Levich Institute Seminar Announcement, 10/13/2009
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Professor Joelle Frechette
Johns Hopkins University
Department of Chemical and Biomolecular Engineering
"Reversible Control of Interfacial Properties "
The external control interfacial properties are at the heart of a wide range of technologies: adhesives, sensors, self-cleaning materials, and lab on a chip technologies. Our efforts in two avenues towards this goal will be described: 1) The molecular control of surface functionality and charge transfer properties and 2) Electrowetting of a nanoscale pore. First, our approach to use ion-pair association to dictate chain spacing in self-assembled monolayers (SAMs) will be detailed. Ion-pair directed assembly allows us to vary directly the coverage to create a film with surface properties (such as wetting, thickness, and electrochemical response) that depend on pH and applied potential. The packing density, uniformity, and electrochemical response of these sub-monolayer films – relative to traditional well-ordered, fully-packed SAMs – have been studied using x-ray photoelectron spectroscopy, contact angle measurements, and electrochemical techniques. Second our efforts to study nanoscale electrowetting and capillary adhesion will be described. Electrowetting on dielectric (EWOD) is a popular method to move fluid in a microchannel or to vary the focal length of fluid lenses. While the phenomenon is relatively well-understood for large (mm) fluid drops, the limits of traditional theories for a fluid drop in a nanoscale channel (and the associated capillary force) have not been tested. Using the surface force apparatus, we have designed experiments that allow us to study electrocapillary phenomena at the nanoscale.
BRIEF ACADEMIC/EMPLOYMENT BACKGROUND:
Joelle Frechette is an assistant professor in the chemical and biomolecular engineering department at Johns Hopkins University. Dr. Frechette received her PhD from Princeton University in chemical engineering and materials science. After postdoctoral work at UC Berkeley where she investigated unwanted adhesion in microelectromechanical syststems, she joined the Hopkins Faculty in 2006. Joelle Frechette was awarded the NSF CAREER award in 2008.
CURRENT RESEARCH INTERESTS:
Professor Frechette's research interests are in the area of surface chemistry, adhesion, wetting, and electrochemistry. Currently she is working on active interfaces and their behavior in confined geometries.