{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T13:47:31Z","timestamp":1780926451265,"version":"3.54.1"},"reference-count":37,"publisher":"MDPI AG","issue":"14","license":[{"start":{"date-parts":[[2023,7,8]],"date-time":"2023-07-08T00:00:00Z","timestamp":1688774400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Discovery Grants from the Natural Science and Engineering Research Council (NSERC) of Canada"},{"name":"NSERC CREATE to INSPIRE program"},{"name":"NSERC CGS-M program"},{"name":"Canada Foundation for Innovation"},{"name":"Natural Sciences and Engineering Research Council of Canada"},{"name":"University of Saskatchewan"},{"name":"Government of Saskatchewan"},{"name":"Western Economic Diversification Canada"},{"name":"National Research Council Canada"},{"name":"Canadian Institutes of Health Research"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Micro electro-mechanical systems (MEMS) combining sensing and microfluidics functionalities, as are common in Lab-on-Chip (LoC) devices, are increasingly based on polymers. Benefits of polymers include tunable material properties, the possibility of surface functionalization, compatibility with many micro and nano patterning techniques, and optical transparency. Often, additional materials, such as metals, ceramics, or silicon, are needed for functional or auxiliary purposes, e.g., as electrodes. Hybrid patterning and integration of material composites require an increasing range of fabrication approaches, which must often be newly developed or at least adapted and optimized. Here, a microfabrication process concept is developed that allows one to implement attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and electrochemistry on an LoC device. It is designed to spatially resolve chemical sensitivity and selectivity, which are instrumental for the detection of chemical distributions, e.g., during on-flow chemical and biological reaction chemistry. The processing sequence involves (i) direct-write and soft-contact UV lithography in SUEX dry resist and replication in polydimethylsiloxane (PDMS) elastomers as the fluidic structure; (ii) surface functionalization of PDMS with oxygen plasma, 3-aminopropyl-triethoxysilane (APTES), and a UV-curable glue (NOA 73) for bonding the fluidic structure to the substrate; (iii) double-sided patterning of silicon nitride-coated silicon wafers serving as the ATR-FTIR-active internal reflection element (IRE) on one side and the electrode-covered substrate for microfluidics on the back side with lift-off and sputter-based patterning of gold electrodes; and (iv) a custom-designed active vacuum positioning and alignment setup. Fluidic channels of 100 \u03bcm height and 600 \u03bcm width in 5 mm thick PDMS were fabricated on 2\u201d and 4\u201d demonstrators. Electrochemistry on-chip functionality was demonstrated by cyclic voltammetry (CV) of redox reactions involving iron cyanides in different oxidation states. Further, ATR-FTIR measurements of laminar co-flows of H2O and D2O demonstrated the chemical mapping capabilities of the modular fabrication concept of the LoC devices.<\/jats:p>","DOI":"10.3390\/s23146251","type":"journal-article","created":{"date-parts":[[2023,7,10]],"date-time":"2023-07-10T01:02:50Z","timestamp":1688950970000},"page":"6251","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry"],"prefix":"10.3390","volume":"23","author":[{"given":"Noah","family":"Atkinson","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tyler A.","family":"Morhart","sequence":"additional","affiliation":[{"name":"Synchrotron Laboratory for Micro and Nano Devices, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Garth","family":"Wells","sequence":"additional","affiliation":[{"name":"Synchrotron Laboratory for Micro and Nano Devices, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Grace T.","family":"Flaman","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eric","family":"Petro","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Stuart","family":"Read","sequence":"additional","affiliation":[{"name":"Mid Infrared Spectromicroscopy Facility, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Scott M.","family":"Rosendahl","sequence":"additional","affiliation":[{"name":"Mid Infrared Spectromicroscopy Facility, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9611-1431","authenticated-orcid":false,"given":"Ian J.","family":"Burgess","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0488-1557","authenticated-orcid":false,"given":"Sven","family":"Achenbach","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2023,7,8]]},"reference":[{"key":"ref_1","first-page":"723","article-title":"Trillion Sensors and MEMS","volume":"30","author":"Kaminaga","year":"2018","journal-title":"Sensor Mater."