In this week's installment of the Physics Colloquium series, Zvonimir Dogic (UCSB) will present “Shape and topological transitions of elastic membranes” at 4:00 PM in Swain W. 119.
Abstract: Changes in the geometry and topology of thin elastic sheets underlie diverse processes across cellular biology, material science, and engineering. W investigate the fundamental properties of such transitions using a model experimental system of colloidal membranes, which assemble when mixing monodisperse micron-long viruses and non-adsorbing polymer. The physics of these micron-thick fluid-like assemblages are analogous to those of two-dimensional lipid bilayers.
However, their micron size allows for visualization of various membrane-based processes that are not possible using nanometer-sized conventional membranes. In one example, we use colloidal membranes to study how a flat 2D disk-like membrane folds into an edgeless vesicle-like structure. In another example, we study how a colloidal membrane composed of rod-like molecules of differing lengths folds into 3D structures. Above a critical concentration of shorter rods flat, 2D membranes become unstable and assume a bewildering variety of different shapes and topologies. Simple arguments suggest that doping colloidal membranes with miscible shorter rods tunes the membrane’s Gaussian modulus, which in turn destabilizes flat 2D membranes.