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The Characterisation and Development of Silicon Microneedle / MEGAN MCNAMEE

Swansea University Author: MEGAN MCNAMEE

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DOI (Published version): 10.23889/SUThesis.71905

Abstract

Oral drug delivery is widely regarded as the ideal administration route due to its ease of manufacture, storage stability, and high patient compliance. In many clinical instances, however, it proves unsuitable due to the hepatic first pass metabolism, which significantly reduces drug bioavailability...

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Published: Swansea 2026
Institution: Swansea University
Degree level: Doctoral
Degree name: EngD
Supervisor: Arora, H., Guy, O., and Ashraf, H.
URI: https://cronfa.swan.ac.uk/Record/cronfa71905
first_indexed 2026-05-14T15:07:30Z
last_indexed 2026-05-15T05:42:01Z
id cronfa71905
recordtype RisThesis
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In response, microneedles (MNs) have garnered increasing attention from public and research sectors, offering painless administration and dose-sparing potential.Silicon MNs were the first devices developed for minimally invasive drug delivery, and recent advances in semi-conductor processing have made their scalable production increasingly feasible. This research aimed to establish evidence for their effective and safe use by characterising their mechanical, biological, and functional performance.Devices were fabricated at 100 mm wafer scale, with process optimisation focused on improving yield and structural fidelity. Devices were produced at heights up to 600 µm with good feature fidelity and yields reaching 82 %. Insertion mechanics were evaluated using digital image correlation (DIC), enabling comparison of strain profiles between MN and hypodermic insertion - the latter served as the clinical gold standard. Over the imaged period, hypodermic needles exerted approximately fourfold greater strain than MNs, indicating the potential for reduced tissue trauma.Biocompatibility of both the silicon substrate and fabricated devices was confirmed using ISO 10993-5 compliant cytotoxicity assays, with no statistically significant impact on the viability of human immortalised keratinocytes. To assess repeatability, dye-based injections into dermal mimics were performed, demonstrating consistent bolus formation and reproducible diffusion. MN injection plumes were uniform in size and morphology, in contrast to the variability observed with hypodermic delivery.To improve compatibility with continuous industrial manufacturing, etch steps were optimised at 150 mm wafer scale, which, when combined with the redesigned layout, resulted in a 140 % increase in usable device die. 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spelling v2 71905 2026-05-14 The Characterisation and Development of Silicon Microneedle 36e8e0d7c0e390efc4442bf7580268cb MEGAN MCNAMEE MEGAN MCNAMEE true false 2026-05-14 Oral drug delivery is widely regarded as the ideal administration route due to its ease of manufacture, storage stability, and high patient compliance. In many clinical instances, however, it proves unsuitable due to the hepatic first pass metabolism, which significantly reduces drug bioavailability and therapeutic efficacy. In response, microneedles (MNs) have garnered increasing attention from public and research sectors, offering painless administration and dose-sparing potential.Silicon MNs were the first devices developed for minimally invasive drug delivery, and recent advances in semi-conductor processing have made their scalable production increasingly feasible. This research aimed to establish evidence for their effective and safe use by characterising their mechanical, biological, and functional performance.Devices were fabricated at 100 mm wafer scale, with process optimisation focused on improving yield and structural fidelity. Devices were produced at heights up to 600 µm with good feature fidelity and yields reaching 82 %. Insertion mechanics were evaluated using digital image correlation (DIC), enabling comparison of strain profiles between MN and hypodermic insertion - the latter served as the clinical gold standard. Over the imaged period, hypodermic needles exerted approximately fourfold greater strain than MNs, indicating the potential for reduced tissue trauma.Biocompatibility of both the silicon substrate and fabricated devices was confirmed using ISO 10993-5 compliant cytotoxicity assays, with no statistically significant impact on the viability of human immortalised keratinocytes. To assess repeatability, dye-based injections into dermal mimics were performed, demonstrating consistent bolus formation and reproducible diffusion. MN injection plumes were uniform in size and morphology, in contrast to the variability observed with hypodermic delivery.To improve compatibility with continuous industrial manufacturing, etch steps were optimised at 150 mm wafer scale, which, when combined with the redesigned layout, resulted in a 140 % increase in usable device die. This research addressed key gaps in silicon MN