Structure And Moisture Conduction Mechanism Of Multilayer Bionic Woven Fabrics And Application Of Solar Interface Evaporatio

At present,due to the rapid increase of world’s human population and the continuous improvement of the level of industrialization,water pollution is becoming an increasingly serious problem on environment,which is a sharp shortage of freshwater resources for human survival and development.Using clean energy for cost-effective desalination is an important way to solve this problem.Solar-driven desalination technology can not only use green energy to produce clean water,but also alleviate the shortage of fossil energy.Solar-driven interfacial evaporation technology uses solar energy to heat the water surface through the evaporator at the interface between water and air to produce steam,which greatly improves the solar photothermal conversion efficiency,and advances the solar driven seawater desalination technology.It is an area of currently intense research.（1）Inspired by the branching structure and transpiration of trees,a tree-shaped biomimetic trilayer woven fabric（TBTWF）with directional water transport performance was weaved by quick-drying Coolmax fiber and hydrophobic polypropylene（PP）fiber.The TBTWF composed by interweaved plain weave layer（PWL）,basket weave layer（BWL）and float layer（FL）,and the continuous warp yarns that moved back and forth in the thickness direction of the fabric provides continuous water transfer pathes for the fabric.The asymmetric structure of the BTWF endows the fabric with excellent directional water management property,which can be tailored by the fineness and the wetting state of weft yarn in the three layers,and the groove structure on surface of the PWL.The resulting TBWF exhibited a high directional water transport index R（435%）.Mechanism for the directional water transport of the BBWF was investigated by analyzing the capillary force,the hydrostatic pressure and the hydrophobic force.Moreover,the universality of the fabric design approach was verified by two kinds of bilayer fabrics which have the analogous texture as the trilayer woven fabric.（2）The TBTWF structure with directional water transport performance was further utilized,and based on this multi-layered bionic structure,the multi-layered tree-shaped biomimetic flax fabric（TBFF）was woven with flax fibers.The obtained TBFF was modified by one-step synthesis of large-area polydopamine-polypyrrole composite（PDA-PPy）nanofibers for a high hydrophilicity and a higher surface area.The hierarchical micro-capillary pores of yarns and macro-interlaced pore structures between the warp and weft yarns in such modified TBFF-PDA-PPy exhibit broadband light absorption,high-efficiency water supply,large evaporation area,and easy steam escape.Therefore,the continuous water transport paths formed by TBFF-PDA-PPy could deliver an attractive evaporation rate of 1.37 kg m^-2 h^-1,where the solar energy conversion efficiency was up to 87.4%under 1 sun illumination.Meanwhile,TBFF-PDA-PPy has good stability and high-efficiency solar desalination performance.（3）In order to further improve the interfacial evaporation performance of the photothermal fabric based on TBFF,the TBFF fabric was carbonized at high temperature,and PPy was coated on the surface of the carbon fiber by electro deposition process,and a new type of PPy-modified carbonized TBFF（CTBFF-PPy）,which can be used as a solar interfacial evaporator for solar desalination.The hydrophilic CTBFF-PPy has continuous water transport channels for efficient water supply to the evaporation interface.The double-scale capillary water formed on the surface of CTBFF-PPy is composed of micro-capillary water in the yarns for efficient interfacial evaporation and macro-capillary water between for desalination,thus improving the evaporation efficiency and desalting performance.Therefore,CTBFF-PPy has excellent solar interfacial evaporation performance(evaporation rate of 1.4kg m^-2 h^-1,solar photothermal conversion efficiency of 91.5%),efficient solar desalination,and long-term salt tolerance without any post-cleaning treatment,and other functions.（4）In order to further reduce the cost,simplify the preparation process and improve the cost-effectiveness,inspired by the self-floating structure and transpiration of water hyacinth,a commercial black superfine denier polypropylene（SDP）fiber and expandable polyethylene（EPE）foam were designed.The interwoven self-floating biomimetic water hyacinth composite woven fabric（BWHCWF）achieves improved cost-effectiveness for solar desalination.In the traditional textile weaving process,the double-scale capillary channels（micro-capillary channels in the yarn and macro-capillary channels between the yarns）are regulated by changing the fiber fineness,size of the EPE foam,yarn twist,yarn density and the weave structure parameters,which further regulates the confined capillary water,water content gradient distribution and temperature gradient distribution on the surface of BWHCWF,so that the water supply and evaporation can reach a dynamic balance,thereby accelerating the evaporation of confined capillary water.Under 1 sun,the evaporation rate of BWHCWF was 1.408 kg m^-2 h^-1 and photothermal conversion efficiency was 92.43%.In addition,the existence of the continuous double capillary channel structure also ensures that the interfacial evaporation is enhanced and exhibits a good resistance to salt deposition.In the actual solar desalination process of BWHCWF,two kinds of solar condensate water devices are designed,including a laboratory condensate water device and a self-floating outdoor condensate water device.The condensed water meets the drinking water standards of World Health Organization（WHO）and U.S.Environmental Protection Agency（EPA）.