Search

Detailed in this paper is the design of a novel handheld electrochemical analyzer system interfaced to a smart phone, which provides versatile and cost-effective solution for real-time sensing applications. It was characterised for electron transfer events associated with chemical and biological samples. The presented design is implemented based on the Arduino nanoopen source electronics prototyping platform. The versatility of the instrument is further demonstrated by employing the electrochemical analyser to a modified electrochemical cell which formed the basis of a DNA biosensor. Cyclic voltammetry technique was used to impose a triangular waveform on an electrochemical cell and the resulting current through the cell was then monitored. The DNA biosensor generated unique electrical signals in real-time between complementary and non-complementary oligonucleotides sequences of the Bacillus cereus DNA. The effects of hybridization and non-specific binding were compared when the probe DNA molecules were immobilized on a conducting polymer matrix. The results showed that the probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to other immobilization methods. The performance of the DNA sensor proved to be effective in terms of selectivity, sensitivity and reproducibility of hybridization events. Analysis of these DNA probes showed that the minimum level of detection was 33.3 pg/ml.

A detailed analysis of scientific work done in transforming radio frequency (RF) signals for tracking an embedded object with special reference to telemetry capsules in the gastro-intestinal (GI) tract is presented in this paper. We fully discuss the mathematics of the necessary stages for transformation from signal to hexadecimal, decimal, to distance up to the stage where the path trajectory is computed. Experimental validation is accomplished by using RF signals at 433MHz, Analog Devices 8052 based microcontroller with ADC capability and a means of transferring the received signal strength intensity voltage converted to digital, from the microcontroller to the personal computer. The primary focus of this paper is a proven practical way of achieving the above tasks by using basic mathematical and computing principles. Consequently, our algorithm-based tracking results for experiments in a liquid medium yielded an average error of less than 21%. These results were validated with the Bland-Altman plots using semi-automated manual measurements as gold standard.

The pressure sensing properties of nanocomposite SnO 2 , TiO 2 , and TiO 2 /ZnO thick film capacitors with interdigitated electrodes are investigated. To form the dielectric layers, the metal oxides powders were respectively mixed with isopropanol, wet ball milled for 24 h, then the mixtures were dried at 120 °C and further the powders were placed under 2 tonnes of pressure to form pellets, which were fired at 1250 °C (rate of 5 °C/min) in a vacuum of 6 × 10 −3 mbar for 5 h, followed by cooling (rate of 3 °C/min). After firing, the resultant nanopowders were mixed with 7 wt.% of polyvinyl butyral (binder) and suitable amount of ethylenglycolmonobutylether (solvent) to form the pastes. These were screen-printed over the Ag electrodes on alumina substrates to form SnO 2 , TiO 2 , and TiO 2 /ZnO capacitor pressure sensors accordingly. The evaluation of pressure sensing properties of these sensors was performed using a HP 4192A Impedance Analyser, which recorded the changes in the values of the capacitances under different mechanical stresses. At the applied load of 5 kPa, the response times of 2.5 s, 5.6 s and 4 s were recorded for SnO 2 , TiO 2 , and TiO 2 /ZnO sensors, respectively. In addition to instant response times, these pressure sensors have the advantage of being reusable, as their electrical properties were restored to the original value after annealing for 2 h at 80 °C. Moreover, one year later after the initial testing, the sensors were still operational and produced similar time responses to pressure.

In this paper we report a label-free detection method of unmodified DNA using polypyrrole as an immobilization matrix by impedance measurement. A probe and a target complementary DNA sequence specific for the bacterial pathogen, Bacillus cereus are used. Impedance measurements are performed without using additional redox probes. The effects of hybridization and non-specific binding are compared when the Probe DNA molecules were immobilized by two different methods: electrochemical adsorption and entrapment. The probe DNA immobilized using electrochemical adsorption yielded better hybridization signals compared to that immobilized using the entrapment method. Control experiments were also performed to prove the specificity of the biosensor in the presence of non complementary DNA. Negligible unspecific binding with the immobilized probe was observed with the electrochemically adsorbed probe, whereas the entrapped probe responded to the non complementary target. The performance of the DNA sensor was characterized using both cyclic voltammetry and impedance spectroscopy techniques and proved to be effective in terms of specificity of hybridization events.

