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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.

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.

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.

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.

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.

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.

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.

In this work, screen-printing onto glass and polymer substrates was used to form capacitors with an active area of 2 × 3 mm2. The dielectric was formed using a polymer paste with TiO2 as the functional ingredient. Devices prepared on glass substrates were tested as strain gauges. Their GF was measured to be 30. This is higher than the standard values (3–15) recorded for gauges based on oxide materials. It is thought that the higher sensitivity is a result of the preparation method and small crystallite size of the TiO2 powder. After quantifying the materials sensitivity, the sensors on polymer substrates were attached to planar and cylindrical surfaces. They were then incorporated into a wireless pressure measurement system, consisting of a small size interface circuit and a transmitter. The receiver outputs a voltage reading corresponding to the sensor capacitance. Each device was placed in a liquid environment so that it could be exposed to hydrostatic pressure. A high sensitivity to pressure changes with low hysteresis was observed. It is thought that this system could be used to wirelessly monitor pressure changes in a variety of difficult to reach environments.

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.

Manganese phthaloyanine polymer thick films were fabricated using screen-printing techniques. The optical parameters were obtained from the analysis of the absorption spectra over a wavelength range of 385-900nm. The d.c. electrical measurements were carried out in a range of 0-30 volts. The effects of γ-radiation on the optical and the electrical properties were investigated for dosimetry applications. The optical energy band gaps of these films showed a decrease in their values with the increase in the radiation dose. The electronic transition has changed from direct allowed for the as-printed films (unexposed to γ-rays) to indirect allowed for the irradiated samples. Both the as-printed and irradiated Ag/MnPc/Ag devices demonstrated a Schottky conduction mechanism. Both the absorbance and the capacitance of the MnPc thick films displayed a highly consistent linear response to γ-ray exposure. Keywords: Optical band gap, γ-rays, Dosimetry, Manganese phthalocyanine, MnPc Introduction

This work investigates the ozone sensing properties of NbO2 thin films operating at room temperature. NbO2 thin films have been deposited on alumina and glass substrates provide with Cu interdigitated electrodes by the Vacuum Thermal Evaporation technique. The optical properties of NbO2 thin films were explored using CARY IE UV-Visible Spectrophotometer. The values of the optical band gap EOPT are estimated in view of the Mott and Davis' theory. The electrical response has been measured by exposing the sensing layers to ozone (ppb). NbO2 films fabricated by this method have shown good sensitivity to environmentally relevant ozone concentrations.

peer-reviewed In this work, a design of wireless system for multisensors 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, resistive and 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 (PLL) to convert the frequency to voltage. A developed pressure sensors based on polyvinylidene fluoride (PVDF) was used to evaluate the performance of the capacitive interface. 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.

Summary form only given. This paper outlines specific variations in recombination coefficients for charged particles (electrons and ions) and how these variations affect the onset of saturation of atmospheric pressure dielectric barrier discharges (DBDs). By solving continuity equations for electrons and ions, with the application of dielectric dependent boundary conditions, in conjunction with the Boltzmann equation, the effect of different recombination processes was modeled numerically. Incorporation of previously unconsidered atmospheric reactions into the continuity equations make this model unique for atmospheric air DBDs. The dependence of the recombination processes on kinetic temperature, field drift and autoionization were investigated and each pulse of the applied AC electric field was considered up to a saturation threshold. Results show a strong dependence of the kinetic temperature of electrons on the recombination coefficient and it was additionally found that the plasma approached saturation more quickly when autoionization was considered.

peer-reviewed A prototype of miniaturized, low power, bi-directional wireless communication system was designed for in vivo pressure monitoring. The capacitive pressure sensors have been developed particularly for the medical field, where packaging size and minimization of the power requirements of the sensors are the major drivers. The pressure sensors have been fabricated using a 2.4 pm thick strain compensated heavily boron doped SiGeB. In order to integrate the sensors with the wireless module, the sensor dice was wire bonded onto TO package using chip on board (COB) technology. The telemetric link and its capabilities to send information have been examined on a test bench. A full pressure range from 0 to ]OkPa was generated using either air or water pressure pumped through connected tubes to simulate the environment similar to the one inside the gastrointestinal (GI) tract.

peer-reviewed 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.

