Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings
Microelectrode array (MEA) is a tool used for recording bioelectric signals from electrically active cells in vitro. In this paper, ion beam assisted electron beam deposition (IBAD) has been used for depositing indium tin oxide (ITO) and titanium nitride (TiN) thin films which are applied as transpa...
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MDPI AG
2020-05-01
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| Series: | Micromachines |
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| Online Access: | https://www.mdpi.com/2072-666X/11/5/497 |
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| author | Tomi Ryynänen Ropafadzo Mzezewa Ella Meriläinen Tanja Hyvärinen Jukka Lekkala Susanna Narkilahti Pasi Kallio |
| author_facet | Tomi Ryynänen Ropafadzo Mzezewa Ella Meriläinen Tanja Hyvärinen Jukka Lekkala Susanna Narkilahti Pasi Kallio |
| author_sort | Tomi Ryynänen |
| collection | DOAJ |
| description | Microelectrode array (MEA) is a tool used for recording bioelectric signals from electrically active cells in vitro. In this paper, ion beam assisted electron beam deposition (IBAD) has been used for depositing indium tin oxide (ITO) and titanium nitride (TiN) thin films which are applied as transparent track and electrode materials in MEAs. In the first version, both tracks and electrodes were made of ITO to guarantee full transparency and thus optimal imaging capability. In the second version, very thin (20 nm) ITO electrodes were coated with a thin (40 nm) TiN layer to decrease the impedance of Ø30 µm electrodes to one third (1200 kΩ → 320 kΩ) while maintaining (partial) transparency. The third version was also composed of transparent ITO tracks, but the measurement properties were optimized by using thick (200 nm) opaque TiN electrodes. In addition to the impedance, the optical transmission and electric noise levels of all three versions were characterized and the functionality of the MEAs was successfully demonstrated using human pluripotent stem cell-derived neuronal cells. To understand more thoroughly the factors contributing to the impedance, MEAs with higher IBAD ITO thickness as well as commercial sputter-deposited and highly conductive ITO were fabricated for comparison. Even if the sheet-resistance of our IBAD ITO thin films is very high compared to the sputtered one, the impedances of the MEAs of each ITO grade were found to be practically equal (e.g., 300–370 kΩ for Ø30 µm electrodes with 40 nm TiN coating). This implies that the increased resistance of the tracks, either caused by lower thickness or lower conductivity, has hardly any contribution to the impedance of the MEA electrodes. The impedance is almost completely defined by the double-layer interface between the electrode top layer and the medium including cells. |
| first_indexed | 2024-03-10T19:50:00Z |
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| language | English |
| last_indexed | 2024-03-10T19:50:00Z |
| publishDate | 2020-05-01 |
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| series | Micromachines |
| spelling | doaj.art-cca83079d64f43f1b94d6d6e96840a802023-11-20T00:30:53ZengMDPI AGMicromachines2072-666X2020-05-0111549710.3390/mi11050497Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro RecordingsTomi Ryynänen0Ropafadzo Mzezewa1Ella Meriläinen2Tanja Hyvärinen3Jukka Lekkala4Susanna Narkilahti5Pasi Kallio6Micro and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33720 Tampere, FinlandNeuro Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, FinlandMicro and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33720 Tampere, FinlandNeuro Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, FinlandMicro and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33720 Tampere, FinlandNeuro Group, Faculty of Medicine and Health Technology, Tampere University, 33520 Tampere, FinlandMicro and Nanosystems Research Group, Faculty of Medicine and Health Technology, Tampere University, 33720 Tampere, FinlandMicroelectrode array (MEA) is a tool used for recording bioelectric signals from electrically active cells in vitro. In this paper, ion beam assisted electron beam deposition (IBAD) has been used for depositing indium tin oxide (ITO) and titanium nitride (TiN) thin films which are applied as transparent track and electrode materials in MEAs. In the first version, both tracks and electrodes were made of ITO to guarantee full transparency and thus optimal imaging capability. In the second version, very thin (20 nm) ITO electrodes were coated with a thin (40 nm) TiN layer to decrease the impedance of Ø30 µm electrodes to one third (1200 kΩ → 320 kΩ) while maintaining (partial) transparency. The third version was also composed of transparent ITO tracks, but the measurement properties were optimized by using thick (200 nm) opaque TiN electrodes. In addition to the impedance, the optical transmission and electric noise levels of all three versions were characterized and the functionality of the MEAs was successfully demonstrated using human pluripotent stem cell-derived neuronal cells. To understand more thoroughly the factors contributing to the impedance, MEAs with higher IBAD ITO thickness as well as commercial sputter-deposited and highly conductive ITO were fabricated for comparison. Even if the sheet-resistance of our IBAD ITO thin films is very high compared to the sputtered one, the impedances of the MEAs of each ITO grade were found to be practically equal (e.g., 300–370 kΩ for Ø30 µm electrodes with 40 nm TiN coating). This implies that the increased resistance of the tracks, either caused by lower thickness or lower conductivity, has hardly any contribution to the impedance of the MEA electrodes. The impedance is almost completely defined by the double-layer interface between the electrode top layer and the medium including cells.https://www.mdpi.com/2072-666X/11/5/497microelectrode array (MEA)ion beam assisted electron beam deposition (IBAD)indium tin oxide (ITO)titanium nitride (TiN)neuronstransparent |
| spellingShingle | Tomi Ryynänen Ropafadzo Mzezewa Ella Meriläinen Tanja Hyvärinen Jukka Lekkala Susanna Narkilahti Pasi Kallio Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings Micromachines microelectrode array (MEA) ion beam assisted electron beam deposition (IBAD) indium tin oxide (ITO) titanium nitride (TiN) neurons transparent |
| title | Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings |
| title_full | Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings |
| title_fullStr | Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings |
| title_full_unstemmed | Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings |
| title_short | Transparent Microelectrode Arrays Fabricated by Ion Beam Assisted Deposition for Neuronal Cell In Vitro Recordings |
| title_sort | transparent microelectrode arrays fabricated by ion beam assisted deposition for neuronal cell in vitro recordings |
| topic | microelectrode array (MEA) ion beam assisted electron beam deposition (IBAD) indium tin oxide (ITO) titanium nitride (TiN) neurons transparent |
| url | https://www.mdpi.com/2072-666X/11/5/497 |
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