Residues from Evaporative Deposition of Colloidal Suspensions as Indicator of Dynamic Surface Tension

Abstract

The technique of evaporative deposition is inexpensive, simple, and underutilized. The pattern from a desiccated droplet of solution indicates properties about the gas, liquid, and solid phase. When a droplet of liquid evaporates from a surface, the pattern left behind is unique to certain conditions. Research on the drying process and pattern formation benefit a range of industries including Inkjet Printers, material engineering, and medical applications. Scientists have researched evaporative deposition for decades and it is still considered to be in the early stages of its potential for applications. Many factors in the surface-liquid interface affect the rate of evaporation, the drying process, the droplet shape, the particle positioning, and the final desiccation pattern. The liquid phase was examined in several experiments using charged fluorescent microspheres. The pattern variability is a result of salt concentration, particle concentration, and particle type. The solid phase substrate was ruby red muscovite mica which presents a high energy surface when freshly cleaved. The surface energy of the mica was examined by aging the cleaved mica in the laboratory atmosphere as well as petri-dishes to observe the change with time. Additionally, the mica substrate was treated in an autoclave and an ethanol bath to investigate the use of freshly cleaved mica in virus fomite studies. The wettability and patterns are similar for the autoclave treated mica and air-cleaved mica of the same age. The ethanol bath mica had different wettability characteristics and desiccation patterns than the air-cleaved mica and therefore the ethanol bath is not a suitable technique for high surface energy experiments with viruses.