Physics Colloquium: Zvonimir Đogić

The Department of Physics is pleased to welcome Professor Zvonimir Đogić for an in-person colloquium on Thursday, March 23, 2023. Đogić is a Soft Matter and Active Matter Physicist at UC Santa Barbara and PI of the Đogić Lab. His research focuses on the rules and laws that govern self-assembly of materials.

The Đogić Lab group creates simple model systems with precisely controllable parameters. This enables rigorous and detailed comparisons between experimental observations and theoretical predictions. The particles they use have simple hard core repulsive interactions. Despite the apparent simplicity of these building blocks, they have demonstrated that it is possible to assemble at least half a dozen unique structures through careful choice of particle shape and chirality. By necessity, their research is highly interdisciplinary. To accomplish their goals, they use a host of experimental techniques, theoretical statistical mechanics, computer simulations, biochemistry, various protein purification techniques and molecular cloning.

Abstract:

Sculpting membrane structure, mechanics and dynamics with active fluids 

Significant progress has been made in our understanding of equilibrium self-assembly. By encoding intermolecular interactions and minimizing free energy, one can rationally design assemblages of remarkable properties. In comparison, our understanding of how large-scale structure and dynamics occur away from equilibrium is less complete. We describe a hierarchical self-organizing process of remarkable complexity. Starting with an initially uniform mixture of microtubule-based active fluid and passive actin filaments, we observe the emergence of structures and dynamical patterns on ever-increasing length scales. Active fluids sculpt the structure, shape, mechanics, and dynamics of the actin network. Eventually, one observes the formation of macroscopically large actin-based thermalized membranes whose out-of-plane bending rigidity and in-plane oscillatory patterns are driven by the enveloping actin fluid. Taken together, these experiments demonstrate a need for developing a theoretical understanding of out-of-equilibrium self-organizing processes.