Characterisation of microneedle replication and flow behaviour in ultrasonic micro-injection moulding through design of experiments

Abstract

This research investigates the impact of process parameters on ultrasonic micro-injection moulding (u-μIM) by studying microneedle replication efficiency, temperature evolution during moulding, melt flow consistency and sonication behaviour. The experimentation comprises of a full-factorial design of experiments using three process variables: sonication time, mould temperature and injection force. The current study presents that; (i) mould temperature was found to be the most influential parameter to tune and optimise micro-feature replication, (ii) consistent ultrasonic micromoulding flows can be achieved using higher mould temperatures, (iii) injection force is a key parameter influencing sonication frequency, a critical aspect of the ultrasonic method to obtain a repeatable manufacturing process. These outcomes will be a datum during development of the manufacturing processes for specific products using the ultrasonic method. The research presented here takes a unique approach to characterise the ultrasonic method for the development of this novel technique, particularly for microneedle patch and medical device production. With this increased level of understanding of u-μIM process characteristics, the method can become an energy efficient and cost-effective alternative to conventional micro-injection moulding processes for delivering high-quality, miniature components.