Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 16: Poster: Colloids and Complex Liquids

CPP 16.28: Poster

Dienstag, 27. März 2012, 18:15–20:45, Poster A

Comparison of time-dependent friction and diffusion coefficients of single blank and DNA-grafted colloids in dilute polymer solutions - Drag reduction by DNA-grafting beyond linear response? — •Olaf Ueberschär, Carolin Wagner, Tim Stangner, Christof Gutsche, and Friedrich Kremer — Institut für Experimentelle Physik I, Universität Leipzig

Recently, we discovered that single DNA-grafted colloids under shear flow in dilute λ-DNA solutions experience a drag force that is significantly reduced compared to equally sized blank microspheres. The maximum extent of this drag reduction was found to amount to 60% compared to the λ-DNA-induced contribution on the drag on blank colloids. Based on previous theoretical work, we proposed an explanation of this effect by analyzing the differences in the Stokes flow field around the blank and grafted colloids. Now, we present new experimental and theoretical results that help to elucidate further the effects of polymer accumulation and depletion around single colloids in dilute polymer solutions under thermal equilibrium and non-equilibrium steady state conditions. Special emphasis is laid on the question whether or not these effects still take place in the linear response regime. For this, we compare the experimental data obtained with our optical tweezers setup and a fast free particle tracking measurements. The two major measurement approaches towards friction coefficients on a single particle level (drag forces in Stokes flow, free diffusion paths) are discussed in detail. Good quantitative agreement with pertinent theoretical predictions further supports our argumentation and conclusions.