{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,28]],"date-time":"2026-03-28T09:43:44Z","timestamp":1774691024476,"version":"3.50.1"},"reference-count":38,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2021,11,11]],"date-time":"2021-11-11T00:00:00Z","timestamp":1636588800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010663","name":"European Research Council","doi-asserted-by":"publisher","award":["695070"],"award-info":[{"award-number":["695070"]}],"id":[{"id":"10.13039\/100010663","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In situ measurements are highly desirable in many microfluidic applications because they enable real-time, local monitoring of physical and chemical parameters, providing valuable insight into microscopic events and processes that occur in microfluidic devices. Unfortunately, the manufacturing of microfluidic devices with integrated sensors can be time-consuming, expensive, and \u201cknow-how\u201d demanding. In this article, we describe an easy-to-implement method developed to integrate various \u201coff-the-shelf\u201d fiber optic sensors within microfluidic devices. To demonstrate this, we used commercial pH and pressure sensors (\u201cpH SensorPlugs\u201d and \u201cFOP-MIV\u201d, respectively), which were \u201creversibly\u201d attached to a glass microfluidic device using custom 3D-printed connectors. The microfluidic device, which serves here as a demonstrator, incorporates a uniform porous structure and was manufactured using a picosecond pulsed laser. The sensors were attached to the inlet and outlet channels of the microfluidic pattern to perform simple experiments, the aim of which was to evaluate the performance of both the connectors and the sensors in a practical microfluidic environment. The bespoke connectors ensured robust and watertight connection, allowing the sensors to be safely disconnected if necessary, without damaging the microfluidic device. The pH SensorPlugs were tested with a pH 7.01 buffer solution. They measured the correct pH values with an accuracy of \u00b10.05 pH once sufficient contact between the injected fluid and the measuring element (optode) was established. In turn, the FOP-MIV sensors were used to measure local pressure in the inlet and outlet channels during injection and the steady flow of deionized water at different rates. These sensors were calibrated up to 140 mbar and provided pressure measurements with an uncertainty that was less than \u00b11.5 mbar. Readouts at a rate of 4 Hz allowed us to observe dynamic pressure changes in the device during the displacement of air by water. In the case of steady flow of water, the pressure difference between the two measuring points increased linearly with increasing flow rate, complying with Darcy\u2019s law for incompressible fluids. These data can be used to determine the permeability of the porous structure within the device.<\/jats:p>","DOI":"10.3390\/s21227493","type":"journal-article","created":{"date-parts":[[2021,11,11]],"date-time":"2021-11-11T23:04:46Z","timestamp":1636671886000},"page":"7493","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Manufacturing of Microfluidic Devices with Interchangeable Commercial Fiber Optic Sensors"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3604-9538","authenticated-orcid":false,"given":"Krystian L.","family":"Wlodarczyk","sequence":"first","affiliation":[{"name":"Research Centre for Carbon Solutions (RCCS), School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK"},{"name":"Applied Optics and Photonics (AOP) Group, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"William N.","family":"MacPherson","sequence":"additional","affiliation":[{"name":"Applied Optics and Photonics (AOP) Group, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7699-4617","authenticated-orcid":false,"given":"Duncan P.","family":"Hand","sequence":"additional","affiliation":[{"name":"Applied Optics and Photonics (AOP) Group, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1643-2863","authenticated-orcid":false,"given":"M. Mercedes","family":"Maroto-Valer","sequence":"additional","affiliation":[{"name":"Research Centre for Carbon Solutions (RCCS), School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, UK"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,11]]},"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","unstructured":"Hughes, M.P., and Hoettges, K.F. (2010). The Application of Microfluidics in Biology. Microengineering in Biotechnology, Springer Science & Business Media.","DOI":"10.1007\/978-1-60327-106-6"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"181","DOI":"10.1038\/nature13118","article-title":"The present and future role of microfluidics in biomedical research","volume":"507","author":"Sackmann","year":"2014","journal-title":"Nature"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.coche.2014.12.001","article-title":"Microfluidics for advanced drug delivery systems","volume":"7","author":"Riahi","year":"2015","journal-title":"Curr. Opin. Chem. Eng."