{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:48:12Z","timestamp":1760240892994,"version":"build-2065373602"},"reference-count":48,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2019,10,24]],"date-time":"2019-10-24T00:00:00Z","timestamp":1571875200000},"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>Presented here is the fabrication and characterization of a tunable microfluidic check valve for use in marine nutrient sensing. The ball-style valve makes use of a rare-earth permanent magnet, which exerts a pulling force to ensure it remains passively sealed until the prescribed cracking pressure is met. By adjusting the position of the magnet, the cracking pressure is shown to be customizable to meet design requirements. Further applicability is shown by integrating the valve into a poly(methyl methacrylate) (PMMA) lab-on-chip device with an integrated optical absorbance cell for nitrite detection in seawater. Micro-milling is used to manufacture both the valve and the micro-channel structures. The valve is characterized up to a flow rate of 14 mL min\u22121 and exhibits low leakage rates at high back pressures (&lt;2 \u00b5L min\u22121 at ~350 kPa). It is low cost, requires no power, and is easily implemented on microfluidic platforms.<\/jats:p>","DOI":"10.3390\/s19214619","type":"journal-article","created":{"date-parts":[[2019,10,25]],"date-time":"2019-10-25T03:20:36Z","timestamp":1571973636000},"page":"4619","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["A Magnetically Tunable Check Valve Applied to a Lab-on-Chip Nitrite Sensor"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2449-7731","authenticated-orcid":false,"given":"Sean C.","family":"Morgan","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, Dalhousie University, 1360 Barrington Street, Halifax, NS B3H 4R2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andre D.","family":"Hendricks","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, Dalhousie University, 1360 Barrington Street, Halifax, NS B3H 4R2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mae L.","family":"Seto","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, Dalhousie University, 1360 Barrington Street, Halifax, NS B3H 4R2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6289-9440","authenticated-orcid":false,"given":"Vincent J.","family":"Sieben","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, Dalhousie University, 1360 Barrington Street, Halifax, NS B3H 4R2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2019,10,24]]},"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","unstructured":"Kaka\u00e7, S., Kosoy, B., Li, D., and Pramuanjaroenkij, A. 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