The application of lateral force microscopy to particle removal in aqueous polymer solutions

An atomic force microscope (AFM) has been used to examine the effect of a typical polymeric dispersant on the adhesion between an iron oxide sphere and a silicon wafer in the presence and absence of shear. Two separate methods for the determination of the lateral spring constant (k(1)) of AFM cantilevers were employed. Determination of k(1) allows the absolute, rather than relative, shear force to be extracted from the lateral force output of the AFM. A comparison is made between the pull-off force (no shear) and the lateral force as the dispersant concentration and loading force are varied. While in both cases the magnitude of the forces decrease with increasing dispersant concentration, the effect is much less marked for the lateral force. A linear increase in removal forces with increasing loading force was observed. For a given load, the removal force is typically an order of magnitude smaller in the presence of shear.