Use Of Sensors Research Articles

Wireless Ion-Selective Electrode Autonomous Sensing System

A paradigm shift in sensing methods and principles is required to meet the legislative demands for detecting hazardous substances in the molecular world. This will encompass the development of new sensing technologies capable of performing very selective and sensitive measurements at an acceptable cost, developed by multidisciplinary teams of chemists, engineers and computer scientists to harvest information from a multitude of molecular targets in health, food and within the environment. In this study we present the successful implementation of a low-cost, wireless chemical sensing system that employs a minimum set of components for effective operation. Specifically, our efforts resulted in a wireless, tri-electrode, ISE pH sensor for use in environmental monitoring. Sensor calibration and validated in situ field trials have been carried out and are presented in this paper.

Brain temperature measurement: A study of in vitro accuracy and stability of smart catheter temperature sensors

The injured brain is vulnerable to increases in temperature after severe head injury. Therefore, accurate and reliable measurement of brain temperature is important to optimize patient outcome. In this work, we have fabricated, optimized and characterized temperature sensors for use with a micromachined smart catheter for multimodal intracranial monitoring. Developed temperature sensors have resistance of 100.79 ± 1.19Ω and sensitivity of 67.95mV/°C in the operating range from15-50°C, and time constant of 180ms. Under the optimized excitation current of 500μA, adequate signal-to-noise ratio was achieved without causing self-heating, and changes in immersion depth did not introduce clinically significant errors of measurements (<0.01°C). We evaluated the accuracy and long-term drift (5days) of twenty temperature sensors in comparison to two types of commercial temperature probes (USB Reference Thermometer, NIST-traceable bulk probe with 0.05°C accuracy; and IT-21, type T type clinical microprobe with guaranteed 0.1°C accuracy) under controlled laboratory conditions. These in vitro experimental data showed that the temperature measurement performance of our sensors was accurate and reliable over the course of 5days. The smart catheter temperature sensors provided accuracy and long-term stability comparable to those of commercial tissue-implantable microprobes, and therefore provide a means for temperature measurement in a microfabricated, multimodal cerebral monitoring device.

Thick-film acoustic emission sensors for use in structurally integrated condition- monitoring applications

Monitoring the condition of complex engineering structures is an important aspect of modern engineering, eliminating unnecessary work and enabling planned maintenance, preventing failure. Acoustic emissions (AE) testing is one method of implementing continuous nondestructive structural health monitoring. A novel thick-film (17.6 μm) AE sensor is presented. Lead zirconate titanate thick films were fabricated using a powder/sol composite ink deposition technique and mechanically patterned to form a discrete thick-film piezoelectric AE sensor. The thick-film sensor was benchmarked against a commercial AE device and was found to exhibit comparable responses to simulated acoustic emissions.

Drifting snow threshold measurements near McMurdo station, Antarctica: A sensor comparison study

Abstract We present the results of an Antarctic spring field study of snow drift threshold measurements made using two custom drift sensors and a commercial parts-counting device. All three sensor types worked well at detecting drifting snow events, but the sensors recorded different magnitudes (particle count per unit time) of drift. Each sensor has a unique detection threshold for particle size, and responded differently to identical wind and snow conditions, although the particle counts from the different sensors are linearly related at low wind speeds. The drift threshold is defined here as the minimum friction velocity at which drifting snow was observed during more than 10% of measurements at that wind speed. The results of this multi-sensor study demonstrate that the drift threshold is lower (friction velocity of 0.2 m/s) for very small particles that are likely transported in suspension than for coarse-grained saltating particles (0.25 m/s). These friction velocities correspond to 10-meter wind speeds of 5.6 and 7.2 m/s respectively for the conditions during this experiment. The commercially available parts counter is recommended as a low-cost alternative to custom-built drift sensors for use in future field studies of drifting and blowing snow.

Acoustic attenuation, phase and group velocities in liquid-filled pipes II: Simulation for spallation neutron sources and planetary exploration

This paper uses a finite element method (FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.

