Dewetting of a droplet induced by the adsorption of surfactants on a glass substrate

Abstract

The dewetting of a surfactant droplet, induced by the adsorption of surfactants on a hydrophilic glass substrate, was observed experimentally. After being dropped onto the substrate, the droplet began shrinking and the speed of shrinkage increases with the surfactant concentration. We explained this dynamics, which is known as reactive dewetting, semi-quantitatively by expanding a simple theoretical model originally proposed and discussed qualitatively by M. E. R. Shanahan and P.-G. de Gennes [Start-up of a reactive droplet, C. R. Acad. Sci. Paris, 1997, 324, 261–268]. In addition, for the surfactant droplet with a concentration near or higher than the critical micelle concentration (CMC), we found that it maintains a large final contact area compared with that in the case of the low surfactant concentration. We discussed this phenomenon by taking the decrease in the vapor–liquid and solid–liquid interfacial tensions into consideration.