Effect of Dispersion Medium and Dominated Evaporation on the Pattern Formation of Colloidal Suspension

Abstract

We study the effect of dispersion medium and dominated evaporation on the drying process and pattern of thin liquid layer colloidal suspention. Panasonic camera is used to capture the drying process and macroscopic pattern. It is shown that drying patterns are sensitive to the dispersion medium. As the volume ratio of ethanol in aqueous ethanol colloidal suspension increases, the evaporation rate increases, and film in the center becomes smaller and thinner, obvious broad-ring pattern can be observed. We suggest that difference in dispersion medium changes the evaporation rate, which has a direct proportional variation with strength of Marangoni convection. Furthermore, convection strength has great influence on self-assembly of colloid particles and the pattern formation of colloidal suspension. We design two simple experiments to change the evaporation rate and convection strength in order to verify the conclusion above. Broad-ring patterns with spray-like round edge at higher evaporation rate are obtained. Uniform film forms at lower evaporation rate.