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Design, fabrication, and penetration assessment of polymeric hollow microneedles with different geometries

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Abstract

Hollow microneedles (HMNs) are minimally invasive needle-like microfeatures usually arranged in arrays designed for drug delivery and body fluid collection in a painless manner. In a recent work, we demonstrated a novel methodology to mass produce hollow polymer microneedles at a low cost. This methodology combines ultrashort pulse laser ablation to create inverse needle shapes in moulds and replication through polymer injection moulding. For a HMN to be functional, it should effectively pierce the skin at a low force and enable fluidic passage through the skin without leakage. This study investigates the impact of different laser scanning strategies on the cavity morphology and analyses how the various geometrical characteristics of the needle influence the penetration efficacy. To assess the penetration behaviour of the replicated HMNs, a combination of agarose gel and Parafilm® is employed as an in vitro testing platform. Furthermore, a correlation between HMN geometry, penetration performance, and modification of polymer material and holding pressure during injection moulding is established. The results indicate that a certain needle length is essential for effective penetration. Moreover, minimising the tip area, a factor significantly affecting penetration force, can be achieved by increasing the eccentricity of the scan-free area and expanding the scanning diameter. However, it is important to consider other functional needle features such as the ridge height or full lumen, which come at a cost to the tip sharpness. This work highlights the multiple interactions between the scanning strategy, the injection moulding process parameters, the needle geometry, and the penetration force. This study provides insights into optimization of the HMN design and the fabrication for enhanced penetration efficacy of functional injection-moulded polymeric HMNs.

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Acknowledgements

The authors would like to thank Olivier Malek from Sirris (department of Precision Manufacturing) for the laser ablation of the microneedle cavities. The KU Leuven XCT Core facility is acknowledged for the 3D image acquisition and quantitative post-processing tools (https://xct.kuleuven.be/).

Funding

This work was funded by the KU Leuven Interdisciplinary Network project IDN/20/011 MIRACLE: Autonomous microfluidic patch for plasmid-based vaccine, as well as the Fonds Wetenschappelijk Onderzoek (FWO)–Vlaanderen SBO project S003923N and SB fellowship 1S31022N. The FWO large infrastructure I013518N project is acknowledged for their financial support of the X-ray infrastructure.

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Authors and Affiliations

  1. Department of Mechanical Engineering and Flanders Make@KU Leuven - M&A, KU Leuven, Leuven, Belgium

    Pol Vanwersch & Sylvie Castagne

  2. Department of Materials Engineering, Diepenbeek Campus, KU Leuven, Diepenbeek, Belgium

    Pol Vanwersch, Tim Evens & Albert Van Bael

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  1. Pol Vanwersch
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  2. Tim Evens
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  4. Sylvie Castagne
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Contributions

Conceptualization, methodology, and investigation were performed by Pol Vanwersch and Tim Evens. The first draft of the manuscript was written by Pol Vanwersch and all authors commented on previous versions of the manuscript.

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Correspondence to Pol Vanwersch.

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Vanwersch, P., Evens, T., Van Bael, A. et al. Design, fabrication, and penetration assessment of polymeric hollow microneedles with different geometries. Int J Adv Manuf Technol 132, 533–551 (2024). https://doi.org/10.1007/s00170-024-13344-x

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  • DOI: https://doi.org/10.1007/s00170-024-13344-x

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