The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Jung-chih Chiao - One of the best experts on this subject based on the ideXlab platform.
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Integrated pH and Sodium Sensor Array Based on Iridium Oxide Film
2018 IEEE SENSORS, 2018Co-Authors: Xuesong Yang, Jung-chih ChiaoAbstract:We have developed a sensor array consisting of an Iridium Oxide (IrOx) electrode for pH measurement, an Iridium Oxide based ion-selective sensor for sodium detection, and two silver chloride (AgCl) reference electrodes. The planar sensor array was fabricated on a flexible substrate with simple fabrication processes. The Iridium Oxide sensing film was synthesized by the sol-gel process. The sodium sensor was fabricated by deposition of a sodium-selective membrane on the Iridium Oxide film. The silver chloride reference electrodes were made by printing. The sensor array was tested in standard pH buffer solutions with or without the existence of sodium. In both scenarios, a promising sensitivity of 61.46 mV/pH in the pH ranges from acid to alkaline at the room temperature was achieved. The potential increases induced by the sodium interference were calibrated by the sodium sensor. The calibrated results show excellent pH responses with minimum interference. The pH and sodium sensor array demonstrates a unique capability to provide accurate pH detection in the environment containing sodium interference.
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Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices
Sensors, 2015Co-Authors: Cuong M Nguyen, Smitha Rao, Hung Cao, Xuesong Yang, Souvik Dubey, Jeffrey Mays, Jung-chih ChiaoAbstract: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.
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Sol-Gel Iridium Oxide-Based pH Sensor Array on Flexible Polyimide Substrate
IEEE Sensors Journal, 2013Co-Authors: Cuong M Nguyen, Smitha Rao, Hung Cao, Uday Tata, Wen-ding Huang, Mu Chiao, Jung-chih ChiaoAbstract:Iridium Oxide pH sensing film is demonstrated with wide pH-sensing ranges, high durability, and small drifts in potentials. Using sol-gel process, a lower fabrication cost and less labor-intensive method, to deposit Iridium Oxide thin films for pH sensing is reported previously by our group with expected advantages. In this paper, we fabricate and test pH sensing characteristics of 4 × 4 anhydrous Iridium Oxide thin-film electrode arrays on flexible substrates. The sensors in arrays exhibit Nernstian potential responses in the range of 57.0-63.4 mV/pH. Stability, repeatability, and hysteresis effects of the pH sensor arrays are examined. A multichannel recording system is built to demonstrate the functionality of the pH sensor arrays in monitoring spatial and temporal pH changes across a surface.
Stuart F. Cogan - One of the best experts on this subject based on the ideXlab platform.
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Sputtered Iridium Oxide Films for Neural Stimulation Electrodes
Journal of biomedical materials research. Part B Applied biomaterials, 2009Co-Authors: Stuart F. Cogan, Julia Ehrlich, Timothy D. Plante, Anton Smirnov, Douglas B. Shire, Marcus D. Gingerich, Joseph F. RizzoAbstract:Sputtered Iridium Oxide films (SIROFs) deposited by DC reactive sputtering from an Iridium metal target have been characterized in vitro for their potential as neural recording and stimulation electrodes. SIROFs were deposited over gold metallization on flexible multielectrode arrays fabricated on thin (15 microm) polyimide substrates. SIROF thickness and electrode areas of 200-1300 nm and 1960-125,600 microm(2), respectively, were investigated. The charge-injection capacities of the SIROFs were evaluated in an inorganic interstitial fluid model in response to charge-balanced, cathodal-first current pulses. Charge injection capacities were measured as a function of cathodal pulse width (0.2-1 ms) and potential bias in the interpulse period (0.0 to 0.7 V vs. Ag|AgCl). Depending on the pulse parameters and electrode area, charge-injection capacities ranged from 1-9 mC/cm(2), comparable with activated Iridium Oxide films (AIROFs) pulsed under similar conditions. Other parameters relevant to the use of SIROF on nerve electrodes, including the thickness dependence of impedance (0.05-10(5) Hz) and the current necessary to maintain a bias in the interpulse region were also determined.
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Sputtered Iridium Oxide films (SIROFs) for low-impedance neural stimulation and recording electrodes
The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2004Co-Authors: Stuart F. Cogan, Timothy D. Plante, Julia EhrlichAbstract:Iridium Oxide films formed by electrochemical activation of Iridium metal (AIROF) or by electrochemical deposition (EIROF) are being evaluated as low-impedance charge-injection coatings for neural stimulation and recording. Iridium Oxide may also be deposited by reactive sputtering from Iridium metal in an oxidizing plasma. The characterization of sputtered Iridium Oxide films (SIROFs) as coatings for nerve electrodes is reported. SIROFs were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and potential transient measurements during charge-injection. The surface morphology of the SIROF transitions from smooth to highly nodular with increasing film thickness from 80 nm to 4600 nm. Charge-injection capacities exceed 0.75 mC/cm/sup 2/ with 0.75 ms current pulses in thicker films. The SIROF was deposited on both planar and non-planar substrates and photolithographically patterned by lift-off.
