Title: Active Topology
Abstract : Topology plays a key role in condensed matter physics, underlying much of our understanding of equilibrium matter in terms of defects in ordered media and topologically protected states. In active systems – collections of entities that consume energy to generate their own motion and forces – topological phenomena can take on new and surprising roles. I will describe some of this behaviors focusing on liquid-crystalline active matter in two dimensions, especially active nematic liquid crystals, to which Aditi Simha made lasting contributions.
Title: Self-Assembled Colloids: From Filaments to 3D Sponges
Abstract : I will provide a brief overview of our group’s work in the area of colloidal self assembly. Colloids that are large enough to allow easy visualization using optical microscopes and are yet small enough to exhibit Brownian motion represent interesting model systems for the study of self assembly processes. I will present work from our group on the assembly of colloids into semiflexible filamentous objects. When such filaments are rendered active, they exhibit enhanced centre of mass diffusivity, resulting from an interplay between diffusophoretic active flows and Brownian conformational fluctuations of the filaments. In recent work, we have demonstrated that thermosensitive filaments can fold to form structures with helix-like geometry. Such filaments are constructed using a facile technique called ice templating. We have also used ice templating to create three dimensional objects with important technological applications.
Title: Nonequilibrium Control of Cellular Organisation
Abstract : A defining feature of eukaryotic cells is the appearance of well defined functional compartmentalisation in the form of membrane-bound organelles. Cellular compartments, such as the Endosomal or Golgi systems, are subject to stochastic trafficking that involves active fission and fusion of cargo vesicles. These are stable structures driven far from equilibrium. I will discuss our current ideas regarding the non equilibrium control of size, shape, spatial position and number of compartments, with special emphasis to the Golgi system.