A two dimensional vision-based force sensor for microrobotic applications

Abstract We present a two-dimensional, vision-based force sensor, capable of sensing micro-Newton level forces for use in microrobotic applications. Our design consists of a planar, elastic mechanism with known force-deflection characteristics. A CCD camera attached to an optical microscope is used to track the deformation of the mechanism as it is used to manipulate objects in a microrobotic test-bed. By observing the displacements of select points in the mechanism, the manipulation forces can be extracted in real-time to achieve force-guided manipulation of micro-scale objects. The modeling, design, microfabrication, calibration and experimental validation of the force sensor for use in a microassembly application are presented here along with preliminary results for next generation designs.

Comparison of two motion sensors for use in cardiac telerehabilitation

We compared the activity estimated by a pedometer and an accelerometer in coronary artery disease patients included in a phase III cardiac rehabilitation programme. Nine patients were divided into two groups and wore the pedometer for four weeks, and then subsequently the accelerometer for four weeks, or vice versa. The recorded daily exercise level (total daily steps and calories burned) was measured for each patient and compared with oxygen uptake and ventilatory threshold measured by ergospirometry at the end of the study. There was a significant correlation between the calories measured by the accelerometer and the ventilatory threshold (i.e. the sub-maximal capacity), r = 0.75 (P = 0.05). There was a significant correlation between the measured steps on the accelerometer and the ventilatory threshold, r = 0.72 (P = 0.07). There were no significant correlations for the pedometer. A questionnaire concerning ease of use of the sensors indicated that the cardiac patients favoured the pedometer.

Wall shear stress hot film sensor for use in gases

The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions.

Multichannel Dosimeter and $\alpha$-Al$_{2}$O$_{3}$:C Optically Stimulated Luminescence (OSL) Fiber Sensors for Use in Radiation Therapy—Evaluation With Photon Beams

A multichannel OSL fiber optic dosimeter based on optically stimulated luminescence (OSL) of alumina is proposed for online in vivo dosimetry (IVD) in radiation therapy (RT). Two types of dosimetric-grade Al2O3:C crystals are compared and show different behavior according to manufacturing process. Metrological validations have been performed with a Saturne 43 LINAC in reference conditions at CEA LIST LNHB (French Ionizing Radiation Reference Laboratory). The dose response of OSL integrals under photon beam irradiation (6, 12, and 20 MV) show sublinearity behavior modeled by second-order equations and exhibit a small energy dependence (between 0.7% and 1.4%), explained by a modified intermediate cavity model adapted to a LINAC photon spectrum. Preclinical tests at Institut Gustave Roussy (IGR) prove that a proper design for a PMMA build-up cap leads to a low dependence vs photon beam orientation (± 1.5% and ± 0.9%) and vs field size in view of surface measurements.

Out-of-plane high-density piezoresistive silicon microwire/p–n diode array for force- and temperature-sensitive artificial whisker sensors

We propose an out-of-plane high-aspect-ratio ‘whisker-like’ microwire array sensor for use in multisite contact force and temperature detection with high spatial resolution. Although the wire element has two terminal electrodes, the device consists of force-sensitive wire arrays where one end of the wire is attached to the substrate and the other end is free to be touched. We fabricated a force-sensitive wire array based on p-type (p-) silicon with 3 µm diameter and 30 µm length (1 Ω cm) assembled over an n-type (n-) silicon substrate (3–6 Ω cm), which resulted in a p-silicon wire/p–n diode system array. Due to the piezoresistance effect of the p-silicon wire, the electrical conductance changes upon contact of an individual wire with an object. The shift in the rectifying current–voltage (I–V) curves of the embedded p–n diode depends on the temperature through the silicon wire. Thus, the same alignment can be used as a force sensor and a temperature sensor. Both force- and temperature-sensitive microwire sensor arrays with a small detection area (∼20 µm2) and high spatial resolution (∼100 µm in pitch) have potential in numerous applications, including artificial electronic fingertips in a robot hand/prosthetics, multisite sensing of contact force, shear force, surface roughness and slip, and local temperature sensing capabilities.

