Fabrication Of PMMA Biomimetic Compound Eye Structure By Nanoimprint Technology Combined With Thermal Deformation And Research Of Its Properties

With the continuous development of micro-opto-electro-mechanical system technology,the traditional optical imaging system has a small field of view,complex imaging structure and other problems can no longer meet the needs of people.The small size and large field of view of the bionic compound eye structure has attracted the interest of many researchers,and various design ideas and production solutions have been proposed for the preparation of the bionic compound eye structure.While these solutions can achieve improved imaging results,they require highly complex preparation processes and the overall system is quite large.Therefore,this paper proposes a miniature bionic compound eye structure for miniaturisation of the imaging system,with the aim of significantly reducing the complexity of the preparation process and the difficulty of assembling the imaging system.The research was carried out in terms of the specific design of the bionic compound eye structure,the preparation method of the microlens array and the transfer technique of the microlens structure,which was achieved through the preparation methods of photolithographic thermal reflow,nanoimprinting and thermal deformation techniques.The paper’s consists of three main sections of work:(1)The working principle and design of the PMMA bionic compound eye structure.Biological compound eyes generally include juxtaposed,neurological overlapping and optical overlapping types.The juxtaposed biological compound eye is made up of a series of independent subeyes that do not interfere with each other,and this independence allows the creature to achieve wide-angle and highly sensitive vision.In this paper,a photoresist template with a shaped microlens array structure is designed based on the working principle of a juxtaposed biological compound eye.This template is used to replicate the PMMA bionic compound eye structure.The shaped microlens arrays include circular,hexagonal and square microlens array structures with circular lens diameters of 10 μm and20 μm respectively,hexagonal microlenses with a 7.5 μm edge length and square microlenses with a15 μm edge length.The aim is to compare the imaging performance of bionic compound eye structures obtained by replicating microlens arrays of different shapes and sizes.(2)Preparation and performance analysis of PMMA bionic compound eye structures.The surface morphology of the microlens array photoresist templates was tested by scanning electron microscopy,and the results showed that the microlenses on the photoresist templates were uniformly distributed and clearly structured.Further,a PDMS flexible template with an opposite structure is replicated on the microlens array photoresist template by casting and turning.The surface morphology and contour of the PDMS flexible stencil were tested by optical microscope and 3D laser microscope respectively.The results show that the PDMS flexible stencil surface lens is clear and uniform,and the lens size is basically the same as that of the photoresist stencil.The PMMA solution dissolved in DMF was then dropped onto the PDMS flexible template and after heating in a vacuum drying oven at 70 oC for 50 minutes,the cured PMMA film was lifted off the PDMS to obtain the PMMA planar microlens array structure.Finally,the PMMA planar microlens array template is thermally deformed on the surface of the steel ball through a thermal deformation process,resulting in a PMMA curved microlens array and a PMMA bionic compound eye structure.The surface morphology and contours of the PMMA bionic compound eye structure were tested by scanning electron microscopy and 3D laser microscopy.(3)Study on the application of PMMA bionic compound eye structure on digital cameras.The optical focusing and imaging performance of the PMMA bionic compound eye structure was tested by optical microscopy.The results show that the PMMA bionic compound eye structure obtained by replicating a hexagonal microlens array with a side length of 7.5 μm has good imaging performance.The bionic compound eye structure was further combined with the XW500 high-speed digital camera to study its optical imaging and photographic effects and compared with the digital camera without the compound eye structure,which showed that the digital camera with the PMMA bionic compound eye structure has a larger field of view and higher resolution.Greatly enhances its shooting effect.