title: Diffusion of microspheres in sealed and open microarrays.
abstract: In several experiments, we study the diffusion of microspheres with different radii in microarrays filled with a variety of aqueous solutions of ethylene glycol. We study diffusion in open and closed (sealed) microarrays. In sealed nanoliter wells, the tracers show pure diffusion, whereas in open reactors, a radial outward-directed evaporation-induced liquid flow is superimposed onto the diffusion. In general, one of the following quantities can be calculated if the others are known: the temperature, the viscosity of the medium, the radius of the microbeads, or the diffusion constant. The estimated diffusion constants in closed microarrays are in good agreement with theoretical predictions based on the Brownian motion. We monitor the motion of the microbeads under a microscope and extract their paths in time from the digital recordings. Ambiguous paths due to the crossing of two trajectories can be detected. We show that low microsphere concentrations or high viscosities do not hamper a robust estimation of the diffusion parameters.
authors.affiliation: Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany. brieger@gwdg.de
authors.forename: B
authors.initials: B
authors.lastname: Rieger
authors.forename: H R C
authors.initials: HR
authors.lastname: Dietrich
authors.forename: L R
authors.initials: LR
authors.lastname: Van Den Doel
authors.forename: L J
authors.initials: LJ
authors.lastname: Van Vliet
mesh_terms: D000465:Algorithms; D004058:Diffusion; D007091:Image Processing, Computer-Assisted; D046228:Microarray Analysis / Q000379:methods*; D018613:Microscopy, Confocal; D008863:Microspheres; D014783:Viscosity