{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T05:06:29Z","timestamp":1783400789930,"version":"3.54.6"},"reference-count":23,"publisher":"MDPI AG","issue":"23","license":[{"start":{"date-parts":[[2025,11,22]],"date-time":"2025-11-22T00:00:00Z","timestamp":1763769600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National Science, Research & Innovation (NSRF) and King Mongkut\u2019s University of Technology North Bangkok","award":["KMUTNB-FF-68-A-04"],"award-info":[{"award-number":["KMUTNB-FF-68-A-04"]}]},{"name":"King Mongkut\u2019s University of Technology North Bangkok (KMUTNB) and the National Science & Technology Development Agency","award":["B.026\/2563"],"award-info":[{"award-number":["B.026\/2563"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper presents the design, fabrication, and experimental validation of a metal 3D-printed mechanically tunable cavity resonator operating in the hybrid TM\u2013coaxial resonant mode for the broadband characterization of liquid permittivity. The proposed structure was developed based on a cylindrical cavity by incorporating a disc-terminated metallic tuning stub, which enables continuous frequency adjustment from 0.5 GHz to 3.0 GHz while maintaining a maximum unloaded Q-factor of 284 at 1 GHz under air-filled conditions. The tuning mechanism allows for precise frequency selection for characterizing materials exhibiting frequency-dependent permittivity. To demonstrate its sensing capability, the resonator was applied to characterize ethanol\u2013water mixtures, where resonant frequency shifts were correlated with ethanol concentration at representative baseline frequencies of 1.00 GHz, 2.00 GHz, and 2.94 GHz. The sensor achieved frequency\/dielectric constant resolutions of 0.39, 1.34, and 4.20 MHz and average concentration errors of 1.25%, 3.73%, and 2.49%, respectively. Moreover, polynomial fitting models enabled the accurate extraction of dielectric constants with an average deviation below 0.5% compared with a commercial dielectric probe system. The combination of frequency tunability, compact geometry, and compatibility with additive manufacturing establishes the proposed cavity resonator as a versatile platform for broadband dielectric spectroscopy, chemical sensing, and liquid characterization.<\/jats:p>","DOI":"10.3390\/s25237145","type":"journal-article","created":{"date-parts":[[2025,11,24]],"date-time":"2025-11-24T14:59:04Z","timestamp":1763996344000},"page":"7145","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Additively Manufactured Mechanically Tunable Cavity Resonator for Broadband Characterization of Liquid Permittivity"],"prefix":"10.3390","volume":"25","author":[{"ORCID":"https:\/\/orcid.org\/0009-0003-0634-0639","authenticated-orcid":false,"given":"Thipamas","family":"Phakaew","sequence":"first","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thet Pai","family":"Oo","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0002-6705-1606","authenticated-orcid":false,"given":"Muhammad","family":"Uzair","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9118-1550","authenticated-orcid":false,"given":"Pruet","family":"Kowitwarangkul","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Piyapat","family":"Chuchuay","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8029-0305","authenticated-orcid":false,"given":"Rungsima","family":"Yeetsorn","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4672-2343","authenticated-orcid":false,"given":"Danai","family":"Torrungrueng","sequence":"additional","affiliation":[{"name":"Department of Teacher Training in Electrical Engineering, Faculty of Technical Education, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7239-9968","authenticated-orcid":false,"given":"Nonchanutt","family":"Chudpooti","sequence":"additional","affiliation":[{"name":"Department of Industrial Physics and Medical Instrumentation, Faculty of Applied Science, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7600-2518","authenticated-orcid":false,"given":"Suramate","family":"Chalermwisutkul","sequence":"additional","affiliation":[{"name":"The Sirindhorn International Thai-German Graduate School of Engineering, King Mongkut\u2019s University of Technology North Bangkok, Bangkok 10800, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,11,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"110373","DOI":"10.1016\/j.jfoodeng.2020.110373","article-title":"Characterisation of Water in Honey Using a Microwave Cylindrical Cavity Resonator Sensor","volume":"292","author":"Li","year":"2021","journal-title":"J. Food Eng."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"110849","DOI":"10.1016\/j.lwt.2021.110849","article-title":"Characterisation and Analysis of Alcohol in Baijiu with a Microwave Cavity Resonator","volume":"141","author":"Li","year":"2021","journal-title":"LWT"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"112690","DOI":"10.1109\/ACCESS.2024.3442890","article-title":"5.58-GHz Modified Jerusalem Patch Sensor for 1%-Precision Ethanol and Methanol Discrimination in Disinfectant Solutions","volume":"12","author":"Chudpooti","year":"2024","journal-title":"IEEE Access"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"108634","DOI":"10.1016\/j.foodcont.2021.108634","article-title":"Detection and Analysis of Metallic Contaminants in Dry Foods Using a Microwave Resonator Sensor","volume":"133","author":"Li","year":"2022","journal-title":"Food Control"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"22600","DOI":"10.1109\/JSEN.2022.3216833","article-title":"Microwave Cylindrical Cavity Resonator Sensor for Detection and Characterization of Contaminants in Lubricating Oil","volume":"22","author":"Li","year":"2022","journal-title":"IEEE Sens. