Research On Key Technologies Of Rapid Manufacturing Three Dimensional Micro/Nano Structures Via Two Photon Polymerization

Three-dimensional micro/nano structures are constitution foundation of the microoptics,microelectronics,microfluidics,microbial stents and metamaterials.Their unique micro morphological structures endow them special properties,such as optical,electrical,magnetic,mechanical and thermal properties.There is an increasing demand of these structures in aerospace,military,communications,biological,medical and other application fields.Two-photon polymerization has broken through the optical diffraction limit.It can fabricate arbitrarily three-dimensional microstructures with nanoscale machining precision.It is considered to be one of the most promising micro-nano machining technology.However,the low fabricating efficiency and limited fabricating range are important obstacles to promote two-photon polymerization technology applied in practical application of engineering.Therefore,it is of great significance to carry out the research on the key technologies of the rapid manufacturing three-dimensional micro/nano structures via two photon polymerization.Aiming at researching on the key technologies of the rapid manufacturing three-dimensional micro/nano structures via two photon polymerization,a large-scale rapid manufacturing system was designed and built,and researches on the mechanism of continuous scanning exposure,new exposure method of quasi static exposure and rapid slicing method were carried out,mainly includes:(1)Designed and constructed a large-scaling two-photon polymerization rapid manufacturing systemAccording to the theory of multi-rigid-body kinematics and homogeneous transformation matrix,a mapping model between the geometric errors of large-stroke linear stages and the position and posture of voxels was established.Sensitivity analysis is conducted at the same time.Key error components were found out.The large-stroke stages were designed with the purpose of reducing key error components.3D elliptical motion a device was installed on the large-stroke linear stage.It can generate 3D elliptical motion of quasi-static exposure to achieve rapid structural manufacturing.A millimeter-scale microfluidic structure was fabricated and measured to verify the large-scaling manufacturing ability and rapid manufacturing ability of estalished platform.(2)Reveal the mechanism of continuous scanning exposure in two-photon polymerizationAccording to the polymerization threshold principle of free radical concentration and energy accumulation theory,proximity effect between adjacent voxels was revealed in two-photon polymerization.The relationship between voxels spacing and the sectional size of formed nanorods were studied.Based on the previous study,the exposure mechanism of continuous scanning method was revealed,and the mapping model between fabricating parameters and sectional size of the nanorods fabricated with continuous scanning method was established.In this paper,the conversion relationship between the time of pinpoint exposure method and the scanning speed of continuous scanning method at a same lateral size of nanorods is derived.In the present work,ascending scan method and cantilever method were used to fabricated intact voxels.The experiental data were used to verify the proposed cross-sectional size model.(3)New method of quasi-static exposure and compensation for photon fluxAiming at improving the fabricated efficiency in two-photon polymerization,a new method of quasi-static exposure was proposed.A 3D elliptical motion device with flexure hinges was developed to acheive quasi-static exposure.In order to achieve rapid and accurate exposure in the quick feed process of long-stroke stages,sample moved along 3D elliptical path to make ultra-short pulse laser beam static relative to sample at expected position.The relationships of operating parameters,such as scanning speed,vibration amplitude,vibration frequency and voxels spacing,were established under the condition of quasi-static exposure method.Experiments were conducted to find out the stable fabricated window of laser power and scanning speed in quasi-static exposure method.The results in quasi-static exposure method were compared with that of continuous scanning method to verify the availablity of quasi static exposure in improving the fabricated efficiency.(4)High precision and rapid slicing technology based on AMF format fileAMF format file was used to describe the geometric profile of 3D microstructures.Optimal slicing and path planning were conducted in this new framework.Taking chess model as an example,the advantages of the new additive manufacturing files(AMF file)in vertex definition,vertex calling and data storage were analysed compared with traditional STL files.In the case of micro spider,the AMF file format was sliced and path planned.In addition,the present work proposed a new adaptive slicing method based on the slice profile data at characteristic direction.Experimental comparison was conducted between adaptive slicing method and uniform slicing method in order to verify the accuracy and efficiency of the proposed slicing method in this paper.