peer-reviewed The aim of this study is to design and develop a wireless sensor system integrating 24 bits analog to digital converter (ADC) and long range RF transceiver unit. The system is reading from two types of sensors, pressure and temperature. The serial communication between the ADC unit and RF transceiver is controlled by Spartan-3 FPGA device. A number of tasks are implemented by the FPGA device like interfacing, buffering and compression. A capacitive interface circuit has been employed for the pressure sensors and it is based on the principle of capacitance-frequency-voltage conversion. The RF transmitter is communicating with the FGPA through handshaking protocol and sending the data through ISM band. The pressure data will be compressed to avoid sending any repeated values aiming further reduction in the power consumption. EI

peer-reviewed Ozone (03) is potentially hazardous to human health and accurate prediction and measurement of this gas is essential in addressing its associated health risks. This paper presents theory to predict the levels of ozone concentration emittedfrom a dielectric barrier discharge (DBD) plasma for ozone sensing applications. This is done by postulating the kinetic model for ozone generation, with a DBD plasma at atmospheric pressure in air, in the form of a set of rate equations. Rate constants are taken from the literature and previously unconsidered ozone producing hydroxyl reactions are incorporated into the work, yielding more accurate results for the concentration of ozone for sensing applications. An application of this work is that knowing levels of ozone produced within an atmospheric DBD plasma allows for ozone sensors to be more accurately tuned to the particular requirements of the plasma system.

peer-reviewed A prototype of miniaturized, low power, bidirectional wireless communication system was designed for in vivo pressure monitoring. The capacitive pressure sensors have been developed particularly for the medical field, where packaging size and minimization of the power requirements of the sensors are the major drivers. The pressure sensors have been fabricated using a 2.4 μm thick strain compensated heavily boron doped SiGeB. In order to integrate the sensors with the wireless module, the sensor dice was wire bonded onto TO package using chip on board (COB) technology. The telemetric link and its capabilities to send information have been examined on a test bench. A full pressure range from 0 to 10kPa was generated using either air or water pressure pumped through connected tubes to simulate the environment similar to the one inside the gastro Intestinal (GI) tract. EI

peer-reviewed In this paper, a miniaturized, low power, bidirectional wireless communication system has been developed to be used for in vivo pressure monitoring. The system prototype consists of miniature FSK transceiver integrated with Microcontroller unit (MCU) in one small package, chip antenna, and capacitive interface circuitry based on Deltasigma (????) modulator. At the base station side, the same transceiver chip is communicating with a PC through a graphical user interface (GUI) to either sends/receives commands/data. Industrial, Scientific and Medical (ISM) 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 (CDC). All the modules of the mixed signal system are integrated in a printed circuit board (PCB) of size 22.46x20.168mm. EI

This paper presents the use of Xilinx ChipScopetrade Pro integrated logic analyzer for Field programmable gate arrays (FPGA) as a board-and system-level diagnostic tool. FPGA designs have become increasingly dense and complex. They are difficult to debug because more and more of the relevant signals are buried deep within the logic fabric. Access to signals in the FPGA, on board or in the system is very restricted whether troubleshooting is done in the lab or in the field. The Xilinx ChipScopetrade Pro integrated logic analyzer has solved much of the problem at the FPGA level. In this work, ChipScopetrade has been used to test and verify a developed system that presents the digital core of a wireless sensor module and it has been implemented in (Spartan 3) based FPGA development board.

peer-reviewed The main goal of this work is to fabricate a miniaturized, low power, bi-directional wireless communication system that can be used for in vivo pressure monitoring. The system prototype consists of miniature FSK transceiver integrated with Microcontroller unit (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 (ISM) 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 (CDC). All the modules of the mixed signal system are integrated in a printed circuit board (PCB) of size 22.46??20.168mm

peer-reviewed The study in this paper is focused on the improvement of a Field Programmable Gate Arrays (FPGA) based design using a hierarchical analysis tool offered by XILINX PlanAhead'TM. During this work, PlanAhead software is used to address any problems on the physical side of our FPGA design flow in order to add more visibility and control. The target system is reading analog information recorded by a biomedical sensor in a transmitting unit attached to the patient. The recorded data is converted digitally using analog to digital converter (ADC) and sent to FSK transmitter through FPGA. Verilog HDL has been used to develop and implement the required functions of the FPGA, such as bus interfacing, data buffering, compression and framing. The system performance has been optimized using a recent comprehensive tool in order to reach and maintain the goals of the design. EI

