{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,19]],"date-time":"2026-06-19T09:02:16Z","timestamp":1781859736947,"version":"3.54.5"},"reference-count":35,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2023,6,2]],"date-time":"2023-06-02T00:00:00Z","timestamp":1685664000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Universidad Carlos III de Madrid and the European Union\u2019s Horizon","award":["801538"],"award-info":[{"award-number":["801538"]}]},{"name":"Universidad Carlos III de Madrid and the European Union\u2019s Horizon","award":["RSPD2023R699"],"award-info":[{"award-number":["RSPD2023R699"]}]},{"name":"King Saud University, Riyadh, Saudi Arabia","award":["801538"],"award-info":[{"award-number":["801538"]}]},{"name":"King Saud University, Riyadh, Saudi Arabia","award":["RSPD2023R699"],"award-info":[{"award-number":["RSPD2023R699"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The permittivity of a material is an important parameter to characterize the degree of polarization of a material and identify components and impurities. This paper presents a non-invasive measurement technique to characterize materials in terms of their permittivity based on a modified metamaterial unit-cell sensor. The sensor consists of a complementary split-ring resonator (C-SRR), but its fringe electric field is contained with a conductive shield to intensify the normal component of the electric field. It is shown that by tightly electromagnetically coupling opposite sides of the unit-cell sensor to the input\/output microstrip feedlines, two distinct resonant modes are excited. Perturbation of the fundamental mode is exploited here for determining the permittivity of materials. The sensitivity of the modified metamaterial unit-cell sensor is enhanced four-fold by using it to construct a tri-composite split-ring resonator (TC-SRR). The measured results confirm that the proposed technique provides an accurate and inexpensive solution to determine the permittivity of materials.<\/jats:p>","DOI":"10.3390\/s23115306","type":"journal-article","created":{"date-parts":[[2023,6,5]],"date-time":"2023-06-05T02:18:29Z","timestamp":1685931509000},"page":"5306","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":33,"title":["Design of a Planar Sensor Based on Split-Ring Resonators for Non-Invasive Permittivity Measurement"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-8263-1572","authenticated-orcid":false,"given":"Mohammad","family":"Alibakhshikenari","sequence":"first","affiliation":[{"name":"Department of Signal Theory and Communications, Universidad Carlos III de Madrid, 28911 Legan\u00e9s, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7203-0039","authenticated-orcid":false,"given":"Bal S.","family":"Virdee","sequence":"additional","affiliation":[{"name":"School of Computing and Digital Media, Center for Communications Technology, London Metropolitan University, 166-220 Holloway Road, London N7 8DB, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Taha A.","family":"Elwi","sequence":"additional","affiliation":[{"name":"Communication Engineering Department, Al-Ma\u2019 Moon University College, Baghdad 1004, Iraq"},{"name":"International Applied and Theoretical Research Centre (IATRC), Baghdad 10001, Iraq"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Innocent D.","family":"Lubangakene","sequence":"additional","affiliation":[{"name":"School of Computing and Digital Media, Center for Communications Technology, London Metropolitan University, 166-220 Holloway Road, London N7 8DB, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Renu K. R.","family":"Jayanthi","sequence":"additional","affiliation":[{"name":"School of Computing and Digital Media, Center for Communications Technology, London Metropolitan University, 166-220 Holloway Road, London N7 8DB, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amer Abbood","family":"Al-Behadili","sequence":"additional","affiliation":[{"name":"Electrical Engineering, College of Engineering, Mustansiriyah University, Baghdad 10052, Iraq"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zaid A. Abdul","family":"Hassain","sequence":"additional","affiliation":[{"name":"Electrical Engineering, College of Engineering, Mustansiriyah University, Baghdad 10052, Iraq"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1416-640X","authenticated-orcid":false,"given":"Syed Mansoor","family":"Ali","sequence":"additional","affiliation":[{"name":"Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5798-398X","authenticated-orcid":false,"given":"Giovanni","family":"Pau","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Architecture, Kore University of Enna, 94100 Enna, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8599-0418","authenticated-orcid":false,"given":"Patrizia","family":"Livreri","sequence":"additional","affiliation":[{"name":"Department of Engineering, University of Palermo, viale delle Scienze BLDG 9, 90127 Palermo, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sonia","family":"A\u00efssa","sequence":"additional","affiliation":[{"name":"Institut National de la Recherche Scientifique (INRS), University of Qu\u00e9bec, Montr\u00e9al, QC H5A 1K6, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2341","DOI":"10.1109\/TBME.2013.2241763","article-title":"Microwave stethoscope: Development and benchmarking of a vital signs sensor using computer-controlled phantoms and human studies","volume":"61","author":"Celik","year":"2014","journal-title":"IEEE Trans. Biomed. Eng."