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1880","DOI":"10.1109\/T-ED.1979.19791","article-title":"A Gas Chromatographic Air Analyzer Fabricated on a Silicon Wafer","volume":"26","author":"Terry","year":"1979","journal-title":"IEEE T Electron. Dev."},{"key":"ref_3","first-page":"21","article-title":"Micro Total Analysis Systems: Microfluidic Aspects, Integration Concept and Applications","volume":"94","author":"Lammerink","year":"1998","journal-title":"Microsyst. Technol. Chem. Life Sci.\u2014Top Curr. Chem."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Menz, M., Mohr, J., and Paul, O. (2001). Microsystem Technology, WILEY-VCH Verlag GmbH.","DOI":"10.1002\/9783527613007"},{"key":"ref_5","unstructured":"Madou, M.J. (2002). Fundamentals of Microfabrication: The Science of Miniaturization, CRC Press. [2nd ed.]."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Gatzen, H.H., Saile, V., and Leuthold, J. (2015). Micro and Nano Fabrication\u2014Tools and Processes, Springer.","DOI":"10.1007\/978-3-662-44395-8"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"468","DOI":"10.1016\/j.sna.2004.10.023","article-title":"A MEMS microvalve with PDMS diaphragm and two-camber configuration of thermo-pneumatic actuator for integrated blood test system on silicon","volume":"119","author":"Takao","year":"2005","journal-title":"Sens. Actuat. A\u2014Phys."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"206","DOI":"10.1016\/j.sna.2003.10.056","article-title":"Polymer micro valve with a hydraulic piezo-drive fabricated by the AMANDA process","volume":"110","author":"Rogge","year":"2004","journal-title":"Sens. Actuat. A\u2014Phys."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1038\/nature05062","article-title":"Control and detection of chemical reactions in microfluidic systems","volume":"442","author":"deMello","year":"2006","journal-title":"Nature"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4940","DOI":"10.1021\/acs.analchem.2c04880","article-title":"Chemical Imaging of Mass Transport Near the No-Slip Interface of a Microfluidic Device using ATR-FTIR","volume":"95","author":"Flaman","year":"2023","journal-title":"Anal. Chem."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"577","DOI":"10.1039\/C6RE00127K","article-title":"Combining microfluidics and FT-IR spectroscopy: Towards spatially resolved information on chemical processes","volume":"1","author":"Perro","year":"2016","journal-title":"React. Chem. Eng."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1016\/j.cej.2017.05.001","article-title":"Infrared thermo-spectroscopic imaging of styrene radical polymerization in microfluidics","volume":"324","author":"Ryu","year":"2017","journal-title":"Chem. Eng. J."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2598","DOI":"10.1039\/C9LC00182D","article-title":"Polymeric microfluidic continuous flow mixer combined with hyperspectral FT-IR imaging for studying rapid biomolecular events","volume":"19","author":"Jang","year":"2019","journal-title":"Lab. Chip."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1016\/j.aca.2018.03.006","article-title":"IR-Compatible PDMS microfluidic devices for monitoring of enzyme kinetics","volume":"1021","author":"Noblitt","year":"2018","journal-title":"Anal. Chim. Acta"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"10000","DOI":"10.1021\/ac4026016","article-title":"Polymeric Infrared Compatible Microfluidic Devices for Spectrochemical Analysis","volume":"85","author":"Barich","year":"2013","journal-title":"Anal. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1781","DOI":"10.1177\/0003702818785640","article-title":"Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectromicroscopy Using Synchrotron Radiation and Micromachined Silicon Wafers for Microfluidic Applications","volume":"72","author":"Morhart","year":"2018","journal-title":"Appl. Spectrosc."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"5776","DOI":"10.1039\/C9AY02248A","article-title":"Micromachined multigroove silicon ATR FT-IR internal reflection elements for chemical imaging of microfluidic devices","volume":"11","author":"Morhart","year":"2019","journal-title":"Anal. Methods"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"14076","DOI":"10.1021\/acs.analchem.1c01614","article-title":"Scanning Aperture Approach for Spatially Selective ATR-FTIR Spectroscopy: Application to Microfluidics","volume":"93","author":"Joly","year":"2021","journal-title":"Anal. Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"565","DOI":"10.1107\/S1600577518017721","article-title":"SyLMAND: A microfabrication beamline with wide spectral and beam power tuning range at the Canadian Light Source","volume":"26","author":"Wells","year":"2019","journal-title":"J. Synchrotron Radiat."