peer-reviewed The aim of this study is to model and design an efficient wireless system that should be easy to integrate with other technologies or infrastructures at a low cost. The system is reading analog information recorded by a biomedical sensor in a transmitting unit attached to the patient. The recorded data is converted digitally using ADC and sent to FSK transmitter through FPGA. Verilog HDL has been used to implement the required functions of the FPGA. SIMULINK software has been used to model and simulate Frequency-Shift Keying (FSK) Transmitter/ Receiver suitable for short-range communications. A two-tone FSK signal is generated, passed through a noisy channel, down converted to baseband and passed to FM detector to restore the original transmitted bit stream. The behavioral HDL design has been interfaced to the SIMULINK model and the overall performance has been verified. EI

In this work, the use of mixed oxide materials, such as Manganese oxide (MnO) and Tellurium dioxide (TeO/sub 2/) in the form of thermally evaporated thin film structures, is explored for gamma radiation dosimetry application. All samples showed an increase in the values of current with the increase in the radiation dose up to certain dose levels.

Thick films of nickel oxide (NiO) were investigated for /spl gamma/-radiation dosimetry purposes. Samples were fabricated using the thick film screen printing technique. Absorption spectra for NiO films were recorded and the values of the optical band gap for as-printed, irradiated and annealed films were calculated. It was found that the optical band gap value decreased as the radiation dose was increased. Samples with an Ag-NiO-Ag sandwich structure were exposed to a /sup 60/Co /spl gamma/-radiation source at a dose rate of 6 Gy/min. The relative change in current increased linearly with increased dosage up to 720 Gy. The I-V characteristics indicated a Poole-Frenkel conduction mechanism. It was found that annealing restored both the electrical and the optical properties of the samples.

peer-reviewed This paper documents the creation of a complete PC-Based humidity sensing system, implemented using LabVIEW from National Instruments. The humidity sensor, which has a measured sensitivity of 0.25%/RH%, is manufactured by thin film technology from a novel combination of SiO/In2O3. Both the humidity sensor and a standard temperature sensor are interfaced to a PC using a front-end signal conditioning circuit. The entire system has been analyzed mathematically and the necessary algorithms for error-compensation have been developed. The resulting measurement system is efficient, accurate and flexible.

This paper documents the manufacture and testing of a humidity sensor based on a combination of In2O3/SiO. A number of different sensor samples have been produced by thermal deposition and the effect of varying the vacuum pressure has also been investigated. The AC and DC conduction mechanisms have been investigated. From the AC conduction studies, the tunneling conduction mechanism has been observed at low frequencies and the hopping conduction mechanism, for the majority of sensor samples, has been observed at high frequencies. The DC conduction mechanisms have indicated the possibility of spacecharge-limited conduction. The sensor with the highest humidity sensitivity of 1.145%/RH% is 85%In2O3/15%SiO, which is produced at a vacuum pressure of 2×10-4 mbar.From the point of view of temperature stability, the 55%In2O3/45%SiO samples produced at a vacuum pressure of 2×10-4 mbar exhibit the lowest temperature sensitivity, 0.3%/oC.

peer-reviewed The dosimetry properties of thermally evaporated Copper Phthalocyanine (CuPc) thin films were investigated. The conduction mechanism of the asdeposited films was found to be space-charge-limited and their relative permittivity was within the range reported by others [l, 2, 3, 41. The Poole-Frenkel effect became more dominant for the irradiated samples and they displayed large increase in permittivity and colour centre density, although the energies of their optical band gap and trapping levels did not change. The observed linear relationship between the absorbance at 615 nrn and the y-radiation doses validated the use of CuPc as an optical sensor dosimeter especially for low radiation doses. Samples showed a higher radiation tolerance after being annealed for one hour at a temperature of only 323 K. Annealing also restored their initial electrical and optical properties.

