ChEMS Seminar: Adsorption, Contact and Adhesion at Elastic and Capillary Interfaces

Friday, May 4, 2018 - 3:00 p.m. to Saturday, May 5, 2018 - 3:55 p.m.
McDonnell Douglas Engineering Auditorium (MDEA)
Joelle Frechette

Department of Chemical and Biomolecular Engineering
Hopkins Extreme Materials Institute
Johns Hopkins University, Baltimore, MD

Abstract: This presentation will first discuss the dynamic (and thermodynamics) of attachment of nanoparticles to fluid interfaces. We will look at the case where the nanoparticles are in dynamic equilibrium between the interface and a bulk phase, and compare their adsorption to that of surfactants. We will demonstrate that the adsorption of nanoparticles competes with the attachment of amphiphilic ions from the bulk phase.  Along with experimental results, we will present a model for the reversible adsorption of nanoparticles to oil-water interfaces that is based on a decrease in interfacial area and interaction between the particles. We show that the model describes well the equilibrium and dynamic conditions.

In the second part, we will present our efforts to understand how soft materials (elastomers, pressure-sensitive adhesives) make contact and adhere under dynamic conditions in fluid environments. In particular, understanding and harnessing the coupling between lubrication pressure and elasticity provides materials design strategies for applications such as adhesives, coatings, microsensors and biomaterials.  Measurements of hydrodynamic interactions between soft surfaces will show how elastic films deform due to viscous forces and how these deformations are similar to those observed with fluid droplets. We will highlight implications for adhesion and soft lubrication and present results with pressure sensitive adhesives.

Bio: Joelle Frechette received her Ph.D. from Princeton University in chemical engineering and materials science in 2005 studying surface forces and adhesion in electrochemical environments. After postdoctoral work at UC Berkeley, where she investigated unwanted adhesion in microelectromechanical systems, she joined the Hopkins faculty in 2006. Frechette was awarded the NSF CAREER award in 2008, the 3M untenured faculty award in 2008, the ONR Young Investigator Award in 2011, and was elected as a Fellow of the American Chemical Society in 2017. Her research interests in the area of colloid and interfacial science include: adhesion in fluid environments, particles at fluid interfaces and surface force measurements.

Host:  Ali Mohraz