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"2975","DOI":"10.1007\/s00542-018-4161-2","article-title":"Optimization of laser writer-based UV lithography with high magnification optics to pattern X-ray lithography mask templates","volume":"25","author":"Achenbach","year":"2019","journal-title":"Microsyst. Technol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"121","DOI":"10.1088\/0960-1317\/7\/3\/010","article-title":"SU-8: A low-cost negative resist for MEMS","volume":"7","author":"Lorenz","year":"1997","journal-title":"J. Micromech. Microeng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1007\/s10404-017-1877-8","article-title":"Six-layer lamination of a new dry film negative-tone photoresist for fabricating complex 3D microfluidic devices","volume":"21","author":"Pfirrmann","year":"2017","journal-title":"Microfluid. Nanofluid."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"6544","DOI":"10.1021\/ac0346712","article-title":"Solvent Compatibility of Poly(dimethylsiloxane)-Based Microfluidic Devices","volume":"75","author":"Lee","year":"2003","journal-title":"Anal. Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"127002","DOI":"10.1088\/0960-1317\/24\/12\/127002","article-title":"Accounting for PDMS shrinkage when replicating structures","volume":"24","author":"Madsen","year":"2014","journal-title":"J. Micromech. Microeng."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"081108","DOI":"10.1063\/1.5070136","article-title":"Polydimethylsiloxane (PDMS) irreversible bonding to untreated plastics and metals for microfluidics applications","volume":"7","author":"Agostini","year":"2019","journal-title":"APL Mater."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"630","DOI":"10.1016\/j.mee.2012.07.085","article-title":"Fabrication and electrical characterisation of an all-PMMA and PMMA\/lipid bi-layer single submicron pore electrophoretic flow detector for biomedical applications","volume":"98","author":"Achenbach","year":"2012","journal-title":"Microelectron Eng."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1644","DOI":"10.1039\/C5LC01460C","article-title":"IR-Live: Fabrication of a low-cost plastic microfluidic device for infrared spectromicroscopy of living cells","volume":"9","author":"Birarda","year":"2016","journal-title":"Lab. Chip."},{"key":"ref_28","unstructured":"Tu, K. (2020). Developing Time-Resolved Synchrotron Infrared Spectroscopy for Spectroelectrochemical Measurements. [Ph.D. Thesis, University of Saskatchewan]."},{"key":"ref_29","unstructured":"(2023, May 26). Norland Products\u2014Norland Optical Adhesive 73. Available online: https:\/\/www.norlandprod.com\/adhesives\/noa%2073.html."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1606","DOI":"10.1364\/OME.7.001606","article-title":"Large-scale high aspect ratio AI-doped ZnO nanopillar arrays as anisotropic metamaterials","volume":"7","author":"Shkondin","year":"2017","journal-title":"Opt. Mater. Express."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"6789","DOI":"10.1364\/AO.51.006789","article-title":"Mid-infrared optical properties of thin films of aluminum oxide, titanium dioxide, silicon dioxide, aluminum nitride, and silicon nitride","volume":"51","author":"Kischkat","year":"2012","journal-title":"Appl. Opt."},{"key":"ref_32","unstructured":"Polyanskiy, M.N. (2023, May 31). Refractive Index Database. Available online: https:\/\/refractiveindex.info."},{"key":"ref_33","unstructured":"Morhart, T. (2021). Surface-Enhanced Spectroelectrochemistry using Synchrotron Infrared Radiation. [Ph.D. Thesis, University of Saskatchewan]."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1351","DOI":"10.1021\/ac60230a016","article-title":"Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics","volume":"37","author":"Nicholson","year":"1965","journal-title":"Anal. Chem."},{"key":"ref_35","unstructured":"Bard, A.J., and Faulkner, L.R. (2000). Electrochemical Methods: Fundamentals and Applications, Wiley. [2nd ed.]."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"3632","DOI":"10.1021\/ac200250s","article-title":"Synchrotron Infrared Radiation for Electrochemical External Reflection Spectroscopy: A Case Study Using Ferrocyanide","volume":"83","author":"Rosendahl","year":"2011","journal-title":"Anal. Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"8722","DOI":"10.1021\/ac401799z","article-title":"Step-Scan IR Spectroelectrochemistry with Ultramicroelectrodes: Nonsurface Enhanced Detection of Near Femtomole Quantities Using Synchrotron Radiation","volume":"85","author":"Rosendahl","year":"2013","journal-title":"Anal. Chem."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/14\/6251\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T20:09:15Z","timestamp":1760126955000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/23\/14\/6251"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2023,7,8]]},"references-count":37,"journal-issue":{"issue":"14","published-online":{"date-parts":[[2023,7]]}},"alternative-id":["s23146251"],"URL":"https:\/\/doi.org\/10.3390\/s23146251","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2023,7,8]]}}}