Levich Institute Seminar Announcement, 09/13/2011
Tuesday, 09/13/2011
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Eric Dufresne
Yale University
School of Engineering and Applied Science

"Caught Between a Drop and a Soft Place: The Deformation of an Elastic Substrate by a Three-Phase Contact Line"


ABSTRACT


Young's classic analysis of the equilibrium of a three-phase contact line ignores the out-of-plane component of the liquid-vapor surface tension. While it has long been appreciated that this unresolved force must be balanced by elastic deformation of the solid substrate, a definitive analysis has remained elusive because conventional idealizations of the substrate involve a singular stress at the contact line. While a number of theories have been presented to cut off the divergence, none of them have provided reasonable agreement with experimental data. We measure surface and bulk deformation of a thin elastic film near a three-phase contact line using fluorescence confocal microscopy. The out-of-plane deformation is well fit by a linear elastic theory incorporating an out-of-plane restoring force due to the surface tension of the gel. This theory predicts that the deformation profile near the contact line is scale-free and independent of the substrate elastic modulus. Time permitting, I will briefly highlight our related work on another class of elastic singularities - the divergence of stress at the tip of a crack.

BRIEF ACADEMIC/EMPLOYMENT HISTORY

Eric Dufresne is the John J. Lee Associate professor of Mechanical Engineering and Materials Science at Yale Unveristy. He has joint appointments in the Departments of Chemical Engineering, Physics and Cell Biology. Dufresne's research focuses on experimental soft condensed matter and biological physics. His experiments typically combine optical microscopy with optical micromanipulation. Current research topics include: interfacial forces; self-assembly of colloidal and biological materials; mechanical singularities; mechanics of cells and tissues. Dufresne received an R&D 100 award for the invention of Holographic Optical Tweezrs in 2002 and the NSF CAREER award in 2006. Research in Dufresne's laboratory is supported by the National Science Foundation and Unilever.

RECENT RESEARCH INTERESTS:

Current research topics include: interfacial forces; self-assembly of colloidal and biological materials; mechanical singularities; mechanics of cells and tissues.