Physical Society Colloquium

Soft materials are a vast and ubiquitous class of structured and complex systems which include polymers, supramolecular aggregates, emulsions, liquid crystals and membranes. All these systems exist in a condensed phase, but none of them can be described unambigously as a liquid or a solid. As opposed to conventional solid materials, the physical properties of soft materials are largely determined by soft and fluctuating interfaces, the physics of which is dominated by entropy.

A prominant example of a soft interface is the lipid bilayer, which is used as a model system to study biomembranes. Lipid bilayers exhibit a substantial degree of in-plane fluctuations and nano-scale heterogeneity. The fluctuations and the nano-scale structure control the mechanical modulii of the membrane, and hence the repulsive entropic interactions with neighboring membranes and surfaces. It is the hypothesis, that the physical properties, specifically lipid-bilayer softness, dynamic structure, and molecular organization, are important regulators of membrane function and the ability of membranes to support biological activity.

The colloquium will focus on fundamental principles rather than specific details and will build on insight obtained from a variety of theoretical and experimental approaches, including field theory, computer simulation, spectroscopy, microscopy, and scattering.