Droplet evaporation is one of the most commonly observed phenomena which plays an important role in many applications such as spray cooling, coating, and inkjet printing. Subjects such as dynamics of the contact line, evaporation-induced phase transitions, and formation of patterns on the substrate interact in the evaporation of droplets. In this work, we investigated the effect of surface mixed wettability on water sessile droplet evaporation. The transient contact angle, center-height, contact radius, surface area, and droplet volume were experimentally measured and numerically calculated. Biphilic surfaces consisting of hydrophobic islands surrounded by hydrophilic area were fabricated. The A\* (Ahydrophobic/Ahydrophilic) value of the surfaces was changed by increasing the diameter of hydrophobic islands from 100µm to 500µm. Visualization was conducted to capture droplet dynamics during evaporation using a high speed camera. According to the obtained results, it was found that there were three distinct stages in the water evaporation process:  a constant contact area mode, a constant contact angle mode, and a mixed-mode that is independent of both the initial quantity of water droplets and the surface mixed wettability index (A\*) of the polymer surfaces. COMSOL software was used for numerical analysis. The receding contact angle, and Marangoni instability in the droplet are two main factors that alter droplet dynamics and droplet evaporation.


Evaporation of Water Droplet on Surfaces With Mixed Weettability

Division / Sponsors: 
Heat Transfer Division (HTD), Fluids Engineering Division (FED)

Heat Transfer Summer Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2020/volume/83709

18th International Conference on Nanochannels, Microchannels, and Minichannels
Paper Proceedings: https://asmedigitalcollection.asme.org/ICNMM/ICNMM2020/volume/83693

Fluids Engineering Division Summer Meeting
Paper Proceedings: https://asmedigitalcollection.asme.org/FEDSM/FEDSM2020/volume/83716

HT-ICNMM2020 - Virtual Conference, SHTC - Virtual Conference, FEDSM2020 - Virtual Conference

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