Fluids at Brown and Fluids and
Thermal Sciences Joint Seminar Series
Tuesday, November 12, 2019
Barus & Holley, Room 190
Jie Feng, University of Illinois
Title: Manipulating Soft Materials with Interfacial Dynamics: from Bubble Bursting to Nanoparticle Denaturation
Abstract: Interfaces between two distinct phases are ubiquitous in nature and many engineering processes. From the fundamental studies in physics, materials and biology, to applications in various fields, interfaces control many aspects of the thermodynamics and dynamics of multi-phase systems. Not surprisingly, questions about the dynamics of interfaces, e.g., their flow and response to forces, occur widely in colloid science, fluid mechanics and other areas of science and engineering. Therefore, understanding various interfacial dynamics remains a canonical problem with strong intellectual interest and broad industrial impacts.
In this talk, we will describe two distinct problems where we investigate the interfacial dynamics of structured complex fluids, and the understandings can be extended to soft materials engineering for applications in the environmental and health science. First, we will present the study of bubble bursting at a compound air-oil-water interface. We document the hitherto unreported formation and dispersal of submicrometer oil droplets into the water column. Surprisingly, the droplet size is selected by the physicochemical interactions rather than by hydrodynamic effects. The implications of the dispersal mechanism for oil-spill remediation and multi-functional nanoemulsion formation will also be demonstrated. Second, we will discuss the evolution of polymeric nanoparticle attachment at an air-liquid interface over time scales from 100 millisecond to a few seconds. We document three distinct stages in the nanoparticle adsorption. In addition to an early stage of free diffusion and a later one with steric adsorption barriers, we find a hitherto unrealized region where the interfacial energy changes due to surface “denaturation” or restructuring of the nanoparticles at the interface. We adopt a quantitative model to calculate the diffusion coefficient, adsorption rate and barrier, and extent of nanoparticle hydrophobic core exposure at different stages. Our findings offer new insights for the interfacial behavior of nanoparticles, as well as the application of their controlled release at the interface.