Towards a novel optical trace oxygen sensor for commerical use

OPTIMALIZATION OF OXYGEN LEVELS IN ROOT SYSTEMS AS EFFECTIVE CULTIVATION TOOL

Fast pesticide detection inside microfluidic device with integrated optical pH, oxygen sensors and algal fluorescence

Oxygen sensors currently afford one of the few opportunities to acquire accurate measurements of a biogeochemical parameter at the same vertical resolution as CTD data. Electrochemical cells have been used to measure dissolved oxygen concentration in a water solution, initially blood (Clark et al., 1953) but soon thereafter aquatic environments (Kanwisher, 1959) for many decades. More recently, optical sensors have been applied to aquatic uses (Klimant et al., 1995). Here we present outlines of procedures on acquisition, processing, and calibration of oxygen data collected from both electrochemical and optical oxygen sensors. We focus only on one model of electrochemical cell, specifically the SeaBird Electronics SBE-43. Here also we provide detailed material on recent experience with acquisition, processing, and calibration of data from optical oxygen sensors, specifically the Aanderaa Data Instruments Optode 3830 and the JFE Alec Rinko Optode. For all sensor types, readers should bear in mind that oceanic oxygen measurement and calibration techniques are subject to improvement. This outline should be viewed only as a supplement to the existing literature, manufacturer documentation, and manufacturer instructions.

Optical fiber evanescent wave sensor for oxygen deficiency detection

The development of a cylindrical-core fiber optic oxygen sensor for fast measurement of oxygen partial pressure (pO2) is described. The fibre sensing element is based on a cylindrical-core waveguide structure formed by a polymer sensing film that contains immobilized Pt (II) complexes. The performance of the fibre optic oxygen sensor was evaluated using luminescence intensity measurement. To determine accurately the response time of the oxygen sensor, a test chamber was used to provide rapid changes in the partial pressure of oxygen. The result showed that the time response of this cylindrical-core fibre based optic oxygen sensor can be less than 0.2 second. The details of the sensor chemistry, experimental system and the results are reported.

Electrochemical NO2 sensors are a promising technology for the collection of fine-granular air quality data. Their low acquisition costs, miniaturized size and low power consumption predestine the sensors for use in mobile sensor networks due to their installation in vehicles. However, the sensors are influenced by sensitivities to changes in measurement conditions (e.g. temperature and relative humidity) during data collection. Therefore, we investigated the feasibility of adapting the data of electrochemical NO2 sensors to a reference measuring system using Machine Learning models. For this purpose, we carried out a field experiment with a vehicle to collect data. In addition to three identical electrochemical NO2 sensors, we installed a reference measuring system and measured the NO2 concentration at the same sampling point outside the vehicle. We implemented several adaptation models by using a Multivariate Linear Regression (MLR) and a Support Vector Regression (SVR) to improve the raw sensor signal. Furthermore, we investigated whether an adaptation concept for a single sensor can be applied to identical sensors as well as to other (unknown) measurement runs. The results of this work show the potential of the sensors for air quality assessment, but the accuracy of the reference sensors is only partially achieved.

In applications of nitrogen (N2) generation, industrial gas manufacturing and food packaging there is a need to ensure oxygen (O2) is absent from the environment, even at the lowest concentration levels. Therefore, there has been an increased growth in the development of trace O2 parts per million (ppm) sensors over the past decade to detect and quantify the concentration of molecular O2 in the environment whether it be dissolved or gaseous O2. The majority of commercially available trace O2 sensors are based on electrochemical, zirconia and paramagnetic technologies. Here, the development of a luminescence-based optical trace O2 sensor is presented. Luminescence-based sensing is now regarded as one of the best techniques for the detection and quantification of O2. This is due to the high detection sensitivity, no O2 is consumed and there are a vast array of luminescent indicators and sensing platforms (polymers) that can be selected to suit the desired application. The sensor will be shown to operate from -30 °C to +60 °C in the 0–1000 ppm and/or 0–1200 μbar partial pressure of oxygen (ppO2) range and is equipped with temperature and pressure compensation. The luminescence non-depleting principle, sensor specifications and miniaturized nature offers an attractive alternative to other sensing technologies and advantages over other luminescence-based O2 ppm sensors.

Preparation of a high stability optical fiber oxygen sensor based on the bilayer sensitive membrane

Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.

