Here we study a model system of monodisperse hard rods in solution. We simulate this system using long rod-like filamentous viruses suspended in a salt solution with a depleting polymer, dextran. Under varying depletant concentrations, these viruses coalesce into a variety of self-assembled structures such as colloidal membranes, twisted ribbons, and liquid crystalline phases. Our study focuses on colloidal membrane structures which form as two-dimensional rafts or closed three dimensional vesicles as hundreds of thousands of viruses align to form solid layers. Study of these colloidal membranes can shed light on the much smaller and faster dynamics of lipid bilayers which form cell membranes.

In this project, we attempt to quantify the force required to deform closed colloidal membrane vesicles. Cross-sections of these vesicles are imaged and their fluctuations are quantified by two different methods. The first measures the tangent angles along the vesicle edge. The second measures variations from an average radius of the vesicle cross-section. The fluctuations are then decomposed into Fourier series. The mode and Fourier coefficient data is plotted and fit to equations for line tension and bend modulus. The derived values are compared between each analysis method. These results are then compared with an independently derived value for the bending modulus which fits the 3D shape of the entire vesicle under gravity.