Levich Institute Seminar Announcement, 05/11/2010
Tuesday, 05/11/2010
2:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Ka Yee Lee
University of Chicago
Department of Chemistry

"Beyond Wrinkles: Stress Relaxation in Lipid Monolayers and Other Elastic Thin Films "


ABSTRACT


Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. The most well characterized forms of stress relaxation in these systems are first order phase transitions. However, once chemical phase transitions have been exhausted, the monolayer undergoes global mechanical relaxations termed collapse. We have previously demonstrated that for lung surfactants, a mixture of lipids and proteins that coats the alveoli to reduce the work of breathing, collapse manifests itself as protrusions of folds into the subphase. These folds remain attached to the monolayer and reversibly reincorporated upon expansion. By studying different types of monolayers, we have shown that this folding transition in monolayers is not limited to lung surfactant films, but rather represents a much more general type of stress relaxation mechanism. Our study indicates that collapse modes are found most closely linked to in-plane rigidity. We characterize the rigidity of the monolayer by analyzing in-plane morphology on numerous length scales. More rigid monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, with the folded state being the final collapse state, while softer monolayers relax in-plane by shearing. For the hard elastic mode of collapse, we have further demonstrated experimentally and theoretically that the folded state is preceded by a wrinkled state.

BRIEF ACADEMIC/EMPLOYMENT HISTORY

  • MS and PhD in Applied Physics, Harvard (1987, 1992)
  • Postdoctoral Fellow, Stanford University, Department of Chemistry, October 1992 - February 1995
  • Postdoctoral Fellow, University of California, Santa Barbara, Department of Chemical Engineering, March 1995 - May 1998
  • Assistant Professor, The University of Chicago, Department of Chemistry, June 1998 - June 2002
  • Assistant Professor, The University of Chicago, Institute for Biophysical Dynamics, September 1999 - June 2002
  • Assistant Professor, The University of Chicago., James Franck Institute, November 2001 - June 2002
  • Associate Professor, The University of Chicago, Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, July 2002 - June 2008
  • Professor, The University of Chicago, Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, July 2008 - present
  • Director, The University of Chicago, Materials Research Science and Engineering Center, July 2009 - present

RECENT RESEARCH INTERESTS
  • Lung surfactant
  • Aggregation of Alzheimer's beta-amyloid peptides
  • Interactions between cholesterol and lipids
  • Membrane sealing by triblock copolymers
  • Membrane disruptive mechanism of antimicrobial peptides
  • Biomimetic materials