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Licensed Unlicensed Requires Authentication Published by De Gruyter April 27, 2022

Predicting the replication fidelity of injection molded solid polymer microneedles

Tim Evens, Sylvie Castagne, David Seveno and Albert Van Bael

Abstract

Microneedles are sharp microscopic features, which can be used for drug or vaccine delivery in a minimally invasive way. Recently, we developed a method to produce polymer microneedles using laser ablated molds in an injection molding process. At this moment, extensive injection molding experiments are needed to investigate the replication fidelity. Accurate predictions of the injection molding process would eliminate these costly and time expensive experiments. In this study, we evaluated the replication fidelity of solid polymer microneedles using numerical simulations and compared the results to injection molding experiments. This study was performed for different sizes of microneedles, different thermoplastics (polypropylene and polycarbonate) and different mold materials (tool steel, copper alloy and aluminium alloy). Moreover, different processing conditions and different locations of the microneedles on the macroscopic part were considered. A good correlation with experimental findings was achieved by optimizing the heat transfer coefficient between the polymer and the mold, while using a multiscale mesh with a sufficient number of mesh elements. Optimal heat transfer coefficients between 10,000 and 55,000 W/m2 K were found for the different combinations of polymer and mold materials, which resulted in an accuracy of the simulated microneedle replication fidelity between 94.5 and 97.0%.


Corresponding author: Tim Evens, Department of Materials Engineering Diepenbeek Campus, KU Leuven, Wetenschapspark 27, 3590 Diepenbeek, Belgium, E-mail:

Funding source: KU Leuvendoi.org/10.13039/501100004040

Award Identifier / Grant number: IDN/20/011 - MIRACLE: Autonomous microfluidic patch for plasmid-based vaccine

Acknowledgments

The authors would like to thank Olivier Malek from the company Sirris, department Precision Manufacturing (Belgium) for laser ablating the microneedle cavities in the mold inserts. We also thank the company SABIC for providing the thermoplastic injection molding materials and the company SimpaTec for their support with the Moldex3D analyses.

  1. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

  2. Research funding: This work was funded by the KU Leuven Interdisciplinary Network project IDN/20/011 - MIRACLE: Autonomous microfluidic patch for plasmid-based vaccine.

  3. Conflict of interest statement: The authors declare no conflicts of interest regarding this article.

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Received: 2021-11-15
Accepted: 2022-03-09
Published Online: 2022-04-27
Published in Print: 2022-07-26

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