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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.

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.

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.

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.

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.

This paper presents a review of developed simulated models for a wireless data acquisition system. The system reads analogue information provided by two sensors used for medical purposes. The real data have been recorded by two, pH and pressure sensors used in diagnosing conditions of the esophagus that are employed to examine the system performance. The created model contains four main simulated units using SIMULINK. The first unit contains the output signal, which is encoded to digital signal based on adapting one of the pulse coding modulation (PCM) algorithms. The second unit simulates the processor function that is responsible for framing, mixing and compressing the incoming bit streams from both sensors. The third unit, where the digital data are modulated and sent through different noisy channels, represents an efficient FSK transmitter/receiver model. At the receiver end, the signal is demodulated and processed inversely to extract the original analogue signal read by the two sensors. In this work, the performance of the systems using different PCM methods will be studied comparatively in order to control the transmission and reduce the amount of data frames sent. This will lead to a significant reduction in power consumption. In addition, the performance of the RF unit through additive White Gaussian noise (AWGN) channel was examined by estimating the average bit error rate (BER) for different carrier frequencies. The effect of the multipath fading, inband/outband interference, and adjacent channel power ratio (ACPR) has also been investigated during system assessment.

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.

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

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.

Presented are the results of investigations of the effects of organic solvent vapours and excess noise measurements on drop-coated poly(vinyl butyral)\carbon black nanocomposite gas sensitive resistors. The devices were shown to exhibit significant resistance changes upon exposure to methanol, propanol and particularly hexanol vapours in the concentration range 1000 to 5000 ppm. The effects of the organic solvent vapours on the noise power spectra of the PVB\CB sensors were also investigated, but results were found to yield no information surplus to that of the DC sensor signal. The large values of 1/f noise observed were attributed to inhomogeneity and discontinuity of the deposited sensing layer. The discontinuity of the drop-coated layer was subsequently confirmed by SEM micrographs of the samples.

This work investigates the effects of gamma-rays on the optical properties of pure and mixed-oxide materials, namely MnO and TeO2 for their possible application as thin film optical gamma radiation sensors. The values of the optical band gap Eopt were obtained in view of the Mott and Davis theory. All samples showed a decrease in Eopt with an increase in radiation dose to a certain level, which was found to be composition dependent. Films with 100 wt.% MnO exhibited the highest sensitivity to low doses of radiation, showing a strong decline in the optical band gap value from 0.64 eV before irradiation to 0.54 eV after a dose of 1.14 mGy. It was experimentally confirmed that both the sensitivity and the working dose range of radiation sensors can be controlled by the composition of the materials used

The 2-step negative resist image by dry etching (2-step NERIME) focused ion beam top surface imaging process is a novel nanolithography technique for creating nanometer scale resist features using conventional DNQ/novolak resists. We present 90nm resist critical dimensions (CDs) over substrate topography using the 2-step NERIME process. We also demonstrate, for the first time, fabrication of 80nm etched features masked using the 2-step NERIME process. The etched nanoscale features exhibit minimal line edge roughness and excellent profile control, and demonstrate the suitability of the 2-step NERIME process as a nanolithography technique for applications requiring nanometer CD and profile control.

This work investigates the use of NiO / Fe2O3 as a room temperature (RT) polymer thick film gas sensor. To find the optimum ratio of NiO to Fe2O3, three compositions were prepared using different molecular percentages (75 / 25, 50 / 50 and 25 / 75 M wt.%) and prepared as a thick film paste. These pastes were then screen-printed onto glass substrates with interdigitated silver (Ag) electrodes. The final composition of each film was determined using XRD analysis. The films were used to detect methanol, ethanol, propanol, toluene, acetone and tetrahydrofuran (THF) at RT. The response of each device was defined using the formula, (Rgas − Rair) / Rair) × 100, where Rair is the resistance of the film in air and Rgas is the resistance of the film after the exposure to gas vapours. For each composition tested, the highest responses where displayed for toluene and propanol. The sensitivity was determined as the first derivative of response. Their sensitivity to 8000 ppm of toluene was calculated to be 0.008%, 0.0058% and 0.0059% per ppm for compositions with 75 / 25, 50 / 50 and 25 / 75 M wt.% of NiO / Fe2O3, respectively. Their sensitivity to propanol was found to be 0.0030%, 0.0029% and 0.0027% per ppm for compositions in the same order as listed previously. The fastest response and recovery times of each device were found after the exposure to 4000 ppm of toluene and propanol at room temperature. Sensor fabricated using composition 75 / 25 M wt.% of NiO to Fe2O3 showed response/recovery times of 30 / 45 s for propanol and 40 / 48 s for toluene.

