Levich Institute Seminar Announcement, 11/03/2009
Tuesday, 11/03/2009
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Shelley L. Anna
Carnegie Mellon University
Department of Chemical Engineering

"Surfactant-Laden Interfaces in Microfluidic Devices "


Microfluidic devices are convenient for producing highly uniform droplets for precise emulsions and lab-on-a-chip devices. However, the minimum droplet size in a microfluidic process is determined by the smallest geometric feature size, typically on the order of tens of microns. Introducing additional physico-chemical effects can help overcome this fundamental limitation. For example, when dissolved surfactants are present in one of the liquid phases, a tipstreaming-like phenomenon occurs, leading to the formation of submicron droplets. We have characterized this phenomenon in detail as a function of fluid properties and flow kinematics. However, we still have only a phenomenological understanding of the role of surfactant in the tipstreaming process. Experiments and recent literature suggest that the adsorption and desorption of surfactants at the interface plays an important role, but there is a lack of available mass transfer parameters for surfactants at oil-water interfaces. To address this knowledge gap, we have developed a new method of measuring the sorption kinetics using microscale bubbles and drops and taking advantage of a recent scaling argument suggesting that mass transfer becomes kinetically limited below a lengthscale intrinsic to the surfactant molecule. Through these two vignettes, this talk will describe our approach to understanding the interaction of surfactant-laden interfaces with strong flows through experimentation, scaling, and analytical modeling.


Dr. Shelley L. Anna is an Associate Professor of Chemical Engineering and Mechanical Engineering at Carnegie Mellon University. She received her Ph.D. in 2000 from Harvard University for research on extensional rheology of polymer solutions. Prior to joining the faculty at Carnegie Mellon University in 2003, she worked at Solutia, Inc., a major manufacturer of polymer films and coatings, and she completed a postdoctoral fellowship at Harvard University in microfluidics and complex fluids. Dr. Anna is a faculty member in the Center for Complex Fluids Engineering and a courtesy faculty in the Department of Physics. She has received a National Science Foundation CAREER Award and the George Tallman Ladd Research Award in the College of Engineering at CMU.


Current research interests center on the behavior of droplets and liquid crystals in microfluidic devices.