This paper reports on investigations into the response mechanism of novel polyaniline composition conductimetric pH sensors and the effects of polymer binder, surfactant and film thickness on this response. It was revealed through X-ray photoelectron spectroscopy, focussed ion beam milling and impedance spectroscopy that the response mechanism was due to the deprotonation of the polymer backbone nitrogen atoms located on the uppermost surface level of the functional material particles. The equivalent circuits for the sensing layer were modelled using the Cole–Cole model for a range of pH environments. The optimum sensing layer composition was determined to contain less than 50 wt.% polymer binder with 5 wt.% surfactant. This composition was determined by examining the effects of both binder and surfactant on the electrical characteristics and sensor response of the composite films. The thickness of the sensing layer was found to have no discernable response on the sensing characteristics of the conductimetric pH sensors.

Novel method of manufacturing micro sensors arrays for biomedical applications using BioForce NanoeNablerTM is reported. The operation of pH and glucose sensing elements is based on the properties of polymers, which exhibit a change in their electrical characteristics (such as resistance or capacitance) on exposure to solutions with different concentrations of pH or glucose. A sensor for glucose was successfully fabricated using the enzyme glucose oxidase immobilized within the polymer poly (o-phenylenediamine). This sensor was then successfully miniaturized utilizing immobilization for a dry process. The concentrations used for the microsensor were between 1 mM and 6 mM. Samples containing different concentrations of glucose were applied to the sensor while the system was being monitored for variances in either current or conductance. The resulting changes in the electrical characteristics of the sensor monitored in real time were found to be proportional to the different concentrations of glucose applied. Microscaled interdigitated electrodes were used for sensors array, with 48 sensors places on one chip. It is envisaged that findings of this work would form the basis for miniaturised point-of-care diagnostic system.

In this paper we present our development of a SF"6/Cl"2-based plasma etch recipe for a LAM Research 4720 etch chamber. Our tungsten plasma etch recipe is used to pattern nanoscale resistor features integrated within a novel IR sensor process. We characterised the nanoscale etch in terms of five primary process parameters using a 16-run V fractional factorial experiment, to provide accurate estimates of all main effects and two-factor interactions. The experimental results determined the target levels for the etch process parameters. Our optimised nanoscale tungsten etch module was then integrated within a CMOS/MEMs-compatible nanobolometer infrared (IR) sensor fabrication flow. Our use of tungsten improves the reliability of the sensor pixels at elevated stress current levels, when compared with equivalent Ti-based pixel structures, and demonstrates the potential of tungsten as a CMOS-compatible nanobolometer material.

Aims: A PCR technique was developed as a reliable and rapid identification method for the Bacillus cereus group species, based on a unique conserved sequence of the motB gene (encoding flagellar motor protein) from B. cereus, Bacillus thuringiensis and Bacillus anthracis. Methods and Results: Primer locations were identified against eight strains of the B. cereus group spp. from nucleotide sequences available in the National Centre for Biotechnology Information database. The PCR assay was applied for the identification of 117 strains of the B. cereus group spp. and 19 strains from other microbial species, with special emphasis on foodborne pathogens. Conclusion: The designed cross-species primers are group specific and did not react with DNA from other Bacillus and non-Bacillus species either motile or not. The primers system enabled us to detect 103 CFU of B. cereus cells per millilitre of sample. Significance and Impact of the Study: Bacillus cereus group spp. belongs to one of the most prevalent foodborne pathogens. Bacterial growth results in production of different toxins; therefore, consumption of food containing >106 bacteria per gram may result in emetic and diarrhoeal syndromes. A rapid and sensitive bacterial detection method is significant for food safety.

Detection of microbial pathogens in food is the solution to the prevention and recognition of problems related to health and safety. New biomolecular approaches for foodborne pathogen detection are being developed to improve the biosensor characteristics such as sensitivity and selectivity, also which is rapid, reliable, cost-effective, and suitable for in situ analysis. Recently, conducting polymers have drawn attention in the development of biosensors. The electrically conducting polymers have numerous features, which allow them to act as excellent materials for immobilization of biomolecules. Also, their unique properties make them appealing alternatives for specific materials currently employed for the fabrication of biosensors. Therefore, this paper presents a comprehensive literature review detailing the salient features of conducting polymers and their application to biosensors with an emphasis on foodborne pathogen detection.

