{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2024,9,16]],"date-time":"2024-09-16T17:51:49Z","timestamp":1726509109069},"reference-count":34,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2021,10,6]],"date-time":"2021-10-06T00:00:00Z","timestamp":1633478400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003052","name":"Ministry of Trade, Industry and Energy","doi-asserted-by":"publisher","award":["Grant N0002310"],"id":[{"id":"10.13039\/501100003052","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"Flexible capacitive humidity sensors are promising for low-cost, wearable, and radio frequency identification sensors, but their nonlinear response is an important issue for practical applications. Herein, the linearity of humidity response was controlled by surface water wettability and operating frequency of sensor, and the mechanism was explained in detail by surface water condensation. For a sensor with a Ag interdigitated electrode (IDE) on a poly(ethylene terephthalate) substrate, the capacitance showed a small linear increase with humidity up to 70% RH but a large nonlinear increase in the higher range. The response linearity was increased by a hydrophobic surface treatment of self-assembled monolayer coating while it was decreased by an ultraviolet\/ozone irradiation for hydrophilicity. It was also increased by increasing the frequency in the range of 1\u2013100 kHz, more prominently on a more hydrophilic surface. Based on experiment and simulation, the increase in sensor capacitance was greatly dependent on the geometric pattern (e.g., size, number, and contact angle) and electrical permittivity of surface water droplets. A larger and more nonlinear humidity response resulted from a larger increase in the number of droplets with a smaller contact angle on a sensor surface with higher water wettability and also from a higher permittivity of water at a lower frequency.<\/jats:p>","DOI":"10.3390\/s21196633","type":"journal-article","created":{"date-parts":[[2021,10,11]],"date-time":"2021-10-11T01:37:49Z","timestamp":1633916269000},"page":"6633","source":"Crossref","is-referenced-by-count":2,"title":["Effects and Mechanism of Surface Water Wettability and Operating Frequency on Response Linearity of Flexible IDE Capacitive Humidity Sensor"],"prefix":"10.3390","volume":"21","author":[{"given":"Woo Seok","family":"Yang","sequence":"first","affiliation":[{"name":"ICT Creative Research Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea"}]},{"ORCID":"http:\/\/orcid.org\/0000-0002-6241-5223","authenticated-orcid":false,"given":"Seungoh","family":"Han","sequence":"additional","affiliation":[{"name":"Department of Robotics, Hoseo University, Asan 31499, Korea"}]},{"given":"Gyu-Ri","family":"Lim","sequence":"additional","affiliation":[{"name":"ICT Creative Research Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea"},{"name":"Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Korea"}]},{"ORCID":"http:\/\/orcid.org\/0000-0001-8105-1640","authenticated-orcid":false,"given":"Hyun You","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Materials Science and Engineering, Chungnam National University, Daejeon 34134, Korea"}]},{"given":"Sung-Hoon","family":"Hong","sequence":"additional","affiliation":[{"name":"ICT Creative Research Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 34129, Korea"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1109\/7361.983470","article-title":"Micromachined water vapor sensors: A review of sensing technologies","volume":"1","author":"Fenner","year":"2001","journal-title":"IEEE Sens. J."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"7881","DOI":"10.3390\/s140507881","article-title":"Humidity sensors principle, mechanism, and fabrication technologies: A comprehensive review","volume":"14","author":"Farahani","year":"2014","journal-title":"Sensors"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1800969","DOI":"10.1002\/admi.201800969","article-title":"Organic thin-film capacitive and resistive humidity sensors: A focus review","volume":"5","author":"Najeeb","year":"2018","journal-title":"Adv. Mater. Interfaces"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"869","DOI":"10.1166\/sl.2011.1633","article-title":"Printed capacitive based humidity sensors on flexible substrates","volume":"9","author":"Reddy","year":"2011","journal-title":"Sens. Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"404","DOI":"10.1016\/j.snb.2007.10.010","article-title":"Capacitive humidity sensors on flexible RFID labels","volume":"132","author":"Oprea","year":"2008","journal-title":"Sens. Actuators B Chem."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"123","DOI":"10.1016\/j.snb.2013.12.117","article-title":"Design and characterization of a low thermal drift capacitive humidity sensor by inkjet-printing","volume":"195","author":"Rivadeneyra","year":"2014","journal-title":"Sens. Actuators B Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"126973","DOI":"10.1016\/j.snb.2019.126973","article-title":"High sensitivity portable capacitive humidity sensor based on In2O3 nanocubes-decorated GO nanosheets and its wearable application in respiration detection","volume":"299","author":"Li","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"112360","DOI":"10.1016\/j.bios.2020.112360","article-title":"One-step and large-scale fabrication of flexible and wearable humidity sensor based on laser-induced graphene for real-time tracking of plant transpiration at bio-interface","volume":"165","author":"Lan","year":"2020","journal-title":"Biosens. Bioelectron."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"13628","DOI":"10.3390\/s140813628","article-title":"Humidity sensors printed on recycled paper and cardboard","volume":"14","author":"Muck","year":"2014","journal-title":"Sensors"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"459","DOI":"10.1016\/j.snb.2019.02.043","article-title":"Design, fabrication and characterization of capacitive humidity sensors based on emerging flexible technologies","volume":"287","author":"Romero","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Boudaden, J., Steinma\u00dfl, M., Endres, H.