Exploring the physics of active particles and active matter
Active particles are motile objects, which can be either living or inert. Some examples are bacteria, artificial microswimmers, actin+myosin assembly in living cells. Collectively they form fluids, liquid-crystals, etc. in the conventional sense. However motility of the constituent particles brings in an unusual twist — activity. As a result a variety of striking and surprising properties with novel physics emerge.
Here, at IISER Tirupati, APP-G has begun to unravel the mysteries of active systems in some of the hardest to understand limits.
Current projects
Dense suspensions of flagellated microswimmers
Dense suspensions of active particles show properties that are distinct from the dilute suspensions. Unusual flows and collective dynamics emerge which are difficult to probe and are poorly understood. Motivated by this Derek is interested in probing active particles in crowded environments. His calculations show that in cramped situations flows around individual swimmers can change dramatically leading to modified interactions between different swimmers. Derek is now probing how these observations show up in the collective dynamics of the whole system.
Active particles in confined fluids
Living active particles such as bacteria and other microorganisms, are often found under various confinements. Having confining boundaries is also common for artificial microswimmer suspensions prepared in laboratories. Yet, owing to the complex levels of the required calculations, theoretical understanding of the confined suspensions are hard to achieve. Taking this as a challenge Ambareesh has shown with patient calculations, how a confining boundary leads to the modified hydrodynamic flows and interactions in a suspension of flagellated microswimmers. The work is supported by preliminary numerical investigations by Chinmay. Ambareesh is now interested in probing how his findings will affect a dense confined suspension.
Control mechanism of the motility of E. coli over biological surfaces
E. coli is an example of living active particles. The control of the motility of E. coli and other bacteria over biological surfaces is sought-after in many medical and biotechnological applications. However, experiments on this direction have been greatly crippled by the limitations on probing the flagella during cell movements. Undeterred by the challenges, Vignesh has instead turned to simulations. He is interested in finding the underlying physics influencing the control mechanisms of bacterial motility. His simulations uses a realistic model of E. coli developed by us in collaborations with Prof. Holger Stark's group at TU Berlin, and the project is carried out with a strong collaboration between the two groups.
Life in a living liquid crystal
Living or active liquid crystals are abundant in biology with various complexities, e.g., they exist inside the cytoplasm of a cell, and are also prepared in laboratories for experimental studies. Fascinated by the rich physics involved, Chinmay is interested in probing how activity and elasticity of the medium affect the properties of suspended objects in the media. He is using numerical simulations and also aims at investigating the system analytically.
