{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T00:56:25Z","timestamp":1777424185873,"version":"3.51.4"},"reference-count":41,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2020,6,27]],"date-time":"2020-06-27T00:00:00Z","timestamp":1593216000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>This study explores three unique approaches for closing valves and channels within microfluidic systems, specifically multilayer, centrifugally driven polymeric devices. Precise control over the cessation of liquid movement is achieved through either the introduction of expanding polyurethane foam, the application of direct contact heating, or the redeposition of xerographic toner via chloroform solvation and evaporation. Each of these techniques modifies the substrate of the microdevice in a different way. All three are effective at closing a previously open fluidic pathway after a desired unit operation has taken place, i.e., sample metering, chemical reaction, or analytical measurement. Closing previously open valves and channels imparts stringent fluidic control\u2014preventing backflow, maintaining pressurized chambers within the microdevice, and facilitating sample fractionation without cross-contamination. As such, a variety of microfluidic bioanalytical systems would benefit from the integration of these valving approaches.<\/jats:p>","DOI":"10.3390\/mi11070627","type":"journal-article","created":{"date-parts":[[2020,6,29]],"date-time":"2020-06-29T05:28:56Z","timestamp":1593408536000},"page":"627","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Closable Valves and Channels for Polymeric Microfluidic Devices"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0327-1223","authenticated-orcid":false,"given":"Charles","family":"Clark","sequence":"first","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8722-5410","authenticated-orcid":false,"given":"M.","family":"Woolf","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sarah","family":"Karstens","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hannah","family":"Lewis","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Aeren","family":"Nauman","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"James","family":"Landers","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Virginia, Charlottesville, VA 22903, USA"},{"name":"Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA 22903, USA"},{"name":"Departments of Mechanical Engineering and Pathology, University of Virginia, Charlottesville, VA 22903, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,6,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2680","DOI":"10.1039\/c004980h","article-title":"Optically addressable single-use microfluidic valves by laser printer lithography","volume":"10","author":"Kurzbuch","year":"2010","journal-title":"Lab Chip"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"483","DOI":"10.1016\/j.biotechadv.2007.05.003","article-title":"Micropumps, microvalves, and micromixers within PCR microfluidic chips: Advances and trends","volume":"25","author":"Zhang","year":"2007","journal-title":"Biotechnol. 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