|
|
Evaporation of simple and complex fluids at different surface wettability
Májek, Juraj ; Ryabov, Artem (advisor) ; Procházka, Marek (referee)
In this work, we investigate the evaporation dynamics of sessile droplets in two scenarios: (i) droplets evaporating on Teflon plasma polymer coated sur- faces, exhibiting anomalously long evaporation lifetime for their size, (ii) drying droplets with liposome suspensions that gradually spread while evaporating. (i) By observing water droplets evaporating on a silicon wafer coated with a Teflon thin film, we discover that the water disintegrates and penetrates the Teflon film. The droplets hide some of their volume underneath, which then does not evaporate. This leads to anomalously long evaporation times. We attribute this effect to structural instability of the Teflon layer, stemming from the contact of non-polar Teflon and polar SiO2. By using Teflon surfaces at most week old, this effect can be prevented. We further identify and describe typical features of the penetration, allowing for its early detection. (ii) We measure the spreading of liposome-laden droplets and find an increase of radius up to 30% of the initial value. During the increase, the droplet contact line spreads in bursts, or protrusions, not uniformly. Existing literature shows that liposomes adsorb on both the air/water and the water/surface interface and reduce the corresponding surface tensions γgl and γsl. We find that when the...
|
guest ::
