| 초록 |
Evaporation characteristics of various droplets on superhydrophobized Si micro-pillar substrate have been investigated experimentally. Processes for forming different droplets, i.e., Cassie, Wenzel, and mixed ones, are developed, such as humidifier mist deposition or vapor condensation. Exposure to humidifier mist has enabled the formation of Cassie droplets, droplets sitting on pillars top with entrapped air underneath. Water vapor condensation has led to the formation of mixed droplets, that is, Cassie droplet with impaled plugs. The mixed droplets have been converted into Wenzel ones by simply adding additional water to them. These droplets have shown different evaporation characteristics. As expectedly, mixed droplets have shown evaporation time in-between of that for Cassie and Wenzel ones. Further, compared to the well-known constant contact angle (CCA) mode of evaporation for Cassie and constant contact diameter (CCD) mode of evaporation for Wenzel droplets, respectively, the evaporation of the mixed droplet have shown the stepwise change in both contact angle and contact diameter. Finally, spontaneous droplet movement, depending on the droplet type, has been traced. While the Cassie drop moves rather randomly during evaporation, the mixed droplet showed predictable movement depending on the size and location of Wenzel plugs. The evaporation characteristics of different droplets can be a valuable help for a wide variety of applications such as self-cleaning, dewing, fog-basking, dropwise/filmwise condensation, etc. |
