Preparation Of Photonic Crystal Hydrogel Materials Based On Microfluidic Technology And Its Application In The Field Of Display

Photonic crystal is a periodic optical nanostructure that affects the motion of photons in the same way that an ionic lattice affects electrons in a solid.Photonic crystals exist in nature in the form of structural coloration and animal reflectors,and one-dimensional photonic crystals are ideal optical materials for managing and controlling optical flow,and have considerable applications in the display field.Compared with traditional colloidal selfassembly,which requires at least several hours to construct,the magnetically responsive onedimensional photonic crystals induced to assemble by an external magnetic field have the advantages of rapid assembly process,fully reversible and easy manipulation.Since the color is derived from the ordered and fragile periodic structure,encapsulating this optical structure in a functional hydrogel can simultaneously achieve the prolongation of lifetime and the integration of the hydrogel function with the structural color of the photonic crystal.Hydrogel microspheres have the same physical and chemical properties and higher specific surface area as ordinary gels,so they can respond more quickly to external stimuli.Therefore,the strategy of orderly assembling magnetic colloidal nanoparticles into functional hydrogel microspheres under the induction of an external magnetic field can endow the hydrogel microspheres with magnetic responsive properties and colorful structural colors,effectively broadening their application fields and enhancing their use value,which is highly in line with the trend of multifunctionalization,miniaturization and integration of modern science.Therefore,how to prepare colloidal nanoparticles and hydrogel microsphere composites with specific functions and application ranges,and realize the customized design of structure and performance through the regulation in material synthesis,is a scientific and technical problem that needs to be solved urgently.Based on this,this paper took monodisperse superparamagnetic ferric oxide colloidal particles as the starting point,and combined magnetic nanomaterials with hydrogel materials through microfluidic technology,aiming to provide a simple and stable solution for large-scale preparation and application of composite hydrogel microspheres.The main research contents are as follows:(1)The synthetic formula and process of magnetic nano-iron tetroxide particles with adjustable particle size were explored by solvothermal method,and the silica-coated ferric oxide(Fe3O4@SiO2)core-shell colloidal nanoparticles were prepared by combining with the improved Stober method,and then modulating an external magnetic field to study the magnetically induced assembly and magnetically responsive structural color modulation of one-dimensional photonic crystal structures.Using ferric trichloride hexahydrate as iron source,ethylene glycol as solvent and reducing agent,sodium citrate as electrostatic stabilizer,and sodium acetate as alkali source,superparamagnetic triiron tetroxide was synthesized by solvothermal method.Then,the tetraethyl orthosilicate is hydrolyzed to form silica coating on its surface to form a core-shell structure.The relationship between the size of Fe3O4@SiO2 nanoparticles and each raw material was analyzed by changing the ratio,and the morphology,size,composition,dispersion performance and magnetic properties of Fe3O4@SiO2 nanoparticles prepared were studied.The assembly behavior of nanoparticles in dispersions induced by an external magnetic field and the structural color of one-dimensional photonic crystals formed by adjusting the particle size and magnetic field strength were studied.The wavelength span of the reflected light of the structural color was successfully covered most of the visible light region,which provided basic experience for the subsequent assembly and application of Fe3O4@SiO2 nanoparticle materials in hydrogel microspheres.(2)Build a microfluidic channel for the construction of monodisperse hydrogel microspheres,and study the relationship between the particle size,shape,and molding process of the microspheres,the microfluidic channel and the liquid flow rate of each component.Janus hydrogel microspheres were prepared by using an aqueous solution containing Ocarboxymethyl chitosan(O-CMC),magnetic Fe3O4@SiO2 colloidal nanoparticles,initiator,acrylamide and 1-vinyl-2-pyrrolidone monomer as the dispersed phase and methyl silicone oil as the continuous phase.The magnetic particles were induced to enrich on the side of the droplet template by an external magnetic field and then cross-linked and solidified.The prepared monodisperse magnetic response Janus self-healing hydrogel microspheres were characterized and analyzed by FT-IR,SEM and other technical means,and its application in repeatable coding and decoding display and directional separation was explored.(3)Finally,a one-dimensional photonic crystal structure was assembled by magnetic field-induced Fe3O4@SiO2 nanoparticles in microfluidic droplets,and then monodisperse selfhealing hydrogel microspheres with structural color were prepared by UV-induced monomer polymerization.The optical properties and microstructure of structural color hydrogel microspheres were characterized by reflectance spectroscopy,SEM and other analytical techniques.Combining self-healing and structural color properties,the application of photonic crystal hydrogel microspheres for multidimensional modeling and reusable Braille writing material was carried out.Self-healing hydrogel microspheres embedded with photonic crystal structures hold promise for complex display applications across scales.