Measuring the change of the conductivity of a Polyaniline (PANI) film while in contact with a solution is considered to be a costeffective tool for pH sensing. The device consists of a PANI film deposited between two identical electrodes, reducing the number of fabrication steps. To ensure the sensors display an optimum response to solutions of different pH values, it is important to understand the effect of the polymer binder, surfactant and film thickness. The effect of varying the amount of Polyvinyl butyral (PVB) and Hypermer (PS3) on the pH sensitivity of screen printed thick film sensors is reported.

In this paper the evolution of species densities up to the saturation limit in pulsed dielectric barrier discharges in atmospheric air plasma is predicted. The saturation limit itself is presented in the form of an exponential equation and is validated by computer modeling of continuity equations and atmospheric reactions coupled with appropriate dielectric dependent boundary conditions. Microdischarge streamer times are treated independently and a profile of the species generation due to all microdischarges within the plasma is presented. Quasi-neutrality is assumed for calculations and a theoretical maximum value for species densities in such a plasma is additionally outlined. Results show a good agreement between simulated and calculated values and serve to illustrate the onset of saturation in atmospheric pressure plasmas in general. Practical conditions of voltage, gap distance and frequency are incorporated so as to make the model as realistic as possible.

A novel multielectrode dielectric-barrier discharge plasma system operating at atmospheric pressure in air, which has improved microbial inactivation properties is described. The interaction of high-voltage components necessary to create the discharge is outlined, and the unique configuration of electrodes driven by power insulated gate bipolar transistors is put forward. Active species gain is in evidence in this system due to the effective feedforward mechanism employed and are validated by carrying out microbial inactivation studies on E. coli. Both active species gain and microbial inactivation hypotheses are verified by numerical modeling.

In this work, a design of wireless system for multi-sensors monitoring has been presented. The main purpose of this research is to develop an efficient telemetry system for measuring water pressure and temperature signals. The system reads data from two types of sensors, temperature (resistive) and pressure (capacitive). Anderson circuit configuration has been used for the resistive sensor, since it offers linear like behavior. The capacitive interface is based on capacitance-frequency-voltage conversion that uses phase lock loop to convert the frequency to voltage. A developed pressure sensors based on polyethylene and polyvinylidene fluoride, were used to evaluate the performance of the capacitive interface. A small size wireless module has been built separately to test the capacitive interface for a certain range of pressure. Two mechanisms have been adopted to reduce the overall power consumption. These are power scheduling and wakeup circuit for the capacitive interface. The first one is implemented fully by the micro-controller unit (MCU) in order to switch on/off all the system units. A wakeup circuit has been designed to interrupt the MCU when it is in the sleep mode and the capacitive samples are changing significantly. A platform for wireless sensor network (WSN) has been developed so that the receiver side can communicate with more than one sensor node.

Ozone sensing properties of mixed oxides of In 2 O 3, ZnO , and SnO 2 in the form of thin films are explored. Exposure to ozone causes defects in the materials, and subsequently causes changes in the materials properties. In this work, a cost-effective, room temperature, real-time ozone monitoring device has been developed. The fabricated sensors are capable of detecting threshold ozone safety levels proposed by the World Health Organization (WHO) while operating at room temperature. Room temperature operation offers many advantages over high temperature operation, such as reduced power consumption, reduced fabrication costs, and ease of implementation into portable devices, such as laptops and mobile phones. The fabrication of these sensors was carried out by means of an Edwards E306A Coating System. Various mixtures of In 2 O 3, ZnO , and snO 2 were deposited in a rectangular pattern on top of copper interdigitated electrodes. X-ray Photo Spectroscopy (XPS) analysis showed that there were levels of impurities in the sensor samples, which were dependant on the fabrication process and parameters. XPS analysis also gave a detailed account of the shifts in binding energies of the thin oxide layers. The results presented show that the highest response to environmentally relevant ozone concentrations is achieved with a very thin sensing layer and a high deposition rate. The performance of the sensors has been investigated and compared.

