Quantitative Analysis of Particle Roughness Measurements From Reflection Interference Contrast Microscopy

Dispersion of contaminants, such as dust and allergens, from surfaces into the air under atmospheric and indoor environmental conditions depends greatly on the particle-surface contact phenomena. Therefore, accurate information about particle roughness and the deformation that occurs when a particle is in contact with a surface is needed to provide improved models of particle resuspension and adhesion. Reflection interference contrast microscopy (RICM) offers a unique “view from below” perspective to study particle-surface contact phenomena; in particular, the capabilities of RICM in particle roughness measurements are explored in this study, by measuring the minimum separation distance between micron-size particles in contact with a flat substrate with a resolution of up to 1 nm. Monodisperse samples of polystyrene latex and glass beads were studied in order to compare surface roughness of different types of particles of similar size. Polydisperse samples of glass beads were also analyzed to compare particle size and surface roughness. Particle size measurements were done with RICM and minimum separation distance values were calculated in two ways to determine the most accurate approach. It was shown that particle size data can be accurately obtained by RICM analysis, and the minimum separation distance that is measured by RICM can be used to show differences in surface roughness between different types of particles.