Study On The Self-assembly And Functionality Of Silk Fibroin

With the development of science and technology,the silk fibroin extracted from silk cocoon is widely used in high-tech fields such as tissue engineering,medical beauty,photoelectric sensing,flexible wearable electronics,etc.It has evolved from traditional textile materials to new functional materials,which has improved people’s lives.The performance of the material is depended on its structure.Further invertigation on the composition and structure of silk fibroin is conducive to the preparation of high-performance silk fibroin materials and broadens their applications in different fields.In order to understand the process of silk fibroin structure assembly and growth,and illustrate its growth mechanism from micro-molecules to bulk materials,this paper first observed the epitaxial growth behavior of silk fibroin on graphite substrate in real time through in-situ atomic force microscopy,and the growth process of silk fibroin from molecule to oriented structure was studied.On the base of this results,the self-assembly process and growth path of the multiphase structure of silk fibroin were studied by increased growth concentration of silk fibroin solution.Subsequently,on the mesoscopic scale,the meso-functionalized silk fibroin was obtained by using silver nanoclusters(AgNCs)as functional substances,the electrical performance of silk fibroin was improved,and the meso-functionalization mechanism of silk fibroin was studied.At the same time,a new type of resistive random access memory has been fabrictated on the macro-scale with this functional material,and the relationship between silk fibroin structure-performance-function has been studied,and the new strategy of"material design-performance optimization-function realization" trinity of silk fibroin has been realized.Through the study of the epitaxial self-assembly process on the micro-scale,it is found that after the silk fibroin regulated by the external environment such as the interaction force between the molecules and the graphite substrate,and it will grow into a two-dimensional periodic array structure during epitaxial growth.As the concentration of the silk fibroin solution increases,multiple growth pathways appear in the process of silk fibroin self-assembly.Under the influence of kinetics,the metastable structure in the solution cannot undergo thermodynamic transformation quickly,and it is prefer directly deposited on the twodimensional periodic array structure to form a film-liked structure,and then thermodynamic transformation occurs in the film structure to form a two-dimensional periodic array structure.At the same time,the two-dimensional periodic array structure can be used as a template to epitaxially form β-crystal.The functionalization of silk fibroin is realized on the mesoscopic scale by adding AgNCs.Structural analysis shows that AgNCs promote the formation of βconformation inside silk fibroin,and give rise to low-potential areas in the silk fibroin film.It is helpful to guide the uniform growth of the conductive path of the device and improve the resistive storage performance of silk fibroin.For example,the switching speed of the device can reach 10-15 ns,and the set voltage of the device is about 0.3 V.This thesis takes micro-scale self-assembly research,meso-scale functionalization research,and macro-scale electrical performance research as the research route,directly observe the growth path of silk fibroin materials,and deeply analyzes the reconstruction of silk fibroin meso-structure.The functionalization strategy elaborated on the relationship between the resistive performance of silk fibroin and its functional structure,discussed the regulation mechanism of silk fibroin from micro to macro,and give a theoretical foundation for the structure analysis,performance research,performance application,and large-scale production of silk fibroin in the future.