(174b) Deposition Patterns From Drying of Colloidal Suspension Droplets

The deposition pattern of particles during the evaporation of a sessile drop was investigated using the finite element method to solve simultaneously the governing equations for the vapor phase concentration, velocity of the fluid and particle concentration in the drop, and the rate of particle deposition on the substrate. It was found that, when the droplet evaporates on the glass substrates when pH is about 7, the repulsion force between the particle and the glass substrate is so large that most of the particles were depositing at the edge during the evaporation, leaving the center part of the substrate only randomly-scattered clusters of the particles forming at the very last stage. In the simulation, without consideration of the interaction force between the particle and the substrate, it would not capture this discontinuous profile seen in the experiment. Here the simulated profile with and without considering the interaction potential will be compared. Experimental results will be compared to the simulation results.