Study On Fabrication,Transferring And Properties Of One-dimensional Photonic Crystals Based On Polymer/TiO₂

As structural color materials,one-dimensional photonic crystals（1DPCs）have the advantages of extensive selection of materials,easy preparation,bright and adjustable colors,and easy functionalization.They are mainly fabricated on rigid planar substrates,and it is difficult to achieve coloring on flexible and non-planar substrates and to form patterns with clear boundaries,so their application range is limited.In order to solve the above problems,in this paper,referring to the transfer printing method,we designed the assembly material structure and morphology to reduce the binding force with the planar substrate,and use solid adhesive materials to achieve the coloring,patterning and functional application of one-dimensional photonic crystal structural colors on multiple substrates by means of transfer printing.The thesis designed to use polymethyl methacrylate（PMMA）nanoparticles with uniform particle size as low refractive index and the first-layer assembly material to reduce the contact area and bonding force with the substrate.Using spin coating,PMMA nanoparticles and nano-TiO₂ with high refractive index were alternately stacked to prepare one-dimensional photonic crystal structural color films.The effects of PMMA concentration,incident angle,water contact angle of substrate and Bragg stack number on the optical properties of photonic crystals were investigated.The results showed that when the polymer concentration increased or the incident angle decreased,the maximum reflectance wavelength red-shifted;otherwise,blue-shifted.The above results are all consistent with the Bragg diffraction formula.When the stack number increased,the reflection intensity increased,and the color of the one-dimensional photonic crystal became brighter.On this basis,the flexible solid polyacrylate pressure-sensitive material with good adhesion performance was used to realize the coloring and patterning of PMMA/TiO₂ 1D PCs on different substrates such as metal,paper,glass,plastic,cotton,silk and so on.The use of solid bonding material overcomes the shortcomings of the liquid adhesive that easily flows and penetrates whithin the PC,and obtains brilliant structural color patterns with clear boundaries.In addition,the structural color films after transfer produced rapid reversible color through the action of blowing,water droplets or ethanol,and the films had good water washing and temperature resistance characteristics.Therefore,the designed flexible 1D PCs structural color films show good application prospects in the field of anti-counterfeiting and detection.In order to improve the flexibility and strength of one-dimensional photonic crystals,a polydimethylsiloxane（PDMS）substrate membrane was first constructed on a rigid substrate,and then the one-dimensional photonic crystals were assembled on the PDMS films.The design introduces polyurethane（PU）nanoparticles with good wear resistance and high mechanical strength as low refractive index materials,alternately stacked with nano-TiO₂ to assemble PU/TiO₂ 1D PCs with uniform color.The effects of PU concentration,spin coating speed and incident light angle on the reflection spectra and color changes of 1D PCs were studied.The flexible structural color films can be obtained by peeling the PDMS base film directly from the substrate.Similarly,with the help of polyacrylate adhesive materials,photonic crystals can be transferred to the fabric surface to achieve flexible structural coloration.Compared with traditional dyeing,this coloration method shows the advantages of environmental friendliness,bright colors,uniformity and stability.The flexible PU/TiO₂1DPCs structural color films have good mechanical strength and flexibility,with the maximum tensile strength of 3.19 MPa and the maximum strain of 148.2%.Therefore,the design and preparation of the flexible structural color films have certain application prospects in the research of visual tension sensing.