A Bionic High-permeable Membrane With Anti-fog, Anti-frost, Anti-fouling And Moisture Self-cleaning Properties

Reflection on the surface of the optical materials not only causes glare and ghost images,and simultaneously affects the display effect such as the lens,laser,display and so on,but also reduces the flux of light of the optical system and the transmittance of its surface,thus lowering the sharpness and contrast of the images.Thus,it is highly desirable to reduce the reflection on the surface of the optical materials.In generally,the traditional antireflection films are composed of porous structure,which is made of layer-by-layer(LbL)assembled nanoparticles or spray nanoparticles(SiO2,TiO2).It is because each nanoporous layer has different porosity,which causes the refractive index to gradually decrease from the glass substrate to the air layer.However,the property of the nanoparticle films may easily degrade due to the structural variation when exposed to the air.It is well known that polymer film has remarkable advantages in chemical stability,low cost,easy and fast processibility,which is an ideal material to replace the nanoparticle films.To date,researches have begun to focus on fabricating antireflection polymer films on the surface of optical materials by the LbL assembly technology.However,these multilayer films may easily fall off from the substrates such as glasses due to the mechanical instability and thermal expansion mismatching.In addition to reflection,fogging,frosting,and contaminants are also the main issues that deteriorate the light harvesting efficiency and imaging quality of optical elements.Fog can form small droplets on the surface of the optical material,which can enhance reflectance and significantly low down the clarity of a transparent interface,resulting in not only inconvenience but also potential danger in daily life.In particular,in a low-temperature and humid environment,fog freezes and becomes frost,which can totally prevent light from passing through a surface.The high development of modern industry and urban construction leads to air pollution.The dust particles which exist in the air can easily adhere to the surface of the solid material under the co-effect of humid environment and static electricity.Dust pollution not only seriously affects the urban appearance,but also weakens the efficient utilization of photoelectric devices to solar energy.The traditional cleaning method of using surfactant,which not only wastes a lot of manpower,financial resources and material resources,aggravates the ecological environmental pollution,but also needs to be repeated cleaning,so this traditional method has little effect.Nature utilizes complex and elegant structural designs to resolve the above problems.Nano-bionics studies found that many insects,such as moths and cicadas,possess eyes or wings with tapered nanocone arrays that exhibit excellent broadband antireflection propertie.The nanocone arrays cause the refractive index to gradually decrease along the normal direction of the base toward air,which can modulate the incident light and effectively suppress the reflectance.The antireflection property of the bionic nanocone structure has been studied for decades.However,the development of other functions(i.e.,dry-style antifogging,antifrosting,antifouling,and moisture cleaning properties)is still in its infancy.Transparent surfaces with multiple functions can simultaneously resolve the four main issues of reflection,fogging,frosting,and contaminants,which can dramatically improve the efficiency and convenience of optical elements and thus are highly desirable for practical applications.Here,we show a practical method of developing bioinspired highly transparent surfaces.Based on tapered-nanopore anodic alumina,a layer of multifunctional bionic nanocone surface is fabricated on a glass substrate by thermal curing of a prepolymer,followed by SiO2 nanoparticle deposition and low-surface-energy fluorosilane modification.Based on the analyses above,this paper based on tapered-nanopore anodic alumina with a period of 200 nm as a template,a layer of polymer film with broadband antireflection,dry-style antifogging,antifrosting,antifouling,and moisture self-cleaning properties is fabricated on the glass substrate.The detailed results and contents are as follows:1.Fabrication of alumina with a period of 200 nm.Based on tapered-nanopore anodic alumina as a template,through the method of prepolymer curing,the three-dimensional(3D)nanocone arrays can firmly adhere to a glass surface due to the combined effects of 3-aminopropyl triethoxy silane(KH550)and hydroxyethyl methacrylate(HEMA).The sample with the polymer nanocone arrays on both sides exhibits an average transmittance of 98.9%in the wavelength range of 380-800 nm,and possesses the antireflection,superhydrophilic antifogging and antifouling properties.2.Silicon dioxide and fluorosilane are modified on the polymer film with nanocone arrays on the glass substrate,then the polymer film is modified from superhydrophilic to superhydrophobic.The sample with the bionic polymer nanocone arrays on both sides exhibits an average transmittance of 98.7%in the wavelength range of 380-800 nm,and possesses the antireflection,dry-style antifogging,antifrosting,antifouling and moisture self-cleaning properties.