I am currently working on the following projects:

The adhesion and dessication of biological cells

The spin-drying of a suspension of biological cells is a proposed method for their preservation and long-term storage, and preliminary experiments have shown promise for these techniques. The process by which a vesicle (a simple model of a cell) sediments onto and adheres to a substrate exhibits a surprisingly complicated dynamical process in which fluid is trapped underneath the vesicle, causing a dimple to form on its underside. Similar phenomena are observed during the sedimentation of viscous droplets, but in the present problem, the elastic properties of the vesicle’s membrane boundary complicate the dynamics. The development of models to understand the adhesive process should give guidance to the time it takes for a vesicle to become well-adhered, and would be applicable much more broadly to thin-film flows beneath elastic membranes.

Once a vesicle is adhered, water is removed from it by drying out the surrounding fluid, which generates an osmotic gradient across the vesicle’s membrane. In regimes where the vesicle is strongly adhered and has a small aspect ratio, it is possible to model the dynamics using a long-wave approximation. I am currently comparing the results of this model to those obtained using boundary-integral simulations.

Viscous buckling phenomena

A thread of viscous fluid that falls onto a surface can buckle owing to the compressive stresses it experiences as it lands. Everyday examples include the pouring of shampoo into ones hand, or of golden syrup onto a slice of toast. A complicated slender-thread model was developed by earlier workers to understand this behaviour, and gave excellent agreement with experiment. My work involves an asymptotic analysis of this model to elucidate the effects of the thread’s (small) bending stiffness, which becomes important in a small boundary layer at the bottom of the thread. This approach extracts the key physical balances that govern the thread’s motion, and results in a much simpler explanation of the observed dynamics.

My future aims are to investigate the effects of an ambient viscous fluid and of a confined geometry, both of which are present in recent microfluidic experiments where similar buckling instabilities have been observed. Such instabilities can potentially be exploited to enhance the diffusive mixing between two fluids, or to facilitate the fabrication of emulsions or foams.

Optimisation of decontamination protocols

A proposed method for the removal of a contaminant from a substrate is the application of a decontaminating fluid, into which the contaminant diffuses and possibly reacts so as to be rendered harmless. The application of a decontaminant layer gives rise to an advection-diffusion-reaction problem, and an analysis of various parameter regimes of this problem provides a better understanding of how such decontamination procedures might be optimised.