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| Poster | FZJ-2014-03834 |
;
2014
Please use a persistent id in citations: http://hdl.handle.net/2128/7921
Abstract: Investigation of the thermodiffusion requires relatively high temperature gradients. The temperature difference at the same time should be small enough because of the temperature dependence of the effect. This can be achieved by reducing the dimensions of the system. Therefore we developed a microfluidic cell which allows us to observe thermophoresis of colloids in the solution. Unlike many existing optical methods our cell is suitable to study big colloids (up to several micrometers) and complex mixtures. The cell can be also applied for investigation of thermophoretic phenomena in biological systems such as living cell and lipid membranes.Our cell consist of three channels (fig 1A): two relatively big ones for providing high flow rate of hot and cold liquid and a small channel in between them which contains the sample to study. The cell is produced either of PDMS by molding on lithographically made Si/SU-8 master or by micromilling the Plexiglas block with a CNC machine. The central channel is made very flat to prevent convection.To characterize the temperature distribution in our cell we used FLIM [1] with Rhodamine B as a temperature sensitive dye. The temperature distribution in the central channel is shown in fig 1B. The temperature difference across the central channel appeared to be around 2°C (the temperature gradient equals 2•104 K/m) although the temperature difference in the cooling and heating channels was much higher (22°C and 47°C respectively) which indicates large temperature drop in the walls.The cell was applied to investigate thermodiffusion of latex microbeads (sulfate modified, 0.5um) in water. The resulting exponential distribution in equilibrium (fig 1C) could be analyzed according to Zhao et al [2]. In order to validate our new method we perform additional measurements with the Thermal Diffusion Forced Rayleigh Scattering setup. Results will be discussed.
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