Construction of a panel of glucose indicator proteins for continuous glucose monitoring

The development of implantable glucose sensors for use in diabetes treatment has been pursued for decades. However, enzyme-based glucose sensors often fail in vivo. In our previous work, we engineered a novel glucose indicator protein (GIP) that can sense glucose without relying on any enzymes and cofactors. Nevertheless, this GIP is unsuitable for blood glucose monitoring due to its low dissociation constant. Here, we report a novel approach to creating a new GIP that can be used to monitor blood glucose level. By disrupting pi–pi stacking around GIP's glucose binding site through site-directed mutagenesis, we showed that GIP's dissociation constant can be manipulated from 0.026 mM to 7.86 mM. This approach yielded four GIP mutants. We showed that one of the mutants can be used to detect glucose from 0 to 32 mM, while another mutant can be employed to visualize intracellular glucose (0–200 μM) within living cells through FRET imaging microscopy measurement.

Microworm optode sensors limit particle diffusion to enable in vivo measurements

There have been a variety of nanoparticles created for in vivo uses ranging from gene and drug delivery to tumor imaging and physiological monitoring. The use of nanoparticles to measure physiological conditions while being fluorescently addressed through the skin provides an ideal method toward minimally invasive health monitoring. Here we create unique particles that have all the necessary physical characteristics to serve as in vivo reporters, but with minimized diffusion from the point of injection. These particles, called microworms, have a cylindrical shape coated with a biocompatible porous membrane that possesses a large surface-area-to-volume ratio while maintaining a large hydrodynamic radius. We use these microworms to create fluorescent sodium sensors for use as in vivo sodium concentration detectors after subcutaneous injection. However, the microworm concept has the potential to extend to the immobilization of other types of polymers for continuous physiological detection or delivery of molecules.

Implantable hybrid chrome silicide temperature sensor for power MEMS devices

In this Letter, an implantable hybrid temperature sensor for use in a micro-scale space in power MEMS devices is proposed. The developed sensor use chrome silicide (CrSi2), which has a very high electromotive force, and nickel as a base metal. Since a thermocouple is an appropriate device to measure temperature at a specific spot, the correlations between the junction sizes and electromotive forces should be verified to reduce the junction size of the thermocouple. Furthermore, it is necessary to verify the performance of the thermocouple implanted in a microdevice by patterning a resistance temperature detector (RTD) on the side of the cold junctions to evaluate the reference temperature of the nickel. The Seebeck coefficients of the CrSi2 thin film thermocouples occur at approximately 70 µV/°C, and the values have been shown to be 1.8 times higher than those of commercial thermocouples. The value of the slope, αNi, which is the temperature coefficient of resistance (TCR) of the nickel RTD is 0.0063/°C at 20°C, whereas the reference value of the TCR of nickel, αNi-ref is 0.0067/°C at 20°C. The third-order polynomial compensation is 99.989% of the regression square value. Based on the verification, a prototype of the hybrid temperature sensor is implanted in a micro methanol–hydrogen peroxide auto-thermal reforming module by stacking six different layers that consist of temperature sensors for the base and different channel figures for the reforming reaction.

An optical fiber Blade Tip Clearance Sensor for Active Clearance Control Applications

Active clearance control has been used to improve efficiency and performance in commercial aircraft engines. This paper describes a optical fiber sensor for active control, which is simple and thin in structure. The sensor system data sampling rate is about 100kHz, and its resolution ratio is better than 0.01mm. Sensor's ability to monitor tip clearance was tested using a rotor test rig and individual blade tip clearances at different speed and a blade failure measurement example was given. The results show: the sensor was able to detect the blade flaws, and have a large bandwidth, high data sampling rate. It will be presented to show the viability of the sensor for use in active clearance control.

Highly Selective Optical Fibre Ammonia Sensor for use in Agriculture

A highly selective optical fibre sensor has been developed for the monitoring of low level atmospheric ammonia concentrations. The measuring technique employed is based on a differential optical absorption approach, which uses a broadband optical source, optical fibres for transmission and a miniature ultraviolet/visible spectrometer for detection. This novel technique for the detection of ammonia has previously been shown to be capable of monitoring concentrations as low as 1ppm without any notable cross-sensitivity issues [1]. The sensor was operated over a number of hours in-situ in an agricultural cattle enclosure and simultaneously with a commercially available ammonia sensor. Results shown herein demonstrate the effectiveness of the developed sensor to operate within the environment accurately, recording concentration levels of between 0 and 2ppm.

