{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,31]],"date-time":"2025-10-31T16:56:07Z","timestamp":1761929767843,"version":"build-2065373602"},"reference-count":28,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2015,3,26]],"date-time":"2015-03-26T00:00:00Z","timestamp":1427328000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>We report a naked eye refractive index sensor with a visible metamaterial absorber. The visible metamaterial absorber consisting of a silver dendritic\/dielectric\/metal structure shows multiple absorption peaks. By incorporating a gain material (rhodamine B) into the dielectric layer, the maximal magnitude of the absorption peak can be improved by about 30%. As the metamaterial absorber is sensitive to the refractive index of glucose solutions, it can function as a sensor that quickly responds to variations of the refractive index of the liquid. Meanwhile, since the response is presented via color changes, it can be clearly observed by the naked eyes. Further experiments have confirmed that the sensor can be  used repeatedly.<\/jats:p>","DOI":"10.3390\/s150407454","type":"journal-article","created":{"date-parts":[[2015,3,26]],"date-time":"2015-03-26T12:08:06Z","timestamp":1427371686000},"page":"7454-7461","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["A Naked Eye Refractive Index Sensor with a Visible Multiple  Peak Metamaterial Absorber"],"prefix":"10.3390","volume":"15","author":[{"given":"Heli","family":"Ma","sequence":"first","affiliation":[{"name":"Smart Materials Laboratory, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710129, China"}]},{"given":"Kun","family":"Song","sequence":"additional","affiliation":[{"name":"Smart Materials Laboratory, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710129, China"}]},{"given":"Liang","family":"Zhou","sequence":"additional","affiliation":[{"name":"Smart Materials Laboratory, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710129, China"}]},{"given":"Xiaopeng","family":"Zhao","sequence":"additional","affiliation":[{"name":"Smart Materials Laboratory, Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710129, China"}]}],"member":"1968","published-online":{"date-parts":[[2015,3,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"509","DOI":"10.1070\/PU1968v010n04ABEH003699","article-title":"The electrodynamics of substances with simultaneously negative values of \u03b5 and \u03bc","volume":"10","author":"Veselago","year":"1968","journal-title":"Sov. Phys. Usp."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"3966","DOI":"10.1103\/PhysRevLett.85.3966","article-title":"Negative refraction makes a perfect lens","volume":"85","author":"Pendry","year":"2000","journal-title":"Phys. Rev. Lett."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"9439","DOI":"10.1039\/c2jm15979a","article-title":"Bottom-up fabrication methods of optical metamaterials","volume":"22","author":"Zhao","year":"2012","journal-title":"J. Mater. Chem."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"977","DOI":"10.1126\/science.1133628","article-title":"Metamaterial electromagnetic cloak at microwave frequencies","volume":"314","author":"Schurig","year":"2006","journal-title":"Science"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"397","DOI":"10.1038\/nature06285","article-title":"\u201cTrapped rainbow\u201d storage of light in metamaterials","volume":"450","author":"Tsakmakidis","year":"2007","journal-title":"Nature"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"071111","DOI":"10.1063\/1.3211867","article-title":"Trapped rainbow effect in visible light left-handed heterostructures","volume":"95","author":"Zhao","year":"2009","journal-title":"Appl. Phys. Lett."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"26","DOI":"10.1016\/j.snb.2012.01.044","article-title":"A planar split-ring resonator-based microwave biosensor for label-free detection of biomolecules","volume":"169","author":"Lee","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"179","DOI":"10.1016\/j.snb.2013.04.113","article-title":"Implementation and testing of a compact and high-resolution sensing device based on grating-coupled surface plasmon resonance with polarization modulation","volume":"185","author":"Ruffato","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"207402","DOI":"10.1103\/PhysRevLett.100.207402","article-title":"Perfect metamaterial absorber","volume":"100","author":"Landy","year":"2008","journal-title":"Phys. Rev. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2342","DOI":"10.1021\/nl9041033","article-title":"Infrared perfect absorber and its application as plasmonic sensor","volume":"10","author":"Liu","year":"2010","journal-title":"Nano Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1443","DOI":"10.1021\/nl204118h","article-title":"Ultrabroadband light absorption by a sawtooth anisotropic metamaterial slab","volume":"12","author":"Cui","year":"2012","journal-title":"Nano Lett."