Study Of The Stability And Timeliness Of Gas-liquid Interface For Superhydrophobic Materials

The superhydrophobic materials always attract people's attention because of many characteristics like self-cleaning, antifogging, drag reduction, low adhesion, and so on. The stability of the gas-liquid interface is the key to the realization of these functions. There is very important significance for practical application of superhydrophobic materials to research the stability and timeliness of the gas-liquid interface. In this paper, the stability and timeliness of the gas-liquid interface are researched through the study of the surface of mosquito compound eye and lotus leaf. The main research work is as follows:1. The structure model of mosquito compound eyes is established based on the classical theory of superhydrophobicity and analysised in the views of superhydrophobicity, stability of interfacial hydrophobicity and thermodynamics. The results indicate that the mosquito eyes have a water contact angle of 150.1°, which is ordinary. The analysis of interfacial stability shows the micronscale and nanoscale structures can resist external pressures of 67.2 Kpa and 181 Kpa respectively, which can effectively resist the wetting from external fog drops. For the fog drops at nanoscale, influenced by the scale effect and line tension, the free energy of analogous Wenzel state is higher than the analogous Cassie state. Therefore, the analogous Cassie state is always formed prior and then the Cassie state is formed during the atomization. Due to the hemisphere shape and close arrangement of microstructure, a conical hydrophobic capillary tube is formed, which can push out the fogdrop from the inside of the microstructures when the fog drop is grown up, and therefore the antifogging property is realized at micron scale. The small sized nanostructure of mosquito compound eyes is the key factor for the realization of antifogging property.2. Lifetime of underwater superhydrophobicity is tested through the continuous recording reflected light intensity variation of superhydrophobic interface in different water depths. The change progress of reflected light with time can be divided into three stages: total reflection stage, rapid decay stage and final stable stage. The duration of the total reflection stage is the lifetime of underwater superhydrophobicity. And it decreases exponentially with the water depth increased. When the water depth is higher than the ultimate depth that the capillary force can resist, the lifetime is further shortened. The vapor-liquid interface stability relys on suspension force produced by the capillary force and the air pressure. Therefor it is great significance for the wide application of superhydrophobic materials under water to improve the ultimate depth that the capillary force can resist.