PurposeCombination of a number of sensors with different response parameters into sensor arrays would enhance the overall performance of the radiation detection system. This paper presents a conceptual approach to the development of sensor arrays system with instantaneous dose and dose rate readout. A dynamic selection of multiple sensors with various sensitivity and accuracy range is implemented by applying pattern recognition (PR) analysis, which maximizes measurement accuracy. A number of relevant PR methods are discussed.Design/methodology/approachThick films based on NiO, ZnO, In2O3, CeO2, TiO2, CuO and CdO are the key sensing elements in the proposed approach. Pure and carbon‐doped metal oxides were screen‐printed on Si wafers to form pn‐heterojunctions. All devices were exposed to a disc‐type 137 Cs source with an activity of 370 kBq. The values of radiation damage of pn‐junctions were estimated from changes in their current‐voltage characteristics.FindingsSensors showed an increase in the values of current with the increase in radiation dose up to certain levels, exceeding these levels results in unstable dosimetric characteristics.Originality/valueThe sensitivity of metal oxide films to γ‐radiation exposure depends on their composition and thickness. Mixing the oxides in different proportions and the addition of conducting particles, such as carbon, alters films susceptibility to radiation. In particular, sensors based on such films have dose response characteristics with certain level of sensitivity and working dose range, conditioned by particular sensing material properties and the device structure.

The aim of this work is to investigate the properties of gas sensors, with active layers that have been prepared by screen-printing. The active layers primarily consist of zinc ferrite (ZnFe 2 O 4 ), which was prepared using iron oxide (Fe 2 O 3 ) and zinc oxide (ZnO) as the raw materials. X-ray diffraction (XRD) was used to confirm the final composition of the powder while SEM was used to examine the grain size. Following this the ZnFe 2 O 4 powder was combined with NiO, TiO 2 , PVB and carbon black to form a thick film paste and deposited on glass substrates with interdigitated electrodes. The sensor was then interfaced with three resistors to form a bridge circuit. The films were used to detect butanol and pentanol in the concentration range 0–1000 ppm and hexanol from 0–250 ppm. The sensitivity of the devices to gas vapours was calculated as Δ V = ( V gas − V o ). The sensitivity increased with increasing gas vapour concentrations. The device showed its highest sensitivity to hexanol followed by pentanol, butanol, propanol, ethanol and finally methanol. The effect of the temperature on the sensitivity of the device to both propanol and toluene has been studied. The effect of adding TiO 2 and NiO to ZnFe 2 O 4 on the response and recovery times was also addressed.

Presented are the results of excess noise measurements on poly(vinyl butyral)\carbon black nanocomposite gas sensitive resistors. The devices were prepared by a drop-coating technique in which a microlitre syringe was used to deposit the materials onto Cu thin-film parallel electrodes. Noise power spectra of the devices under bias currents ranging from 80 to 150 μA were obtained. The detection limits were found to be 6.3 ppm, 5.2 ppm and 68 ppb for methanol, propanol and hexanol vapour, respectively. The noise index was also evaluated for the devices, with a value of approximately 29 dB being measured.