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Shaji, M., and Akhtar, M.J. (2013, January 14\u201316). Microwave coplanar sensor system for detecting contamination in food products. Proceedings of the IEEE MTT-S International Microwave and RF Conference, New Delhi, India.","DOI":"10.1109\/IMaRC.2013.6777723"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2411","DOI":"10.1109\/TMTT.2015.2451110","article-title":"Design and analysis of shielded vertically stacked ring resonator as complex permittivity sensor for petroleum oils","volume":"63","author":"Kulkarni","year":"2015","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_4","first-page":"3217","article-title":"Circular microfluidic substrate integrated waveguide resonator sensor for materials characterization","volume":"11","author":"Bahar","year":"2016","journal-title":"ARPN J. Eng. Appl. Sci."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"7628","DOI":"10.1109\/JSEN.2016.2599099","article-title":"A microfluidic-integrated SIW lab-on-substrate sensor for microliter liquid characterization","volume":"16","author":"Silavwe","year":"2016","journal-title":"IEEE Sens. J."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1451","DOI":"10.1109\/TMTT.2005.845211","article-title":"Equivalent circuit models for split ring resonators and complementary split ring resonators coupled to planar transmission lines","volume":"53","author":"Baena","year":"2005","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Nogueira, J.K.A., Oliveira, J.G.D., Paiva, S.B., Neto, V.P.S., and D\u2019Assun\u00e7\u00e3o, A.G. (2022). A compact C-SRR-based sensor for characterization of the complex permittivity of dielectric materials. Electronics, 11.","DOI":"10.3390\/electronics11111787"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"439","DOI":"10.1002\/mmce.20635","article-title":"Split rings for metamaterial and microwave circuit design: A review of recent developments","volume":"22","author":"Naqui","year":"2012","journal-title":"Int. J. RF Microw. Comput. Aided Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"265","DOI":"10.1109\/TMTT.2005.861664","article-title":"New microstrip filters based on complementary split rings resonators","volume":"54","author":"Bonache","year":"2006","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Al-Behadili, A.A., Mocanu, I.A., Codreanu, N., and Pantazica, M. (2020). Modified split ring resonators sensor for accurate complex permittivity measurements of solid dielectrics. Sensors, 20.","DOI":"10.3390\/s20236855"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1070\/PU1968v010n04ABEH003699","article-title":"The Electrodynamics of Substances with Simultaneously Negative Values of \u03b5 and \u00b5","volume":"10","author":"Veselago","year":"1967","journal-title":"Sov. Phys. Uspekhi"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2075","DOI":"10.1109\/22.798002","article-title":"Magnetism from conductors and enhanced nonlinear phenomena","volume":"47","author":"Pendry","year":"1999","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Caloz, C., and Itoh, T. (2005). Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications, Wiley-IEEE Press.","DOI":"10.1002\/0471754323"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"9971","DOI":"10.1109\/JSEN.2018.2873544","article-title":"Microwave sensor for detection of solid material permittivity in single\/multilayer samples with high quality factor","volume":"18","author":"Kiani","year":"2018","journal-title":"IEEE Sens. J."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"563","DOI":"10.1109\/LMWC.2014.2318900","article-title":"Complementary split-ring resonators for measuring dielectric constants and loss tangents","volume":"24","author":"Lee","year":"2014","journal-title":"IEEE Microw. Wireless Compon. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"247","DOI":"10.1109\/TMTT.2015.2503764","article-title":"Noncontact measurement of complex permittivity and thickness by using planar resonators","volume":"64","author":"Yang","year":"2016","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"3864","DOI":"10.1109\/TMTT.2016.2610423","article-title":"Transmission lines loaded with pairs of stepped impedance resonators: Modeling and application to differential permittivity measurements","volume":"64","author":"Naqui","year":"2016","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Puentes, M., Wei\u00df, C., Sch\u00fc\u00dfler, M., and Jakoby, R. (2011, January 5\u201310). Sensor array based on split ring resonators for analysis of organic tissues. Proceedings of the IEEE MTT-S International Microwave Symposium, Baltimore, MD, USA.","DOI":"10.1109\/MWSYM.2011.5973328"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"16111","DOI":"10.1109\/JSEN.2022.3191345","article-title":"Dual-band independent permittivity sensor using single-port with a pair of U-shaped structures for solid material detection","volume":"22","author":"Alam","year":"2022","journal-title":"IEEE Sens. J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"972","DOI":"10.1109\/TMTT.2012.2231877","article-title":"A microwave and microfluidic planar resonator for efficient and accurate complex permittivity characterization of aqueous solutions","volume":"61","author":"Chretiennot","year":"2013","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"679","DOI":"10.1109\/TMTT.2014.2300066","article-title":"Novel microwave microfluidic sensor using a microstrip split-ring resonator","volume":"62","author":"Abduljabar","year":"2014","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1345","DOI":"10.1109\/JSEN.2013.2295312","article-title":"High-sensitivity metamaterial-inspired sensor for microfluidic dielectric characterization","volume":"14","author":"Ebrahimi","year":"2014","journal-title":"IEEE Sens. J."},{"key":"ref_23","first-page":"3501104","article-title":"Microwave Spoof Surface Plasmon Sensor for Dielectric Material Characterization","volume":"6","author":"Mira","year":"2022","journal-title":"IEEE Sens. Lett."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"10647","DOI":"10.1109\/JSEN.2021.3063112","article-title":"Phase-variation microwave sensor for permittivity measurements based on a high-impedance half-wavelength transmission line","volume":"21","author":"Su","year":"2021","journal-title":"IEEE Sens. J."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Hong, J.-S., and Lancaster, M.J. (2001). Microstrip Filters for RF\/Microwave Applications, John Wiley & Sons, Inc.","DOI":"10.1002\/0471221619"},{"key":"ref_26","unstructured":"(2023, May 26). RT\/duroid\u00ae 5870 Laminates. Available online: https:\/\/www.rogerscorp.com\/advanced-electronics-solutions\/rt-duroid-laminates\/rt-duroid-5870-laminates."},{"key":"ref_27","unstructured":"(2023, May 26). RT\/duroid\u00ae 5880 Laminates. Available online: https:\/\/www.rogerscorp.com\/advanced-electronics-solutions\/rt-duroid-laminates\/rt-duroid-5880-laminates."},{"key":"ref_28","unstructured":"(2023, May 26). PTFE. Available online: https:\/\/www.directplastics.co.uk\/pdf\/datasheets\/ptfe-data-sheet.pdf."},{"key":"ref_29","unstructured":"(2023, May 26). Alumina Substrates. Available online: https:\/\/www.maruwa-g.com\/e\/products\/ceramic\/000256.html."},{"key":"ref_30","unstructured":"(2023, May 26). RO3003G2\u2122 Laminates. Available online: https:\/\/www.rogerscorp.com\/advanced-electronics-solutions\/ro3000-series-laminates\/ro3003g2-laminates."},{"key":"ref_31","unstructured":"(2023, May 26). RO3006\u2122 Laminates. Available online: https:\/\/www.rogerscorp.com\/advanced-electronics-solutions\/ro3000-series-laminates\/ro3006-laminates."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"27450","DOI":"10.1109\/JSEN.2021.3124329","article-title":"Low-cost CSRR based sensor for determination of dielectric constant of liquid samples","volume":"21","author":"Buragohain","year":"2021","journal-title":"IEEE Sens. J."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"8006511","DOI":"10.1109\/TIM.2022.3210937","article-title":"A dual-band resonator sensor for low permittivity characterization","volume":"71","author":"Liu","year":"2022","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1687","DOI":"10.1109\/TMTT.2022.3222419","article-title":"Design of uncoupled and cascaded array of resonant microwave sensors for dielectric characterization of liquids","volume":"71","author":"Chavoshi","year":"2023","journal-title":"IEEE Trans. Microw. Theory Tech."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1234","DOI":"10.1109\/JSEN.2022.3225662","article-title":"A low-cost and accurate microwave sensor system for permittivity characterization","volume":"23","author":"Pourafzal","year":"2023","journal-title":"IEEE Sens. J."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/11\/5306\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T19:48:21Z","timestamp":1760125701000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/11\/5306"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,6,2]]},"references-count":35,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2023,6]]}},"alternative-id":["s23115306"],"URL":"https:\/\/doi.org\/10.3390\/s23115306","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,6,2]]}}}