Study On Fabrication Of Microlens Arrays By Nanoimprint Technology Based On Two-dimensional Ordered PS Template

With the continuous improvement of the current level of technology and the increasing integration of industrial manufacturing,more and more components are required to develop in a direction of miniaturization and weight reduction.As an important branch of micro-structured devices,micro-optical components play a unique role in the field of optical information and micro-optics.Widely used in the field of photoelectric sensing and optical communication systems,and the emergence of array optical components is an important support for the rapid development of micro-optics.In this paper,a high-fill factor,size-controllable microlens array was prepared by nanoimprinting two-dimensional ordered PS colloidal crystal film technology,and the feasibility of preparing nano-scale microlens array based on this technology was analyzed.Firstly,two-dimensional ordered colloidal crystal films were assembled by using polystyrene?PS?colloidal particles,and then the colloidal crystal structure was replicated by nanoimprint technology and make a template on Polydimethylsiloxane?PDMS?.Finally,the PDMS template with crystal structure is transferred to the specified material for secondary imprinting to complete the fabrication of the microlens array.The main research contents include the synthesis of PS colloidal particles,the preparation of two-dimensional ordered PS colloidal crystal film and the UV nanoimprinting photosensitive composite film.And in the research,the following conclusions were drawn:?1?PS colloidal particles can be conveniently prepared by the soap-free emulsion polymerization method,and the particles have a good spherical shape and uniform size.Secondly,particles of different particle sizes can be obtained by adjusting the mass ratio of styrene monomer to methacrylic acid and the concentration of the initiator.?2?A two-dimensional ordered PS colloidal crystal film was prepared by spin-coating.The wetting property of PS can be improved by adding absolute ethanol to the PS colloidal particle emulsion.Characterization of the crystal film by scanning electron microscopy?SEM?showed that ethanol can enhance the order of particles in the crystal film,but it also increases the probability of the multilayer film structure.And at 2000 rpm,when the volume ratio of anhydrous ethanol to deionized water in the PS colloidal particle emulsion is 0.8-1.0,the defects in the colloidal crystal film are less,the particle arrangement is tighter,and the coverage area of the single-layer film structure is relatively Larger.?3?A two-dimensional ordered PS colloidal crystal film was prepared by spin-coating.By adding a certain concentration of sodium dodecyl sulfate?SDS?solution to the PS colloidal particle emulsion,the distribution of PS colloidal particles in water can be effectively improved.The characterization results of the crystal film by SEM and UV-Vis spectrophotometer show that the addition of SDS is beneficial to obtain the film structure of the single-layer PS colloidal particles.At the same time,the line defects in the film are also better improved,but the coverage area of the film is reduced,and at2000 rpm,when the concentration of the added SDS solution is 2_wt%,the colloidal crystal film has a more ordered film structure.And a larger membrane coverage area.?4?A large-area two-dimensional ordered PS colloidal crystal film can be obtained by transferring the PS colloidal crystal film obtained by spin coating to the water surface for secondary self-assembly,From the results of the SEM,it can be concluded that the low-coverage problem of the PS colloidal crystal film can be greatly improved by the air-liquid surface self-assembly again.Moreover,the ordering of the particles in the film is more orderly.Compared with a single self-assembly method,the solution has the advantages of quickly obtaining large-area two-dimensional PS colloidal crystals.?5?Using nanoimprint technology,the two-dimensional PS colloidal crystal structure is copied onto PDMS and cured,and then the cured template is coated on the titania-based organic-inorganic composite optical waveguide film to obtain nano-sized microlenses array with high fill factor.The results of atomic force microscopy?AFM?and SEM measurements show that the microlens has a good profile,which proves that nanoimprint technology can be used to prepare nanometer-sized microlens arrays.In addition,since the photosensitive film can exhibit different refractive indices at different temperatures,a new idea for fabricating a variable refractive index microlens array is provided.