Electrochemical Oxygen Sensor Research Articles

Experimental investigation of the effect of polymer matrices on polymer fibre optic oxygen sensors and their time response characteristics using a vacuum testing chamber and a liquid flow apparatus

Very fast sensors that are able to track rapid changes in oxygen partial pressure (PO2) in the gas and liquid phases are increasingly required in scientific research – particularly in the life sciences. Recent interest in monitoring very fast changes in the PO2 of arterial blood in some respiratory failure conditions is one such example. Previous attempts to design fast intravascular electrochemical oxygen sensors for use in physiology and medicine have failed to meet the criteria that are now required in modern investigations. However, miniature photonic devices are capable of meeting this need. In this article, we present an inexpensive polymer type fibre-optic, oxygen sensor that is two orders of magnitude faster than conventional electrochemical oxygen sensors. It is constructed with biologically inert polymer materials and is both sufficiently small and robust for direct insertion in to a human artery. The sensors were tested and evaluated in both a gas testing chamber and in a flowing liquid test system. The results showed a very fast T90 response time, typically circa 20ms when tested in the gas phase, and circa 100ms in flowing liquid.

A Monolithically Integrated Pressure/Oxygen/Temperature Sensing SoC for Multimodality Intracranial Neuromonitoring

A fully integrated SoC for multimodality intracranial neuromonitoring is presented in this paper. Three sensors including a capacitive MEMS pressure sensor, an electrochemical oxygen sensor and a solid-state temperature sensor are integrated together in a single chip with their respective interface circuits. Chopper stabilization and dynamic element matching techniques are applied in sensor interface circuits to reduce circuit noise and offset. On-chip calibration is implemented for each sensor to compensate process variations. Measured sensitivity of the pressure, oxygen, and temperature sensors are 18.6 aF/mmHg, 194 pA/mmHg, and 2 mV/°C, respectively. Implemented in 0.18 m CMOS, the SoC occupies an area of 1.4 mm × 4 mm and consumes 166 μW DC power. A prototype catheter for intracranial pressure (ICP) monitoring has been implemented and the performance has been verified with ex vivo experiment.

Ultra-sensitive optical oxygen sensors for characterization of nearly anoxic systems.

Oxygen quantification in trace amounts is essential in many fields of science and technology. Optical oxygen sensors proved invaluable tools for oxygen measurements in a broad concentration range but until now neither optical nor electrochemical oxygen sensors were able to quantify oxygen in the sub-nanomolar concentration range. Herein we present new optical oxygen sensing materials with unmatched sensitivity. They rely on the combination of ultra-long decaying (several hundred milliseconds lifetime) phosphorescent boron- and aluminium-chelates and highly oxygen-permeable and chemically stable perfluorinated polymers. The sensitivity of the new sensors is improved up to 20-fold compared to state-of-the-art analogues. The limits of detection are as low as 5 parts per billion, volume in gas phase under atmospheric pressure or 7 picomolar in solution. The sensors enable completely new applications for monitoring of oxygen in previously inaccessible concentration ranges.

Permeability of subcutaneous tissues surrounding long-term implants to oxygen

Certain types of implanted medical devices depend on oxygen supplied from surrounding tissues for their function. However, there is a concern that the tissue associated with the foreign body response to implants may become impermeable to oxygen over the long term and render the implant nonfunctional. We report oxygen flux recordings from electrochemical oxygen sensor devices with wireless telemetry implanted in subcutaneous porcine tissues. The devices remained implanted for up to 13 weeks and were removed with adjacent tissues at specified times for histologic examination. There are four main observations: (1) In the first few weeks after implantation, the oxygen flux to the sensors, or current density, declined to a sustained mean value, having unsynchronized cyclic variations around the mean; (2) The oxygen mass transfer resistance of the sensor membrane was negligible compared to that of the tissue, allowing for a sensitive estimate of the tissue permeability; (3) The effective diffusion coefficient of oxygen in tissues was found to be approximately one order of magnitude lower than in water; and (4) Quantitative histologic analysis of the tissues showed a mild foreign body response to the PDMS sensor membrane material, with capillaries positioned close to the implant surface. Continuous recordings of oxygen flux indicate that the tissue permeability changes predictably with time, and suggest that oxygen delivery can be sustained over the long term.

Methane-oxygen electrochemical coupling in an ionic liquid: a robust sensor for simultaneous quantification.