Gamma radiation and ozone sensing properties of mixed oxides in the form of thermally evaporated thin films are explored. External effects, such as radiation and ozone cause defects in the materials they interact with, cause changes in the material properties. An Edwards E306A thermal coating system was used for the mixed oxides thin films deposition. Cu electrodes were manufactured on the substrate via thermal evaporation, photoresist was spin-coated over it and was exposed to UV light via acetate containing the desired inter-digitated electrode patterns. After the exposure, the substrate was placed in a developer solution and then rinsed in water and placed in the etching solution to reveal the electrode pattern. The optical properties of the films were explored using CARY 1E UV-Visible Spectrophotometer. The influence of gamma radiation on the electrical properties of the films was traced via the measurements of conductance versus radiation dose, which were recorded in real-time using HP 4277A LCZ impedance analyzer at a frequency of 1 kHz. The fact that the explored thin films were sensitive to both gamma radiation and ozone exposure enables the development of cost-effective real-time monitoring system for personnel protection and environmental monitoring. This novel approach would allow the manufacture of the sensor system with multiple sensor heads during one technological process, whereas various shielding materials or pattern recognition could be employed to differentiate between the effects of ozone and gamma radiation on the mixed oxide thin film sensors.

Dielectric breakdown in ceramics and composites has previously been determined by the dielectric breakdown model, dependent only on the electric field strength at a certain point and intermolecular distance in a lattice. This does not take into account quantum aspects of the lattice structure into account. The present model takes into account quantum variations of particles in conjunction with different particle characteristics. Dielectric breakdown patterns are characterised by their quantum breakdown probabilities and studies are carried out as a function of the applied electric field, temperature and specific material constants responsible for breakdown, such as the mean free path and the potential barrier present.

A novel cost-effective gamma radiation monitoring system based on metal oxide thick films is presented. The changes in Bi2O3/Nb2O5 thick film capacitors were monitored in real time under the influence of gamma radiation using miniaturized, low power, bi-directional wireless communication system. The capacitive interface circuitry was based on a Delta-sigma (ΣΔ) modulator using switched capacitor (SC) circuit architecture with integrated on-chip temperature sensor.

This paper reports a new model for a wireless microsensor data acquisition system that can be used in diagnosing abnormalities in the esophagus. The proposed system incorporates pressure sensors for measuring the strength and pattern of muscle contractions that occur in the esophagus. Real data recorded by a manometry device, that detects pressure changes using developed sensors within a sealed cavity, is employed to assess the performance of the proposed system. Three different pulse coding modulation (PCM) and successive approximation register (SAR) analog to digital conversion algorithms are used for the channel coding. The created models were simulated and tested using SIMULINK® software. A behavioral model for FSK transceiver suitable for short-range applications has been developed. The transceiver system performance was tested under different conditions and the output simulation results were presented. The obtained output results from the different models are discussed.

Interdigitated capacitors have the potential to be used in pressure sensing applications requiring small size, high reliability and cost effective production. Such sensors have applications in wireless pressure monitoring of bodily fluids for the research and diagnosis of a number of medical conditions in cardiology, pulmonology and gastroenterology. In this work, the sensitivity of Polyvinyl Butyral (PVB)/carbon-black composites to pressure is evaluated with these applications in mind. The devices are fabricated by drop coating solutions containing PVB and 5, 10, 15 and 20% carbon black onto interdigitated electrodes. The optimum carbon loading for pressure sensing applications up to 2500 kPa was determined for these composites using a tensile tester. The highest sensitivity was recorded for samples with 5% carbon black. These devices were successfully integrated into a prototype wireless interface, transmitter and receiver system. The response (25 mV), hysteresis (4.78%) and repeatability (10.76%) under hydrostatic pressure ranging from 0–17 kPa were measured. Finally, the devices temperature dependence was investigated.