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"200","DOI":"10.1016\/j.snb.2018.01.211","article-title":"A Microwave Cavity Resonator Sensor for Water-in-Oil Measurements","volume":"262","author":"Sharma","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Asadi, R., Li, C., Mousavi, S., Mousavi, S.M., Vahdani, R., Ye, X., and Kim, D.B. (2024, January 5\u20139). Design of the TM010 Mode Cylindrical Cavity Resonator for PCB Dielectric Characterization. Proceedings of the IEEE EMCSIPI Symposium, Phoenix, AZ, USA.","DOI":"10.1109\/EMCSIPI49824.2024.10705488"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Steiner, C., Walter, S., Malashchuk, V., Hagen, G., Kogut, I., Fritze, H., and Moos, R. (2020). Determination of the Dielectric Properties of Storage Materials for Exhaust Gas Aftertreatment Using the Microwave Cavity Perturbation Method. Sensors, 20.","DOI":"10.3390\/s20216024"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"103","DOI":"10.2528\/PIER09030904","article-title":"Broadband measurements of dielectric properties of low-loss materials at high temperatures using circular cavity method","volume":"92","author":"Li","year":"2009","journal-title":"Prog. Electromagn. Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1109\/TDEI.2006.1667730","article-title":"A review of RF and microwave techniques for dielectric measurements on polar liquids","volume":"13","author":"Gregory","year":"2006","journal-title":"IEEE Trans. Dielectr. Electr. Insul."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"2633","DOI":"10.1109\/22.473190","article-title":"Extended cavity perturbation technique to determine the complex permittivity of dielectric materials","volume":"43","author":"Meng","year":"1995","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1139","DOI":"10.1109\/TDEI.2007.4339473","article-title":"Microwave measurements of dielectric properties using a closed cylindrical cavity dielectric resonator","volume":"14","author":"Sheen","year":"2007","journal-title":"IEEE Trans. Dielectr. Electr. Insul."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Kawabata, H., Tanpo, H., and Kobayashi, Y. (2003, January 2\u201310). A Rigorous Analysis of a TM010 Mode Cylindrical Cavity to Measure Accurate Complex Permittivity of Liquid. Proceedings of the 33rd European Microwave Conference, Munich, Germany.","DOI":"10.1109\/EUMC.2003.177587"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Kawabata, H., and Kobayashi, Y. (2005, January 4\u20136). Accurate Measurements of Complex Permittivity of Liquid Based on a TM101 Mode Cylindrical Cavity Method. Proceedings of the 2005 European Microwave Conference, Paris, France.","DOI":"10.1109\/EUMC.2005.1608870"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"504","DOI":"10.1109\/TMTT.2014.2387057","article-title":"An Accurate Radially Stratified Approach for Determining the Complex Permittivity of Liquids in a Cylindrical Microwave Cavity","volume":"63","author":"Barmatz","year":"2015","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Kanpan, P., Khansalee, E., Puangngernmak, N., and Chalermwisutkul, S. (2012, January 16\u201318). TM010 Mode Cylindrical Cavity for Complex Permittivity Measurement of Liquid Using Field Analysis Technique. Proceedings of the 2012 9th International Conference on Electrical Engineering\/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON), Phetchaburi, Thailand.","DOI":"10.1109\/ECTICon.2012.6254274"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Sangdao, C. (2019, January 6\u20138). Feasibility Study of Dielectric Measurement Using a Concentric Cylindrical Cavity. Proceedings of the 2019 7th International Electrical Engineering Congress (iEECON), Hua Hin, Thailand.","DOI":"10.1109\/iEECON45304.2019.8938889"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Zhang, Y., Fan, Z., Zhu, H., Gao, C., Yu, C., Niu, X., and Li, E. (2025). Complex Permittivity Measurement of Materials with a Wide Loss Tangent Range Based on Multiholes Cylindrical Resonant Cavity. IEEE Microw. Wirel. Technol. Lett., Early Access.","DOI":"10.1109\/LMWT.2025.3561050"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Faz, U., Siart, U., and Eibert, T.F. (2015, January 16\u201318). A Cylindrical Cavity Resonator for Material Measurements with Coupled Resonant Modes for Sensing and Position Offset Compensation of the Dielectric Specimen. Proceedings of the 2015 German Microwave Conference (GeMiC), Nuremberg, Germany.","DOI":"10.1109\/GEMIC.2015.7107746"},{"key":"ref_20","unstructured":"Pozar, D.M. (2012). Microwave Engineering, John Wiley & Sons, Inc.. [4th ed.]."},{"key":"ref_21","unstructured":"Metal, D. (2024). 316L v.2 Stainless Steel PureSinter Furnace, Desktop Metal, Inc."},{"key":"ref_22","unstructured":"Metal, D. (2025, July 29). (Desktop Metal). Available online: https:\/\/www.desktopmetal.com\/."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"54","DOI":"10.30678\/fjt.149389","article-title":"On the Surface Roughness of 316L Stainless Steel Fabricated Using L-PBF Additive Manufacturing","volume":"41","author":"Yildiz","year":"2024","journal-title":"Tribologia\u2013Finn. J. Tribol."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/23\/7145\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,11,24]],"date-time":"2025-11-24T15:03:47Z","timestamp":1763996627000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/25\/23\/7145"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,11,22]]},"references-count":23,"journal-issue":{"issue":"23","published-online":{"date-parts":[[2025,12]]}},"alternative-id":["s25237145"],"URL":"https:\/\/doi.org\/10.3390\/s25237145","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,11,22]]}}}