Research Projects

Active matter, comprising motile and interacting units (like bacterial cells or vibrating rods), can self-organize into perplexing material behaviour like mesoscale turbulence and vortex lattices. These flow states often exhibit deviant physical properties like anomalous diffusion, odd viscosity and elasticity, and pattern-formation. Living materials, hence, emerge as a transcending alternative to traditional, inanimate materials, and promise design revolutions ranging from self-actuating microfluidics to dynamic coatings and intelligent membranes. The fundamental shift will be in the ability these materials hold to respond to stimulus and external variability by reconfiguring their organization and it's emergent properties, in a completely autonomous manner. Most important steps towards this goal, therefore, are threefold: Uncovering the mechanisms of self-organisation across realistic systems, finding their unifying principles, and thence taming active flows. Almost all research so far has dealt with a greatly idealized situation involving homogeneous active fluids, while there is ample evidence that natural environments impose or induce heterogeneity within active materials, that manifest as variable activity. While it leads to nontrivial flows and fundamental challenges, heterogeneity can be a potent tool to modify and control active flows as well. This project aims to explain, and then exploit heterogeneity in active flows for emergence control and design of intelligent materials. We shall build upon our expertise in active matter, turbulence and structure identification techniques to understand several pertinent questions regarding heterogeneously active turbulence, employing detailed numerical simulations of generalized continuum hydrodynamics. First, we shall test the role of activity patterning in arresting turbulence, and study the interactions between coexisting flow phases via emergent interfaces. A key aim shall be to find out whether passive, minimal, activity patterns can be designed to achieve persistent flows or controlled mixing realisable in experiments. Secondly, we shall take a structures approach to identify flow patterns, using generalized correlations and local multifractality, and deploy studies where activity is modulated in a structure-informed manner. This will allow seeding or inhibiting structures at will, extremely important in spot-mixing microfluidic applications, and flow feedback-control in devices. Lastly, we will consider activity as an advecting scalar that modifies the flow as it spreads and diffuses, opening interesting parallels to combustion and flame-propagation dynamics. We shall study if injection of active fluids into passive ones can induce living fluid properties. All these questions aim towards developing maximum reconfigurability within living fluids, with a minimal of control, paving the road towards an intrinsic intelligence in living materials.