Research On Efficient Fabrication Of Micropillars And Helical Structures Based On Spatial Light Modulation

Femtosecond laser two-photon polymerization has been widely used in the fabrication of various 3D microstructures,including micromechanical devices,metamaterials,micro-robots,micro-optical devices,etc.,due to its unique advantages of high resolution,arbitrary 3D shaping and various machinable materials.However,the traditional two-photon polymerization adopts a layered point-by-point scanning processing method,which is low efficiency and hinders the large batch production.Therefore,improving the processing efficiency of two-photon polymerization has important research value and application value.Spatial light modulator can flexibly modulate the light field into target light pattern.Combined with the light field modulation and two-photon polymerization processing,the corresponding three-dimensional structure can be prepared quickly and efficiently.This processing method has a broad application prospect.In this dissertation multi-foci parallel processing based on spatial light modulator and capillary force guided self-assembly are combined to achieve flexible fabrication of hierarchical self-assembly structures.In addition a new strategy to generate the helical structured fight field is proposed,and the single exposure processing of the micro helical structure is realized.The basic composition of liquid crystal on silicon spatial light modulator and the principle of light modulation are presented in this dissertation.The important phase recovery algorithms in computer-generated holograms,GS algorithm and GSW algorithm,are introduced.The phase holograms of the corresponding incident light can be calculated by the iterative algorithms for the generation of multi-foci beams,the line-shaped beams,pattern-shaped beams and complex 3D structured beams.By loading the phase holograms on spatial light modulator,femtosecond laser can be modulated into target light field,which can be used for efficient molding of 3D structures.In this dissertation,multi-foci femtosecond laser two-photon polymerization processing is combined with capillary-force-driven self-assembly to realize the effic ie nt fabrication of hierarchical microstructures.By adjusting the number and spatial distribution of the focal points of the multi-foci light field flexibly with spatial light modulator,the self-assembled structures with different patterns are fabricated.The application of multi-foci parallel processing in the field of particle in-situ capture is studied.This method can achieve high efficiency of particle in-situ capture.Besides,we proposed a novel method to generate helical structured light.This method can flexibly modulate the pitch,direction(left-hand/right-hand)and period of the helical structured light Based on this method,other complex helical structured light,such as the double helical light,can be generated.The femtosecond laser is modulated into helical structured light by a spatial light modulator,and the helical micromotor can be fabricated by single exposure in photoresist The size of the micromotor can be adjusted by changing the parameters of the helical structured light.After the deposition of nickel on the surface of the helical micromotors,the steering and actuation of micromotors can be realized by a rotating magnetic field.