While classical mean field treatments such as DLVO address the interesting particle pair potentials arising from competing attractions and repulsions, the fascinating features result from differences in the range and strength of the attractions and repulsions. Most real systems have the additional complication of surface heterogeneity, for instance producing locally attractive and repulsive regions on the surface, with these regions ranging from the nano-scale to the micro-scale in size. When the length scale of the heterogeneity approaches that of the particles, the results are mostly easy to anticipate. However, when the heterogeneity length scale is tiny, on the order of nanometers, unusual behaviors result. This talk will describe systematic experiments that provide quantitative insights into the consequences of interfacial heterogeneity, for instance explaining how particles with strong negative zeta potentials can be highly attractive as a result of electrostatic heterogeneity.

Particle manipulation using heterogeneous physico-chemical and hydrodynamic interactions

244th National Meeting (2012)

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