COLLOIDAL PARTICLES AT WATER-GLASS INTERFACE - ANALYZING VIDEOMICROSCOPIC DATA

Direct videomicroscopic observations provide a powerful tool for inves tigations on the deposition of colloidal particles at liquid-solid int erfaces. However, the technique is also capable of producing artefacts caused mainly by limited resolution. In the present contribution we d iscuss the possibilities and limitations of videomicroscopic observati ons, focussing thereby on an application example, namely particle depo sition from flow in a parallel plate channel in the presence of a repu lsive barrier. We outline algorithms for the determination of the rele vant quantities, indicate the pitfalls, and provide correction formula s. Special attention is paid to the kinetics of particle release, name ly to the accurate determination of the distribution of the times the particles spend adhering to the surface. In our example the kinetics o f the release is found to be highly nonexponential, but an adequate fi t of the measured distribution of adhesion times is obtained with a st retched exponential exp[-(beta tau)(nu)], where nu approximate to 0.5 and beta approximate to 3 x 10(-5) s(-1). (C) 1998 Academic Press.