{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T07:20:27Z","timestamp":1769930427360,"version":"3.49.0"},"reference-count":31,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2022,1,28]],"date-time":"2022-01-28T00:00:00Z","timestamp":1643328000000},"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>This study aimed to design and fabricate planar constricted\u2013expanded structures that are integrated into paper-based channels in order to enhance their chaotic advection and improve their mixing performance. Chromatography papers were used to print paper-based microfluidics using a solid-wax printer. Three different constricted\u2013expanded structures\u2014i.e., zigzag, crossed, and curved channels\u2014were designed in order to evaluate their mixing performance in comparison with that of straight channels. A numerical simulation was performed in order to investigate the mixing mechanism, and to examine the ways in which the planar constricted\u2013expanded structures affected the flow patterns. The experimental and numerical results indicated that the proposed structures can successfully mix confluents. The experimental results revealed that the mixing indices (\u03c3) rose from the initial 20.1% (unmixed) to 34.5%, 84.3%, 87.3%, and 92.4% for the straight, zigzag, curved, and cross-shaped channels, respectively. In addition, the numerical calculations showed a reasonable agreement with the experimental results, with a variation in the range of 1.0\u201311.0%. In future, we hope that the proposed passive paper-based mixers will be a crucial component in the application of paper-based microfluidic devices.<\/jats:p>","DOI":"10.3390\/s22031028","type":"journal-article","created":{"date-parts":[[2022,1,29]],"date-time":"2022-01-29T01:43:27Z","timestamp":1643420607000},"page":"1028","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["Paper-Based Microfluidics Perform Mixing Effects by Utilizing Planar Constricted\u2013Expanded Structures to Enhance Chaotic Advection"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5553-5833","authenticated-orcid":false,"given":"Chen-Hsun","family":"Weng","sequence":"first","affiliation":[{"name":"Medical Device Innovation Center, National Cheng Kung University, Tainan 70403, Taiwan"}]},{"given":"Pei-Pei","family":"Hsu","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Automation Engineering, I-Shou University, Kaohsiung 84001, Taiwan"}]},{"given":"An-Yu","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Automation Engineering, I-Shou University, Kaohsiung 84001, Taiwan"}]},{"given":"Jr-Lung","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Mechanical and Automation Engineering, I-Shou University, Kaohsiung 84001, Taiwan"}]}],"member":"1968","published-online":{"date-parts":[[2022,1,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"677","DOI":"10.1016\/j.snb.2017.12.034","article-title":"Recent advances and applications of micromixers","volume":"259","author":"Lee","year":"2018","journal-title":"Sens. Actuators B Chem."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1038\/scientificamerican0189-56","article-title":"The mixing of fluids","volume":"260","author":"Ottino","year":"1989","journal-title":"Sci. Am."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"R1","DOI":"10.1088\/0960-1317\/15\/2\/R01","article-title":"Micromixers\u2014A review","volume":"15","author":"Nguyen","year":"2005","journal-title":"J. Micromech. Microeng."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"274","DOI":"10.3390\/mi8090274","article-title":"A review on micromixers","volume":"8","author":"Zhang","year":"2017","journal-title":"Micromachines"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"268","DOI":"10.1109\/JMEMS.2020.2975560","article-title":"Multiphysics Analysis and Practical Implementation of a Soft \u03bc-Actuator-Based Microfluidic Micromixer","volume":"29","author":"Annabestani","year":"2020","journal-title":"J. Microelectromech. Syst."},{"key":"ref_6","unstructured":"Annabestani, M., Mohammadzadeh, H., Aghassizadeh, A., Azizmohseni, S., and Fardmanesh, M. (May, January 30). Active Microfluidic Micromixer Design using Ionic Polymer-Metal Composites. Proceedings of the 27th Iranian Conference on Electrical Engineering (ICEE), Yazd, Iran."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"10217","DOI":"10.1039\/C5AY01061F","article-title":"Ionic electroactive polymer actuators as active microfluidic mixers","volume":"7","author":"Meis","year":"2015","journal-title":"Anal. Methods"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1109\/84.846699","article-title":"Passive mixing in a three-dimensional serpentine microchannel","volume":"9","author":"Liu","year":"2000","journal-title":"J. Microelectromech. Syst."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"5306","DOI":"10.1021\/ac0257389","article-title":"Patterning flows using grooved surfaces","volume":"74","author":"Stroock","year":"2002","journal-title":"Anal. Chem."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"647","DOI":"10.1126\/science.1066238","article-title":"Chaotic mixer for microchannels","volume":"295","author":"Stroock","year":"2002","journal-title":"Science"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1039\/b305892a","article-title":"A novel in-plane passive microfluidic mixer with modified Tesla structures","volume":"4","author":"Hong","year":"2004","journal-title":"Lab Chip"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2479","DOI":"10.1016\/j.ces.2004.11.033","article-title":"Micromixers\u2014A review on passive and active mixing principles","volume":"60","author":"Hessel","year":"2005","journal-title":"Chem. Eng. Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"774","DOI":"10.1016\/j.bios.2015.10.032","article-title":"Fabrication techniques for microfluidic paper-based analytical devices and their applications for biological testing: A review","volume":"77","author":"Xia","year":"2016","journal-title":"Biosens. Bioelectron."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"129681","DOI":"10.1016\/j.snb.2021.129681","article-title":"Paper-based microfluidics: Simplified fabrication and assay methods","volume":"336","author":"Nishat","year":"2021","journal-title":"Sens. Actuators B Chem."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Boobphahom, S., Ly, M.N., Pyun, N., Kwon, O.-S., Rodthongkum, N., and Shin, K. (2020). Recent Advances in Microfluidic Paper-Based Analytical Devices toward High-Throughput Screening. Molecules, 25.","DOI":"10.3390\/molecules25132970"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"78109","DOI":"10.1039\/C5RA09188H","article-title":"Fabrication of paper-based microfluidic analysis devices: A review","volume":"5","author":"He","year":"2015","journal-title":"RSC Adv."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Lim, H., Jafry, A.T., and Lee, J. (2019). Fabrication, Flow Control, and Applications of Microfluidic Paper-Based Analytical Devices. Molecules, 24.","DOI":"10.3390\/molecules24162869"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1016\/j.colsurfa.2015.12.033","article-title":"A comparative study of paper-based microfluidic devices with respect to channel geometry","volume":"492","author":"Jafry","year":"2016","journal-title":"Colloids Surf. A Physicochem. Eng. Aspects"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1318","DOI":"10.1002\/anie.200603817","article-title":"Patterned paper as a platform for inexpensive, low-volume, portable bioassays","volume":"46","author":"Martinez","year":"2007","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"120","DOI":"10.1039\/C6LC01250G","article-title":"Microfluidic PDMS on paper (POP) devices","volume":"17","author":"Shangguan","year":"2017","journal-title":"Lab Chip"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1497","DOI":"10.1002\/elps.200800563","article-title":"Rapid prototyping of paper-based microfluidics with wax for low-cost, portable bioassay","volume":"30","author":"Lu","year":"2009","journal-title":"Electrophoresis"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"649","DOI":"10.1007\/s00542-012-1469-1","article-title":"Investigation of wax and paper materials for the fabrication of paper-based microfluidic devices","volume":"18","author":"Zhong","year":"2012","journal-title":"Microsyst. Technol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"9258","DOI":"10.1039\/c3ra40828k","article-title":"Inkjet printing: An integrated and green chemical approach to microfluidic paper-based analytical devices","volume":"3","author":"Maejima","year":"2013","journal-title":"RSC Adv."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"441","DOI":"10.1016\/j.colsurfb.2009.09.032","article-title":"Biosurface engineering through ink jet printing","volume":"75","author":"Khan","year":"2010","journal-title":"Colloids Surf. B Biointerfaces"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"7091","DOI":"10.1021\/ac901071p","article-title":"Understanding wax printing: A simple micropatterning process for paper-based microfluidics","volume":"81","author":"Carrilho","year":"2009","journal-title":"Anal. Chem."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"6580","DOI":"10.1039\/C4AN01624F","article-title":"One-step polymer screen-printing for microfluidic paper-based analytical device (\u03bcPAD) fabrication","volume":"139","author":"Sameenoi","year":"2014","journal-title":"Analyst"},{"key":"ref_27","unstructured":"Green, H.C. (2019). Improving Paper-Based Microflfluidic Mixing with the Incorporation of Flow Disrupting Structures. [Master\u2019s Theses, Louisiana Tech University]."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"773","DOI":"10.1039\/C2LC21065G","article-title":"Uniform mixing in paper-based microfluidic systems using surface acoustic","volume":"12","author":"Rezk","year":"2012","journal-title":"Lab Chip"},{"key":"ref_29","first-page":"194","article-title":"A new method for paper porosity estimation","volume":"3","author":"Ku","year":"2018","journal-title":"TechConnect Briefs"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"205","DOI":"10.1016\/j.apnum.2013.07.001","article-title":"Navier\u2013Stokes\/Forchheimer models for filtration through porous media","volume":"72","author":"Cimolin","year":"2013","journal-title":"Appl. Numer. Math."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"757","DOI":"10.1088\/0960-1317\/16\/4\/012","article-title":"Active micro-mixers utilizing a gradient zeta potential induced by inclined buried shielding electrodes","volume":"16","author":"Lin","year":"2006","journal-title":"J. Micromech. Microeng."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/3\/1028\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T22:10:02Z","timestamp":1760134202000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/22\/3\/1028"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,1,28]]},"references-count":31,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2022,2]]}},"alternative-id":["s22031028"],"URL":"https:\/\/doi.org\/10.3390\/s22031028","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,1,28]]}}}