{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T11:38:52Z","timestamp":1785411532349,"version":"3.56.0"},"reference-count":52,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T00:00:00Z","timestamp":1782432000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000780","name":"European Union","doi-asserted-by":"crossref","award":["101130915"],"award-info":[{"award-number":["101130915"]}],"id":[{"id":"10.13039\/501100000780","id-type":"DOI","asserted-by":"crossref"}]},{"award":["101130915"],"award-info":[{"award-number":["101130915"]}],"id":[{"id":"https:\/\/ror.org\/019w4f821","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100025294","name":"Research Ireland","doi-asserted-by":"crossref","award":["13\/RC\/2094-P2"],"award-info":[{"award-number":["13\/RC\/2094-P2"]}],"id":[{"id":"10.13039\/501100025294","id-type":"DOI","asserted-by":"crossref"}]},{"award":["13\/RC\/2094-P2"],"award-info":[{"award-number":["13\/RC\/2094-P2"]}],"id":[{"id":"https:\/\/ror.org\/010t7sr36","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Research Ireland Centre for Software and Climate+ Co-Centre","award":["22\/CC\/11103"],"award-info":[{"award-number":["22\/CC\/11103"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper presents a proof-of-concept investigation into a novel hermetically sealed tunable-medium Extrinsic Fabry\u2013P\u00e9rot Interferometer (EFPI) temperature sensor architecture. A series of tuneable-sensitivity EFPI temperature sensors is demonstrated, comprising a large-diameter fused silica diaphragm with a 800 \u03bcm diameter, significantly exceeding conventional designs (typically \u223c125 \u03bcm), with polished diaphragm thicknesses ranging from 28 to 49 \u03bcm, housed in hermetically sealed rigid melting point capillaries with a 1.8 mm internal diameter. By exploiting thermally induced pressure differentials generated by a tunable Krytox GPL 105 oil\/air fill fraction within the sealed rigid cavity, the sensors demonstrate a continuously tuneable sensitivity design space spanning 0.45 to 190 nm\/K. An exact nonlinear thermal pressure model is derived and validated, replacing the linearised approximation which is shown to be inapplicable at fill fractions approaching unity. The low-sensitivity configuration (0.45 nm\/K) was characterised at the National Standards Authority of Ireland (NSAI) National Metrology Laboratory against ITS-90 fixed points: the Triple Point of Water (273.16 K) and the Gallium Fixed Point (302.9146 K), with traceability to the International Temperature Scale of 1990 (ITS-90), yielding an instrument-limited resolution of &lt;1.1 mK, consistent with the metrological validation environment. The high-sensitivity configurations (21 and 190 nm\/K) were characterised on a laboratory bench, achieving instrument-limited theoretical resolutions of &lt;24 \u03bcK and &lt;2.6\u00a0\u03bcK respectively, pending future metrological validation. The 190 nm\/K sensitivity represents an improvement of approximately 21.7\u00d7 over the closest directly comparable prior Citationutilised fusion splicing and manual polishing. Future development priorities include metrological validation of the high-sensitivity configurations, long-term stability characterisation, thermal cycling, and progression towards an all-glass hermetically sealed construction.<\/jats:p>","DOI":"10.3390\/s26134071","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T05:49:33Z","timestamp":1782712173000},"page":"4071","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Large-Diameter Diaphragm Fabry\u2013P\u00e9rot Interferometer for High-Sensitivity Temperature Sensing Using a Hermetically Sealed Tunable Medium: Up to 190 nm\/K"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0004-9861-2482","authenticated-orcid":false,"given":"Anthony","family":"Weir","sequence":"first","affiliation":[{"name":"Center for Robotics and Intelligent Systems (CRIS), Department of Electronic and Computer Engineering, University of Limerick, V94 T9PX Limerick, Ireland"},{"name":"School of Engineering, University of Limerick, V94 T9PX Limerick, Ireland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dubhaltach Mac","family":"Lochlainn","sequence":"additional","affiliation":[{"name":"NSAI National Metrology Laboratory, Griffith Avenue Ext., Glasnevin, D11 E527 Dublin, Ireland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helio","family":"Musselwhite-Veitch","sequence":"additional","affiliation":[{"name":"Center for Robotics and Intelligent Systems (CRIS), Department of Electronic and Computer Engineering, University of Limerick, V94 T9PX Limerick, Ireland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7589-1384","authenticated-orcid":false,"given":"Gerard","family":"Dooly","sequence":"additional","affiliation":[{"name":"Center for Robotics and Intelligent Systems (CRIS), Department of Electronic and Computer Engineering, University of Limerick, V94 T9PX Limerick, Ireland"},{"name":"School of Engineering, University of Limerick, V94 T9PX Limerick, Ireland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2009-9709","authenticated-orcid":false,"given":"Dinesh Babu","family":"Duraibabu","sequence":"additional","affiliation":[{"name":"Department of Mechatronic Engineering, School of Engineering and Design, Atlantic Technological University, Ash Ln, Ballytivnan, F91 YW50 Sligo, Ireland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,26]]},"reference":[{"key":"ref_1","first-page":"459","article-title":"Sur les franges des lames minces argent\u00e9es et leur application \u00e0 la mesure de petites \u00e9paisseurs d\u2019air","volume":"12","author":"Fabry","year":"1897","journal-title":"Ann. 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