Research On Mask Image Planning Used In Projection Stereolithography For Bio-scaffold

As one of the important components of tissue engineering,biological scaffolds are composed of interconnected pore network structures,which have the functions of supporting cell colonization,migration,growth and differentiation.With the rise of 3D printing technology,rapid prototyping technology has been introduced into the field of bio-scaffolds preparation.As one of the most promising technology for preparing biological scaffolds,the mask image projection based stereolithography(MIP-SL)technology is superior to all other rapid prototyping technologies in terms of precision and resolution in the preparation of bio-scaffolds.Currently most MIP-SL systems directly use a mask image in building the related layer,which often leads to larger shrinkage deformation.Mask planning for block,grayscale transformation have been researched by many researchers.However,on the one hand,the mask based on image segmentation has room for improvement,and less research has been carried out on the measurement of resin shrinkage and deformation in light curing.On the other hand,the traditional mask grayscale control method has the disadvantages of difficulty in reproduction and poor performance.In response to the above deficiencies,this article conducts the following work:(1)A mask segmentation planning scheme was extended basing on image segmentation technology,where the author proposes to use multiple squares,hexagons,and triangles to segment the mask.Then combined with the digital image correlation(DIC)method,the shrinkage and deformation of the resin during the light curing process can be measured.The results showed that the deformation of the bio-scaffold resin during the curing process showed a sharp increase at first and a partial decrease at the later stage.Square,regular hexagon,and triangular mask image planning can reduce shrinkage of light-cured molded parts by 29.04%,25.14%,and 5.43%,respectively.(2)A DIC resin deformation test platform was built,Including making resin speckles,selecting and analyzing major components,designing and manufacturing industrial camera holders and applying DIC image processing software.In addition,verification and influencing factor analysis experiments were performed,the results showed that speckle had little effect on the light curing of the resin,and the DIC test system was overall reliable.(3)Based on the characteristics of the biological scaffold mask,a new mask image grayscale control method is proposed.The structural unit image is divided into small area unit modules,and the optimal gray value is solved for the unit modules by using the ergodic search method.Finally,a new mask image is obtained by replacement and combination for stereolithography.(4)Experiments on light intensity function acquisition of single pixel,stereo lithography simulation based on light intensity function,and mask grayscale control experiments were performed.The results show that the light intensity distribution function of a single pixel has a similar-Gaussian distribution,and the light intensity energy between adjacent pixels will affect each other.The gray-scale control scheme can effectively improve the reduction degree of the cured shape of the resin,and has a beneficial effect on the accuracy of curing molding and the formation of complex structures.Compared with non-processing and commonly used grayaverage processing methods,the gray-scale control method contributes to the smallest overall size during curing.