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Electrodeposited Iridium Oxide for neural stimulation and recording electrodes
IEEE transactions on neural systems and rehabilitation engineering : a publication of the IEEE Engineering in Medicine and Biology Society, 2001Co-Authors: R.d. Meyer, Stuart F. Cogan, T.h. Nguyen, R.d. RauhAbstract:Iridium Oxide films formed by electrodeposition onto nonIridium metal substrates are compared with activated Iridium Oxide films (AIROFs) as a low impedance, high charge capacity coating for neural stimulation and recording electrodes. The electrodeposited Iridium Oxide films (EIROFs) were deposited on Au, Pt, PtIr, and 316 LVM stainless steel substrates from a solution of IrCl4, oxalic acid, and K2CO3. A deposition protocol involving 50 potential sweeps at 50 mV/s between limits of 0.0 V and 0.55 V (versus Ag AgCl) followed by potential pulsing between the same limits produced adherent films with a charge storage capacity of >25 mC/cm2. Characterization by cyclic voltammetry and impedance spectroscopy revealed no differences in the electrochemical behavior of EIROF on non-Ir substrates and AIROF. The mechanical stability of the Oxides was evaluated by ultrasonication in distilled water followed by dehydration and rehydration. Stability under charge injection was evaluated using 200 micros, 5.9 A/cm2 (1.2 mC/cm2) cathodal pulses. Loss of Iridium Oxide charge capacity was comparable for AIROFs and the EIROFs, ranging from 1% to 8% of the capacity immediately after activation or deposition. The EIROFs were deposited and evaluated on silicon microprobe electrodes and on metallized polyimide electrodes being developed for neural recording and stimulation applications.
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Characterization and variability of intracortical Iridium Oxide microelectrodes
Proceedings of the 25th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (IEEE Cat. No.03CH37439), 1Co-Authors: Stuart F. Cogan, Timothy D. Plante, P.r. Troyk, D.e. Detlefsen, J. Ehrlich, Douglas B. Mccreery, Leo A. Bullara, M. BakAbstract:Over 200 Iridium microelectrodes with activated Iridium Oxide (AIROF) charge-injection sites were evaluated in vitro by cyclic voltammetry and voltage transient measurements during current pulsing. Variability in the electrochemical behavior of these nominally identical microelectrodes was correlated with variations in the amount of AIROF present and the physical condition of the charge-injection tip. Electrolyte leakage under polymer insulation and delamination of AIROF both gave rise to characteristic shapes in cyclic voltammograms which could be used to identify their presence.
Cuong M Nguyen - One of the best experts on this subject based on the ideXlab platform.
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Sol-Gel Deposition of Iridium Oxide for Biomedical Micro-Devices
Sensors, 2015Co-Authors: Cuong M Nguyen, Smitha Rao, Hung Cao, Xuesong Yang, Souvik Dubey, Jeffrey Mays, Jung-chih ChiaoAbstract: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.
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Sol-Gel Iridium Oxide-Based pH Sensor Array on Flexible Polyimide Substrate
IEEE Sensors Journal, 2013Co-Authors: Cuong M Nguyen, Smitha Rao, Hung Cao, Uday Tata, Wen-ding Huang, Mu Chiao, Jung-chih ChiaoAbstract:Iridium Oxide pH sensing film is demonstrated with wide pH-sensing ranges, high durability, and small drifts in potentials. Using sol-gel process, a lower fabrication cost and less labor-intensive method, to deposit Iridium Oxide thin films for pH sensing is reported previously by our group with expected advantages. In this paper, we fabricate and test pH sensing characteristics of 4 × 4 anhydrous Iridium Oxide thin-film electrode arrays on flexible substrates. The sensors in arrays exhibit Nernstian potential responses in the range of 57.0-63.4 mV/pH. Stability, repeatability, and hysteresis effects of the pH sensor arrays are examined. A multichannel recording system is built to demonstrate the functionality of the pH sensor arrays in monitoring spatial and temporal pH changes across a surface.
Julia Ehrlich - One of the best experts on this subject based on the ideXlab platform.