It is important to know the behaviour of materials under the influence of radiation for the effective design of novel sensor systems. Optical properties of bismuth germinate (Bi 4 Ge 3 O 12 —BGO) thin films were investigated in terms of their perception to gamma radiation exposure. An Edwards E306A vacuum thermal coating system was used for thin films deposition. BGO films with a thickness of 200 nm were exposed to a disk-type 137 Cs gamma radiation source with an activity of 370 kBq. Optical properties of the films were investigated using CARY IE UV-Visible Spectrophotometer. Calculated optical band gap for as-deposited BGO thin film was 1.95 eV. Gamma radiation induced changes in the optical properties of thin films, which could be explained by the variation in the degree of disorder. From the density-of-state model, it is known that optical band gap decreases with an increasing degree of disorder of the amorphous phase. Electrical properties of BGO thin films were recorded in real time using a low power capacitive interface system with a high resolution, which is based on Delta-sigma modulator. At doses from 0 to 1.5 mGy little if any changes in the capacitance were measured. This could be explained by co-existence of two processes, namely creation and annihilation of defects under the influence of radiation. After a threshold dose of 1.5 mGy creation of defects becomes more prevailing and the BGO film capacitance has gradually increased in value from 2.97 pF to 7.09 pF after irradiation with a 2.44 mGy dose.

Advances in semiconductor sensor technology, medical diagnostics, and health care needs a rapid boost in research into novel miniaturized pH sensors, which can be used in vivo for continuous patient monitoring. Requirements for the in vivo sensor are materials biocompatibility, high measurement precision, a response time of an order of less than seconds, and the possibility of continuous 24-h monitoring. Monitoring of the pH values is important in the study of tissue metabolism, in neurophysiology, cancer diagnostics, and so forth. Muscle pH can be used to triage and help treat trauma victims as well as to indicate poor peripheral blood flow in diabetic patients. Clearly, to avoid infection and spread of diseases, all in vivo monitoring devices should be single-use/disposable, which puts strict requirement on their price. This paper reviews the wide range of methods and materials used for in vivo measurement of pH levels, such as using the optical fibers, pH-sensitive polymers, ion-sensitive field effect transistors, near infrared spectroscopy, nuclear magnetic resonance, and fluorescent pH indicators.

Purpose – To develop a wireless sensor micro‐systems containing all the components of data acquisition system, such as sensors, signal‐conditioning circuits, analog‐digital converter, embedded microcontroller unit (MCU), and RF communication modules. This has now become the focus of attention in many biomedical applications.Design/methodology/approach – The system prototype consists of miniature FSK transceiver integrated with MCU in one small package, chip antenna, and capacitive interface circuitry based on Delta‐sigma modulator. At the base station side, an FSK receiver/transmitter is connected to another MCU unit, which send the received data or received instructions from a PC through a graphical user interface GUI. Industrial, scientific and medical band RF (433 MHz) was used to achieve half duplex communication between the two sides. A digital filtering has been used in the capacitive interface to reduce noise effects forming capacitance to digital converter. All the modules of the mixed signal syst...

Both gamma radiation and ozone sensing properties of mixed oxides in the form of thin films are explored. External effects, such as radiation and ozone, cause defects in the materials it interacts with and, consequently, it causes changes in their properties. These changes manifest themselves as the alterations in both the electrical and the optical parameters, which are being measured and employed for dosimetry sensor development. An Edwards E306A thermal coating system was used for In2O3:ZnO:SnO2 (90%:5%:5%) films deposition. For the electrical properties measurements, Cu electrodes were manufactured on the glass substrate via thermal evaporation of Cu; then AZ5214 photoresist was spin-coated over it and exposed to ultraviolet (UV) light via the acetate, containing the desired electrodes patterns. After the exposure, the substrate was placed in Electrolube PDN250ML developer solution and then rinsed in water and placed in the etching solution of SEMO 3207 fine etch crystals to reveal the electrode pattern. The optical properties of In2O3:ZnO:SnO2 thin films were explored using CARY 1E UV–visible spectrophotometer. The values of the optical band gap Eopt are estimated in the view of the Mott and Davis’ theory. Doping of In2O3 with 5% ZnO and 5% SnO2 dramatically changes the overall structure of the film and thus affects its sensing to gamma radiation and ozone. Mixing metal oxides in certain proportions provides a tool for controlling the sensors response.

