-
[show abstract]
[hide abstract]
ABSTRACT: This paper reports on the development and testing of a polyaniline-based conductimetric pH sensor. The sensor functions successfully in both the pH range for stomach acid (pH1.0-pH2.0) and for human blood (pH7.0-pH8.0). Experiments were performed by exposing the sensors to buffer solutions with pH values in the ranges identified. The sensors demonstrated reproducible and repeatable results with little hysteresis being recorded between experiments, along with a response time of approximately 1 min in acidic solutions and 2 min in buffers with pH values in the blood pH range. In the case of measurements made in the blood pH range, a novel memory effect was observed, which corresponds to a permanent ldquorecordingrdquo of the pH measurement into the electrical characteristics of the film. This memory effect only applies to measurements made in alkaline pH ranges and is due to the deprotonation of the polyaniline material in the sensing layer. The sensor reported in this paper has the potential to be a more economically viable option when compared to other approaches being used for commercial applications.
IEEE Sensors Journal 06/2009; · 1.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We combine electron beam lithography (EBL) with conventional microscale metal deposition and etch process technologies, to fabricate bolometer devices with nanoscale feature critical dimensions (CDs). We report the creation of titanium (Ti) bolometer devices with 70 nm minimum feature CDs, and total bolometer film thicknesses ranging between 40 nm and 120 nm. Our new nanobolometer devices integrate with conventional CMOS and MEMS fabrication processing, to create thermally isolated sensors with nanoscale feature sizes on a 0.5 mum CMOS base process. We present temperature coefficient of resistance (TCR) data for our new devices, and report a nanobolometer TCR performance of 0.22%/K at 70 nm CDs, a TCR value comparable to figures reported for Ti-based uncooled microbolometer devices.
Nanotechnology, 2008. NANO '08. 8th IEEE Conference on; 09/2008
-
[show abstract]
[hide abstract]
ABSTRACT: Novel method for microarrays manufacture using BioForce NanoeNabler<sup>trade</sup> was successfully employed for developing sensors for biomedical applications, namely pH and glucose monitoring. It is envisaged that findings of this work would form the basis for miniaturised diagnostic system for a wide range of applications.
Nanotechnology, 2008. NANO '08. 8th IEEE Conference on; 09/2008
-
[show abstract]
[hide abstract]
ABSTRACT: The novel system is presented that utilises change in the resonant frequency and impedance as an indicator of the pH level of the solution, brought in contact with a sensor. Mixed metal oxides of Bi<sub>2</sub>O<sub>3</sub> and Nb<sub>2</sub>O<sub>5</sub> formed the basis for thick film capacitive sensors investigated in this research work. AD5933 impedance converter was used to monitor real-time changes in the electrical properties of tested capacitors. The system showed superior sensitivity to the pH level, with instant response being recorded. Heating the sensors restored their initial properties, and they were repeatedly used for pH sensing. It is envisaged that findings of this work would form the basis for compact system employed for real-time pH monitoring.
Sensors Applications Symposium, 2008. SAS 2008. IEEE; 03/2008
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
IEEE Sensors Journal 02/2008; · 1.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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 system are integrated in a printed circuit board of size 22.46?×?20.168?mm. Findings – An innovation circuits and system techniques for building advanced smart medical devices have been discussed. Low-power consumption and high reliability are among the main criteria that must be given priority when designing such wirelessly powered microsystems. Switched capacitors readout circuits have been found to be suitable for pressure sensing low-power applications. Research limitations/implications – The presented wireless prototype needs a second phase of development that will lead to a further reduction in both size and power consumption. Currently, the main limitation of the RF system is the number of working hours according to the selected battery. Practical implications – The developed system was found to be useful in terms of measuring pressure and temperature in a system of either slow or fast physical change. It would be a good idea to explore the system performance in human or animal trials. Originality/value – This paper fulfils useful information for capacitive interface circuitries and presents a new short-range wireless system that has different design features.
Microelectronics International 12/2007; 25(1):3-14. · 0.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This work describes the fabrication and development of a polyaniline based conductimetric pH sensor. Two types of drop coated polyaniline films were investigated and it was found that the undoped emeraldine base polyaniline produces the best electrical response to pH. The results obtained show that the lowest conductance of these films occurs at the lowest pH value (pH2), with the conductance increasing with increasing pH. It is thought that this response is due to effects from the polymer binder, which is used to increase adhesion between the pH-sensitive film and the substrate.
Electronics Technology, 30th International Spring Seminar on; 06/2007
-
[show abstract]
[hide abstract]
ABSTRACT: Due to the demand for accurate, reliable and highly sensitive pH sensors, research is being pursued to find new materials to achieve this goal. An important branch of materials to be investigated for this purpose are the semiconducting metal oxides. This work uses titanium monoxide thick films in conjunction with an interdigitated electrode pattern to produce a conductimetric pH sensor. Its advantages over other methods include simpler construction and it is more economical. It was noted that upon contact with a solution, the resistance of the film increases. No meaningful relationship was observed between the resistance and pH for these devices. When a DC bias is applied to the device, a linear decrease was recorded in the relative changes in current through the device and conductance of the film against increasing pH values. Low frequency AC signals also produce a similar response. However, a slow response time and poor repeatability were also observed.
