実験統計物理：臨界カシミア力の微視的研究

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Colloidal systems have been since the beginning of the century as model physical systems to prove very important results in physics. From the sedimentation experiments of Perrin, that settled the atomic dispute, to the more recent studies of the glass transition in colloidal glasses [E.Weeks Science 2000]. We study a potential tool to control the aggregation and migration of these colloidal systems : The Casimir Force. The system we are using is a PMMA-colloid suspension, in Cis-Decalin and BromoCyclohexane, with several polymer concentration. Our goal is to measure the interaction between large TiO2 probe colloids that are trapped with optical tweezers inside the sample. We want to measure the casimir force between the two probes, as a function of distance, but also as a function of the probes motion.Throughout our research, we've developed several original techniques: such as a chemistry of the binary fluid and a programming image analysis in Matlab and acquisition routines in Labview to systematize the experiment. In the past year, we have finalized the optical trapping, and installed a mechanical stage, and a piezo stage for finer position control and higher repeatability. We also have measured the impact of the polymer concentration on viscosity and surface tension of the binary liquid.