title: Rotational Fourier tracking of diffusing polygons.
abstract: We use optical microscopy to measure the rotational Brownian motion of polygonal platelets that are dispersed in a liquid and confined by depletion attractions near a wall. The depletion attraction inhibits out-of-plane translational and rotational Brownian fluctuations, thereby facilitating in-plane imaging and video analysis. By taking fast Fourier transforms (FFTs) of the images and analyzing the angular position of rays in the FFTs, we determine an isolated particle's rotational trajectory, independent of its position. The measured in-plane rotational diffusion coefficients are significantly smaller than estimates for the bulk; this difference is likely due to the close proximity of the particles to the wall arising from the depletion attraction.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Kenny
authors.initials: K
authors.lastname: Mayoral
authors.forename: Terry P
authors.initials: TP
authors.lastname: Kennair
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zhu
authors.forename: James
authors.initials: J
authors.lastname: Milazzo
authors.forename: Kathy
authors.initials: K
authors.lastname: Ngo
authors.forename: Michael M
authors.initials: MM
authors.lastname: Fryd
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Mason
mesh_terms: D004058:Diffusion; D005583:Fourier Analysis; D008853:Microscopy; D055620:Optical Phenomena; D011327:Printing; D012399:Rotation