Abstract: Soft materials are found in a host of application areas, from biotechnology and 3D printing to adhesives and soft devices. However understanding and controlling the behavior of very soft materials is an ongoing challenge. The Soft Materials and Interfaces group focuses on understanding the physics and mechanics of soft polymeric materials, including but not limited to gels, elastomers, and viscoelastic fluids, with an emphasis on responses at or near interfaces. When materials are sufficiently soft or the characteristic size scale is sufficiently small, soft solids display liquid-like characteristics – properties traditionally reserved for liquids emerge as an important part of the material response. In this talk, we introduce situations where combinations of solid and liquid characteristics control the mechanics of deformable interfaces. In particular, we discuss the importance of surface tension, surface stress, and phase separation for the interaction between a small adhesive particle and a soft elastomer. Based on confocal microscopy and colloidal probe experiments, a modified contact mechanics model is proposed. In the second part, we demonstrate tunable adhesive behavior of transient hydrogel networks that are crosslinked with metal-coordination bonds. Time permitting, we will introduce our current knowledge on how a liquid drop interacts with the surface of a soft polymer gel.
Bio: Jonathan Pham is an Assistant Professor of Materials Engineering at the ÌÇÐÄvlog¹Ù·½Èë¿Ú. He received a PhD in Polymer Science and Engineering from the University of Massachusetts Amherst where he investigated nanoparticle assembly and mechanics. During this time, he was a Chateaubriand fellow at ESPCI-ParisTech investigating deformation of microscale helical filaments in microfluidics. Prior to joining Kentucky, he was a Humboldt Postdoctoral Fellow at the Max Planck Institute for Polymer Research working on a range of topics, including cell-surface interactions and liquid drop impact.
Research: