{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,22]],"date-time":"2026-01-22T11:56:16Z","timestamp":1769082976373,"version":"3.49.0"},"reference-count":28,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2018,9,26]],"date-time":"2018-09-26T00:00:00Z","timestamp":1537920000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100011263","name":"FP7 Nanosciences, Nanotechnologies, Materials and new Production Technologies","doi-asserted-by":"publisher","award":["FP7-CP-IP 214249"],"award-info":[{"award-number":["FP7-CP-IP 214249"]}],"id":[{"id":"10.13039\/100011263","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["FIS2015-70862"],"award-info":[{"award-number":["FIS2015-70862"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003329","name":"Ministerio de Econom\u00eda y Competitividad","doi-asserted-by":"publisher","award":["SEV-2013-0295"],"award-info":[{"award-number":["SEV-2013-0295"]}],"id":[{"id":"10.13039\/501100003329","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Hydrogel materials offer many advantages for chemical and biological sensoring due to their response to a small change in their environment with a related change in volume. Several designs have been outlined in the literature in the specific field of hydrogel-based optical sensors, reporting a large number of steps for their fabrication. In this work we present a three-dimensional, hydrogel-based sensor the structure of which is fabricated in a single step using thermal nanoimprint lithography. The sensor is based on a waveguide with a grating readout section. A specific hydrogel formulation, based on a combination of PEGDMA (Poly(Ethylene Glycol DiMethAcrylate)), NIPAAm (N-IsoPropylAcrylAmide), and AA (Acrylic Acid), was developed. This stimulus-responsive hydrogel is sensitive to pH and to water. Moreover, the hydrogel has been modified to be suitable for fabrication by thermal nanoimprint lithography. Once stimulated, the hydrogel-based sensor changes its topography, which is characterised physically by AFM and SEM, and optically using a specific optical set-up.<\/jats:p>","DOI":"10.3390\/s18103240","type":"journal-article","created":{"date-parts":[[2018,9,26]],"date-time":"2018-09-26T10:39:58Z","timestamp":1537958398000},"page":"3240","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Integrated 3D Hydrogel Waveguide Out-Coupler by Step-and-Repeat Thermal Nanoimprint Lithography: A Promising Sensor Device for Water and pH"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7757-9901","authenticated-orcid":false,"given":"Achille","family":"Francone","sequence":"first","affiliation":[{"name":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7051-5910","authenticated-orcid":false,"given":"Timothy","family":"Kehoe","sequence":"additional","affiliation":[{"name":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9132-6609","authenticated-orcid":false,"given":"Isabel","family":"Obieta","sequence":"additional","affiliation":[{"name":"Tecnalia Research &amp; Innovation, Mikeletegi 2, E-20009 San Sebasti\u00e1n, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4061-3410","authenticated-orcid":false,"given":"Virginia","family":"Saez-Martinez","sequence":"additional","affiliation":[{"name":"Tecnalia Research &amp; Innovation, Mikeletegi 2, E-20009 San Sebasti\u00e1n, Spain"}]},{"given":"Leire","family":"Bilbao","sequence":"additional","affiliation":[{"name":"Tecnalia Research &amp; Innovation, Mikeletegi 2, E-20009 San Sebasti\u00e1n, Spain"}]},{"given":"Ali Z.","family":"Khokhar","sequence":"additional","affiliation":[{"name":"Division of Biomedical Engineering, University Glasgow, Rankine Building, Glasgow G12 8LT, UK"}]},{"given":"Nikolaj","family":"Gadegaard","sequence":"additional","affiliation":[{"name":"Division of Biomedical Engineering, University Glasgow, Rankine Building, Glasgow G12 8LT, UK"}]},{"given":"Claudia Delgado","family":"Simao","sequence":"additional","affiliation":[{"name":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain"}]},{"given":"Nikolaos","family":"Kehagias","sequence":"additional","affiliation":[{"name":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9986-2716","authenticated-orcid":false,"given":"Clivia M.","family":"Sotomayor Torres","sequence":"additional","affiliation":[{"name":"Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona, Spain"},{"name":"Institucio Catalana de Recerca i Estudis Avan\u00e7ats (ICREA), 08010 Barcelona, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2018,9,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"42","DOI":"10.1016\/j.mtchem.2018.02.004","article-title":"Hydrogels as intelligent materials: A brief review of synthesis, properties and applications","volume":"8","author":"Mahinroosta","year":"2018","journal-title":"Mater. 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