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Indexed by:期刊论文

Date of Publication:2017-04-05

Journal:COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS

Included Journals:SCIE、EI

Volume:518

Page Number:283-294

ISSN No.:0927-7757

Key Words:Droplet shape evolution; Interface free energy gradient; Driving force; Resistance; Wetting transition

Abstract:A model about the shape evolution and wetting transition of a droplet on superhydrophobic surfaces during evaporation was founded through analyzing the driving force and resistance on the three phase contact line (TPCL) of the droplet. The driving force to shift the TPCL was derived by calculating the gradient of interface free energy and the resistance was based on adhesion. The calculation results show that the volume reduction process of a droplet will undergo several stages. The first one is the constant contact line (CCL) stage with the resistance on TPCL larger than driving force. The second period is the constant contact angle (CCA) stage when the driving force is greater than the resistance. Later, the TPCL will move down along micro pillars until the substrate is wetted and the wetting transition is completed. Then, the drop will experience another CCL period before entering into the mixed mode stage. The evolution of droplet on micro/nano hierarchical surfaces is similar to that on micro structure surfaces, but with shorter CCL stage and without obvious contact angle reduction after the wetting transition because only micro structure is wetted. Finally, the reasonable agreement between the model and experimental results has been illustrated.