December 11, 2015 @ 3:30 pm - 4:30 pm
In the interest of building community and collaboration in HEMI, we are initiating the HEMI Friday Colloquium series. Speakers in this series will be members of the JHU community, both from within and from outside of HEMI. They will occur about once per month, initiating with a social time from 3:00-3:30 with snacks and beverages, followed by a talk from 3:30-4:30, with snacks and beverages continuing. The idea is for this to be much more casual than the typical seminar, with a lot of discussion and interaction.
Approach to in Contact in Fluids for Soft and Structured Surfaces
Joelle Frechette, Department of Chemical and Biomolecular Engineering
Surface topography and elastic compliance alter the dynamic of contact and adhesion forces in fluid environments. For tree frogs these factors play an important role in their locomotion and adhesion to wet or flooded surfaces. Central to the adhesion and locomotion of tree frogs is their structured toe pads, which consist of hexagonal arrays of compliant epithelial cells separated by a network of interconnected channels. In this talk we will discuss our measurements of hydrodynamic forces and associated spatiotemporal elastic deformation to understand how surface topography and elastic compliance affect how surfaces make contact and their adhesion during retraction. Our experiments highlight important length scales for hydrodynamic drainage of past structured surfaces and the importance of elastic deformation during the approach of compliant surfaces. In particular we observe that elastic deformation prevents the surfaces from making contact via the formation of a dimple in the elastic film. The growth kinetics of the dimple follows a scaling derived for droplets and bubbles. We find excellent agreement between the experiments and lubrication theory combined with viscoelasticity, but also show systematic deviations that are attributed to the shear deformation associated with layering effects.
Joelle Frechette received her PhD from Princeton University in Chemical Engineering and Materials Science in 2005 studying adhesion in electrochemical environment. After postdoctoral work at UC Berkeley where she investigated unwanted adhesion in microelectromechanical systems, she joined the Hopkins Faculty in 2006. Joelle Frechette was awarded the NSF CAREER award in 2008 and the ONR Young Investigator Award in 2011. Her research interests are in the area of interfacial science, adhesion, wetting, and colloids.
Seminar will be held in Malone Hall, Room G33/35 and will begin at 3:30 PM.