Analysis of Contact Interactions between a Rough Deformable Colloid and a Smooth Substrate.

A model was developed for the effect of van der Waals interactions between a rough, deformable, spherical colloid and a flat, smooth, hard surface in contact. The model demonstrates the significant effect of colloid roughness on removal force. Small changes in colloid roughness produce large changes in the predicted removal force. Several authors attribute discrepancies in the observed interaction force between particles and surfaces to colloid roughness, and our model supports their hypotheses. Experimental data documenting the force required to remove colloids of polystyrene latex from silica substrates in aqueous solution were collected during AFM studies of this system. When colloid roughness exists, as is the case in this work, our model bounds the observed removal force. The predicted range of removal forces is in better quantitative agreement with our removal force data than are forces predicted by classical DLVO theory. Copyright 2000 Academic Press.