UC Santa Barbara

The field of soft matter seeks to understand materials which easily deform in response to applied stresses. Several systems have served as foundational models in soft matter, including liquid crystals, liquid phase separations and membranes. In this thesis, I investigated the dynamics of these classic soft materials, by building and characterizing new several model systems.

First, I detail initial work on a 3D active nematic. I doped a three-dimensional liquid crystal with biologically-based active filaments that produced turbulent-like mixing of the material. These chaotic flows generated neutral disclination lines, which we show behave in accordance with nematic hydrodynamic models.

Next, I developed a model system to study an actively-driven liquid-liquid phase separations. This system consisted of an active phase that contained microtubule bundles, and a passive phase, separated by a soft interface. The active bundles generated stresses that resulted in complex interfacial dynamics. We used this system to measure values of the active stress generated by the microtubule bundles, a defining measurement that has eluded the field.

Lastly, I quantitatively studied vesicle formation using colloidal membranes as a model system. I observed the transformation from a flat membrane to a closed vesicle via a gravity-assisted pathway. Subsequently, I showed that the shape change accompanying vesicle closure can be understood by minimizing the elastic energy. Additionally, I investigated membrane disassembly caused by continuous vesicle shrinking. I demonstrated that the shape change dynamics associated with vesicle shrinking followed an energy-minimizing pathway through the area-dependent energy landscape.