{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T01:34:25Z","timestamp":1760232865270,"version":"build-2065373602"},"reference-count":61,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2022,12,6]],"date-time":"2022-12-06T00:00:00Z","timestamp":1670284800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"University of Sheffield Medical Research Council Confidence"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Cervical tissue hydration level is one of the most important parameters to monitor in the early diagnosis of preterm birth. Electrical-impedance-spectroscopy-based techniques are often used, but they suffer from limited accuracy. Open microwave coaxial probes have been widely used as a broadband dielectric characterization technique for human tissue samples due to their versatility, but with limited accuracy due to their nonresonant nature. In this work, a resonant microwave open coaxial probe with multiple harmonic resonances is proposed as a sensing platform for tissue-hydration-level monitoring. The mechanical design was analyzed and verified by finite-element full 3D electromagnetic simulation and experiments. Dominant sources of errors and the ways to mitigate them were discussed. In vitro experiments were carried out on human cervix samples to verify the precision and accuracy by comparing the results to a commercial skin-hydration sensor. The proposed sensor shows mean fractional frequency shift of (3.3 \u00b1 0.3) \u00d7 10\u22124 per unit % over the entire data. This translates into an absolute frequency shift (\u0394fN) of 252 \u00b1 23 kHz\/%, 455 \u00b1 41 kHz\/%, and 647 \u00b1 57 kHz\/% at second, fourth, and sixth harmonic resonance, respectively.<\/jats:p>","DOI":"10.3390\/s22239527","type":"journal-article","created":{"date-parts":[[2022,12,7]],"date-time":"2022-12-07T04:38:54Z","timestamp":1670387934000},"page":"9527","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Cervical Tissue Hydration Level Monitoring by a Resonant Microwave Coaxial Probe"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1108-293X","authenticated-orcid":false,"given":"Heungjae","family":"Choi","sequence":"first","affiliation":[{"name":"School of Engineering, Cardiff University, 14-17 The Parade, Cardiff CF24 3AA, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Emilia","family":"Barker","sequence":"additional","affiliation":[{"name":"School of Clinical Dentistry, University of Sheffield, 19 Claremont Crescent, Sheffield S10 2TA, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9933-0912","authenticated-orcid":false,"given":"Ali A.","family":"Abduljabar","sequence":"additional","affiliation":[{"name":"College of Engineering, University of Basrah, Basrah 61002, Iraq"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dilly","family":"Anumba","sequence":"additional","affiliation":[{"name":"Department of Oncology and Metabolism, JW4\/40, Level 4, Jessop Wing, Tree Root Walk, Sheffield S10 2SF, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Adrian","family":"Porch","sequence":"additional","affiliation":[{"name":"School of Engineering, Cardiff University, 14-17 The Parade, Cardiff CF24 3AA, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,12,6]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2022, May 18). 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