Current sensor devices for the detection of methane or natural gas emission are either expensive and have high power requirements or fail to provide a rapid response. This report describes an electrochemical methane sensor utilizing a non-volatile and conductive pyrrolidinium-based ionic liquid (IL) electrolyte and an innovative internal standard method for methane and oxygen dual-gas detection with high sensitivity, selectivity, and stability. At a platinum electrode in bis(trifluoromethylsulfonyl)imide (NTf2)-based ILs, methane is electro-oxidized to produce CO2 and water when an oxygen reduction process is included. The in situ generated CO2 arising from methane oxidation was shown to provide an excellent internal standard for quantification of the electrochemical oxygen sensor signal. The simultaneous quantification of both methane and oxygen in real time strengthens the reliability of the measurements by cross-validation of two ambient gases occurring within a single sample matrix and allows for the elimination of several types of random and systematic errors in the detection. We have also validated this IL-based methane sensor employing both conventional solid macroelectrodes and flexible microfabricated electrodes using single- and double-potential step chronoamperometry.

Изучение работы твердоэлектролитного датчика кислорода в газах в условиях, имитирующих процессы водородной очистки циркуляционных контуров перспективных РУ с тяжелыми жидкометаллическими теплоносителями

Изучение работы твердоэлектролитного датчика кислорода в газах в условиях, имитирующих процессы водородной очистки циркуляционных контуров перспективных РУ с тяжелыми жидкометаллическими теплоносителями

Zirconia-Based Electrochemical Oxygen Sensor for Accurately Determining Water Vapor Concentration

By varying the control voltages of commercially available zirconia-based automotive exhaust gas oxygen sensors, other oxygen-containing molecules such as H2O and CO2 can be measured. Typical water concentration sensors that measure relative humidity via swelling of certain polymers have a narrow temperature range of operation (typically < 120{degree sign}C) and limited accuracy of about {plus minus} 0.4% absolute. Initial measurements with modified zirconia oxygen sensors, both in the laboratory and on engine dynamometers, have shown that water vapor concentration in a gas stream can be measured accurately to {plus minus} 0.1% over the range from 0-20 vol% H2O at temperatures up to 800{degree sign}C.

Zirconia-based Electrochemical Oxygen Sensor for Accurately Determining Water Vapor Concentration

not Available.

Design of a microfluidic respirometer for semi-continuous amperometric short time biochemical oxygen demand (BODst) analysis

This paper presents the design of a miniaturized electrochemical respirometer to monitor organic content in water samples semi-continuously, in contrast to current biochemical oxygen demand, BOD, methods. We demonstrate the use of finite element method simulations as design tool for a novel concept microfluidic respirometer. The device is based on a flow cell separated by a thin membrane from a bioreactor. Simulations show that once membrane material and thickness are chosen, oxygen supply rate still provides sufficient flexibility to allow the measurement of samples spanning a very wide range of organic matter concentrations. The design presented here uses an electrochemical oxygen sensor, and the whole system is amenable to fabrication using standard microfabrication and rapid prototyping techniques.

Solid electrolytes for use in lead–bismuth eutectic cooled nuclear reactors

The operating temperature of electrochemical oxygen sensors can likely be lowered by reducing the solid electrolyte resistance. Most often, these sensors use yttria partially stabilized zirconia (e.g. (Y2O3)0.05(ZrO2)0.95, (5-YSZ)) as solid electrolyte. In this paper, we discuss the use of better conducting ceramics than yttria partially stabilized zirconia, as solid electrolytes for oxygen sensors that can be applied in lead–bismuth eutectic (LBE) cooled nuclear reactors. Two stabilized zirconia ceramics ((Y2O3)0.08(ZrO2)0.92, (8-YSZ); (Sc2O3)0.1(CeO2)0.01(ZrO2)0.89) are investigated as well as a hypostoichiometric perovskite-type La0.8Sr0.2Ga0.8Mg0.2O3-δ. The results of microstructural analyses, thermochemical stability tests in LBE (at 360°C), as well as mechanical tests and four-probe d.c. conductivity measurements (at 300–800°C) are discussed and compared with the results that were obtained for a commercially available 5-YSZ (Friatec AG, Germany)1http://www.friatec.de/content/friatec/en/Ceramics/FRIALIT-DEGUSSIT-Oxide-Ceramics/downloads/Materials.pdf (this URL was last accessed on February 7th, 2012).1. Of the three studied ceramics, 8-YSZ was identified as the most promising solid electrolyte to reduce the operating temperature of electrochemical oxygen sensors.

