(730a) Double Layer Forces in the Presence of Charge Heterogeneities

The study of particle deposition at solid-liquid interfaces has been the subject of numerous investigations due to its great importance in a large number of technological applications. The transport and fate of colloidal particles in underground reservoirs, and its impact in the facilitated spreading of contaminants, makes particle capture and reentrainment a crucial issue in environmental applications. In all cases, deposition is a complex process that includes competing contributions from different electrostatic effects, dispersion forces, Brownian motion and hydrodynamic interactions.  Surface charge heterogeneities in particular, provide a means of precisely tailoring the interactions between particles and surfaces.

Here we are investigating the role of charge heterogeneities on double layer forces using direct force measurements in the Surface Force Apparatus. The surface heterogeneities consist of an ordered array of positive patches patterned onto mica via chemical vapor deposition.  The force profile between the patterned surface and bare mica are directly measured in the surface force apparatus.  The force profiles are compared to the force profiles between two bare (negatively charged) mica surfaces and two positive surfaces. Comparisons are made between the measured force profiles and DLVO theory.