Research On Photopolymerization Additive Manufacturing Methods Associated With Experiments Of Micro Magnetic Functional Devices With Three-dimensional Geometry

Additive manufacturing based on photopolymerization has been widely recognized in fabricating magnetic functional devices,due to its disadvantage in sophisticated-structure,multi-material,multi-scale and integrated-function manufacturing.However,on account of the aggregation and precipitation of the magnetic micro/nanoparticles,as well as the strong absorption of projected light,it’s difficult to mitigate the trade-off between resin stability and concentration of magnetic particles.Low solid loading of magnetic particles,poor stability,and large minimum feature size make it difficult to meet the requirements in manufacturing of complex three-dimensional magnetic microstructures in magnetic functional devices.In response to the above problems,this work proposes a solution by both improving additive manufacturing speed and resin stability,to reduce the influence of aggregation and precipitation of the magnetic micro/nanoparticles.After that,facing to the functional requirements of accurate operation and large deformation in microscale magnetic functional devices featuring three-dimensional geometry,the manufacturing method integrating sophisticated geometries,dispersed magnetic particles and swelling of hydrogel was developed.Single-material flexible magnetic functional devices and multi-material large-deformation functional devices were achieved based on the integrated control in geometry and material property.In order to improve the speed of microstereolithography,a micro-continuous liquid interface production(μCLIP)system featuring pixel size of 7.58×7.58μm~2and moving speed up to 250μm/s was firstly established.Theoretical model of curing depth inμCLIP was established and experimentally demonstrated,which guarantees the Z-axis manufacturing accuracy.Influence of Gaussian distribution in projected power and continuous washing of liquid photosensitive resin on XY-direction dimensional error were studied,and the method for error compensation based on grayscale modulation at edges was proposed.Effect of the oxygen distribution in deadzone on surface roughness was investigated,and spin coating method is used to prepare a polydimethylsiloxane(PDMS)film as the oxygen permeable window,which significantly improves the uniformity of oxygen distribution in deadzone and reduces the surface roughness.Stability theory in colloidal and magnetic fluid was introduced in magnetic resin to improve the solid loading and stability of magnetic micro/nanoparticles,in which influences of materials,particle size,concentration and surface modification of magnetic particles as well as viscosity of liquid resin were investigated.A magnetic resin with up to 30 wt.%solid loading of magnetic nanoparticles featuring spatial stability longer than 72 h was developed,and showed the capability in additive manufacturing of microscale sophisticated geometry with high speed.Magnetic and mechanical properties of the magnetic resins were investigated and provide the materials basis for fabricating magnetic functional devices.In meeting the functional requirements of accurate operation in magnetic functional devices,the design and manufacturing method integrated with sophisticated geometries and materials properties were introduced,in which the functional devices consist of large-volume magnetic response units and thin flexible hinges to enhance magnetically actuated deformation.The proposed flexible magnetically actuated structures are theoretically and experimentally analysed and actuated by gradient magnetic field.A flexible magnetic grasping microgripper as well as a flexible magnetic covering microgripper were designed and fabricated,and the capability of micro-operation in multiple environments for multiple targets was experimentally demonstrated.In meeting the functional requirements of large deformation in magnetic functional devices,the manufacturing method of flexible hydrogel hinges featuring tunable Young’s modulus to enhance magnetic actuated deformation was proposed.A modulus tunable hydrogel photopolymerizable resin was developed to fabricated the flexible hinges,which keeps high Young’s modulus during additive manufacturing process,while the Young’s modulus reduces more than 10000 times after absorbing water(swelling).Connection of the multi-material interface was enhanced by doping with homogeneous materials and gradient moduli matching.A magnetically-active iris device coupled with magnetic resin and hydrogel resin was designed and manufactured.The capability of magnetically actuated large deformation was experimentally demonstrated.