Inkjet Printing of Nanoporous Gold Electrode Arrays on Cellulose Membranes for High-Sensitive Paper-Like Electrochemical Oxygen Sensors Using Ionic Liquid Electrolytes

A simple approach to the mass production of nanoporous gold electrode arrays on cellulose membranes for electrochemical sensing of oxygen using ionic liquid (IL) electrolytes was established. The approach, combining the inkjet printing of gold nanoparticle (GNP) patterns with the self-catalytic growth of these patterns into conducting layers, can fabricate hundreds of self-designed gold arrays on cellulose membranes within several hours using an inexpensive inkjet printer. The resulting paper-based gold electrode arrays (PGEAs) had several unique properties as thin-film sensor platforms, including good conductivity, excellent flexibility, high integration, and low cost. The porous nature of PGEAs also allowed the addition of electrolytes from the back cellulose membrane side and controllably produced large three-phase electrolyte/electrode/gas interfaces at the front electrode side. A novel paper-based solid-state electrochemical oxygen (O(2)) sensor was therefore developed using an IL electrolyte, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF(6)). The sensor looked like a piece of paper but possessed high sensitivity for O(2) in a linear range from 0.054 to 0.177 v/v %, along with a low detection limit of 0.0075% and a short response time of less than 10 s, foreseeing its promising applications in developing cost-effective and environment-friendly paper-based electrochemical gas sensors.

Aspects of minimizing steel corrosion in liquid lead-alloys by addition of oxygen

Minimizing steel corrosion in liquid lead-alloys by addition of oxygen requires devices for efficient oxygen transfer and reliable oxygen sensors. The accuracy of electrochemical oxygen sensors is analyzed using theoretical considerations and results from experiments in stagnant lead–bismuth eutectic (LBE). Additionally, the feasibility of gas/liquid oxygen-transfer and the long-term performance of electrochemical sensors in flowing liquid metal are addressed on the basis of the operating experience of the CORRIDA loop, a facility for testing steels in flowing LBE.

Two‐compartment method for determination of the oxygen transfer rate with electrochemical sensors based on sulfite oxidation

The dissolved oxygen concentration is a crucial parameter in aerobic bioprocesses due to the low solubility of oxygen in water. The present study describes a new method for determining the oxygen transfer rate (OTR) in shaken-culture systems based on the sodium sulfite method in combination with an electrochemical oxygen sensor. The method replaces the laborious titration of the remaining sulfite by an on-line detection of the end point of the reaction. This method is a two-step procedure that can be applied in arbitrary flasks that do not allow the insertion of electrodes. The method does not therefore depend on the type of vessel in which the OTR is detected. The concept is demonstrated by determination of the OTR for standard baffled 1-L shake flasks and for opaque Ultra Yield™ flasks. Under typical shaking conditions, k(L) a values in the standard baffled flasks reached values up to 220 h(-1) , whereas the k(L) a values of the Ultra Yield flasks were significantly higher (up to 422 h(-1) ).

Design and testing of electrochemical oxygen sensors for service in liquid lead alloys

Electrochemical oxygen sensors currently used for measuring the chemical potential of oxygen in liquid lead alloys were investigated by five European laboratories, focussing on factors influencing the accuracy of the sensor output, the long-term performance in experimental facilities and methods of testing the sensors before installation and during operation in a plant. The design of different electrochemical oxygen sensors is introduced, along with the experimentally determined sensor reliability and appropriate testing methods. The reported results summarize the results of Task 4.2.4 within Domain 4 (DEMETRA) of the integrated project (IP) EUROTRANS that was funded by the EURATOM 6th Framework Programme.

Oxygen sensor for low temperature applications

It is shown that the electrochemical oxygen sensor recently proposed as a new one is neither new nor useful.

Response of electrochemical oxygen sensors to inert gas–air and carbon dioxide–air mixtures: Measurements and mathematical modelling

Electrochemical oxygen gas sensors are widely used for monitoring the state of inertisation of flammable atmospheres and to warn of asphyxiation risks. It is well established but not widely known by users of such oxygen sensors that the response of the sensor is affected by the nature of the diluent gas responsible for the decrease in ambient oxygen concentration. The present work investigates the response of electrochemical sensors, with either acid or alkaline electrolytes, to gas mixtures comprising air with enhanced levels of nitrogen, carbon dioxide, argon or helium. The measurements indicate that both types of sensors over-read the oxygen concentrations when atmospheres contain high levels of helium. Sensors with alkaline electrolytes are also shown to underestimate the severity of the hazard in atmospheres containing high levels of carbon dioxide. This deviation is greater for alkaline electrolyte sensors compared to acid electrolyte sensors. A Computational Fluid Dynamics (CFD) model is developed to predict the response of an alkaline electrolyte, electrochemical gas sensor. Differences between predicted and measured sensor responses are less than 10% in relative terms for nearly all of the gas mixtures tested, and in many cases less than 5%. Extending the model to simulate responses of sensors with acid electrolytes would be straightforward.

