While traditional fluid mechanics focusses on the rheology of the fluid alone, many biological and microfluidic applications require the channel walls to be deformable. Our research has shown that the deformability of the channel walls can induce or suppress hydrodynamic instabilities which cause laminarturbulent transition in tubes and channels. While it is well known that laminar-turbulent transition in rigid tubes occurs at a Reynolds number near 2000, we find that in flow through soft, deformable tubes, the laminar flow becomes unstable at much lower Reynolds number. Interfacial instabilities that occur in multi-layer flows are shown to be suppressed by tuning the properties of the deformable wall, and this can be potentially used in polymer processing applications.

Another major thrust is to understand ageing and effect of deformation on a variety of soft glassy materials such as concentrated suspensions, glassy polymers and polymer nanocomposites. The common theme in all these systems is their jammed state wherein primary entity (particle or molecular segment) is physically arrested due to overall crowding of constituents. In such a state, the system explores only a small part of the phase space thereby leading to a glassy behavior. Recently we showed that how rheological characterization can give profound insight into the ageing of colloidal glasses compared to that of colloidal gels. We also investigated the effect of deformation on ageing suspensions and how influence of the same on relaxation dynamics can be used to predict long time rheological behavior of these materials.