| Water is the origin of all things and the root of all life.The hydrophobic water collection effect of natural organisms is the most amazing.The dew on spider silk in the morning,the growth of cacti in the desert,and the desert beetles that replenish water in the desert are all related to the hydrophobic water collection effect.Learning from nature and interdisciplinary development in recent years,many scientific researchers in many disciplines are learning about nature,hoping to draw inspiration from the excellent results of biological evolution in nature,so that the learning and imitation of biological hydrophobic water collection effect will continue to appear,and many hydrophobic projects have been designed and prepared.There are various materials such as fibers,nanomaterials,metal meshes,etc.on the water-collecting surface,and there are various test methods such as chemistry,physics and biology.This paper chooses to use the trichomes of the Sarracenia leaves as the bionic prototype,uses the aluminum alloy plate as the raw material,and uses laser processing technology to construct the surface of the simulant Sarracenia rib structure to obtain the hydrophobic water collection coupling effect of the Sarracenia-like,and analyze the surface display of the bionic structure.The droplet directional transport behavior and delayed evaporation effect in the process of hydrophobic water collection.The main research contents are as follows:1)Select the leaf trichomes of Sarracenia and analyze the microscopic morphology of the leaf trichomes by scanning electron microscope.The results show that the leaf trichomes are slender needle-shaped as a whole,and their surface is composed of two high-rib structures(high-rib structure and low-rib structure),forming a composite multi-level high-low rib-like hierarchical texture groove structure.The effect of multi-level gradient composite structure on the surface wettability of leaf trichomes was studied.The wet contact state of water droplets on the surface is analyzed.The water collection behavior model of leaf trichomes was established,and the size effect and contribution mechanism of surface microstructure characteristics on surface wettability and water collection were discussed.2)Inspired by the trichomes of Sarracenia leaves,laser processing technology is used to obtain a bionic flat rib structure with a micro-nano composite structure and a bionic high and low rib hierarchical structure on the aluminum alloy surface.Using scanning electron microscope to observe the two-dimensional morphology of the surface microstructure,it is found that the surface of the bionic flat rib structure has an even-spaced rib structure,and there are a large number of micro-nano-scale particles and micro-scale protrusions on the surface of the rib structure;The measurement found that the surface of the bionic hierarchical structure with high and low ribs has rib structures of different heights.The height ratio between high and low ribs is close to 2:1.The top of the high rib surface has a double tip structure.It is composed of micro-nano particles,and the surface of the high-rib structure also has micro-nano particles,pores and micro-protrusions,indicating that the surface of the bionic rib structure has obtained a micro-nano double rough structure.3)The hydrophobicity of the surface of the bionic rib structure is studied.The wettability test on the bionic surface found that the contact angle of the bionic flat rib structure reached 155°±1.6°;The surface morphology and structure of the bionic high and low rib hierarchical structure make it have the similar morphology and hydrophobic characteristics of the trichomes of the Sarracenia leaves,and the water contact angle reaches 157°±1.2°.Both surfaces achieve high static contact angles and low rolling angles.Studies believe that the increased roughness of the bionic surface and more surface oxide components(decreasing surface energy)make more droplets come into contact with the tip of the rib structure.The recessed part between the ribs is air,which reduces the solid-liquid contact area and causes the surface to change from hydrophilic to super-hydrophobic.At the same time,the adhesion of the surface was tested,and it was found that the surface of the bionic structure has excellent low adhesion.The surface of the bionic high and low rib hierarchical structure has obvious dynamic anisotropy due to the contribution of the height difference between the rib structures.When the degree is 3°,the water droplets can roll freely along the rib structure direction only by its own gravity,and will be intercepted by the high rib structure when rolling in the vertical rib direction.Analysis suggests that the superhydrophobicity of the surface of the biomimetic structure allows the droplets to maintain a very good spherical shape on the surface,and the low adhesion makes it easy for the droplets to detach from the surface of the biomimetic structure.The dynamic anisotropy exhibited by this hydrophobic high and low rib structure enables the droplets to achieve directional rolling,which in turn can contribute to directional water transport.4)The water collection of the surface of the bionic rib structure is studied.A water collection simulation test was carried out on a self-made water collection test platform,and the size effect,action mechanism and wetting mode between the hydrophobic surface structure morphology and water collection performance were discussed.The results show that within the same water collection time,the droplet removal rate of the bionic flat-rib structure is 74.6%,which is 5 times that of a smooth surface,and the net water collection volume is 4.7 times higher than that of a smooth surface;The droplet removal rate of the series of bionic high and low rib hierarchical structure is 76.2%,which is close to the flat rib structure,which is also 5 times the droplet removal rate of a smooth surface,and the net water collection is 7 times higher than that of a smooth surface,indicating that both surfaces are exhibited.Excellent water collection performance,and the high and low rib structure can make the surface get more water collection than the flat rib structure.According to analysis,on the one hand,the dynamic anisotropy exhibited by the hydrophobic high and low rib structure makes the droplets show directional rolling,which makes it easier to gather the liquid phase and form a large amount of liquid for directional transportation;on the other hand,the high rib structure is in the water collection performance.The pinning effect of the contact line is stronger,so that the droplets have more opportunities to contact the water mist and absorb water molecules on the surface of the structure,thereby obtaining a stronger driving force.At the same time,the influence of different combination structures of high ribs and low ribs on the net water collection is discussed.It is found that a moderate increase in the number of low ribs can increase the water collection rate,but when the proportion of low ribs is too large,it will have a negative impact on water collection performance.The study found that the high-low-low-low-high bionic structure has the highest droplet removal rate,which is the optimal parameter for fast sliding of the condensed droplets on the water film formed on the structure.5)Analyze the evaporation characteristics of the surface of the bionic structure.It is found that the delayed evaporation time of droplets on the surface of the bionic flat rib structure is 1.41 times that of the smooth surface;the maximum droplet evaporation time of the series of bionic high and low rib hierarchical structures is 1.36 times that of the smooth surface,all exhibiting good delayed evaporation behavior.It is an important factor for the two types of bionic surfaces to exhibit excellent water collection performance.During the evaporation process,the average evaporation volume per unit time of the bionic flat-rib structure is 35.1% lower than that of the smooth surface,the interface stability is good,the wettability can be maintained above the hydrophobic state,and the water collection performance is continuously improved;From high-low-low-high bionic structure to high-low-low-low-low-high bionic structure,as the proportion of low ribs increases,the delayed evaporation performance gradually decreases,it shows that the superhydrophobic biomimetic surface with tighter and regular structure has less liquid volume loss during the evaporation process,and has better delayed evaporation performance.The comparison results show that both the bionic flat rib structure and the bionic high and low rib hierarchical structure have delayed evaporation performance,thereby protecting the surface water collection performance,and the delayed evaporation performance of the two structures is similar,while the high and low rib hierarchical structure has stronger water collection performance.It is much better than the flat rib structure,so the surface of the bionic high and low rib structure has more water collection. |
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