Simulation And Design Of Optical Paths For Micro-nano Fabrication Of Micro-stereolithography Systems

Complex three-dimensional micro-nano structures are widely used in microelectromechanical systems,microfluidic chips,micro-optical components,microsensors and other fields.Traditional micro-nano processing methods are costly,timeconsuming,and unable to fabricate micro-nano structures with high aspect ratio.Microstereolithography based on DMD(Digital Micromirror Device),which uses DMD as a dynamic mask,can realize the fabrication of digital stereoscopic micro-nano structures.Compared with the traditional processing method or other immediate lithography techniques,the DMD-based lithography system is less costly and more efficient.In this paper,a DMD-based microstereolithography system is built by simulating and designing the system optical path in COMSOL Multiphysics,and a hydrogel 3D micro-nano structure is fabricated using the system.This paper firstly introduces the principles of different 3D lithography techniques and the development status of DMD-based lithography.The components of the DMD-based microstereolithography system are described,the advantages and disadvantages of various lithography light sources are compared,and the selection of light sources is completed.The commonly used beam shaping scheme is analyzed,and the overall optical path structure of the system is determined.The simulation of the commonly used uniform beam devices in the illumination system was carried out by using COMSOL Multiphysics,and the design of the illumination system was completed by combining the theories of illumination uniformity,energy power and optical expansion volume.A combined prism was introduced as a relay system,and the prism angle was calculated in detail to realize the separation of the illumination optical path from the imaging optical path.The projection objective for lithography processing was designed,and the image quality of the designed objective was evaluated.After the optimized design,the diffuse spot of each field of view was smaller than the size of a single DMD pixel.Then the coupling model of illumination optical path and projection optical path was established in COMSOL Multiphysics.The reasons for the raster effect of the DMD were analyzed and eliminated by adjusting the system coherence factor.Finally,the fabrication of hydrogel microstructures was completed by using the actual built microstereolithography system,and the personalized and batch processing of hydrogel microstructures was realized,which verified the feasibility of this optical path design.