Study On The Surface And Water Collection Characteristics Of Superhydrophobic-superhydrophilic Biomimetic Structure Prepared By Laser

Spontaneous water collecting is carried out by using the coupling effect of surface tension gradient formed by bionic composite wetting surface and Laplace pressure difference caused by bionic gradient structure,which has a broad application prospect in the preparation of water catchment devices.It is of great significance to alleviate the shortage of water resources.At present,the water harvesting strategy based on compound wettability biomimetic gradient structure surface has some problems,such as small unit area,bionic gradient structure can not be applied in large area due to curvature limitation,weak self-driving ability and so on.It rarely uses superhydrophobic-superhydrophilic surface and has weak self-driving ability.In order to solve these problems,the water collection strategy of "divisional collection-multi-stage transportation" is proposed in this paper.The superhydrophobic-superhydrophilic bionic coupled gradient structure surface is prepared by laser secondary etching.The droplets on the large surface are collected and transported through multi-segment lap gradient channels,and the related research on their water collection characteristics is carried out.The main work is as follows:1.Aiming at the preparation of superhydrophobic-superhydrophilic composite wetting surface,the laser processing technology was studied.Firstly,the superhydrophobic microstructure model is established for theoretical analysis,and then the femtosecond laser processing technology of superhydrophobic surface is explored by combining wettability and laser ablation theory.Finally,the superhydrophobic modified layer is removed by nanosecond laser and the superhydrophilic biomimetic gradient structure is prepared at the same time,which provides the technological basis for follow-up experiments.2.Aiming at the phenomenon that the bionic triangular shape structure with the change of curvature gradient has a self-driving effect on the droplets.In order to obtain the gradient structure with the best water collection performance,the influence mechanism of this gradient structure on droplet motion was explored.On the basis of condensation experiment and force analysis,the influence mechanism of gradient structure parameters(angle and length)on collection performance is analyzed,and the effect of the combination of the two channels on its gain is explored by making use of the fact that linear channels can be covered in a large area.It is concluded that the mesh linear channel with a spacing of 300 ?m and a distribution of 15 °has the best water catchment performance.3.In order to solve the problem that the driving force will be lost when the curvature radius of gradient structure is too large,the strategy of lapping transportation with triangular gradient structure to provide continuous driving is put forward,and the influence of different connection rate on droplet self-driving performance is discussed.The directional transport performance of the lap structure is verified by designing transportation channels with different lap directions.On the basis of the above research,a bionic coupled water collection pattern structure is designed,and the water collection efficiency in the vertical direction is 242.9% and 125.9% higher than that of a single superhydrophilic and superhydrophobic surface,respectively.At the same time,the stability of the large-scale surface "divisional collection-multi-stage transportation" water collection system is verified,and the water collection mechanism is analyzed.