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Vac-and-fill: A micromoulding technique for fabricating microneedle arrays with vacuum-activated, hands-free mould-filling

Lookup NU author(s): Emma Hutchinson, Dr Wing Man LauORCiD, Dr Tarek Abdelghany, Dr Katarina Novakovic, Dr Keng Wooi NgORCiD



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


We report a simple and reproducible micromoulding technique that dynamically fills microneedle moulds with a liquid formulation, using a plastic syringe, triggered by the application of vacuum (‘vac-and-fill’). As pressure around the syringe drops, air inside the syringe pushes the plunger to uncover an opening in the syringe and fill the microneedle mould without manual intervention, therefore removing inter-operator variability. The technique was validated by monitoring the plunger movement and pressure at which the mould would be filled over 10 vacuum cycles for various liquid formulation of varying viscosity (water, glycerol, 20% polyvinylpyrrolidone (PVP) solution or 40% PVP solution). Additionally, the impact of re-using the disposable syringes on plunger movement, and thus the fill pressure, was investigated using a 20% PVP solution. The fill pressure was consistent at 300–450 mbar. It produced well-formed and mechanically robust PVP, poly(methylvinylether/maleic anhydride) and hydroxyethylcellulose microneedles from liquid formulations. This simple and inexpensive technique of micromoulding eliminated the air entrapment and bubble formation, which prevent reproducible microneedle formation, in the resultant microneedle arrays. It provides a cost-effective alternative to the conventional micromoulding techniques, where the application of vacuum (‘fill-and-vac’) or centrifugation following mould-filling may be unsuitable, ineffective or have poor reproducibility.

Publication metadata

Author(s): Smith E, Lau WM, Abdelghany TM, Vokajlovic D, Novakovic K, Ng KW

Publication type: Article

Publication status: Published

Journal: International Journal of Pharmaceutics

Year: 2024

Volume: 650

Print publication date: 25/01/2024

Online publication date: 14/12/2023

Acceptance date: 12/12/2023

Date deposited: 21/12/2023

ISSN (print): 0378-5173

ISSN (electronic): 1873-3476

Publisher: Elsevier BV


DOI: 10.1016/j.ijpharm.2023.123706

PubMed id: 38103704


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Funder referenceFunder name
The Northern Accelerator, United Kingdom