Due to the increasing demand for accurate, reliable and highly sensitive pH sensors, research is ongoing to find new materials and methods to achieve this goal. An approach that shows promise in the pH-sensing field is the conductimetric pH sensor. It has the advantage of simpler construction over its potentiometric counterpart and may prove less expensive in mass production. It also meets the criteria for possible future miniaturization. This work attempts to qualify tin oxides (SnO and SnO2) as sensing materials in conductimetric interdigitated pH sensors. Both materials are tested over a range of frequencies that cover all major operating areas of the devices. Sensors are subjected to testing with pH buffers in the range pH 2–11, and all changes in their electrical parameters are recorded. It was found that SnO and SnO2 operated at low frequencies produces the best response to pH change. Tests produced a notable increase in conductance for both materials, and the magnitude of the increase in conductance is directly related to the pH of the test solution. No meaningful relationship was observed for either material at higher frequencies.

Decomposition of food is caused by microorganisms, which produce odorous gases as a result of metabolic products. The early detection and control of these organisms provides a longer shelf life and prevents food poisoning. The identification of aerobic and anaerobic bacterial cultures in food can take up to 3 days or longer using existing laboratory techniques. Conducting polymer nanocomposite (CPC) materials are of special interest to the gas sensor industry where arrays of polymer composites may be used to detect gases and odours. These composite gas sensors operate at room temperature, which provides an advantage over thick film metal oxide gas sensors. CPC sensors are composed of conducting particles embedded into an insulating polymer matrix. The resistance changes of the sensors in the array are used to produce a pattern that corresponds to the vapour under investigation. This study presents the use of an array of CPC sensors for real time analysis and quantification of the odours given off a selection of food borne pathogens including Salmonella spp., Bacillus cereus and Vibrio parahaemolyticus.

Accurate pressure readings are essential tools in a wide range of applications. For example in monitoring intracranial pressure for patients with head injuries or tyre pressure to improve automobile safety. With this in mind, a real time monitoring system, which displays the change in sensor capacitance with pressure on a PC, has been developed. Thick film capacitors with an oxide dielectric layer formed using niobium pentoxide (Nb 2 O 5 ), titanium dioxide (TiO 2 ) and cerium dioxide (CeO 2 ) are investigated using this system. SEM was used to examine the morphology and particle size of the thick films. To aid in the development of a suitable interface circuitry, the frequency and temperature dependence of each device is investigated. Each sensor was then subjected to pressures in the region of 0–100 kPa. The results show that capacitors with an Nb 2 O 5 dielectric layer were most sensitive. It is thought that this is due to its particle size.

The electrical properties of PVDF thick film capacitors under gamma radiation are investigated. To increase the conductivity of the films, they were filled with 4 and 6 wt.% of carbon, which is close to the percolation threshold. Screen-printing was used for film fabrication. All films were exposed to a disk-type 137 Cs source with an activity of 370 kBq. Changes in I – V characteristics were measured after each exposure dose. A tenfold increase in the values of current was recorded after a dose of 228 μGy for C-PVDF films with a thickness of 23.97 μm and 6 wt.% carbon doping. A higher dose of 342 μGy resulted a decrease in the values of current. Thicker films showed an increase in the values of current with irradiation to a dose of 798 μGy. PVDF + carbon system has potential applications in low-dose radiation dosimetry. The high current induced by radiation caused heating and electroforming of the device, due to the metal inclusions from the Ag contact material. It was noticed that as-printed films of 23.97 μm in thickness, tend to electroform at about 12 V, whereas films irradiated with 171 μGy showed a strong electroforming effect at a lower voltage of 5 V. For that reason, proper design of dosimetry systems is essential to eliminate such effects. Gamma radiation sensitivity of counterpart PVDF thick films with 4 wt.% carbon doping was studied via capacitance-dose measurements in real time, since these samples were less conductive. Irradiation of this sensor with doses from 1.15 to 2.5 mGy caused a considerable monotonic increase in the values of its capacitance from 2.92 to 12.37 pF. Accordingly, sensors with 4 wt.% of carbon could sustain higher radiation doses, but had poor sensitivity to radiation of lower level.

During the last 10 years, a large interest has developed in the preparation of nanocomposite structures by embedding inorganic nanoparticles into polymeric materials. These materials combine the properties of the inorganic fillers with the processability and flexibility of polymers. The versatility of polymer nanocomposite systems is of special interest to the gas sensor industry where arrays of polymer/carbon black composites have been used to identify gases and odours. These polymer gas sensors provide selectivity based on their chemical structures and operate at room temperature, which provide advantages over thick-film metal oxide gas sensors. ZnFe 2 O 4 and ZnO have excellent stability, high sensitivity, low fabrication complexity and moderate operating temperatures, which are ideal properties for a gas sensing material. In this work, the development of a thick-film ZnFe 2 O 4 /ZnO sensor, which operates at room temperature and a drop-coated conducting polymer composite sensor containing 30 w/w% ZnFe 2 O 4 /ZnO nanoparticles is discussed. The sensors were tested in a fully automated test rig and showed promising results for the detection of alcohol vapours.

