Start
Sep 19, 2013 - 17:00
End
Sep 19, 2013 - 18:00
Venue
Creativity Hall (Room #118) Chemical Engineering Department
Event Type
Speaker
Dr. Rohini Gupta Post-doctoral Fellow at University of Pennsylvania
Title
Tuning fluid−surface interactions via manipulation of interfacial functionality and topography
Abstract: Sensing transduction and actuation in the next generation of “smart” micro-/nanoscale devices will require exquisite control and manipulation of interfacial functionality and topography. Here I will discuss our efforts to tune interfacial properties by modulating wetting or hydrodynamic interactions. The interactions dominant within a few nanometers of a fluid−surface interface dictate properties such as adhesion friction and spreading. Modulating such interactions therefore can lead to dramatic changes in response of the fluid−surface interface. For example spreading of a liquid drop on a surface in response to charging of the underlying dielectric (referred to as electrowetting on dielectric) can lead to drop motion and is employed for digital microfluidics electronic displays and variable-focus lenses. We studied electrowetting at length scales ranging from nanoscopic to macroscopic and our results unequivocally establish the underlying mechanism and nanoscale limits of this approach. Furthermore we designed an approach where molecular reorientation at the fluid−surface interface is used to control macroscopic shape and motion of drops that are subjected to a constant driving force on a chemically homogeneous surface. I will also discuss our current work on understanding the effect of surface chemistry and topography on the wetting of cryogenic fluids. Systems operating in fluid environments such as robots traversing flooded surfaces necessitate modulation of dynamic interactions i.e. drag or friction. I will discuss how surface structures that form draining channels such as those inspired by tree frog toe pads can be designed to modulate hydrodynamic interactions. Using direct force measurements we extracted scaling arguments that can be employed for the optimised design of reversible biomimetic adhesives for flooded surfaces.About the Speaker: Rohini Gupta is a chemical engineer with expertise in colloid and interfacial science. She received her B. Tech. in Chemical Engineering from Malaviya National Institute of Technology Jaipur (India) in 2007. In 2013 she received her Ph.D. in Chemical and Biomolecular Engineering from the Johns Hopkins University (USA) under the guidance of Prof. Joëlle Fréchette for her work on molecular and nanoscale electrowetting as well as biomimetic adhesives. Currently she is a post-doctoral fellow working on wetting of cryogenic fluids with Profs. Kathleen J. Stebe and Daeyeon Lee at the Department of Chemical and Biomolecular Engineering University of Pennsylvania (USA). As an undergraduate she received the Young Engineering Fellowship in 2006 and pursued research under the guidance of Prof. Santhanam Venugopal at the Department of Chemical Engineering Indian Institute of Science (India). During her Ph.D. she received the Peebles Award for Graduate Student Research and Alan Gent Distinguished Student Paper Award conferred by the Adhesion Society during the 34th Annual Meeting as well as Langmuir Student Paper Award during the 86th ACS Colloid and Surface Science Symposium. Her teaching experience includes undergraduate thermodynamics and graduate interfacial phenomena. She has also mentored a number of undergraduate and high school students while they were working on her research projects and as a result three of them were co-authors of a publication in Langmuir. Her research interests are pharmaceutical energy environmental and sensing applications that rely on micro-/nanoscale colloidal and interfacial phenomena.