PhD student in the Eiser group
My project is on Thermophoresis.
Thermophoresis is the transport of colloids in a temperature gradient. It is a simple and feasible technique for particle separation and can be used to gain specific information about interparticle interactions. Although Thermophoresis has been identified as an interfacial phenomenon (Figure 1), its exact physical nature is still poorly understood.
Existing theoretical approaches to Thermophoresis make use of rather different assumptions and have mainly been discussed independently so far. Further, a general confusion between thermodynamic and hydrodynamic forces has led to a misinterpretation of certain thermodiffusive contributions in recent literature. We have introduced a model for Thermophoresis that uses the rate equation of a chemically active colloidal component. In addition to the out-of-equilibrium character of thermodiffusion, our approach incorporates a kinetic bias that can naturally account for hydrodynamic cross-effects.
We test the theoretical predictions from this model with experiments on aqueous suspensions of negatively charged colloids. Our method is based on the observation of the colloidal steady state distribution in a closed cell (Figure 2), using conventional Bright-field microscopy. This method is practically free from intrinsic biases, such as local heating, and has the advantage of capturing all single and multiple particle contributions to Thermophoresis.