{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,17]],"date-time":"2025-12-17T18:07:10Z","timestamp":1765994830818,"version":"build-2065373602"},"reference-count":43,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2021,5,11]],"date-time":"2021-05-11T00:00:00Z","timestamp":1620691200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"La Red Nacional Espanyola de Microfluidica","award":["RED2018-102829-T"],"award-info":[{"award-number":["RED2018-102829-T"]}]},{"name":"European regional development Funds (FEDER)","award":["CTQ2017-84966-C2-1-R"],"award-info":[{"award-number":["CTQ2017-84966-C2-1-R"]}]},{"name":"Spanish Ministry of Economy and Competitivity","award":["CTQ2017-84966-C2-1-R"],"award-info":[{"award-number":["CTQ2017-84966-C2-1-R"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Microfluidic paper-based analytical devices (\u00b5PADs) are a promising technology to enable accurate and quantitative in situ assays. Paper\u2019s inherent hydrophilicity drives the fluids without the need for external pressure sources. However, controlling the flow in the porous medium has remained a challenge. This study addresses this problem from the nature of the paper substrate and its design. A computational fluid dynamic model has been developed, which couples the characteristics of the porous media (fiber length, fiber diameter and porosity) to the fluidic performance of the diffusion-based \u00b5PAD sensor. The numerical results showed that for a given porous membrane, the diffusion, and therefore the sensor performance is affected not only by the substrate nature but also by the inlets\u2019 orientation. Given a porous substrate, the optimum performance is achieved by the lowest inlets\u2019 angle. A diffusion-based self-referencing colorimetric sensor was built and validated according to the design. The device is able to quantify the hydronium concentration in wines by comparison to 0.1\u20131.0 M tartaric acid solutions with a 41.3 mM limit of detection. This research showed that by proper adjustments even the simplest \u00b5PADs can be used in quantitative assays for agri-food applications.<\/jats:p>","DOI":"10.3390\/s21103328","type":"journal-article","created":{"date-parts":[[2021,5,11]],"date-time":"2021-05-11T22:53:40Z","timestamp":1620773620000},"page":"3328","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Flow Control in Porous Media: From Numerical Analysis to Quantitative \u03bcPAD for Ionic Strength Measurements"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3496-2833","authenticated-orcid":false,"given":"Pouya","family":"Mehrdel","sequence":"first","affiliation":[{"name":"Mechanical Engineering Department\u2014Microtech Lab., Universitat Politecnica de Catalunya, C\/Colom 7-11, CP 08222 Terrassa, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1687-0196","authenticated-orcid":false,"given":"Hamid","family":"Khosravi","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department\u2014Microtech Lab., Universitat Politecnica de Catalunya, C\/Colom 7-11, CP 08222 Terrassa, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6701-4285","authenticated-orcid":false,"given":"Shadi","family":"Karimi","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department\u2014Microtech Lab., Universitat Politecnica de Catalunya, C\/Colom 7-11, CP 08222 Terrassa, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0082-9770","authenticated-orcid":false,"given":"Joan Antoni L\u00f3pez","family":"Mart\u00ednez","sequence":"additional","affiliation":[{"name":"Department of Mining, Industrial and ICT Engineering (EMIT), Universitat Politecnica de Catalunya, AV. Bases de Manresa 61-73, CP 08240 Manresa, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1368-3950","authenticated-orcid":false,"given":"Jasmina","family":"Casals-Terr\u00e9","sequence":"additional","affiliation":[{"name":"Mechanical Engineering Department\u2014Microtech Lab., Universitat Politecnica de Catalunya, C\/Colom 7-11, CP 08222 Terrassa, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"368","DOI":"10.1038\/nature05058","article-title":"The origins and the future of microfluidics","volume":"442","author":"Whitesides","year":"2006","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.aca.2017.11.010","article-title":"Review on microfluidic paper-based analytical devices towards commercialisation","volume":"1001","author":"Akyazi","year":"2018","journal-title":"Anal. 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