The aim of this work is to investigate the effect of increasing the carbon black and the sensing layer thickness on the response of a sensor. Three sensors of 60/40 mol% ZnO/Fe2O3 with different percentages of carbon black (1.5, 2 and 2.5 wt%) were fabricated on alumina substrates and copper thin film electrodes. The base resistance of the 1.5 wt% carbon black sensor was 4 M Ω while for the 2 wt% carbon black sensors it was 25.50 k Ω . The lowest base resistance was recorded with the 2.5 wt% carbon black sensor to be 8.2 k Ω . The sensors were used to detect propanol in the concentration range 2500–5000 ppm, increasing with a step size of 500 ppm, at room temperature. The responses of the sensors were determined as ((Rgas−Rair)/Rair)×100 while the sensitivity was calculated as the slope of the graphs. The sensitivity was increased as the amount of carbon black decreased. The sensitivities of the sensors to propanol at room temperature were 0.0105, 0.005 and 0.002%/ppm for the three sensors. On the other hand, four sensors have different thickness were fabricated used by the same manner. It was found that the response of the sensor increased relatively as the thicknesses of the sensing layer decreased. Results show that the one-layer sensor has the highest response, followed by a decrease in the responses for sensors with higher numbers of layers, 2, 3, 4 and 5 successively.

This study investigates gas sensitive resistors fabricated by screen-printing inks created from a mixture of NiO-TiO2 and containing a poly(vinyl butyral) binder for the detection of alcohol vapors at room temperature. It was found that these films exhibited a significant resistance change in response to the vapors, while also displaying an inherent selectivity, proving most sensitive to toluene and propanol vapor; with comparatively low responses exhibited towards ethanol and methanol vapors. It is proposed that swelling of the polymer binder used in the fabrication of the NiO-TiO2 thick-films, rather than oxygen ion induced majority carrier modulation in the oxides, is the significant factor in causing the electrical resistance of the films to increase upon exposure to the organic solvent vapors. Very fast response and recovery times of 9 s and 16 s, respectively were recorded for the devices upon exposure to 4000 ppm step changes in propanol concentration. For comparative analysis, poly(vinyl butyral)/carbon black composites were fabricated from a by a drop-coating technique. The superior sensitivities and response times of the screen-printed sensors were attributed to the (SEM confirmed) highly porous structure attained by the thick-film devices, caused by the excessive free-volume induced in the polymer-binder matrix by the oxide materials. The results suggest that the effects of the polymer binder, even when present in comparatively small amounts, cannot be ignored in certain sensing applications

Remote pressure monitoring is of particular importance in medical and environmental applications as it is less labour intensive, safer and offers peace of mind to the general public. To meet this demand, a prototype system has been developed and used to evaluate thick-film pressure sensors with an oxide dielectric layer. The circuit is based on the principle of capacitance-frequency-voltage conversion and has been designed to minimize power consumption. Each device was tested under hydrostatic pressure in the range 0-17 kPa and assessed in terms of sensitivity, hysteresis, repeatability, creep and temperature effects. The results show that this approach may be used for the fabrication of cost effective, reliable devices for wireless pressure sensing applications

This review considers techniques employing radio frequency (RF) as well as ultrasound signals for tracking. Medical capsules have been employed since the SOs to measure various physiological parameters in the human body. Examples are temperature, pH, or pressure inside the gastrointestinal (GI) tract. The development and subsequent incorporation of new technology into reasonably priced, commercially available devices have made ultrasound and RF devices readily accessible for medical diagnosis. Some applications for telemetry capsules are drug delivery, and collection of tissue/fluid samples. Samples are taken from the GI to understand or treat diseases where diagnosis can only be made by taking a biopsy from the intestinal walls. Such biopsies have traditionally been performed using customized endoscopes. In order for a telemetry capsule to be effective in the above named tasks, accurate knowledge of the location of the capsule within the body during tests is necessary. As such, methods for calcu...

