title: Thermophoretic depletion follows Boltzmann distribution.
abstract: Thermophoresis, also termed thermal diffusion or the Soret effect, moves particles along temperature gradients. For particles in liquids, the effect lacks a theoretical explanation. We present experimental results at moderate thermal gradients: (i) Thermophoretic depletion of 200 nm polystyrene spheres in water follows an exponential distribution over 2 orders of magnitude in concentration; (ii) Soret coefficients scale linearly with the sphere's surface area. Based on the experiments, it is argued that local thermodynamic equilibrium is a good starting point to describe thermophoresis.
authors.affiliation: Applied Physics, Center for Nanoscience, Ludwig Maximilians University München, Amalienstr. 54, D-80799 München, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Duhr
authors.forename: Dieter
authors.initials: D
authors.lastname: Braun
mesh_terms: D004058:Diffusion; D005453:Fluorescence; D044085:Microfluidics; D008856:Microscopy, Fluorescence; D011137:Polystyrenes / Q000737:chemistry*; D016008:Statistical Distributions; D013696:Temperature; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D011137:Polystyrenes; D014867:Water