Determination of interaction forces of (sub)-micron sized particles via the capillary rise method and colloidal probe atomic force microscopy: A combined approach

Hypothesis

The adhesion forces of particles in the submicron range play a decisive role in many particle processes such as agglomeration. These forces are influenced by many factors such as particle size, surface roughness, and contact area. The quantification of these influences should be possible by linking adhesion forces, measured with colloidal probe atomic force microscopy (cp-AFM), and surface energy, measured with the capillary rise method, using different adhesion force models.

Experiments

Silica-silica (SiO₂-SiO₂), polystyrene-polystyrene (PS-PS) and mixed adhesive force contacts of micrometer-sized particles were measured by cp-AFM. The surface energy was determined by the capillary rise method using the Owens-Wendt-Rabel-Kaelble (OWRK) method. Various adhesive force models were used to link the experimentally measured forces. In the adhesive force models, the particle size, the distance between the particles, and the roughness were varied.

Findings

Adhesion forces measured with the AFM can be linked to the OWRK method via adhesion force models such as the particle–particle Van-der-Waals (VDW) model, Rumpf’s roughness model, and a proprietary model for multiple particle–particle interactions with the surface energy. The main influencing factors are the substrate and particle roughness as well as their plastic or elastic behavior, which influences the contact area of the adhesive contact.