submitted by stottrup@augsburg.edu
This week is Biophysics Week, and Augsburg is hosting an Affiliate Event with the Biophysical Society. Anna Gaffney, a University of Chicago graduate student, will share her research in lipid monolayer reorganization, elasticity, and phase transitions with Augsburg University undergraduates. All are welcome! The seminar begins Friday at 11:20 in Oren Gateway 201. The abstract and title are below.
TITLE: Relaxing Under Stress: Developing a Generalized Material Model for Highly Compressed Lipid Monolayers
ABSTRACT: Lipid monolayers are membranes that self-assemble at the air-water interface and are found biologically in the ears, eyes, and lungs. Studying their responses to mechanical forces and stress can supply information to both the lipid and thin sheet fields. Mechanically, highly compressed lipid monolayers can be represented as elastic sheets. In this sense, at some critical stress, these sheets must undergo instabilities. Some do this through out-of-plane collapse, while others relax in-plane. This in-plane relaxation is experimentally observed with fluorescence microscopy (FM) and is characterized as reorganization of condensed domains within a softer matrix. These different modes of instability are accessible by tuning lipid monolayer softness, inspiring our search for a generalized material model with similar tunability. The elastic models that are currently used to describe out-of-plane collapse have been unsuccessful in capturing in-plane relaxation. We hypothesize this is because the matrix is relaxing through strain localization in the form of shear banding. Simulation results from models that incorporate FM-derived condensed domain morphology show that if we trigger shear banding in the matrix around domains, the domains can reorganize and reproduce the experimental in-plane relaxation morphology. Our findings expand understanding of lipid monolayer mechanical response and can be applied to broader research in other thin sheet systems as well.