-E., Drost, A., Eisele, I., Kutter, C., and M\u00fcller-Buschbaum, P. (2018). Polyimide-based capacitive humidity sensor. Sensors, 18.","DOI":"10.3390\/s18051516"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"1220","DOI":"10.1109\/T-ED.1985.22104","article-title":"A polyimide-based capacitive humidity sensor","volume":"32","author":"Schubert","year":"1985","journal-title":"IEEE Trans. Electron Devices"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1862","DOI":"10.1149\/1.2085886","article-title":"A capacitive-type humidity sensor using cross-linked poly(methyl methacrylate) thin films","volume":"38","author":"Matsuguchi","year":"1991","journal-title":"J. Electrochem. Soc."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/j.snb.2004.08.028","article-title":"A capacitive humidity sensor using cross-linked cellulose acetate butyrate","volume":"106","author":"Lacabanne","year":"2005","journal-title":"Sens. Actuators B Chem."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Comini, E., Faglia, G., and Sberveglieri, G. (2009). Chapter 3: Capacitive-type relative humidity sensor with hydrophobic polymer films. Solid State Gas Sensing, Springer.","DOI":"10.1007\/978-0-387-09665-0"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"212","DOI":"10.1016\/j.snb.2018.10.061","article-title":"Highly transparent humidity sensor with thin cellulose acetate butyrate and hydrophobic AF1600X vapor permeating layers fabricated by screen printing","volume":"281","author":"Zhou","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Fan, Z., Zhi, C., Wu, L., Zhang, P., Feng, C., Deng, L., Yu, B., and Qian, L. (2019). UV\/ozone-assisted rapid formation of high-quality tribological self-assembled monolayer. Coatings, 9.","DOI":"10.3390\/coatings9110762"},{"key":"ref_18","first-page":"37374","article-title":"Stability of UV\/ozone-treated thermoplastics under different storage conditions for microfluidic analytical devices","volume":"7","author":"Lin","year":"2017","journal-title":"RCS Adv."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"966","DOI":"10.1016\/j.jallcom.2017.09.092","article-title":"Simple fabrication of superoleophobic titanium surfaces via hierarchical microhorn\/nanoporous structure growth by chemical acid etching and anodization","volume":"728","author":"Lee","year":"2017","journal-title":"J. Alloys Compd."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"125013","DOI":"10.1088\/1361-6641\/aae96a","article-title":"Graphene-filter-mounted tin-oxide-nanowire-transistor for chemical sensor","volume":"33","author":"Kang","year":"2018","journal-title":"Semicond. Sci. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1804","DOI":"10.1038\/s41467-018-03954-x","article-title":"Transparent and attachable ionic communicators based on self-cleanable triboelectric nanogenerators","volume":"9","author":"Lee","year":"2018","journal-title":"Nat. Commun."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"434","DOI":"10.1109\/JSEN.2006.870161","article-title":"Design principles for multichannel fringing electric field sensors","volume":"6","author":"Li","year":"2006","journal-title":"IEEE Sens. J."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"913","DOI":"10.1109\/TIM.2018.2855538","article-title":"Design and characterization of a fringing field capacitive soil moisture sensor","volume":"68","author":"Goswami","year":"2019","journal-title":"IEEE Trans. Instrum. Meas."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.apsusc.2014.05.129","article-title":"Experimental study on surface modification of PET films under bipolar nanosecond-pulse dielectric barrier discharge in atmospheric air","volume":"313","author":"Liu","year":"2014","journal-title":"Appl. Surf. Sci."},{"key":"ref_25","unstructured":"K\u00fcchler, F., F\u00e4rber, R., and Franck, C.M. (July, January 22). Humidity and temperature effects on the dielectric properties of PET film. Proceedings of the 38th IEEE Electrical Insulation Conference (EIC), Virtual."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"327","DOI":"10.1016\/j.cplett.2011.01.027","article-title":"Dielectric spectroscopy of water at low frequencies: The existence of an isopermitive point","volume":"503","year":"2011","journal-title":"Chem. Phys. Lett."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"182","DOI":"10.4313\/TEEM.2013.14.4.182","article-title":"Humidity sensor using an air capacitor","volume":"14","author":"Choi","year":"2013","journal-title":"Trans. Electr. Electron. Mater."},{"key":"ref_28","unstructured":"Cular, S. (2021, June 01). The Measurement and Uncertainty of Air Dielectric Capacitors from 1 kHz to 10 MHz, Available online: https:\/\/www.osti.gov\/servlets\/purl\/1504063."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1859","DOI":"10.1166\/jnn.2014.9108","article-title":"Water condensation: A multiscale phenomenon","volume":"14","author":"Jensen","year":"2014","journal-title":"J. Nanosci. Nanotechnol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"250","DOI":"10.1038\/s41586-020-2978-1","article-title":"Capillary condensation under atomic-scale confinement","volume":"588","author":"Yang","year":"2020","journal-title":"Nature"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"14532","DOI":"10.1021\/la503615a","article-title":"Droplet nucleation on a well-defined hydrophilic\u2013hydrophobic surface of 10 nm order resolution","volume":"30","author":"Yamada","year":"2014","journal-title":"Langmuir"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"094101","DOI":"10.1063\/1.3200951","article-title":"Spatial control in the heterogeneous nucleation of water","volume":"95","author":"Varanasi","year":"2009","journal-title":"Appl. Phys. Lett."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"23687","DOI":"10.1038\/srep23687","article-title":"3D imaging of water-drop condensation on hydrophobic and hydrophilic lubricant-impregnated surfaces","volume":"6","author":"Kajiya","year":"2016","journal-title":"Sci. Rep."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"7383","DOI":"10.1021\/acs.langmuir.0c00915","article-title":"Molecular dynamics simulations of water condensation on surfaces with tunable wettability","volume":"36","author":"Ranathunga","year":"2020","journal-title":"Langmuir"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/19\/6633\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,7,19]],"date-time":"2024-07-19T19:14:55Z","timestamp":1721416495000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/19\/6633"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,6]]},"references-count":34,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2021,10]]}},"alternative-id":["s21196633"],"URL":"https:\/\/doi.org\/10.3390\/s21196633","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,10,6]]}}}