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Recently, Todd Squires of Harvard University and Michael Brenner of MIT have proposed an explanation for some of the experimental results, incorporating hitherto overlooked effects of hydrodynamics. 1 Their model produces quantitative agreement with measurements, by Amy Larsen and David Grier at the University of Chicago, of the behavior of two colloidal particles near a single wall. 2 Hints of attraction A typical charge-stabilized latex colloidal suspension consists of spheres with diameters on the order of 1 mm or smaller, dispersed in water. Sulfate or other groups on the spheres dissociate in solution, producing a large surface charge density on the spheres. The spheres are surrounded by counterions that are many times more numerous and much smaller than the spheres. |