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Project

Injection moulding polymer microneedles using laser ablated moulds

Microneedles are needle-like microscopic structures used to pierce the skin in order to either deliver medical substances, or to extract fluids from a body for sampling purposes. These needles are usually arranged in an array with individual needle lengths ranging from 25 to 2000 μm. Micro-sized needles offer various advantages compared to traditional hypodermic needles, such as a pain free delivery of medical substances. However, manufacturing microneedles represents a real challenge and a mass production process with high volume outputs at low cost is currently lacking.

A promising manufacturing process which fits these criteria is polymer injection moulding. By applying the negative geometry of the microneedles on a mould cavity, millions of polymer microneedle systems can be produced at a low cost. However, within the current state of the art, methods for applying the negative of the microneedles on the injection mould are limited to expensive and time consuming precision techniques. Besides, manufacturing microneedle cavities with a sharp tip has proven to be very difficult with these techniques, while small tip-radii are essential for microneedles to effectively penetrate the skin.

In this thesis, a production methodology for the fabrication of high volume, low cost polymer microneedles was developed. This methodology consists of a laser ablation process to produce cone-shaped microneedle cavities, which are afterwards replicated using injection moulding. First, insights are established in the influence of the laser scanning parameters on the geometry of the ablated microneedle cavities, being the cavity depth, the cavity base diameter and the shape of the needle flank. Next, the effect of various parameters on the replication fidelity and uniformity is investigated, being (i) the geometry of the microcavity, (ii) the location of the microneedles on the macroscopic product, (iii) the polymer characteristics, (iv) the mould material, and (v) the injection moulding technique (conventional injection moulding and injection compression moulding) with corresponding processing parameters. Furthermore, it is demonstrated that numerical flow simulations can be used to accurately predict the replication fidelity, in order to prevent extensive experimental injection moulding experiments.

A valorisation plan is then proposed which includes an identification of the target group that can benefit from the obtained research results, and an estimation on the market size is provided. The position of the developed methodology in the market is presented together with an economical evaluation. From an industrial point of view, the developed methodology is proven to be a suitable mass manufacturing technique to produce high volume, low cost polymer microneedles. Additionally, a key advantage of the methodology is its flexibility, which allows the development of microneedles with different shapes and dimensions in various thermoplastics.

Date:1 Jan 2019 →  22 Mar 2023
Keywords:Micro manufacturing, Polymer injection moulding, Microneedles
Disciplines:Polymer processing, Microfabrication and manufacturing
Project type:PhD project