Adhesion between particles and nano-structured films
Adhesion between particles and solid surfaces is a key factor in many industrial applications. The surface forces causing adhesion of particles to substrates are studied here. Specifically, the main focus of this work is to understand, measure and predict the net adhesion force distributions (primarily in terms of van der Waals forces) between particles (of sizes in the micron to nanometer range) and chemically homogeneous/heterogeneous thin films (of thickness varying on nano-scale). ^ The 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. A finite interfacial volume integration (FIVI) based approach was developed to model the observed forces while accounting specifically for the morphological and chemical heterogeneities of the interacting surfaces. Specifically, this study has developed a detailed understanding of particle adhesion, and has quantified the relative importance of the geometry, surface roughness and medium properties on the adhesion of the approaching bodies as their sizes are scaled from micro- to nano-scale. In addition, the simulator developed in this study predicts the adhesion of particles to chemically heterogeneous surfaces (e.g. substrates having nanoscale features of different materials imprinted on the surface) including the effects of the discontinuity in the interfacial composition. This facilitates prediction of the dynamics of particle motion as particles approach nanopatterned surfaces. Finally, the modeling and simulation protocols developed describe the adhesion behavior of particles towards ultra-thin films as a function of coated film thickness and composition. ^
Stephen P. Beaudoin, Purdue University.
Engineering, Chemical|Engineering, Materials Science