Research On Micro-Nano Additive Manufacturing Technology Based On DMD Projection

Complex three-dimensional(3D)micro/nanostructures have huge industrial demands in the fields of micro-electro-mechanical system(MEMS),biomedicine,new energy,wearable devices,healthcare and so on.However,the existing 3D printing system is still difficult to meet the requirements of industrial applications for high-precision,low-cost,and batch manufacturing of complex 3D micro/nanostructures in terms of printing resolution,print quality,speed,cost,and materials.Projection micro-stereolithography(P?SL)is a low cost,high throughput additive fabrication technique capable of manufacturing a variety of highly complex,3D structures with microscale architecture and submicron precision.In order to break through the printing resolution of the existing 3D printing system,the horizontal printing resolution and vertical printing resolution of the P?SL system were studied.In terms of the horizontal printing resolution,the optical system consisting of the illumination system and projection system was designed based on the digital micromirror device(DMD)to meet the requirements of highprecision imaging.The optical resolution of the designed projection system reaches submicron.In the aspect of vertical printing resolution,the leveling characteristics of the free liquid surface were studied when the thickness of the resin layer is tens of microns through simulation and experiment.An effective scheme for leveling resin surface by constraining resin surface was proposed and realized on the mechanical structure,which solved the problem of unsatisfactory layer thickness in the former scheme.In addition,the control system of the P?SL system was designed preliminarily,and the experimental prototype was constructed.Finally,the printing performance of the prototype was verified by experiments.According to the design parameters of the optical system and the positioning accuracy of the micro-displacement platform,the printing resolution of the P?SL system can reach 1um in both horizontal and vertical directions theoretically.In the actual manufacturing process,the printing resolution will inevitably be affected by many factors such as the physical-chemical characteristics of resin,temperature,exposure time,mechanical error,etc.In order to explore the actual printing accuracy of the prototype,long plates of different widths and beams of different thicknesses were printed in the experiment.According to the experimental results,the minimum size error of the long plate with an ideal width of 5?m in the horizontal direction is1.8?m,and the minimum size error of the beam with an ideal thickness of 10?m in the vertical direction is 2.6?m.Based on the current printing accuracy,a honeycomb structure with a minimum feature size of 10?m was successfully printed,which preliminarily verified the manufacturing capability of the constructed prototype for the complex 3D micro/nanostructures.