Automated video microscopic imaging and data acquisition system for colloid deposition measurements

An optical video microscopic system and image processing and data extraction and manipulation routines are developed for in situ detailed quantification of the deposition of colloids onto an arbitrary surface and determining their concentration distribution across the bulk suspension. The system produces a relatively large field of view (approximately 330 x 245 microm) and utilizes dark-field light microscopy to visualize colloids as small as approximately 0.3 microm in diameter at the surface and in the bulk suspension with a sufficient resolution (approximately 0.5 microm). On real-time basis, the routines automate various tasks from image capturing and processing to data manipulation, extraction, and display. The extracted data include: (i) surface concentration and flux of deposited, attached, and detached colloids, (ii) surface concentration and flux of arriving and departing colloids, (iii) distribution of colloids in the bulk suspension in the direction perpendicular to the deposition surface, and (iv) spatial and temporal distributions of deposited colloids. This article provides detailed description of the system and its image processing and data extraction and manipulation routines. Representative results of the deposition of 0.3-microm-diameter polystyrene colloids onto a glass surface, from a flowing suspension in a 0.02-cm-aperture parallel-plate channel, are presented and discussed.