Ultrasonic Plasticization Microinjection Precision Molding of Polypropylene Microneedle Arrays

Ultrasonic plasticization microinjection molding (UPMIM) presents a great application prospect in the PP microneedle array molding field by virtue of significant reduction of melt viscosity, energy, and material saving. In order to achieve efficient, rapid, and high-volume fabrication of polymer microneedle arrays, this paper presents a method for the preparation of polypropylene (PP) microneedle arrays with a high replication rate and good mechanical and penetration properties. The micromilling technology is adopted to prepare the metal core at first, and then, UPMIM is used for the preparation of PP microneedle arrays. The influence of the ultrasonic effect on plasticization rate, viscosity, and crystalline property of PP is mastered in this research. The molding experimental results show that the maximum replication rate of the PP microneedle array can reach 98.6 ± 0.6%, achieving the precision molding of the PP microneedle array. The test results of mechanical and penetration performance show that the PP microneedle array presents the approximate displacement─force character under different compression speeds and owns good mechanical performance; the PP microneedle array can completely pierce into the 0.1 and 0.2 mm silica membrane and the surface of pig skin, showing a good penetration performance. Therefore, UPMIM can prepare the PP microneedle array efficiently and accurately and presents important application value in its mass production.