Sterilization is a physical or chemical process that eliminates microbial life from a surface, equipment, medication, etc. Because of the severity of the process to meet the sterilization criteria and definition there is no singular sterilization applicable to all healthcare and other products including drugs, polymers, devices and materials. The sterility of sensors used in medical applications, for biochemical investigations, operation of biotechnological reactors, etc., is a necessary but difficult-to-achieve prerequisite for the use of sensors. There is a lack of reliable data about effects of different sterilization procedures on optical sensors. Therefore, the influences, effects and compatibility of diverse sterilization procedure on optical polymer oxygen sensors were investigated. Before and after sterilization, the absorption/emission spectra and the response of the sensor to different concentrations of oxygen were measured and Stern–Volmer plots were calculated. Based on the obtained results from measurements the compatibilities of the different sterilization procedures and polymer oxygen sensors were determined.

We are developing a range of sphincter sensors for use in Gastroenterology and Urology diagnostic applications, such as Reflux and Urinary Incontinence. Urinary Incontinence costs the NHS in the UK around pound600 million per annum so there is a clear need for improved diagnostic methods such as the sensors being developed. As part of this process a reusable interface unit will be developed which can connect to existing diagnostic equipment thus reducing the impact on the clinicians using the products developed. Initially the interface unit will communicate to the equipment by the use of wires and with future iterations it will enable the clinician to carry out ambulatory studies by storing the data remotely and then wirelessly transmitting the data to the diagnostic equipment. The current methods of measuring sphincter closures are water perfused and solid-state micro-tip catheters. Both have advantages and disadvantages - The water-perfused catheters are slow to respond, single use and also can be tricky to set-up correctly. The solid-state micro-tip catheters are quick to respond, very expensive and are re-usable which has contamination issues. The products developed within Healthy Aims will overcome these shortcomings and will enable clinicians to obtain fast accurate diagnostic results. To date the project has developed a gauge that meets the specifications and has identified a number of different ways in which to manufacture the final device and is confident that by the end of the project a urethral sensor will be going through clinical trials. A number of clinical education seminars have been held to increase the awareness of the project and to ensure that the development is in-line with current clinical thinking. The future of wireless diagnostics for Gastroenterology and Urology will enable more 'natural' diagnosis and possibly treatment of patients suffering with certain conditions. For example, the current method of diagnosing urinary incontinence focuses on a small time period in the patients working day. By having systems that can monitor the bladder over a number of days we will provide clinicians with more information with which to treat the patient. If this data can be wirelessly transmitted to the clinician from the patient's home, then remote diagnosis becomes a real benefit to the patients and clinicians alike.

The typical response characteristics of most optical oxygen sensors include downward curving Stern–Volmer plots and often multi-exponential luminescence decay profiles in the absence and presence of oxygen. The wide range of different response features exhibited by optical oxygen sensors is usually attributed to different degrees of heterogeneity in the sensor films. This heterogeneity is described in this paper by a log-Gaussian distribution in the natural luminescent lifetime of the oxygen-quenchable lumophore, τo, and the quenching rate constant, kq. A ‘log-Gaussian distribution in τo and kq’ model is used to generate theoretical response profiles which exhibit the same disparate range of features as real optical oxygen sensors. However, unlike other models, such as the ‘two-site’ model, the ‘log-Gaussian distribution in τo and kq’ model generates model parameter values which are physically plausible and consistent at all partial pressures of oxygen, pO2. The model is used to fit successfully the Stern–Volmer plots and luminescent decay profiles reported for a number of different optical oxygen sensors. For each of the real sensors examined, the values of the model parameters KSV,mdl, ρ1, ρ2 and τo,mdl which give the best fit to the observed data are reported. The latter data allows prediction of the response features of the associated optical oxygen sensor at any value of pO2

This paper describes recent progress towards the development and qualification of a highly distributed, multi-point, all optical pressure and temperature compensated, fiber optic oxygen sensor (FOxSense™) system for closed-loop monitoring and safety of the oxygen ullage environment inside fuel tanks of military and commercial aircraft. The alloptical FOxSense™ system uses a passive, multi-parameter (O2/T&P) fiber optic sensor probe with no electrical connections leading to the sensors install within the fuel tanks of an aircraft. The all optical sensor consists of an integrated multi-parameter fiber optic sensor probe that integrates a fuel insensitive fluorescence based optical oxygen optrode with built-in temperature and pressure optical optrodes for compensation of temperature and pressure variants induced in the fluorescence response of the oxygen optrode. The distributed (O2/T&P) fiber optic sensors installed in the fuel tanks of the aircraft are connected to the FOxSense optoelectronic system via a fiber optic cable conduit reaching to each fuel tank in the aircraft. A multichannel frequency-domain fiber optic sensor read-out (FOxSense™) system is used to interrogate the optical signal of all three sensors in real-time and to display the fuel tank oxygen environment suitable for aircraft status and alarm applications. Preliminary testing of the all optical fiber optic oxygen sensor have demonstrated the ability to monitor the oxygen environment inside a simulated fuel tank in the range of 0% O2 to 40% O2 concentrations, temperatures from (-) 40°C to (+) 60°C, and altitudes from 0-ft to 40,000-ft.