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Sputtered Iridium Oxide Films for Neural Stimulation Electrodes
Journal of biomedical materials research. Part B Applied biomaterials, 2009Co-Authors: Stuart F. Cogan, Julia Ehrlich, Timothy D. Plante, Anton Smirnov, Douglas B. Shire, Marcus D. Gingerich, Joseph F. RizzoAbstract:Sputtered Iridium Oxide films (SIROFs) deposited by DC reactive sputtering from an Iridium metal target have been characterized in vitro for their potential as neural recording and stimulation electrodes. SIROFs were deposited over gold metallization on flexible multielectrode arrays fabricated on thin (15 microm) polyimide substrates. SIROF thickness and electrode areas of 200-1300 nm and 1960-125,600 microm(2), respectively, were investigated. The charge-injection capacities of the SIROFs were evaluated in an inorganic interstitial fluid model in response to charge-balanced, cathodal-first current pulses. Charge injection capacities were measured as a function of cathodal pulse width (0.2-1 ms) and potential bias in the interpulse period (0.0 to 0.7 V vs. Ag|AgCl). Depending on the pulse parameters and electrode area, charge-injection capacities ranged from 1-9 mC/cm(2), comparable with activated Iridium Oxide films (AIROFs) pulsed under similar conditions. Other parameters relevant to the use of SIROF on nerve electrodes, including the thickness dependence of impedance (0.05-10(5) Hz) and the current necessary to maintain a bias in the interpulse region were also determined.
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Sputtered Iridium Oxide films (SIROFs) for low-impedance neural stimulation and recording electrodes
The 26th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2004Co-Authors: Stuart F. Cogan, Timothy D. Plante, Julia EhrlichAbstract:Iridium Oxide films formed by electrochemical activation of Iridium metal (AIROF) or by electrochemical deposition (EIROF) are being evaluated as low-impedance charge-injection coatings for neural stimulation and recording. Iridium Oxide may also be deposited by reactive sputtering from Iridium metal in an oxidizing plasma. The characterization of sputtered Iridium Oxide films (SIROFs) as coatings for nerve electrodes is reported. SIROFs were characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and potential transient measurements during charge-injection. The surface morphology of the SIROF transitions from smooth to highly nodular with increasing film thickness from 80 nm to 4600 nm. Charge-injection capacities exceed 0.75 mC/cm/sup 2/ with 0.75 ms current pulses in thicker films. The SIROF was deposited on both planar and non-planar substrates and photolithographically patterned by lift-off.
Kenneth G. Kreider - One of the best experts on this subject based on the ideXlab platform.
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Thin Film Ruthenium Oxide - Iridium Oxide Thermocouples
MRS Proceedings, 1991Co-Authors: Kenneth G. KreiderAbstract:ABSTRACTRuthenium Oxide and Iridium Oxide have outstanding resistance to corrosion. These Oxides are also excellent electrical conductors and have been used as biochemical charge injection electrodes. Their unique electrical and electrochemical properties have also led to their consideration as high temperature pH electrodes. Thin films are the most useful form for these applications as they permit the miniaturization of fast response sensors and electrodes.This study was used to characterize the thermoelectric and electrical conductance parameters of ruthenium and Iridium Oxide sputtered thin films. The electric and thermoelectric properties of the thin films were found to be sensitive to the annealing temperature of the sputtered Oxides. The properties of the film are related to the microstructure, stoichiometry and crystal structure as determined by x-ray diffraction. Heat treatments were used to stabilize the thermoelectric response and the thermal coefficient of resistivity.
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Iridium Oxide thin-film stability in high-temperature corrosive solutions
Sensors and Actuators B: Chemical, 1991Co-Authors: Kenneth G. KreiderAbstract:Abstract The stability of sputtered Iridium Oxide films is investigated after exposure to pH 4, 7, and 10 solutions at 200 °C (15 bar) and 245 °C (40 bar). These reactively sputtered films are being considered as pH-sensing electrodes in high-temperature high-pressure saline solutions such as those found underground in potential nuclear repositories. The sputtered Iridium Oxide films (SIROF) have a linear response of approximately 53–58 mV per pH at room temperature under a wide range of solution conditions. Other advantages include their ruggedness, small size, high voltage/low impedance output, and the low cost of fabrication. To evaluate their stability the films are exposed in a Teflon-lined bomb for up to 70 h at high temperature. The pH testing of 50 samples includes cycling between pH 2 and pH 12 before and after exposure. Changes of the potential intercept and the slope are most severe after acidic conditions at 250 °C. It is found that ion-assisted deposition helps to maintain film adherence and continuity on the alumina substrates during exposure to 200 °C solutions.