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Sosa-Hernandez, E.J., Villalba-Rodriguez, A.M., Romero-Castillo, K.D., Aguilar-Aguila-Isaias, M.A., Garcia-Reyes, I.E., Hernandez-Antonio, A., Ahmed, I., Sharma, A., Parra-Saldivar, R., and Iqbal, H.M.N. (2018). Organs-on-a-Chip Module: A Review from the Development and Applications Perspective. Micromachines, 9.","DOI":"10.3390\/mi9100536"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1016\/j.coph.2019.09.008","article-title":"Microfluidics for personalized drug screening of cancer","volume":"48","author":"Menon","year":"2019","journal-title":"Curr. Opin. Pharmacol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"238","DOI":"10.1016\/j.jpha.2018.12.001","article-title":"Application of microfluidic chip technology in pharmaceutical analysis: A review","volume":"9","author":"Cui","year":"2019","journal-title":"J. Pharm. Anal."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"e2154","DOI":"10.1002\/rmv.2154","article-title":"Microfluidic devices for detection of RNA viruses","volume":"31","author":"Basiri","year":"2021","journal-title":"Rev. Med. Virol."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Niculescu, A.-G., Chircov, C., Birca, A.C., and Grumezescu, A.M. (2021). Fabrication and Applications of Microfluidic Devices: A Review. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22042011"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Winkler, S., Gr\u00fcnberger, A., and Bahnemann, J. (2021). Microfluidics in Biotechnology: Quo Vadis. Advances in Biochemical Engineering\/Biotechnology, Springer.","DOI":"10.1007\/10_2020_162"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Jaywant, S.A., and Airf, K.M. (2019). A Comprehensive Review of Microfluidic Water Quality Monitoring Sensors. Sensors, 19.","DOI":"10.3390\/s19214781"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Karadimitriou, N.K., and Hassanizadeh, S.M. (2012). A review of micromodels and their use in two-phase flow studies. Vadose Zone J., 11.","DOI":"10.2136\/vzj2011.0072"},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Yu, X.-Y. (2016). Microfluidics in CO2 Capture, Sequestration, and Applications. Advances in Microfluidics-New Applications in Biology, Energy, and Materials Sciences, IntechOpen.","DOI":"10.5772\/60788"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"430","DOI":"10.1016\/j.fuel.2016.08.058","article-title":"An experimental investigation of nanoparticle-stabilized CO2 foam used in enhanced oil recovery","volume":"186","author":"Guo","year":"2016","journal-title":"Fuel"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2740","DOI":"10.1039\/C7LC00301C","article-title":"Microfluidic and nanofluidic phase behaviour characterization for industrial CO2, oil and gas","volume":"17","author":"Bao","year":"2017","journal-title":"Lab Chip"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"6178","DOI":"10.1002\/2017WR020850","article-title":"Micro-PIV measurements of multiphase flow of water and liquid CO2 in 2-D heterogeneous porous micromodels","volume":"53","author":"Li","year":"2017","journal-title":"Water Resour. Res."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Gogoi, S., and Gogoi, S.B. (2019). Review on microfluidic studies for EOR application. J. Pet. Explor. Prod. Technol., 1\u201315.","DOI":"10.1007\/s13202-019-0610-4"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"e2019WR025420","DOI":"10.1029\/2019WR025420","article-title":"Assessing the Kinetics and Pore-Scale Characteristics of Biological Calcium Carbonate Precipitation in Porous Media using a Microfluidic Chip Experiment","volume":"56","author":"Kim","year":"2020","journal-title":"Water Resour. Res."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Jahanbakhsh, A., Wlodarczyk, K.L., Hand, D.P., Maier, R.R.J., and Maroto-Valer, M.M. (2020). Review of microfluidic devices and imaging techniques for fluid flow study in porous geomaterials. Sensors, 20.","DOI":"10.3390\/s20144030"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"4228","DOI":"10.1021\/es204096w","article-title":"Dewetting of silica surfaces upon reactions with supercritical CO2 and brine: Pore-scale studies in micromodels","volume":"46","author":"Kim","year":"2012","journal-title":"Environ. Sci. