The interactions between micron- and nano-particles and rough surfaces are of great importance and have numerous applications in surface science and biotechnology. It is essential to have estimates of surface/intermolecular forces between interacting bodies to describe and to manipulate the nature of interactions (adhesion or removal) between them. The focus of this work is to understand and predict the net adhesion force (in terms of van der Waals and electrostatic forces) between particles of sizes in the micron to nanometer range and thin films.
Specifically, adhesion forces were measured between micron- and nano-sized particulates and a series of substrates using atomic force microscopy (AFM) in dry and aqueous environments. The observed forces were modeled using a macroscopic computational approach. Precise mathematical representations of the geometry and surface morphology of the interacting surfaces were generated. The mathematical surfaces of the particle and substrate were then discretized into many small cylindrical elements. For the systems of interest in this study, the electrostatic force was negligible compared to the van der Waals force when the particle and substrates were in contact (~4 Å separation). The van der Waals force was determined by integrating the interactions between all opposing cylindrical elements across the particle- substrate interface. A good agreement between the measured and predicted adhesion force was obtained.
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