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"221101","DOI":"10.1063\/1.4767646","article-title":"Ultra-thin perfect absorber employing a tunable phase change material","volume":"101","author":"Kats","year":"2012","journal-title":"Appl. Phys. Lett."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"031910","DOI":"10.1063\/1.4813914","article-title":"Isotropic Mie resonance-based metamaterial perfect absorber","volume":"103","author":"Liu","year":"2013","journal-title":"Appl. Phys. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"207403","DOI":"10.1103\/PhysRevLett.104.207403","article-title":"Infrared spatial and frequency selective metamaterial with near-unity absorbance","volume":"104","author":"Liu","year":"2010","journal-title":"Phys. Rev. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"945","DOI":"10.1364\/OL.36.000945","article-title":"A terahertz polarization insensitive dual band metamaterial absorber","volume":"36","author":"Ma","year":"2011","journal-title":"Opt. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1524","DOI":"10.1364\/OL.36.001524","article-title":"Polarization insensitive terahertz metamaterial absorber","volume":"36","author":"Grant","year":"2011","journal-title":"Opt. Lett."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"154102","DOI":"10.1063\/1.4757879","article-title":"Triple-band terahertz metamaterial absorber: Design, experiment, and physical interpretation","volume":"101","author":"Shen","year":"2012","journal-title":"Appl. Phys. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"735","DOI":"10.1038\/nature09278","article-title":"Loss-free and active optical negative-index metamaterials","volume":"466","author":"Xiao","year":"2012","journal-title":"Nature"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"031907","DOI":"10.1063\/1.4737643","article-title":"Light amplification in zero-index metamaterial with gain inserts","volume":"101","author":"Zhu","year":"2012","journal-title":"Appl. Phys. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"12688","DOI":"10.1364\/OE.19.012688","article-title":"Overcoming the losses of a split ring resonator array with gain","volume":"19","author":"Fang","year":"2011","journal-title":"Opt. Express"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"3523","DOI":"10.1002\/adfm.200800444","article-title":"Multiple pass-band optical left-handed metamaterials based on random dendritic cells","volume":"18","author":"Liu","year":"2008","journal-title":"Adv. Funct. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"21101","DOI":"10.1051\/epjap\/2010031","article-title":"Metamaterial absorber with random dendritic cells","volume":"50","author":"Zhu","year":"2010","journal-title":"EPJ. Appl. Phys."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2382","DOI":"10.1364\/JOSAB.26.002382","article-title":"Metamaterial absorber with dendritic cells at infrared frequencies","volume":"26","author":"Zhu","year":"2009","journal-title":"J. Opt. Soc. Am. B"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"181910","DOI":"10.1063\/1.4827824","article-title":"A green-light gain-assisted metamaterial fabricated by self-assembled electrochemical deposition","volume":"103","author":"Li","year":"2013","journal-title":"Appl. Phys. Lett."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"2348","DOI":"10.3390\/s100302348","article-title":"Refractive index sensor based on a 1D photonic crystal in a microfluidic channel","volume":"10","author":"Nunes","year":"2010","journal-title":"Sensors"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"34008","DOI":"10.1209\/0295-5075\/107\/34008","article-title":"All-optical on-chip sensor for high refractive index sensing in photonic crystals","volume":"107","author":"Liu","year":"2014","journal-title":"Europhys. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1208008","DOI":"10.3788\/CJL201441.1208008","article-title":"Accurate measurement of the refractive index D-Glucose solution at various concentrations at different temperature","volume":"41","author":"Song","year":"2014","journal-title":"Chin. J. Lasers"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"091902","DOI":"10.1063\/1.4794170","article-title":"Metamaterial optical refractive index sensor detected by the naked eye","volume":"102","author":"Wang","year":"2013","journal-title":"Appl. Phys. Lett."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/4\/7454\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T20:43:59Z","timestamp":1760215439000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/15\/4\/7454"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2015,3,26]]},"references-count":28,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2015,4]]}},"alternative-id":["s150407454"],"URL":"https:\/\/doi.org\/10.3390\/s150407454","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2015,3,26]]}}}