My research work primarily focuses on the investigation of active polar fluids that are driven out of equilibrium through an 'active' drive. I build these so-called 'fluids' using micron-sized spherical particles suspended in oil that 'flow' together, hence termed 'active fluid'.

The particles are activated using a D.C. electric field (around a range of 3V/micron), causing them to exhibit a persistent rolling motion. This electro-rotation was first observed by a scientist named 'Quincke' and hence called Quincke rollers. As the rollers move/propel, they generate hydrodynamic perturbations, which cause the neighbouring rollers to reorient and coordinate their mutual direction of motion. This leads to the swarming of rollers that show macroscopic direction motion, which is popularly called 'flocking' behavior. Yes, the same flocking behavior that is seen in cattle, birds, and fish. When millions of such rollers are assembled, the flocks turn in spontaneous flows with broken rotational symmetry, which we call active flows.

If two or more of these active fluids are mixed, they can homogeneously mix or phase-separate based on how we confine them, causing the formation of rich multicomponent phases unique to such non-equilibrium systems. For my doctoral research, I have been studying the formation of these phases by conducting these experiments and also developing a generalized n-component hydrodynamic model to describe this fluid mixture behavior.

If we confine the rollers in a circular well, we observe that a mixture of active fluids spontaneously demixes. I explain this phase-separation behavior in detail using experimental and analytical techniques in my article published in the Physical Review Letters, which is a (Q1) physics journal. You can watch this beautiful, spontaneous demixing in the video below