Solid/liquid Interfacial Wettability Regulation And The Investigation For Its Application Of Directional Liquid Transport

The unique surface wettability of natural organisms provides new ideas for the preparation of artificial superwetting bionic surfaces.Recent years,starting from the wettability of biological surfaces,researchers had gradually revealed the law of solid-liquid interfacial wettability.Combined with modern micro-nano processing technologies,a variety of bionic superwetting surfaces were successfully developed and their potential applications in various fields had been preliminarily explored.For example,the superwetting surfaces which can realize directional liquid transport has shown unique advantages in water/fog collection,oil-water separation,microfluidics,electric energy harvesting,enhanced heat transfer and sensors.However,in various forms of interfacial liquid dynamic manipulation,the understanding of the dynamic interaction mechanism of solid-liquid interface is not deep enough.The resulted problems including the maximum limit droplets driving efficiency on interfacial directional liquid transport,the new strategy of wettability regulation,and the new application of interfacial directional liquid transport still need to be further explored.In response to the above problems,in this paper,based on the three factors affecting the wettability of solid-liquid interface(external field intervention,surface energy modification and micro-nano structure),taking advantage of the corresponding wettability regulation law,three functional surfaces that can realize liquid directional transport were prepared.Directional liquid transport mechanism and the liquid manipulation law in different ways were studied emphatically.The extreme efficiency droplet driving based on dielectricwetting regulation is realized.A new strategy of tunable oil-water separation is proposed,by which modify the surface energy of textile and adjust the wettability by mechanical stretching.The new application of self-priming interface solar evaporator based on microstructure wettability regulation was explored.Main results are summarized as follows:(1)Based on the wettability regulation of dielectrowetting,an electric field enabled droplet directional transport device was prepared.Single-plate digital microfluidics is the technology of droplet manipulation in open format,which has many advantages including convenient sampling and easy cleaning of surface contamination.However,it still surfer from limitations such as unstable droplet manipulation and low driving efficiency.Based on the research and analysis of the dynamic behavior of dielectric wetting,the quantitative evaluation of droplet driving performance is realized by constructing the mathematical model.To maximumly improves driving efficiency,the optimal time interval of external voltage applied on adjacent electrodes could be calculated.Experimentally,through constructing a system platform for droplets driving,continuous directional droplets transport on different paths and droplet-based carrier transport are realized,indicating excellent stability of continuous directional droplets manipulation.This work provides a new method to improve the droplet driving efficiency on single-plate digital microfluidics,which is of great significance to improve the droplet driving efficiency and handling stability.(2)Utilizing textile surface energy modification,based on the wettability regulation by mechanical stretching,the stretchable superwetting membrane for oil-water separation were prepared.In view of the current practical problems including non-tunable separation speed and blockage in oil-water separation,we proposed to modify the surfaces of stretchable textiles and then prepared stretchable separation membranes with different superwettabilities.Taking advantage of the as-prepared membranes,the separation of both light oil(?_water>?_oil)water mixture and heavy oil(?_water<?_oil)water mixture were successfully realized.On this basis,the influence of textile substrate stretching on wettability and directional penetration of liquid through textile were studied in detail.In the application of oil-water separation,the period of surface structure and pore size of separation membrane can be changed the through textile stretching.Thus,not only the tunable oil-water separation speed is realized,but also the self-combing performance of solid impurities was achieved,which is of great significance to the improvement of oil-water separation efficiency and practical engineering application.(3)Based on the wettability regulation of microstructure,the interfacial solar evaporator with structured surface imparted directional liquid self-transport was prepared.The interfacial solar evaporator based on porous materials suffer from small heating area,insufficient water supply,and blockage caused by salt deposition,which makes it difficult in engineering application.In this paper,a structured surface with directional liquid transport was prepared based on microstructures wettability regulation,which was further applied in the fabrication of interfacial solar evaporator.The anisotropic inverted pyramid PDMS micro-groove array(discrete anisotropy)was constructed by 3D printing and soft lithography,and the doping of PDMS with graphene powder endow it excellent photothermal performance.The as-prepared solar evaporator not only realizes self-priming directional water transport guaranteeing sufficient water supply,but also greatly increases the photothermal conversion.Structured surface solar evaporator exhibit excellent desalination effects of seawater and purification ability of acidic sewage.This method plays an important role in promoting the large-scale application of interfacial solar evaporation technology.