Sensing of biologically relevant d-metal ions using a Eu(iii)-cyclen based luminescent displacement assay in aqueous pH 7.4 buffered solution

1·Eu·BPS was developed as a luminescent lanthanide sensor for use in displacement assays for detection of d-metal ions by monitoring the changes in the europium emission, which was quenched for iron(II), with a detection limit of ∼10 pM (0.002 μg L(-1)) for Fe(II) in buffered pH 7.4 solution.

Potentiometric Determination of Ketotifen Fumarate in Pharmaceutical Preparations and Urine Using Carbon Paste and PVC Membrane Selective Electrodes

This study compares between unmodified carbon paste (CPE; the paste has no ion pair) and polyvinyl chloride (PVC) membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF), where sodium tetraphenylborate (NaTPB) was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10−7 to 10−2 mol L−1. The electrodes show Nernstian slope value of 52.51 ± 0.20 and 51.51 ± 0.25 mV decade−1 for CPE and PVC membrane electrodes at 30°C, respectively. The potential is nearly stable over the pH range 3.0–6.0 and 2.0–7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets), and biological fluid (urine). The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97 ± 0.53 and 98.62 ± 0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method.

Virtual sensors for use in information measurement systems

A model of a virtual sensory system consisting of a set of physical and virtual sensors and a supervisor is presented. Levels of the hierarchy for each type of sensor are considered. At the physical level of integration, a uniform interface is provided along with access to specific devices, while at the virtual level data are provided for the upper level and the supervisor.

Optimized design of remote point diffractive optical sensors

We present an optimization study of surface relief grating based sensors for use in opticalremote point sensing. Our study includes the effects of geometrical characteristics of thephotonic structure on the efficiencies of the first and second diffraction orders and theexhibited sensor responsivities of these orders. Our predictions are verified experimentallywith measurements of surface relief gratings patterned by direct laser ablation onSiO2 sol–gel nanocomposite material with embeddedNiCl2 nanocrystals developed for ammonia sensing.

Ratiometric fluorescence-based dissolved carbon dioxide sensor for use in environmental monitoring applications

The focus of this work is on the development and characterisation of a fluorescence-based ratiometric sol-gel-derived dissolved carbon dioxide (dCO(2)) sensor for use in environmental monitoring applications. Fluorescence-based dCO(2) sensors are attractive as they facilitate the development of portable and low-cost systems that can be easily deployed outside the laboratory environment. The sensor developed for this work exploits a pH fluorescent dye 1-hydroxypyrene-3,6,8-trisulfonic acid, ion-paired with cetyltrimethylammonium bromide (HPTS-IP), which has been entrapped in a hybrid sol-gel-based matrix derived from n-propyltriethoxysilane along with the liphophilic organic base. The sensor spot deposited on a cover slip has been interrogated with a robust, ratiometric optical probe that combines effective fluorescence excitation and detection and thus facilitates the production of a highly sensitive sensor system using low-cost optoelectronic components. The probe design involves the use of dual-LED excitation in order to facilitate ratiometric operation and uses a silicon PIN photodiode. HPTS-IP exhibits two pH-dependent changes in excitation bands, which allows for dual excitation ratiometric detection as an indirect measure of the dCO(2). Such measurements are insensitive to changes in dye concentration, leaching and photobleaching of the fluorophore and instrument fluctuations unlike unreferenced fluorescence intensity measurements. The performance of the sensor system is characterised by a high degree of repeatability, reversibility and stability. Calculated limit of detection for the sensor was 35 ppb. The sensor probe was used to monitor dCO(2) levels in a laboratory-based aquatic habitat, and the expected diurnal pattern was clearly visible. The influence of temperature, biofouling and photobleaching on sensor performance has been also investigated.