Design,Fabrication And Properties Of Biomimetic Functional Surfaces Based On Typical Butterfly Wings

With the liberation of human society's productivity,people's demand for new materials is increasing.The excellent properties of materials depend not only on their inherent chemical compositions,but also on their own exterior structures.During the long-term evolution of billions of years,under the brutal natural selection,special surface structures with excellent performance have gradually been formed on organisms' surfaces of species in nature.The emergence of these natural and novel micro-/nanostructures provides new ideas and references for the design and development of new-generation biomimetic functional surfaces.Among these natural selectionoptimized surface structures,multiscale hierarchical micro-/nanostructure is one of the most typical structures.The main feature is that it is always ultrafine,cross-scale and hierarchical.Usually,the structure consists of micro-/nanoscale units that are assembled and arranged to form a multi-level structure.It can exhibit certain specific functions.At present,although the fabrication methods for biomimetic functional surfaces are tremendous,such as machining,wet etching,laser lithography,chemical modification,in terms of the ultrafine three-dimensional(3D)multiscale hierarchical micro-/nanostructures,there are certain limitations for single fabrication method to get satisfying products.These limitations are not conducive to the accurate reproduction of the biomimetic structures and the artificial reappearance of the excellent performance of the natural structures.Moreover,the specific structure-function relationship between a particular multiscale hierarchical micro-/nanostructure and its corresponding functional properties has not been fully revealed.Therefore,questing for a suitable biomimetic fabrication method to construct functional surfaces with 3D ultrafine multiscale hierarchical micro-/nanostructures is still an open challenge in the field of bionic engineering.The exploration and reveal of the correlation between biomimetic micro-/nanostructures and their excellent performance is essential to promote biomimetic functional surfaces from “similarity in form” to “similarity in inherence”,which are also the hotspots and difficulties that have always existed in the research field of biomimetic/bioinspired materials.Inspired by the colorful and varied butterflies in nature,this dissertation herein selected four types of butterflies as biological prototypes,including Trogonoptera brookiana butterfly,Papilio palinurus butterfly,Morpho terrestris butterfly and Morpho didius butterfly,and focused on the feature areas of their wing scales with typical multiscale hierarchical micro-/nanostructures.Although their micro-/nanostructures are quite different,they all possess excellent properties.Firstly,the butterfly wing surfaces were cleaned,dried and shaped by a chemical pretreatment.Secondly,the macroscopic morphology of the butterfly wings and multiscale micro-/nanostructure on the wing scales were well characterized by optical and electron microscopes.Their chemical composition and element distribution were also investigated.Then,based on the microscopic characterization data of the multiscale hierarchical structures,digital modeling software was used to reconstruct a series of 3D models of the feature structures.These 3D models provide model support for the subsequent biomimetic design,theoretical simulation and mechanism explanation.Afterwards,a wet chemical approach using feature areas of the wing scales as biotemplates was adopted,which combines sol-gel method with acid etching technique at high temperature.Through the regulation and optimization of the process parameters in the biomimetic fabrication process,4 kinds of structurized biomimetic functional surfaces were obtained on the transparent glasses.Subsequently,the morphological and structure features of the biomimetic functional surfaces were microscopically characterized.The results confirmed that these biomimetic functional surfaces possess multiscale hierarchical micro-/nanostructures that are similar to the original wing scales.Thus,the initial purpose of “similarity in form” was achieved.Performance tests toward different application scenarios showed that the obtained 4 biomimetic functional surfaces possess different specific characteristics respectively,namely high transmittance and antireflection characteristics,self-stable structural colors,active antifogging characteristics and differential sensitive responses toward organic vapors.To some degree,these performances are consistent with the biological prototypes' characteristics.Thus,the ultimate goal of “similarity in inherence” was also achieved.In summary,according to the bionic principle,this dissertation starts from original butterfly wings.On the basis of full and systematic investigation of their multiscale hierarchical micro-/nanostructures,a “3-in-1” wet chemical approach was developed to obtain biomimetic functional surfaces inspired by typical butterfly wings.By controlling and improving the fabrication process and reaction condition,4 kinds of biomimetic functional surfaces with multiscale hierarchical micro-/nanostructures were finally achieved.All of them exhibit unique and desirable surface properties that are similar with the performance of original butterfly wings.Meanwhile,with the help of theoretical models and numerical simulations,the intrinsic relationship between multiscale hierarchical micro-/nanostructures and their excellent surface performance of typical butterfly wings and corresponding biomimetic surfaces was further revealed.It is anticipated that this dissertation could provide advanced design strategies and theoretical basis to inspire the development and application of new-generation biomimetic optoelectronic materials,structural color materials,antifogging materials,sensing materials and other related devices.