Sensors Applications Symposium, 2007. SAS '07. IEEE; 03/2007
-
[show abstract]
[hide abstract]
ABSTRACT: 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
IEEE Sensors Journal 02/2007; · 1.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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 Delta-sigma (SigmaDelta) 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 22.46 x 20.168 mm.
Sensors, 2006. 5th IEEE Conference on; 11/2006
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Biomolecular Engineering 11/2006; 23(5):253-7. · 3.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Journal of Materials Science Materials in Electronics 08/2006; 17(9):767-778. · 1.08 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A novel cost-effective real-time gamma radiation monitoring system based on metal oxide thick films was designed and tested. The changes in capacitances of ZnO and SnO<sub>2</sub> thick film capacitors with interdigitated electrodes 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 (SigmaDelta) modulator using switched capacitor (SC) circuit architecture with integrated on-chip temperature sensor. At the base station side, an frequency shift keying (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. All the modules of the mixed signal system are integrated in a printed circuit board (PCB) of size 22.46times20.168 mm. The overall system supply voltage is 2.7 V maximum. <sup>137</sup>Cs source with an activity of 370 kBq was used. An increase in the values of capacitance with radiation was recorded for both films to a certain dose level, determined by the material of sensitive layer.
Electronics Technology, 2006. ISSE '06. 29th International Spring Seminar on; 06/2006
-
[show abstract]
[hide abstract]
ABSTRACT: This paper examines the sensitivity of polyvinylidene fluoride (PVDF) and polyvinyl butyral (PVB) capacitors to pressures ranging from 0-100 kPa. The capacitors were formed by screen-printing onto flexible substrates and have an active area of 2 times 3 mm<sup>2</sup>. There are no moving parts and as a result the complexity of sensor design, fabrication and packaging issues may be reduced. After fabrication, sensors were adhered to planar and cylindrical surfaces and interfaced with an AD7746 24-bit capacitance to digital converter. This allowed precise measurements to be taken. It has high linearity and accuracy and can accept up to 17 pF absolute capacitance. The pressure was applied by housing the sensor in an airtight container and pumping air into the system to increase the pressure. It was found that PVDF devices on planar surfaces exhibited the largest response to the application of pressure. This was further increased for devices placed on cylindrical surfaces. It is thought that this is due to cracking of the thick film upon bending of the substrate. The results suggest that PVDF and PVB are suitable candidate materials for use in a pressure monitoring system.
Electronics Technology, 2006. ISSE '06. 29th International Spring Seminar on; 06/2006
-
[show abstract]
[hide abstract]
ABSTRACT: Present methods for investigation of the GI tract are invasive, distressing for the patient, and give a low diagnostic yield. Wireless, radio telemetry capsules, capable of monitoring physiological changes or visualizing the GI tract are noninvasive and could realize a faster time to diagnoses along with improved treatment of both organic diseases and functional disorders. Consequently, the patient's quality of life would improve. In this paper, early radiotelemetry capsules and the motivating factors for their development are discussed. Following this, prototype and commercially available digestible microsystems making use of microelectronics and microelectromechanical systems are presented. It is shown that these capsules have the potential to combine the functions of their predecessors and furthermore can be used for visualizing the gastrointestinal tract. These systems have the potential to improve diagnostic yield and, in the future, treatment of disease using these capsules should become a reality.
Critical Reviews in Biomedical Engineering 02/2006; 34(2):163-86.
-
[show abstract]
[hide abstract]
ABSTRACT: Purpose – 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) for the fabrication of a wireless pressure sensor microsystem is presented. Design/methodology/approach – 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 drawbacks of using this technology are examined. Findings – MEMS for use in wireless monitoring of pressure in the GI tract have been investigated. It has been shown that capacitive pressure sensors are particularly suitable for this purpose. Sensors fabricated for wireless continuous monitoring of pressure have been reviewed. Great progress, especially using surface micromachining, has been made in recent years. However, despite these advances, some challenges remain. Originality/value – Provides a review of the capabilities of MEMS.
Sensor Review 11/2005; 25(4):277-286. · 0.60 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The 2-step negative resist image by dry etching (2-step NERIME) focused ion beam (FIB) top surface imaging (TSI) process has been previously reported as an excellent technique for patterning nanometer scale features in DNQ/novolak based photoresists on silicon substrates. In this paper we demonstrate that the 2-step NERIME process can be used to pattern nanometer scale resist features on different substrate materials and topography substrates.
MEMS, NANO and Smart Systems, 2005. Proceedings. 2005 International Conference on; 08/2005
-
[show abstract]
[hide abstract]
ABSTRACT: 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.
Medical Engineering & Physics 07/2005; 27(5):347-56. · 1.62 Impact Factor
-
Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 2005. 28th International Spring Seminar on; 02/2005
-
[show abstract]
[hide abstract]
ABSTRACT: 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</sub>, CeO<sub>2</sub>, TeO<sub>2</sub>, In<sub>2</sub>O<sub>3</sub>, SiO and MnO, and polymers, such as CuPc, NiPc, MnPc and CoPc, were used as the active constituents in the fabrication of γ-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</sup>Co and <sup>137</sup>Cs sources were used to expose the samples to γ-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 γ-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 γ-radiation dosimeter applications.
IEEE Transactions on Nuclear Science 11/2004; · 1.45 Impact Factor
