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Next: Optical Ratchets Up: Colloidal Dynamics and Interactions Previous: Electrostatic Interactions

Depletion Interactions

Dinsmore, Yodh, and Pine [44] used blinking optical tweezers to measure the depletion interactions mediated by small polymer chains between colloidal hard spheres and asperities in nearby surfaces. The entropically driven attraction of a sphere to a surface had been inferred from the observation of surface crystallization [45] and had been measured by Prieve and coworkers using evanescent wave scattering [46, 47]. The optical tweezer measurement demonstrates depletion forces acting on a single particle and suggests the possibility of measuring sphere-sphere interactions.



David G. Grier
Mon Feb 17 21:35:47 CST 1997