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Open AccessArticle

Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices

1
Department of Electrical Engineering, University of Texas, Arlington, TX 76019, USA
2
Department of Electrical Engineering, ETS, Montreal, QC H3C 1K3, Canada
*
Author to whom correspondence should be addressed.
Sensors 2015, 15(2), 4212-4228; https://doi.org/10.3390/s150204212
Received: 17 December 2014 / Accepted: 6 February 2015 / Published: 12 February 2015
(This article belongs to the Special Issue Sol-Gel Based Sensors and Devices)
Flexible iridium oxide (IrOx)-based micro-electrodes were fabricated on flexible polyimide substrates using a sol-gel deposition process for utilization as integrated pseudo-reference electrodes for bio-electrochemical sensing applications. The fabrication method yields reliable miniature on-probe IrOx electrodes with long lifetime, high stability and repeatability. Such sensors can be used for long-term measurements. Various dimensions of sol-gel iridium oxide electrodes including 1 mm × 1 mm, 500 µm × 500 µm, and 100 µm × 100 µm were fabricated. Sensor longevity and pH dependence were investigated by immersing the electrodes in hydrochloric acid, fetal bovine serum (FBS), and sodium hydroxide solutions for 30 days. Less pH dependent responses, compared to IrOx electrodes fabricated by electrochemical deposition processes, were measured at 58.8 ± 0.4 mV/pH, 53.8 ± 1.3 mV/pH and 48 ± 0.6 mV/pH, respectively. The on-probe IrOx pseudo-reference electrodes were utilized for dopamine sensing. The baseline responses of the sensors were higher than the one using an external Ag/AgCl reference electrode. Using IrOx reference electrodes integrated on the same probe with working electrodes eliminated the use of cytotoxic Ag/AgCl reference electrode without loss in sensitivity. This enables employing such sensors in long-term recording of concentrations of neurotransmitters in central nervous systems of animals and humans. View Full-Text
Keywords: dopamine; Nernst-response; neurotransmitter sensors; pseudo-reference electrodes; sol-gel IrOx dopamine; Nernst-response; neurotransmitter sensors; pseudo-reference electrodes; sol-gel IrOx
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Nguyen, C.M.; Rao, S.; Yang, X.; Dubey, S.; Mays, J.; Cao, H.; Chiao, J.-C. Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices. Sensors 2015, 15, 4212-4228.

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