The mechanical and frictional properties of polystyrene microspheres (PS) of different diameter (50 – 500 nm) and different surface chemistries (regular, amine, and carboxylate) were studied by atomic force microscopy, force spectroscopy, and lateral force microscopy. A technique for modifying the mechanical properties was developed and used to provide a set of PS samples over which we had control of the elastic modulus without corresponding changes in the chemical bonds. Lateral force microscopy was used to translate asymmetric, nanoscale particles of controlled size, surface chemistry and moduli. Silicon wafers were used as substrate. The effects of work of adhesion, elastic modulus of PS samples, and contact radius between particle and substrate have been studied for different modes of particle translation under external force. There was a significant decrease in elastic modulus when submerged in pure ethanol. A pattern in modulus values depending on the size of PS samples, was also observed. The interfacial surface energy measured for carboxylate functionalized PS sample was larger than amine functionalized PS sample. The elastic moduli and adhesion data were used to fit in theoretical models to predict the translation force for PS samples. AFM cantilevers of different stiffness (4.5 N/m and 45 N/m) were used for lateral force microscopy. The observed mechanical behavior and frictional properties are interpreted and tested against the theoretical model.

Rolling and sliding friction characterization of polystyrene microspheres (PS) using force spectroscopy and lateral force microscopy

255th National Meeting (2018)

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