The influence of instrumental parameters on the particle-surface interaction measurements using colloidal probe AFM in viscous liquids

Understanding surface adhesion in liquids is of great significance for both fundamental study of suspension rheology and industry such as suspension mixing. However, the key factors that influence adhesion between non-deformable particles and surfaces in highly viscous fluids have not been well understood. Here we used colloidal probe atomic force microscope (AFM) techniques to study the adhesion forces △F in viscous liquids by tuning the instrumental parameters such as contact force, contact time, approach and retraction velocities. The data are well described by a theoretical model that includes the adhesion and the hydrodynamic forces, acting on the colloidal probe. We thereby find that the retraction velocity is the most significant factor that influenced the adhesion measurements, particularly in viscous liquids, due to the hydrodynamic effects. In addition, a thinner lubrication film between the particle and the surface would lead a higher △F, which is due to a higher contact force with some contact time prior to retraction