Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry
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...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-07-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/23/14/6251 |
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| author | Noah Atkinson Tyler A. Morhart Garth Wells Grace T. Flaman Eric Petro Stuart Read Scott M. Rosendahl Ian J. Burgess Sven Achenbach |
| author_facet | Noah Atkinson Tyler A. Morhart Garth Wells Grace T. Flaman Eric Petro Stuart Read Scott M. Rosendahl Ian J. Burgess Sven Achenbach |
| author_sort | Noah Atkinson |
| collection | DOAJ |
| description | 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 μm height and 600 μm width in 5 mm thick PDMS were fabricated on 2” and 4” 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 H<sub>2</sub>O and D<sub>2</sub>O demonstrated the chemical mapping capabilities of the modular fabrication concept of the LoC devices. |
| first_indexed | 2024-03-11T00:41:35Z |
| format | Article |
| id | doaj.art-fd5dba8b2e9546c093312cb1264cf3af |
| institution | Directory Open Access Journal |
| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-11T00:41:35Z |
| publishDate | 2023-07-01 |
| publisher | MDPI AG |
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| series | Sensors |
| spelling | doaj.art-fd5dba8b2e9546c093312cb1264cf3af2023-11-18T21:15:06ZengMDPI AGSensors1424-82202023-07-012314625110.3390/s23146251Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared SpectroelectrochemistryNoah Atkinson0Tyler A. Morhart1Garth Wells2Grace T. Flaman3Eric Petro4Stuart Read5Scott M. Rosendahl6Ian J. Burgess7Sven Achenbach8Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, CanadaSynchrotron Laboratory for Micro and Nano Devices, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, CanadaSynchrotron Laboratory for Micro and Nano Devices, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, CanadaDepartment of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9, CanadaDepartment of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, CanadaMid Infrared Spectromicroscopy Facility, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, CanadaMid Infrared Spectromicroscopy Facility, Canadian Light Source Inc., Saskatoon, SK S7N 2V3, CanadaDepartment of Chemistry, University of Saskatchewan, Saskatoon, SK S7N 5C9, CanadaDepartment of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, CanadaMicro 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 μm height and 600 μm width in 5 mm thick PDMS were fabricated on 2” and 4” 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 H<sub>2</sub>O and D<sub>2</sub>O demonstrated the chemical mapping capabilities of the modular fabrication concept of the LoC devices.https://www.mdpi.com/1424-8220/23/14/6251micro electro-mechanical systems (MEMS)Lab-on-Chip (LoC)microfabricationpolydimethylsiloxane (PMDS)UV lithographybonding |
| spellingShingle | Noah Atkinson Tyler A. Morhart Garth Wells Grace T. Flaman Eric Petro Stuart Read Scott M. Rosendahl Ian J. Burgess Sven Achenbach Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry Sensors micro electro-mechanical systems (MEMS) Lab-on-Chip (LoC) microfabrication polydimethylsiloxane (PMDS) UV lithography bonding |
| title | Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry |
| title_full | Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry |
| title_fullStr | Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry |
| title_full_unstemmed | Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry |
| title_short | Microfabrication Process Development for a Polymer-Based Lab-on-Chip Concept Applied in Attenuated Total Reflection Fourier Transform Infrared Spectroelectrochemistry |
| title_sort | microfabrication process development for a polymer based lab on chip concept applied in attenuated total reflection fourier transform infrared spectroelectrochemistry |
| topic | micro electro-mechanical systems (MEMS) Lab-on-Chip (LoC) microfabrication polydimethylsiloxane (PMDS) UV lithography bonding |
| url | https://www.mdpi.com/1424-8220/23/14/6251 |
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