Yttria-stabilized zirconia closed end tubes prepared by electrophoretic deposition

The electrophoretic deposition technique was used for the preparation of ZrO 2:8 mol% Y 2O 3 (yttria-stabilized zirconia, 8YSZ) closed end tubes for application in high temperature oxygen sensing devices. The 8YSZ ceramic suspensions with different average particle sizes were investigated looking for the best conditions for electrophoretic deposition of thin wall closed end ceramic tubes. High deposition rate of the ceramic particles onto graphite were obtained with isopropanol as solvent and 4-hydroxybenzoic acid as dispersant, with good surface quality of the deposited layer. The green tubes were dried and sintered at 1500 °C, and their properties were analyzed by X-ray diffraction for determination of the structural phases, scanning probe microscopy for observation of grain morphology, and impedance spectroscopy for evaluation of the oxide ion electrical resistivity. Pt/YSZ tube/Pt electrochemical cells were assembled for exposure to oxygen in the 60–650 ppm range using an electrochemical YSZ oxygen pump and sensor system. The signal response of the electrophoretic deposited sensor was similar to the response of the sensor of the oxygen pump. Several thin wall 4 mm diameter × 30 mm length closed end tubes may be obtained in a single operation, showing the ability of this technique for processing large quantities of tubular solid electrolytes with electrical properties suitable for use in high temperature devices.

ChemInform Abstract: Solid-State Electrochemical Oxygen Sensors for Operation at Room Temperature

Abstract Solid-state oxygen sensors workable at ambient temperature are becoming increasingly important in various application fields such as bioprocess control and medical diagnosis. Research trends in the development of such solid-state oxygen sensors are described briefly. Attention is then focused on the structure and sensing characteristics of solid electrolyte sensors using LaF3, which have recently been shown to operate at room temperature for the potentiometric sensing of gaseous oxygen as well as dissolved oxygen in water.

Electrochemical Oxygen Sensors for Corrosion Control in Lead-Cooled Nuclear Reactors

Abstract Liquid metals have been used in various applications in nuclear systems. Lead-bismuth eutectic (LBE) is foreseen as a coolant and target for neutron generation in accelerator-driven systems (ADS), whereas pure lead will be used as coolant in Gen IV-type lead-cooled fast reactors (LFR). The advantage of heavy liquid metal alloys is their high thermal conductivity and their relative safety in case of an accident. A major problem in non-isothermal systems is the corrosion of their structural components, consisting mainly of ferritic/martensitic and austenitic stainless steels, since the solubility of dissolved elements depends strongly on temperature. The formation of oxide scales on structural components is considered a viable approach to limiting the corrosion rates. To maintain a specific oxygen content in lead or LBE, an oxygen control system (OCS) is crucial. This requires continuous measurement of the oxygen activity in the liquid metal by means of electrochemical sensors. It must be assured that no oxides of the liquid metal itself are formed; otherwise, the system can be blocked. Therefore, this paper addresses the development of oxygen sensors for corrosion control of martensitic and austenitic steels in a lead-bismuth eutectic system at Forschungszentrum Karlsruhe (FZK, Eggenstein-Leopoldshafen, Germany).

Magnetic sensor particles: an optimized magnetic separator with an optical window

Magnetically separable optical sensor particles represent a good alternative for conventional electrochemical and fibre-optical oxygen and pH sensors. Further improving the suitability of magnetically separable optical sensor particles, we reconstructed the separation adapters. Computer simulations of magnetic fields indicated that an assembly of radially magnetized rings is preferred. We investigated different materials and dimensions of adapters and improved commercially available, axially magnetized rings using a magnetically soft iron cone together with the rings. Adapters simulating a radially magnetized ring were constructed out of several block magnets arranged like a star around an optical fibre. These adapters collected the sensor particles exactly in the field of view ensuring high efficiency and, on top of that, showed a higher resistance of the resulting sensor spot against shear forces in stirred liquid. All adapters were characterized in a stirred flask recording signal intensity versus stirrer speed plots.