Design And Fabrication Of High-performance Biomimetic Structural Materials Based On Micro/Nanoscale Building Blocks

Natural biological structural materials,although composed of relatively fragile inorganic mineral components(such as calcium carbonate,calcium phosphate and silica)and a small amount of soft organic polymers(such as protein and polysaccharide),often exhibit amazing mechanical properties far beyond components due to their exquisite hierarchically ordered structure and interface.These hierarchical structures and mechanical properties achieved by limited material composition under mild conditions,make natural biological structural materials model systems pursued by material scientists and engineers.Researchers analyze the multiscale structure of natural materials,correlate their excellent properties and extract the biomimetic design principles.Then,they use rich synthetic building blocks,develop biomimetic assembly strategies,and expect to design and fabricate new-style high-performance biomimetic structural materials that replace the existing engineering materials.In recent years,great advances have been made in the design and fabrication of biomimetic structural materials.However,it is still challenging to construct three-dimensional bulk biomimetic structural materials with accurate micro/nano structures and interfaces.The application of high-performance macroscopic three-dimensional bulk biomimetic structural materials faces many key scientific and technical problems.Developing highly efficient,low-energy and eco-friendly biomimetic assembly and interfacial design strategies will help accelerate the pace of practical applications of biomimetic structural materials and has attracted widespread attention.In this dissertation,we first analyze the fundamental micro/nanoscale building blocks,multiscale architectures and performance of natural biological materials including fish scale(Arapaima gigas),dactyl club(Odontodactylus scyllarus),bone and nacre.Then,we review the progress of biomimetic structural materials in terms of building blocks and assembly strategy in recent years.Based on the limitations and problems in the field of biomimetic structural materials,we further develop several universal and efficient biomimetic assembly and interfacial design strategies for optimally assembling onedimensional and two-dimensional micro/nanoscale building blocks,in order to achieve controllable fabrication of high-performance biomimetic structural materials.The main achievements can be summarized as follows:1.Inspired by the micro/nanofiber-based twisted plywood structure and the strengthening/toughening mechanisms of natural Arapaima gigas fish scale,we developed a biomimetic assembly strategy that combines wet sliding brushing and laminating,in order to achieve flexible arrangement of one-dimensional micro/nanofibers and achieve biomimetic twisted plywood structure.Using hydroxyapatite microfibers and sodium alginate biopolymer as fundamental constituents,we successfully replicated the multiscale plywood structure and mechanical mechanisms of natural materials to synthetic materials.The resultant biomimetic twisted plywood structural materials exhibit high damage tolerance.It is worth noting that,the developed biomimetic assembly strategy is universal,which provides a viable method to design and fabricate biomimetic fiber-based composites.2.Inspired by the “brick-and-mortar” layered structure and strengthening/toughening mechanisms of natural nacre,we developed a scalable fabrication strategy for highperformance,large-sized biomimetic nacre-like composites with fine structure.The fabrication strategy contains two steps including solvent evaporation induced assembly and laminating.Solvent evaporation can induce horizontal assembly of anisotropic nanosheets into ordered layered microfilms,and stacking can further assemble microfilms into macroscopic three-dimensional layered bulk materials.The combined fabrication strategy has the advantages of mildness,flexibility,high efficiency,scalability and universality,and lays a methodological foundation for the design and fabrication of advanced biomimetic structural materials that are truly practical for applications.3.On the basis of the biomimetic hierarchical fabrication strategy proposed above,inspired by the multi-level interface and superior performance of natural nacre,we proposed a multiscale polymer-based soft-rigid dual-network interfacial design concept to optimize the interface interactions between nanosheet elements and between microfilm elements,in order to optimize the properties of macroscale biomimetic layered materials from the perspective of the interface control.The soft-rigid dualnetwork molecular structure was constructed by using the flexible molecule of polyvinyl alcohol and the rigid molecule of phenolic prepolymer(resol).By adjusting the component proportion of the soft-rigid dual-network,the comprehensive properties of the macroscale biomimetic nacre-like bulk materials can be precisely adjusted.The multiscale interfacially optimized biomimetic nanocomposite exhibits excellent interface enhancement efficiency,mechanical properties,moisture resistance and thermal stability.The proposed soft-rigid dual-network interfacial design strategy is mild and versatile,providing a novel approach to construct more high-performance biomimetic structural materials.