The cruel reality of today's world forces mankind to be alert and prepared for all kinds of terrorist threats, including exposure to radiation. There is a need for cost-effective alternatives to existing commercially available real-time gamma radiation dosimeters. In this paper, numerous oxides such as NiO, CeO/sub 2/, TeO/sub 2/, In/sub 2/O/sub 3/, SiO, MnO, etc., and their mixtures in different proportions were used as the basis for such a substitute. Thin- and thick-film devices were made in the form of resistors and capacitors, structures with interdigitated electrodes, and pn-junctions. These, in different mixtures, were found to change their sensitivity when exposed to /spl gamma/-rays. In general, thin-film devices were found to be more sensitive to lower doses of radiation than the counterpart thick films. However, it was experimentally demonstrated that it is possible to fabricate a device that would satisfy the requirement of a particular application, such as the sensitivity to /spl gamma/-radiation exposure and working dose regions. Based on the above data, these structures might be regarded as a cost-effective alternative for room-temperature real-time /spl gamma/-radiation dosimetry.

Telemetry capsules have existed since the 1950s and were used to measure temperature, pH or pressure inside the gastrointestinal (GI) tract. It was hoped that these capsules would replace invasive techniques in the diagnosis of function disorders in the GI tract. However, problems such as signal loss and uncertainty of the pills position limited their use in a clinical setting. In this paper, a review of the capabilities of MicroElectroMechanical Systems (MEMS) and thick film technology (TFT) for the fabrication of a wireless pressure sensing microsystem is presented. The circuit requirements and methods of data transfer are examined. The available fabrication methods for MEMS sensors are also discussed and examples of wireless sensors are given. Finally the limitations of each technology are examined.

Throughout this work radiation-induced changes in the optical, electrical and structural properties of mixed and carbon filled metal oxides were studied. Oxides such as NiO, CeO2, TeO2, In2O3, SiO and MnO in the form of thin and thick films were used. The properties of the materials undergo changes by the influence of γ-rays. The degree of these radiation-induced changes serves as a measure of received radiation dose. Deep understanding of physical properties of the materials under the influence of radiation is vital for the effective design of dosimeters. In this work all films were exposed to a disk-type 137Cs source with an activity of 370 kBq. Carbon filling and mixing oxides in various proportions was found to control the properties of semiconductor films in terms of their susceptibility to radiation exposure. For example, planar NiO thick film structures with Ag interdigitated electrodes showed an increase in the values of current with the increase in radiation dose up to 171 μSv. Doping of NiO thick films with 0.1 wt.% of carbon resulted in larger increments in the values of current and the increasing the working range to 2720 μSv. The possibility to fabricate a device that would satisfy the requirement of particular application, in this case the sensitivity to γ-radiation exposure and working dose region, was experimentally demonstrated.

In recent years, number of studies investigating the use of capacitance effects in mechanical transducers has been undertaken. It was found that changing the dimensions of the chemical constitution of the dielectric material could change the nominal value of the parallel plate. This fact has been used to develop sensors that measure quantities such as strain, acceleration, gas concentration, humidity, etc. [1] . This paper is focused on developing a low-cost pressure sensitive device using thick film technology. The paper illustrates the original design specifications and how the sensor and signal conditioning circuitry performed against expectations. One of the design constrains was ensuring the operation of the sensor in a hostile operating conditions. Several device configurations were made based on both commercial Cermet and a PZT pastes. The relative performance of these materials as a dielectric-sensing element is compared in terms of their sensitivity, repeatability, and hysteresis. An efficient signal conditioning circuitry has been developed. The purpose of the circuitry is to allow the interface to make control decisions based on accurate stable pressure readings obtained by at the circuit. In this paper, the full system design of the pressure sensor and compensation circuitry was considered.

The effect of surfactants on the properties of poly(vinyl acetate) (PVAc)/carbon black (CB) composite gas sensors was examined. Percolation curves of the composites with and without surfactant were prepared. The percolation curves of surfactant treated composites showed that the resistivity of the composite was increased due to better dispersion of the CB and also the prevention of the CB from reagglomerating after shear mixing. TEM images were used to investigate the effect of adding surfactant to the composites. These images confirmed that the surfactants significantly improved the level of dispersion of CB in the composites and prevented reagglomeration of the CB. The response (ΔR/R%) was increased by addition of surfactants and implies that increased dispersion increases response to methanol vapour.

