxane (PDMS) gels and rigid glass substrates. We report experiments that combine sensitive, high-speed force measurements with 2D and 3D optical imaging. By varying the asperity size, adhesion energy, and gel material properties, we gain insight into the fundamental physical processes that dominate soft contact with rough surfaces across length and time scales.

Katharine E. Jensen is an Assistant Professor of Physics at Williams College. She earned her A.B. in Physics at Princeton, then spent two years as a researcher at MIT Lincoln Laboratory. She completed her Ph.D. in Physics at Harvard studying structures and defects in soft crystals and glasses. Her postdoctoral research investigating soft interface mechanics started at Yale in the Department of Mechanical Engineering and Materials Science and later moved to the Department of Materials at ETH Zürich. At Williams, her lab’s research focuses on the mechanics of soft materials and highly-deformable interfaces, including work with soft adhesive materials, fluid surface instabilities, and the biophysics of plants harnessing energy from water. Her work at Williams and with Williams students has been recognized with major research grants from both the National Science Foundation and the American Chemical Society, as well as the 2023 Outstanding Early Career Adhesion Scientist Award from the Adhesion Society.

Katharine Jensen,  Assistant Professor, Williams College

Host: Michelle Driscoll