Research Projects

Rationale: Suspensions of active particles in a fluid are known to generate spontaneous flows. Several experiments using suspensions of cytoskeletal elements, bacteria and algae, and janus catalysts have demonstrated these spontaneous flows. These flows originate from the fact that energy is input locally by the active particles and then a collective motion arises from the interaction of active particles. Some advancement has been made in understanding the mechanism behind the collective motion of active particles. It is expected that the spontaneous flows generated by such active fluids could be in any direction since the system is isotropic to start with. On the other hand, one of the projected applications of studying spontaneous flows in active systems is to design self pumping devices. A crucial component for such a design is the ability to control and predict the directionality of the spontaneous flows. This is a question that has not been addressed by the scientific community. Hence, the current project will investigate and establish how symmetry broken surfaces (corrugated boundaries) can be used to break the translational and rotational symmetry of the spontaneous flows generated by active systems. Scientific objectives: How does a wavy/corrugated/toothed surface interact and modify active fluid flows? Can the translational/rotational symmetry breaking of a confining surface be reflected in spontaneous flows generated in active systems? What criteria can be used to quantify the extent of symmetry breaking of the surface? What are the universal principles/parameters that dictate the fluid flow direction (translational and rotational motion) that can be used to design engineering devices based on active systems? Hypotheis/Model/Simulations: The investigations will utilize an active fluid model called active nematic. Active nematic is a complex fluid, assumed to consist of elongated entities. These elongated entities represent the hydrodynamic stress exerted by the cytoskeletal elements, bacteria or janus catalysts. We will use hybrid lattice Boltzmann simulations to conduct the investigations. The project will involve computer intensive simulations of active nematic fluids in various channel geometries (channels with different profiles) as well as windmill structures (obstacles placed in active fluid). Significance: Physics of active systems have attracted a lot of attention from scientists recently. However, very little effort has been put forward to translating this knowledge base into an application. The current proposal originates from this gap since the mechanisms that yield spontaneous flows in active systems are developed. However, predictability of the direction of flow is currently lacking. Generating this knowledge base will help engineers to design devices for self pumping and energy extraction at very small length scales using biological materials.