Zinc and iron oxide thick film gas sensors were fabricated using screen-printing technology on glass substrates that had silver interdigitated electrodes. The sensor was used to detect methanol, ethanol and propanol with a concentration range of 0–8000 ppm. Using the formula to calculate a change in resistance, ΔR = Rgas − Rair, resistance was seen to increase linearly alongside increasing concentrations of the gas vapours. The sensor showed the highest sensitivity to propanol followed by ethanol and methanol when the operating temperature was 25 °C. The sensitivities (slope of graphs) of methanol, ethanol and propanol changed from 0.07, 0.5, and 3.54 to 0.075, 0.115, and 0.5 Ω/ppm when the operating temperature was increased from 25 to 50 °C. The response/recovery times of the sensor for 4000 ppm at room temperature were, 10/10, 15/20 and 40/70 s for methanol, ethanol and propanol, respectively. X-ray diffraction (XRD) was used to examine the final composition of the film, while scanning electron microscopy (SEM) was used to examine the final composition of grain size. The final composition has two phases: ZnO and ZnFe2O4

This paper investigates the use of NiO particles to enhance the vapour sensing properties of polyethylene adipate (PEA)\carbon black (CB) composite materials. Four PEA\CB suspensions were prepared with 0, 10, 20 and 30 w/w% NiO, respectively. Hypermer PS3 surfactant was shear mixed into each of the suspensions for 300 s to achieve a homogenous dispersion and to prevent reagglommeration of both the CB and NiO particles. A 0.1 μl drop of each composite was deposited between Cu electrodes on a printed circuit board (PCB) substrate using a microlitre syringe. The samples were allowed to dry for 24 h in an oven at 333 K to remove any remaining solvent. After preparation, the sensors were exposed to propanol and butanol at concentrations ranging from 0 to 25 000 ppm in steps of 5000 ppm. The response of the PEA\CB sensors improved significantly as the concentration of NiO particles in the material increased and maximum relative differential responses as high as 37% and 92.8% were recorded after exposure to 25 000 ppm propanol and butanol, respectively. This high response can be explained using the Flory–Huggins interaction parameter along with structural changes in the polymer composite caused by the addition of NiO. This paper concludes that NiO particles can be used as a method to increase the sensitivity of existing conducting polymer composite gas sensing materials.

The development of a sensor microsystems containing all the components of data acquisition system, such as sensors, signal‐conditioning circuits, analog‐digital converter, interface circuits and embedded microcontroller (MCU), has become the focus of attention in many biomedical applications. A review of the microsystems technology is presented in this paper, along with a discussion of the recent trends and challenges associated with its developments. A basic description of each sub‐system is also given. This includes the different front end, mixed analog‐digital, power management, and radio transmitter‐receiver circuits. These sub‐system designs are presented and discussed in a comparative study and final remarks are made. The performance of each sub‐system is assessed regarding many aspects related to the overall system performance.

Numerous efforts were devoted to investigating the influence of radiation on metal oxides and polymer materials for dosimetry applications. Metal oxides, such as NiO, LaFeO/sub 3/, CeO/sub 2/, TeO/sub 2/, In/sub 2/O/sub 3/, SiO and MnO, and polymers, such as CuPc, NiPc, MnPc and CoPc, were used as the active constituents in the fabrication of /spl gamma/-radiation sensors. Thin and thick film devices were made in various topologies to form resistors, capacitors, pn-junctions and transistors. It was found that the properties of the active films (and, hence, their sensitivity to radiation) could be controlled by doping their constituent materials with carbon and mixing them in different proportions. The /sup 60/Co and /sup 137/Cs sources were used to expose the samples to /spl gamma/-radiation. Current-voltage characteristics, optical absorption spectra, Raman spectra, SEM and XRD measurements were recorded for the samples after each exposure procedure and values of radiation damage were estimated. Thin film devices were found to be more sensitive to radiation than their thick film counterparts. Annealing was used to restore the properties of thick film devices after they were damaged with radiation. Thick films could be therefore reused on a repeatable basis, but thin film devices could not, as the heat treatments necessary for annealing were found to cause diffusion of the electrode materials. In this work, the possibility of fabricating a device that would satisfy the requirement of a particular application, such as sensitivity to /spl gamma/-radiation and working dose region, was experimentally demonstrated. Based on the findings, these devices were found to provide a cost-effective alternative for room temperature real time /spl gamma/-radiation dosimeter applications.

