The Improvement Effect and Mechanism of Longitudinal Ultrasonic Vibration on the Injection Molding Quality of a Polymeric Micro-Needle Array.

Shan Gao,Zhongjun Qiu,Junhao Ouyang

doi:10.3390/polym11010151

Abstract

A polymeric micro-needle array with high quality has been fabricated using a longitudinal ultrasonic-assisted micro-injection molding (LUμIM) method. To realize the practicability and stability in actual industrial processing, this paper is aimed at studying the improvement mechanism of ultrasonic vibration on the molding quality. The melt-filling process in the micro-needle array cavity is simulated, and the improvement effect of ultrasonic vibration is discussed. The enhancement effect of ultrasonic vibration on material properties of polypropylene and polymethylmethacrylate parts are experimentally investigated. The results show that in the manufacturing of the micro-needle array part using LUμIM, the mold-filling quality is improved by the enhanced melt filling capability and pressure compensation effect, which are caused by the increased corner viscosity gradient, reduced the filling time and melt viscosity under ultrasonic vibration. Material properties of both the semi-crystalline polymer and amorphous polymer could be enhanced by the transformation of micromorphology. It is proved that for a semi-crystalline polymer, this novel method could be employed as a material properties enhancement method, and an optimal excitation voltage of ultrasonic vibration is obtained to achieve the best material properties.

Highlights

Micro-needle array parts have already been applied in a number of domains, including medicine [1,2], biology [3,4], and micro-electromechanical systems [5,6], because of various excellent material properties, stable chemical properties, and good biological compatibility of polymer materials.Micro-injection molding is an important method for the production of micro-needle array parts with advantages consisting of low manufacturing cost, short production cycle, mass-production, good repeatability, simple process, etc. [7,8]
This study focused on the improvement effect and mechanism of ultrasonic vibration on the
This study focused on the improvement effect and mechanism of ultrasonic vibration on the molding quality of microneedle array parts fabricated by LUμIM method, including the improvement molding quality of microneedle array parts fabricated by LUμIM method, including the of mold filling quality and enhancement of material properties

Summary

Introduction

Micro-needle array parts have already been applied in a number of domains, including medicine [1,2], biology [3,4], and micro-electromechanical systems [5,6], because of various excellent material properties, stable chemical properties, and good biological compatibility of polymer materials.Micro-injection molding (μIM) is an important method for the production of micro-needle array parts with advantages consisting of low manufacturing cost, short production cycle, mass-production, good repeatability, simple process, etc. [7,8]. Micro-injection molding (μIM) is an important method for the production of micro-needle array parts with advantages consisting of low manufacturing cost, short production cycle, mass-production, good repeatability, simple process, etc. The high melt viscosity and frozen layer in the microcavity will lead to molding defects and a low mold-filling quality, which often occurs in the production of microneedle array parts, and still cannot be solved perfectly by conventional injection molding technology [9,10]. These problems of molding quality limit the highly cost-efficient mass production of microneedle array parts with high integrity

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