Research On High-speed Injection Molding Technology Of PLA Medical Beauty Microneedle

As a new drug delivery method,microneedle drug delivery technology can use microneedle arrays to generate microchannels on the skin surface,thereby breaking the blocking effect of stratum corneum barriers on drugs,so that cosmetic skin care products or drugs can give full play to their beauty or treatment.Effect.Microneedles based on polymer materials have the advantages of painless,high efficiency,good biocompatibility,etc.,and have attracted more and more attention.At the same time,micro-injection molding technology has become one of the key technologies for polymer microneedle molding due to its advantages of high production efficiency,stable molding,low production cost,and large-scale mass production.In this paper,PLA medical and cosmetic microneedles were mainly prepared based on microinjection molding technology,and the optimal process parameters were explored.At the same time,TPU was used to modify PLA to prepare microneedle products with excellent substrate toughness.The specific research content of the paper is as follows:(1)An eye patch-shaped microneedle structure is proposed,which is crescent-shaped,with a base thickness of 0.5 mm and a width of 56 mm.The microneedle patch has a total of 238 microneedle needles,the shape of the needles is a triangular pyramid,the length of the bottom surface is 0.4 mm,the height is 0.6 mm,and the distance between the needles is 1.5 mm.The gate method adopts side gate,the length of the main channel is 35 mm,the overall shape is truncated cone,and the branch channel is a combination of cuboid and trapezoidal table.(2)Moldflow software was used to simulate and analyze the microneedle forming process in high-speed injection molding.The simulation results show that controlling the injection speed between 250 mm/s and 400 mm/s can shorten the filling time of microneedles to 0.013 s,a reduction of 90%.The warpage deformation and volume shrinkage tend to be stable and the deformation is small,and the quality of the patch molding is better.(3)On the basis of the previous simulation results,an orthogonal experiment table was designed,and the optimal molding process for the diameter of the tip of the microneedle was obtained by using the range analysis:mold temperature 45 ℃,melt temperature 200 ℃,injection speed 360 mm/s,Holding time 4 s,holding pressure 50 MPa.The morphology and size,mechanical strength,penetration performance,drug release performance and skin pinhole healing time of PLA microneedle patches with the best process were characterized.The efficiency was 3.5 times that of untreated skin,and the pinholes in the mouse skin were basically healed after 25 min.At the same time,the coated microneedle was prepared by using the best technology microneedle,and the puncture experiment results showed that the coated microneedle could pierce the skin and effectively achieve drug delivery.(4)PLA was modified with TPU to prepare microneedle products with high strength and good toughness.The phase morphology,impact properties,fluidity of the mixture,and the mechanical strength and penetration performance of the mixed microneedles were analyzed.The experimental results show that compared with pure PLA microneedles,the toughness of the hybrid microneedles has been greatly improved,and the mechanical properties are good,which can pierce the skin without breaking during the process of puncturing the skin.PLA/TPU microneedles were prepared with roller microneedles,and their puncture effect was characterized.The experimental results showed that the roller microneedles could pierce two layers of sealing film(252 μm)smoothly,which met the requirement of piercing the stratum corneum of the skin.Feasibility of PLA/TPU roller microneedles for biomedical applications.