Foam Electrokinetic Separation

This is an interdisciplinary project between the Departments of Mathematical Sciences and Chemical Engineering. It will focus on the investigation of electrokinetic phenomena in foams and free liquid films. A potential application is in developing a novel separation technique for biological entities such as proteins and cells that are useful in pharmaceutical industry. As the full set of equations describing a foam or a free liquid film in an externally applied electric field (hydrodynamic equations and electric field equations together with the Nernst-Plank equations for ionic concentrations and corresponding boundary conditions) is not easily suitable for analytical and numerical treatment, we will first aim to derive reduced-order model equations which will still capture the key physics of the problem. To obtain some initial insight, we will start with simpler idealised cases (e.g. model foam plateau borders as being two-dimensional, and model the liquids as being perfect dielectrics) gradually increasing the level of complexity and eventually including the effects of surfactants and electrokinetic phenomena. We will, for example, study the stability of a foam in an applied electric field (which generally has a destabilising effect) to delineate parameter regimes under which stability can be achieved and the foam does not break up (understanding this is important for the potential applications mentioned above). It will be particularly important to understand which mechanisms could be used to stabilise the foam, and for this we will, for example, study the effect of various surfactants on the stability of the foam. We will also analyse flow patterns in foams/free liquid films generated by an applied electric field. Although the reduced models will provide great insight into the behaviour of electrified foams and free liquid films, such models are not universal and have restricted ranges of validity. To obtain more complete understanding, the research will be supplemented with direct numerical simulations (using e.g. the software package Comsol). In addition, we plan to perform laboratory experiments involving of state-of-the-art flow visualization tools (such as particle image velocimetry).