Design,fabrication And Performance Of The Coupled Bionic Antifogging Surface

Atomization can cause light to not directly penetrate the material surface,which not only has a serious impact on the efficiency of the material,but also produces many problems or even dangers to our daily life.For example,the fog on the surface of the laparoscopic lens will affect the smooth progress of the operation.Sea bridges and ships are exposed to moisture for a long time,which is easy to lead to aging and corrosion.Fog on the windshield of aircraft and cars is an important cause of traffic accidents.The fog on the surface of the solar panel will reduce the conversion efficiency of the photovoltaic cell.The fog on the surface of the agricultural greenhouse will directly affect the metabolism of the crop.In addition,under some extreme low temperature conditions,which may bring significant safety hazards,such as aircraft,wind turbines,high-voltage transmission,telecommunications equipment and heat exchangers,etc.,if frost or excessive uneven water condensation occurs on these surface,the operation efficiency of the equipment will be reduced,and even the whole system will be paralyzed.In summary,the research on antifogging(AF)materials is of great significance.In recent years,although the research on AF surface has made great progress,there are still some major challenges in its development.For example,how to skillfully design the texture structure of the AF surface,how to make AF surface with antireflection,self-cleaning,wear resistance,etc.,how to realize large-scale production without being limited to the laboratory.“New Principles and New Methods for Designing and Preparing of New Materials” is one of the basic researches for the key deployment of major national strategic tasks,this was recently put forward in a series of policy guidance documents,such as the “13th Five-Year National Science and Technology Innovation Planning” and the “Outline of the National Program for Long-and Medium-Term Scientific and Technological Development(2006-2020)”.Among them,“Material Surface Engineering”,“High Performance Film Material”,and “Intelligent/Bionic /Supermaterial” have also been mentioned many times in the documents.In this paper,from the perspective of coupled bionics,the compound eye of mayfly nymphs was selected as the research object.The AF function of the compound eye was studied by the spray simulation test system and the contact angle(CA)test method.It was found that the AF behavior of compound eye was divided into three stages.The AF mechanism of compound eye of mayfly nymphs was revealed by the wettability theory.Inspired by the compound micro-structure array of the larvae,four kinds of regular biomimetic microstructure array models were established,and the relationship between surface wettability and bionic microstructure and surface energy of the material was obtained.Combining different biomimetic microstructures,morphology,and materials,the three stages of AF behavior of compound eyes of mayfly nymphs were imitated,and three kinds of coupled bionic AF surfaces with different wettability and excellent performance were obtained.The main contents of this paper are as follows:Firstly,the ecological characteristics of mayfly were studied,and the compound eyes of the mayfly nymphs were selected as the research object of this paper.The metallographic microscope(OLYMPUS,PMG3)and scanning electron microscope(JEOL,JSM-6700F)were used to characterize the three-dimensional structure of compound eye surface.It was found that a flat ellipsoid array with uniform size and order was distributed on the surface of the compound eye,and the surface of the single flat ellipsoid was smooth and there was no nanostructure.Using 3D super-depth of field microscope(KEYENCE,VHX-5000)as the observation equipment,through the simulation AF test method,it was found that the AF behavior of compound eye was divided into three stages,and a three-dimensional model of the microscopic structure of the compound eye surface of the mayfly nymphs was established.The fogdrop was divided into two sizes,and the AF mechanism at different stages was revealed by the wettability theory.Then,inspired by the microstructural array of the compound eye surface of the mayfly nymphs,four regular biomimetic microstructure arrays were designed and their corresponding wetting models were analyzed.The following conclusions were drawn:(1)The convex microstructural array is more suitable for the design of hydrophobic surface,and the concave microstructural array is more suitable for the design of hydrophilic surface.(2)For the Cassie model,the relationship between apparent CA and surface energy parameter is mainly determined by the layout of the microstructural array,and is not affected by the shape of the microstructural array.(3)For the Wenzel model,the relationship between apparent CA and surface energy parameter is mainly determined by the shape of the microstructural array,and is not affected by the layout of the microstructural array.It provides a theoretical basis for the design and fabricate of the next bionic microstructure AF surface.Finally,combined with different biomimetic microstructures,morphology,and materials,the three stages of AF behavior of the compound eye of the mayfly nymphs were imitated,respectively,and three kinds of coupled bionic AF surfaces with different wettability and excellent performance were obtained and studied theoretically and experimentally.(1)Fabrication and performance study of coupled bionic superhydrophobic antifogging surface: combined with UV lithography and reverse mould method,a set of regular periodic structure was designed on the polydimethylsiloxane(PDMS)film(PF)surface.The surface roughness is composed of micropillared array(MPA)and nanometer silicon dioxide(Si O2)particles,and the dynamic behavior of fog drops on the surface of PF-coupled MPA and Si O2 coatings was carefully observed and analysed.The results show that the coupling amplification effect of MPA and Si O2 coatings is the direct reason for the realization of superhydrophobic AF.(2)Fabrication and performance study of coupled bionic superhydrophilic antifogging surface: a kind of AF with excellent mechanical properties was prepared by using polymethyl methacrylate(PMMA)as the substrate combined with wet etching and reverse mould method.In the visible wavelength range(400~800nm),after spraying the coupled PMMA(CP)film for 6min,the average transmittance of the C-P film remained at 92.26%.After 100°C steam test for 10 s,the C-P film still remained transparent and clear appearance,in addition,the synergistic effect of the inverted pyramid microstructure and silica sol makes the film also have good antireflection and superhydrophilicity.Among them,the addition of silane coupling agent KH550 enhances the hardness,wear resistance and adhesion of C-P film significantly.(3)Fabrication and performance study of coupled bionic lubricant antifogging surface: UV-lithography and reverse mould method were used to prepare regular papillae-like microstructure arrays(PMAs),PF surface was treated using trimethoxy(1H,1H,2H,2H-heptadecafluorodecyl)silane(FAS),and then using perfluorinated lubricating oil Krytox 1506 as the lubrication layer to infiltrate surface,smooth PDMS film(BLPF)was fabricated successfully.The optical properties of the samples were compared and analyzed in detail,the average reflectance of BLPF is reduced by 2.4% in the visible light range(400-800 nm),and the maximum transmittance of BLPF in the long wavelength range(700-800 nm)is 90.5%.After the BLPF surface was sequentially sprayed by the generated fog for about 90 s,the maximum transmittance in the short-wavelength range(400-500 nm)is over 60%,and the maximum transmittance in the long-wavelength range(500-800 nm)is close to 90%.In addition,the BLPF surface is superior to solid dust in self-cleaning performance against liquid contaminants.In this paper,some progress has been made on the research on the coupled bionic AF surface,and the analytical method can provide a theoretical basis for the mechanism analysis of the other AF surface.The biomimetic micro-structure and the preparation material can provide a new design idea for the research of a novel high-efficiency AF surface.