Miniature sensors, which are rugged and reliable in nature, are essential to meet the growing demand for environmental and biomedical monitoring systems. Developing such sensors using screen-printing and drop coating techniques allows the combination of two cost effective and flexible technologies. Using this approach, a wide variety of materials could be combined to produce sensors with the desired physical properties. Silver electrodes were screen-printed onto alumina substrates, while polymer/carbon-black composites based on polyvinyl butyral, polyvinyl acetate and polystyrene were deposited by drop coating. The addition of surfactant resulted in a more even dispersion of carbon-black throughout the composites, which was observed by TEM. The frequency dependence of the composites also confirmed this result. Pressure was applied using a Lloyd Instruments LR50k in the range 0–2500 kPa and the sensitivity was taken to be the slope of the graph. It was found that the materials displayed a high sensitivity to pressure with good repeatability. Detailed studies of the composites temperature dependency showed that each material has a negative temperature coefficient and were particularly sensitive when the temperature was brought below room temperature. This was improved by coating the sample surface.

In this work, the pressure sensing properties of polyethylene (PE) and polyvinylidene fluoride (PVDF) polymer films were evaluated by integrating them with a wireless data acquisition system. Each device was connected to an integrated interface circuit, which includes a capacitance to frequency converter (C/F) and an internal voltage regulator to suppress supply voltage fluctuations on the transponder side. The system was tested under hydrostatic pressures ranging from 0 to 17 kPa. Results show PE to be the more sensitive to pressure changes, indicating that it is useful for the accurate measurement of pressure over a small range. On the other hand PVDF devices could be used for measurement over a wider range and should be considered due to the low hysteresis and good repeatability displayed during testing. It is thought that this arrangement could form the basis of a cost-effective wireless monitoring system for the evaluation of environmental or physiological processes.

This paper investigates an array of thick-films gas sensors made from polymer, iron oxide and manganese oxide. The films were printed onto glass substrates with silver electrodes. The effects of different gas vapours on the devices at room temperature were investigated. The response of the sensors was defined as, Δ R = (( R gas − R air )/ R air ) × 100 and was seen to increase with increasing gas vapour concentration. It was observed that various film compositions showed a higher response to propanol and toluene than that to chloroform, ethanol and hexane. The response of the sensors to the gas vapours was seen to change depending on the composition used to form the sensing layer. For example, sensor S 4 was formed using PVB and 1.5 wt.% carbon black and displayed a higher response to 5000 ppm propanol (43.27) than that to toluene (19.43). While the response of S 3 , with a sensing layer composed of 75/25% Fe 2 O 3 /MnO 2 and 5 wt.% PVB binder and 1.5 wt.% carbon black to the same concentration of propanol and toluene at room temperature was 62.57 and 45.95%, respectively.

Strain gauges and pressure sensors are necessary tools for automotive, aerospace and biomedical monitoring applications. Of the various types of material, which can be used in their fabrication, oxides allow a degree of flexibility in their design. Furthermore, these devices are more rugged and cost effective than semiconductor sensors and have a higher sensitivity than metal-foil gauges. In this paper, the development of thin and thick film sensors based on oxides such as V2O5, CeO2, Bi2O3, In2O3, RuO2, TiO2, MgO and Nb2O5 is discussed. The devices are evaluated in terms of their sensitivity or gauge factor, linearity, hysteresis and long term stability. Furthermore, different device configurations, planar and sandwich are compared. It is found that the devices presented in this work have sensitivity comparable to that of semiconductor gauges, with good long-term stability. This is particularly true of the sandwich devices. It is observed that oxide based strain gauges may offer an alternative to existing commercial gauges, for example, in applications involving load cells, torque wrenches and limb implants.

The properties of the materials undergo changes by the influence of γ-rays. The degree of these changes could serve as a measure of the received radiation dose. Deep understanding of physical properties of the materials under the influence of radiation is vital for the effective design of devices for radiation-sensing applications. Mixing oxides in various proportions was found to control the radiation-sensing properties of the semiconductor films in terms of their sensitivity to γ-radiation exposure and working dose region.