Seminar Series: Gerold Willing, Ph.D. – Friday, 3/23/2018, 11:00 A.M.

JSNN Seminar Series

Title: “Using Nanoparticle Halos to Stabilize Complex Fluids: From Fundamental Research to Application Studies on The International Space Station.”

Speaker: Gerold Willing, Ph.D.
Job Title: Associate Professor
Department of Chemical Engineering
University of Louisville

Date and Time: Friday, 03/23/2018, 11:00 A.M.
Location: JSNN Auditorium

2907 E. Gate City Blvd., Greensboro, NC 27401


Complex fluids, consisting of a discrete phase suspended within a continuous fluid phase, are utilized in numerous commercial and industrial applications. A significant concern in these systems is the long term stability of the discrete phase as this leads to issues with product shelf life. In one of the more common examples of a complex fluid, known as a sol, the stability of solid particles in the micro- to nanometer size range is governed by the interaction forces between individual particles. These forces can be modified by controlling the pH and electrolyte concentration of the liquid phase. Additionally, the addition of other materials such as surfactants and surface active polymers can also alter the interaction between the particles.

A newer method to controlling the stability of a sol is to introduce a second set of smaller, typically nanoscale particles to the system. By controlling the size, charge, and concentration of these particles relative to the primary particles, one can control the stability of the system. For years, the exact nature of this stabilization mechanism was unclear and the subject of much debate within the literature. Based on atomic force microscopy based measurements, we believe that we have discerned the series of interaction forces responsible for the stabilization mechanism known as Nanoparticle Haloing. We are now using our theory to design sols based on silsesquioxane microparticles with tunable surface chemistry so that they will form colloidal crystal structures during gravity settling. To determine if the crystal structure can be modified based by tuning the stability the sol, we are performing identical experiments in the microgravity environment offered onboard the Interaction Space Station. Through these experiments, we hope to create different crystal structures that can serve as optical switches and filters for use in the telecommunications industry.


Dr Gerold Willing is an Associate Professor in the Department of Chemical Engineering at the University of Louisville. Prior to his faculty appointment, he served as a Postdoctoral Associate in the Materials Science Division at Argonne National Laboratory. He hold a BS and PhD in Chemical Engineering from the University of Wisconsin-Madison and Auburn University, respectively. His research interests fundamental and applied studies on colloidal systems, especially sols and gels. These include utilizing Atomic Force Microscopy to directly measure interaction forces in Nanoparticle Haloing systems and determining the heat transfer enhancement in nanofluids. He also has research interests in polymer and rubber degradation mechanisms, developing sustainable methods for recycling rubber, and enhancing engineering education through the use of peer mentors in freshman and sophomore year engineering core courses.