Simulation And Experimental Research On Precision Hot Embossing Of Polymer Microneedle Array

In recent years,polymer microneedle arrays had been widely used in drug injection,local anesthesia and cosmetic surgery due to their excellent biocompatibility,mechanical properties and machinability.Precision hot embossing was one of the effective ways to realize high efficiency and high precision manufacturing of polymer microneedle arrays.However,the molding quality of polymer microneedle array is affected by several hot embossing parameters,which was prone to many defects such as shrinkage deformation,insufficient filling and stress concentration,resulting in low yield of polymer microneedle arrays.Based on this,this paper combined finite element simulation and molding experiment to study the molding process of polystyrene microneedle arrays precision hot embossing.The main research contents are as follows:(1)The thermal-mechanical properties of polystyrene were studied.Thermal-mechanical properties such as thermal expansion coefficient and specific heat capacity were measured.The thermos-viscoelastic model of the material was established,and the stress relaxation parameters were calculated and the results were fitted by creep compression test and stress relaxation analysis,which laid a theoretical foundation for the subsequent research.(2)The shape and size of polystyrene microneedle array were designed.The finite element models of polystyrene microneedles with different shapes and sizes were established,and the stress and strain distributions of the microneedles with different sizes and shapes were investigated under the same load.The results showed that the structure of triangular pyramid microneedles was the most stable under stress,and the conical table microneedles could effectively avoid the defects of stress concentration.The higher the height and the smaller the bottom diameter of the microneedle were,the greater the lateral bending deviation and stress occurred during the stress.In order to achieve painless puncture,improve the puncture success rate and reduce the molding difficulty of the microneedle,combined with the simulation analysis results,the shape and size of the microneedle were determined as:conical table microneedle,height 700μm,bottom diameter 400μm.(3)The simulation analysis of polystyrene microneedle arrays precision hot embossing process was completed.Established the thermal-mechanical coupling field polystyrene microneedle arrays finite element model of the precision hot embossing,hot embossing process parameters was discussed on polystyrene microneedle arrays forming stress,temperature distribution and the influence of filling depth,the results showed that the heating rate increases,preliminary form the greater the degree of uneven temperature distribution and thermal stress.With the increase of hot embossing temperature,the forming stress decreases first and then increases.The forming stress decreases with the increase of the thickness of the preform and the decrease of the hot embossing rate and the amount of pressing.The average filling depth increases with the increase of hot embossing temperature and pressing quantity,and the decrease of hot embossing rate and preform thickness.(4)The hot embossing experiment of polystyrene microneedle arrays was carried out.The influence of hot embossing process parameters on the average filling depth of polymer microneedle arrays was discussed and compared with the simulation results.The results showed that the simulation results are consistent with the experimental results when the hot embossing temperature was lower than 125℃.Finally,the mechanical properties of the arrays were analyzed by nano indentation instrument,and its mechanical stability and safety were verified.