Objective: On the basis of preliminarily verifying the use of ultra-fast reaction polymer matrix optical fiber oxygen sensor and its measuring system to record the continuous and dynamic changes of carotid artery oxygen partial pressure (PaO2), in order to analyze and discuss the influence of lung ventilation on the continuous and dynamic changes of PaO2, we designed a whole animal experimental study in vivo. Methods: Four hybrid goats were selected, and the skin was cut and exposed directly under general anesthesia and tracheal intubation. The oxygen sensor, connected with the measuring system, was inserted directly into the left carotid artery to continuously record the dynamic changes of PaO2. With normal minute ventilation,mechanical ventilation is implemented through three tidal volumes: normal tidal volume (VT=15 ml/kg, Rf=20 bpm), half tidal volume (halved VT, doubled Rf) and double tidal volume (doubled VT, halved Rf). Each tidal volume was stable for 10~15 min respectively. We analyzed and calculated the average values of PaO2, the fluctuation magnitudes of PaO2 changes between breaths of last 180 s and the delay times of lung-carotid artery were. We analyzed the effects of different tidal volumes. Results: The heart rate and blood pressure of living goats were maintained stable during the mechanical ventilation experiment with normal ventilation volume Lung-carotid artery delay time is 1.4~1.8 s (about 3 heartbeats at this time). Under normal tidal volume of mechanical ventilation, the average value of PaO2 was (102.94±2.40, 99.38~106.16) mmHg, and the fluctuation range was (21.43±1.65, 19.21~23.59) mmHg, accounting for (20.80± 1.34, 18.65~22.22)% of the average value. Under the condition of halving tidal volume, the average value of PaO2 was maintained at (101.01±4.25, 94.09~105.66) mmHg, which was slightly decreased but not significant (P>0.05 compared with normal mechanical ventilation), but the fluctuation range of PaO2 was significantly reduced to (18.14±1.43, 16.46~20.05) mmHg, accounting for 17.5% of the average value. Under double tidal volume mechanical ventilation, although the average value of PaO2 increased slightly remained at (106.42±4.74, 101.19~114.08) mmHg (P>0.05 compared with normal mechanical ventilation and P<0.05 compared with half tidal volume mechanical ventilation), the fluctuation magnitude of PaO2 increased significantly to (26.58±1.88, 23.46~28.46)mmHg. Conclusion: Inspiration and expiration of normal lung ventilation are the initial factors for the increase and decrease of PaO2 in carotid artery. Under normal ventilation, halving tidal volume and doubling tidal volume significantly changed the fluctuation magnitude of PaO2, but the average value of PaO2 changed only slightly, while the lung-carotid delay time was similar.

Sensitivityenhancement of optical oxygen sensors is crucial forthe characterization of nearly anoxic systems and oxygen quantificationin trace amounts. In this work, for the first time we presented theintroduction of silver nanowires (AgNWs) as a sensitivity boosterfor optical oxygen sensors based on AgNWs–palladium octaethylporphine–poly(methylmethacrylate) (AgNWs@PdOEP–PMMA) microfiber mats prepared byelectrospinning. Herein, a series of sensing microfiber mats withdifferent loading ratios of high aspect ratio AgNWs were fabricated,and the corresponding sensitivity enhancement was systematically investigated.With increasing incorporated ratios, the AgNWs@PdOEP–PMMA-sensingmicrofiber mats exhibited a swift response (approx. 1.8 s) and a dramaticsensitivity enhancement (by 243% for the range of oxygen concentration0−10% and 235% for the range of oxygen concentration 0–100%)when compared to the pure PdOEP–PMMA microfiber mat. Additionally,the as-prepared sensing films were experimentally confirmed to behighly photostable and reproducible. The advantages of AgNW-inducedsensitivity enhancement could be useful for the rational design andrealization of revolutionary highly sensitive sensors and expectedto be readily applicable to many other high-performance gas sensordevices.