The aim of this study is to model and design an efficient wireless system that is easy to integrate with other technologies or infrastructures at a low cost. The system would read analogue information recorded by a biomedical sensor in a transmitting unit attached to the patient. The recorded data are converted digitally using analogue-to-digital converter and sent to frequency-shift keying (FSK) transmitter through field programmable gate arrays (FPGAs). Verilog-HDL has been used to implement the required functions of the FPGA, such as bus interfacing, data buffering, compression and data framing. On the other hand, Simulink® software has been used to model and simulate FSK transmitter/receiver architecture suitable for short-range communications. Basically, a two-tone FSK signal is generated and passed through a noisy channel, which is then downconverted to baseband and passed to the frequency-modulating detector to restore the original transmitted bit stream. These illustrate how easily the mixed signal modelling can be well mapped into hardware description language (HDL) and mathematical programming techniques. The developed simulation models are used to explore the design change options. The behavioural HDL design has been interfaced to the Simulink model using system generator in a co-simulation environment, and the overall performance has been verified.

This paper reports on the development of a flexible nanopatterning approach using the NanoeNablerTM to manufacture miniaturised sensor arrays platform for real-time water quality assessment. Traditionally biosensors are fabricated by lithography, screen printing, inkjet printing, spin-or deep-coating methods to immobilize the sensing element onto substrate pre-patterned with electrodes. NanoeNablerTM patterning method is benchmarked against other currently adapted approaches for cost-effective sensors arrays manufacture. Sensors measuring ~1 µm diameter or more can be patterned for further employment in molecularly imprinted polymer structures. Notably, the dimensions of the sensor depend on the fluid being patterned and on the interaction forces between the substrate and the patterning tool. Thus, careful selecting of patterning parameters is vital for repeatable and controlled manufacture of sensors to guarantee superior sensitivity. The reported nanopatterning method is capable of accurately placing attoliter to femtoliter volumes of liquids, including proteins and DNAs, onto any substrate, thus making it an ideal technology for biomedical sensors. A custom-made 1 cm2 silicon wafer with 48 interdigited electrodes sensor heads was used as a platform for the multi-sensor array with potential use in a wide range of real-time monitoring applications.

Thin films of tellurium dioxide (TeO/sub 2/) were investigated for /spl gamma/-radiation dosimetry purposes. Samples were fabricated using thin film vapour deposition technique. Thin films of TeO/sub 2/ were exposed to a /sup 60/Co /spl gamma/-radiation source at a dose rate of 6 Gy/min at room temperature. Absorption spectra for TeO/sub 2/ films were recorded and the values of the optical band gap and energies of the localized states for as-deposited and /spl gamma/-irradiated samples were calculated. It was found that the optical band gap values were decreased as the radiation dose was increased. Samples with electrical contacts having a planar structure showed a linear increase in current values with the increase in radiation dose up to a certain dose level. The observed changes in both the optical and the electrical properties suggest that TeO/sub 2/ thin film may be considered as an effective material for room temperature real time /spl gamma/-radiation dosimetry.

In this work, an investigation of the pressure-sensing properties of a silicone rubber was conducted. Small amounts of carbon black were added to the silicone during fabrication and the effect on the sensitivity was explored. A full investigation of the mechanical and electrical properties of each composition shows that adding carbon black to the material greatly increases its sensitivity to pressure. This increase in sensitivity appears to be related to improvements in the material’s permittivity, which increases with carbon loading.

Thick films of Nickel oxide (NiO) in the form of pn-junctions and planar structures with interdigitated electrodes were investigated for γ-radiation dosimetry purposes. Samples were fabricated using the thick film screen-printing technique. All devices were exposed to a disc-type 137 Cs source with an activity of 370 kBq. They showed an increase in the values of current with the increase in radiation dose up to a certain level. Performance parameters of the devices, such as sensitivity to γ-radiation exposure and working dose region, were found to be highly dependant on the composition of the materials used. Keywords: Nickel Oxide; Thick Films; Gamma Radiation; PN-junction; Interdigitated Electrodes Introduction Accurate dosimetry traceable to national standards underpins the protection of the general public and workers across a wide range of activities including general engineering, radiation processing, nuclear power generation, research and use of radiation in medicine and defence. To meet this demand, considerable research into new sensors is underway, including efforts to enhance the sensors performance through both the materials properties and manufacturing technologies. The development of sensors needs to take advantages of the new performances obtained by controlling the physical and chemical properties of the materials. Metal oxides are widely used in many technological applications, such as coating, catalysis, electrochemistry, optical fibers, sensors, etc [1, 2]. Metal oxide sensors have been utilised for several