Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: POSTERS Colloids and Liquids

CPP 39.10: Poster

Thursday, March 26, 2009, 17:00–19:30, P3

Investigating fluctuation and dissipation of optically trapped colloids — •Olaf Ueberschär, Christof Gutsche, Jörg Reinmuth, and Friedrich Kremer — Universität Leipzig, Germany

Fluctuation and dissipation as the dominant mechanisms behind the well-observable Brownian motion of micron-sized particles are investigated and quantified on a single molecule level by means of optical tweezers technique. Using an outstandingly fast optical diffraction image analysis routine with a sampling frequency of 10 kHz combined with an automated data acquisition loop, we deduce the size of the colloid under study and the temperature of the heat bath interacting with it. Comparing blank and DNA-grafted colloids (DNA properties: molecular weight of 2800 base pairs, contour length of approximately 400 nm), the underlying mechanisms of dissipation are analyzed on a single colloid level. Bridging experiment and theory, we have adapted an experiment first carried out by Wang et al. in 2002 [1] in which the first experimental evidence for the validity of the fluctuation theorem (FT) was given. We find quantitative agreement with the FT being widely considered as the system-size and timescale independent generalization of the second law of thermodynamics. Eventually, we compare entropy production and consumption rates of blank and grafted colloids.

References: [1]G.M. Wang, E.M. Sevick, E. Mittag, D. J. Searles, and D. J. Evans, Phys. Rev. Lett. 89, 050601 (2002).