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"044111","DOI":"10.1063\/1.4955155","article-title":"A microfluidic optical platform for real-time monitoring of pH and oxygen in microfluidic bioreactors and organ-on-chip devices","volume":"10","author":"Shaegh","year":"2016","journal-title":"Biomicrofluidics"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1016\/j.mex.2019.03.025","article-title":"A semi-experimental procedure for the estimation of permeability of microfluidic pore network","volume":"6","author":"Pradhan","year":"2019","journal-title":"MethodsX"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1007\/s11242-018-1000-y","article-title":"Manufacturing a micro-model with integrated fibre optic pressure sensors","volume":"122","author":"Zarikos","year":"2018","journal-title":"Transp. Porous Med."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Lei, K.F. (2014). Review on Impedance Detection of Cellular Responses in Micro\/Nano Environment. Micromachines, 5.","DOI":"10.3390\/mi5010001"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1036","DOI":"10.1039\/D0LC01133A","article-title":"Microfluidic electrical impedance assessment of red blood cell-mediated microvascular occlusion","volume":"21","author":"Man","year":"2021","journal-title":"Lab Chip"},{"key":"ref_26","first-page":"1","article-title":"Thermal Measurement Techniques in Analytical Microfluidic Devices","volume":"100","author":"Davaji","year":"2015","journal-title":"J. Vis. Exp."},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Viefhues, M. (2020). Analytics in Microfluidic Systems. Advances in Biochemical Engineering\/Biotechnology, Springer.","DOI":"10.1007\/10_2020_131"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"233501","DOI":"10.1063\/1.4984897","article-title":"Lab-on-chip microfluidic impedance measurement for laminar flow ratio sensing and differential conductivity difference detection","volume":"110","author":"Kong","year":"2017","journal-title":"Appl. Phys. Lett."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"748","DOI":"10.1016\/j.snb.2016.01.050","article-title":"Online analysis of oxygen inside silicon-glass microreactors with integrated optical sensors","volume":"228","author":"Ehgartner","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"2693","DOI":"10.1039\/C7LC00538E","article-title":"Integration and application of optical chemical sensors in microbioreactors","volume":"17","author":"Gruber","year":"2017","journal-title":"Lab Chip"},{"key":"ref_31","unstructured":"(2021, April 21). pH SensorPlug. Available online: https:\/\/www.presens.de\/products\/detail\/ph-sensorplug."},{"key":"ref_32","unstructured":"(2021, September 09). Medical Pressure Montoring. Available online: https:\/\/fiso.com\/wp-content\/uploads\/2018\/10\/MC-00263_-Medical-Pressure-Monitoring-Product-Datasheet_R7.pdf."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"17115","DOI":"10.3390\/s150717115","article-title":"Optical fibre pressure sensors in medical applications","volume":"15","author":"Poeggel","year":"2015","journal-title":"Sensors"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"20215","DOI":"10.1038\/s41598-019-56711-5","article-title":"Maskless, rapid manufacturing of glass microfluidic devices using a picosecond pulsed laser","volume":"9","author":"Wlodarczyk","year":"2019","journal-title":"Sci. Rep."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Wlodarczyk, K.L., Carter, R.M., Jahanbakhsh, A., Lopes, A.A., Mackenzie, M.D., J Maier, R.R., Hand, D.P., and Maroto-Valer, M.M. (2018). Rapid laser manufacturing of microfluidic devices from glass substrates. Micromachines, 9.","DOI":"10.3390\/mi9080409"},{"key":"ref_36","unstructured":"Giancoli, D.C. (2016). Pressure in fluids. Physics-Principles with Applications, Pearson Education Ltd."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Schomburg, W.K. (2011). Membranes. Introduction to Microsystem Design, Springer.","DOI":"10.1007\/978-3-642-19489-4"},{"key":"ref_38","unstructured":"(2021, November 09). Microfluidic ChipShop Lab-on-a-Chip Catalogue 06\/2013. Available online: http:\/\/www.microfluidic-chipshop.eu\/Download\/Lab-on-a-chip_06-2013_150dpi.pdf."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/22\/7493\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:28:34Z","timestamp":1760167714000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/22\/7493"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,11,11]]},"references-count":38,"journal-issue":{"issue":"22","published-online":{"date-parts":[[2021,11]]}},"alternative-id":["s21227493"],"URL":"https:\/\/doi.org\/10.3390\/s21227493","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,11,11]]}}}