Micron-scale apparatus for measurements of thermodiffusion in liquids

A micro-scale beam deflection technique for measurements of thermodiffusion in liquid mixtures was analyzed. An ac temperature fields over a micron-scale sampling region was employed in comparison to traditional beam deflection techniques. It was shown that the micron-scale geometry of the apparatus speeds up equilibration by a factor of ≈300, in comparison to conventional beam deflection methods. The results show that the thermodiffusion experiments on 26 nm polystyrene colloids with carboxyl functionality (COOH) in water yield Soret coefficients of S _T=-0.28±0.025 K ^-1.