Investigations into γ-radiation-induced changes in the electrical properties of CeO2 thick films of various structures were carried out for dosimetry purposes. The detection of radiation was based on the fact, that properties of the materials undergo changes upon the influence of γ-radiation. Carbon doping was used to control the resistivity of the CeO2 polymer thick films. Screen-printed capacitors, resistors and pn-junctions were exposed to a disc-type 137 Cs source with an activity of 370 kBq. All devices showed an increase in the values of current with the increase in radiation dose up to a certain level. Capacitors could be recommended for high-dose applications, as they showed consistent changes in conductance and capacitance values with an increase in radiation dose up to 6.12 mSv. Resistors doped with 0.2 wt.% of C showed gradual increase in the values of current with the increase in dose up to 4.42 mSv, whereas resistors with 0.5 wt.% of C sustained a lower dose of 1.7 mSv and were damaged on further exposure. pn-Junctions formed with CeO2 films, printed on single side polished P〈1 0 0〉 silicon wafers, exhibited the most sensitivity to γ-radiation. They showed significant increase in the values of leakage current with the increase in dose up to 0.57 mSv and are therefore suitable for low-dose dosimetry applications.

Throughout this work oxides are considered as appropriate cost-effective materials for radiation sensing. Thin films of TeO2, In2O3 and SiO and their mixtures were used in this study for the fabrication of pn-junctions. The detection of radiation is based on the fact that properties of the materials undergo changes by the influence of γ-rays. A number of various pn-junctions were made that differ in their materials composition. All the devices were exposed to 60 Co or 137 Cs radiation sources and their current–voltage (I–V) characteristics were examined. Samples made with p-type material (TeO2) and n-type oxides mixture (50 wt.% of In2O3 and 50 wt.% of SiO) showed clearly pronounced pn-junction behaviour. However, the response of these devices to radiation was not consistent as samples were too susceptible to environmental conditions. Devices based on TeO2/In2O3 oxide materials mixtures (p-type) and sulphur (n-type) were more stable and exhibited Zener diode behaviour. It was found that devices with a mixture of 90 wt.% of TeO2 and 10 wt.% of In2O3 have sustained a higher breakdown voltage compared to those with pure TeO2. To improve the stability of the devises response, a number of pn-junctions were manufactured on Si wafers. Samples with TeO2/Si and (In2O3+SiO)/Si configurations were tested. An increase in the values of current with the increase in radiation in a certain dose range makes these devices suitable for dosimetry purposes.

A focused-ion-beam (FIB) machine is a versatile tool used extensively in the integrated circuit (IC) industry for conducting failure analysis, prototype fabrication, and device repair. Lithography can also be performed using FIB for direct patterning of photoresists without using a mask. The FIB technique has several advantages over other maskless processes, such as direct-write e-beam lithography; ion-beam patterning of the photoresist offers higher resist sensitivity and lesser backscattering/proximity effects than the e-beam patterning. In this paper, we investigated a new FIB lithography process, called NERIME (negative resist image by dry etching). The NERIME process is a single-layer resist scheme, which implements a Ga+ FIB exposure of DNQ/novolak-based resists, followed by a near-ultraviolet (NUV) flood exposure, silylation, and oxygen dry etching. The NERIME process could not only yield both positive and negative images, but also achieve a nanometer resolution down to 65 nm and a high aspect ratio for the processed patterns. The principle of the negative image formation was also investigated by TEM and found to be due to the creation of a thin gallium oxide mask layer during etching. The NERIME process could be utilized for specific CMOS processing steps for the next generation technology nodes, such as high-resolution lithography over topographical surfaces.

This paper reviews the range of sensors used in electronic nose (e‐nose) systems to date. It outlines the operating principles and fabrication methods of each sensor type as well as the applications in which the different sensors have been utilised. It also outlines the advantages and disadvantages of each sensor for application in a cost‐effective low‐power handheld e‐nose system.