Rheology and interfacial behaviour of suspensions of motile particles
When a bunch of motile (i.e. self-propelled) bacteria get together, they really have a party! Their collective motion is dominated by large scale patterns such as eddies and jets, and remind one of the patterns observed in large flocks of birds, or shoals of fish. We are interested in understanding the how these fascinating feats of self-organization affect the rheology of the suspension as a whole. We think this is important in explaining curious patterns observed at the edge of expanding bacterial colonies.
Why are flagella helical?
Flagellar propulsion in bacteria and other motile microbes is a beautiful example of fluid-structure interaction. We are exploring how natural flagella work, so that we may one day be able to design efficient propulsion and steering systems for self-propelled microscopic swimming robots. Currently, we are trying to understand why evolution has chosen flagella to be helical.
How does a "dead" virus outside a cell recognize and latch on to diffusing targets sites on the surfaces of fluctuating membranes? The answer may lie in the tiny flows generated by the diffusive motion of the virus and the membrane.
Complex flows of polymer solutions
Small amounts of polymeric additives can dramatically alter the dynamic properties of otherwise Newtonian liquids in flow. This has in fact been used in the industry in a range of applications such as ink-jet printing, agricultural spraying, turbulent-drag reduction etc. While it is known that the ability of polymer molecules to stretch out in regions where the flow has strong a extensional component has something to do with all of this, we still do not have a detailed predictive understanding.