literature, including fabrication throughput, potential cytotoxicity, and performance benchmarking. Furthermore, this work developed a standardised methodology for device performance assessment and demonstrated feasibility for the scaled manufacture of both hollow and solid silicon MNs. E-Thesis Swansea Microneedles, silicon, semi-conductors, skin model, strain 13 3 2026 2026-03-13 10.23889/SUThesis.71905 A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information. COLLEGE NANME COLLEGE CODE Swansea University Arora, H., Guy, O., and Ashraf, H. Doctoral EngD COATED M2A funding from KLA, the European Social Fund via the Welsh Government (c80816), and the Engineering and Physical Sciences Research Council COATED M2A funding from KLA, the European Social Fund via the Welsh Government (c80816), and the Engineering and Physical Sciences Research Council 2026-05-15T12:06:15.5139688 2026-05-14T15:58:59.9417086 Faculty of Science and Engineering School of Engineering and Applied Sciences - Materials Science and Engineering MEGAN MCNAMEE 1 71905__36746__7384be6534f542f1bb4e9f91d2bdc643.pdf 2026_McNamee_M.final.71905.pdf 2026-05-15T12:02:14.4936910 Output 20987765 application/pdf E-Thesis – open access true Copyright: the author, Megan Jessica McNamee, 2026. Distributed under the terms of a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). true eng https://creativecommons.org/licenses/by-nc-nd/4.0/
title The Characterisation and Development of Silicon Microneedle
spellingShingle The Characterisation and Development of Silicon Microneedle
MEGAN MCNAMEE
title_short The Characterisation and Development of Silicon Microneedle
title_full The Characterisation and Development of Silicon Microneedle
title_fullStr The Characterisation and Development of Silicon Microneedle
title_full_unstemmed The Characterisation and Development of Silicon Microneedle
title_sort The Characterisation and Development of Silicon Microneedle
author_id_str_mv 36e8e0d7c0e390efc4442bf7580268cb
author_id_fullname_str_mv 36e8e0d7c0e390efc4442bf7580268cb_***_MEGAN MCNAMEE
author MEGAN MCNAMEE
author2 MEGAN MCNAMEE
format E-Thesis
publishDate 2026
institution Swansea University
doi_str_mv 10.23889/SUThesis.71905
college_str Faculty of Science and Engineering
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hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Engineering and Applied Sciences - Materials Science and Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Materials Science and Engineering
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description Oral drug delivery is widely regarded as the ideal administration route due to its ease of manufacture, storage stability, and high patient compliance. In many clinical instances, however, it proves unsuitable due to the hepatic first pass metabolism, which significantly reduces drug bioavailability and therapeutic efficacy. In response, microneedles (MNs) have garnered increasing attention from public and research sectors, offering painless administration and dose-sparing potential.Silicon MNs were the first devices developed for minimally invasive drug delivery, and recent advances in semi-conductor processing have made their scalable production increasingly feasible. This research aimed to establish evidence for their effective and safe use by characterising their mechanical, biological, and functional performance.Devices were fabricated at 100 mm wafer scale, with process optimisation focused on improving yield and structural fidelity. Devices were produced at heights up to 600 µm with good feature fidelity and yields reaching 82 %. Insertion mechanics were evaluated using digital image correlation (DIC), enabling comparison of strain profiles between MN and hypodermic insertion - the latter served as the clinical gold standard. Over the imaged period, hypodermic needles exerted approximately fourfold greater strain than MNs, indicating the potential for reduced tissue trauma.Biocompatibility of both the silicon substrate and fabricated devices was confirmed using ISO 10993-5 compliant cytotoxicity assays, with no statistically significant impact on the viability of human immortalised keratinocytes. To assess repeatability, dye-based injections into dermal mimics were performed, demonstrating consistent bolus formation and reproducible diffusion. MN injection plumes were uniform in size and morphology, in contrast to the variability observed with hypodermic delivery.To improve compatibility with continuous industrial manufacturing, etch steps were optimised at 150 mm wafer scale, which, when combined with the redesigned layout, resulted in a 140 % increase in usable device die. This research addressed key gaps in silicon MN literature, including fabrication throughput, potential cytotoxicity, and performance benchmarking. Furthermore, this work developed a standardised methodology for device performance assessment and demonstrated feasibility for the scaled manufacture of both hollow and solid silicon MNs.
published_date 2026-03-13T12:07:46Z
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score 10.699861

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