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E. Jafer

Bio: E. Jafer is an academic researcher from University of Limerick. The author has contributed to research in topics: Capacitive sensing & Wireless sensor network. The author has an hindex of 10, co-authored 35 publications receiving 367 citations.

Papers
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Journal ArticleDOI
Arous Arshak1, Khalil Arshak1, D. Morris1, Olga Korostynska1, E. Jafer1 
TL;DR: In this article, the authors investigated the strain sensing properties of interdigitated and sandwich capacitors, using titanium dioxide as the dielectric, and found that the sensors showed a high degree of linearity with low hysteresis.
Abstract: In this work the strain sensing properties of interdigitated and sandwich thick film capacitors, using titanium dioxide as the dielectric, are investigated. By pre-firing the TiO 2 powder and forming a polymer thick film paste the use of expensive paste ingredients, such as ruthenium or palladium oxide, was avoided. After firing, XRD was used to verify the composition and crystallite size of the TiO 2 powder, while SEM allowed the particle sizes of the powder to be examined. It was found that the powder has a crystallite and particle size, which is less than 1 μm. Following this, the sensors were fabricated by screen-printing onto glass substrates and placed in a cantilever beam arrangement so that the change in their capacitance with strain could be measured. The gauge factor, which demonstrates the devices sensitivity, was found by dividing the fractional change in capacitance by the applied strain. A gauge factor of 5 and 30 was recorded for interdigitated and sandwich capacitors, respectively. In the case of sandwich capacitors, this gauge factor is higher than normally achieved using oxide films (3–15). Furthermore, the sensors showed a high degree of linearity with low hysteresis. The TCC has been measured for temperatures ranging from 25 to 70 °C so that the effect of temperature on the devices is known. Values, typical of thick film capacitors (876–2834 ppm/°C) have been recorded for temperatures up to 60 °C. Finally, ac electrical measurements have been used to shown that tunnelling is the dominant conduction mechanism within the TiO 2 film.

36 citations

Journal ArticleDOI
TL;DR: 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 and the limitations of each technology are examined.

35 citations

Journal ArticleDOI
Olga Korostynska1, Khalil Arshak1, D. Morris1, Arous Arshak1, E. Jafer1 
TL;DR: In this paper, the electrical properties of PVDF thin film capacitors under gamma radiation were investigated, and the effect of gamma radiation on the conductivity of thin PVDF films was investigated.
Abstract: 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.

33 citations

Journal ArticleDOI
Khalil Arshak1, D. Morris1, Arous Arshak1, Olga Korostynska1, E. Jafer1 
TL;DR: A prototype system has been developed and used to evaluate thick-film pressure sensors with an oxide dielectric layer based on the principle of capacitance-frequency-voltage conversion and has been designed to minimize power consumption.
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

29 citations

Proceedings ArticleDOI
10 May 2006
TL;DR: The Xilinx ChipScopetrade Pro integrated logic analyzer 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.
Abstract: 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.

27 citations


Cited by
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Journal ArticleDOI
TL;DR: The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics, despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets as discussed by the authors.
Abstract: Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.

622 citations

Journal ArticleDOI
TL;DR: The results suggest that functionalized TiO2, and presumably other nanoparticles, can be surface-engineered for targeted cancer therapy.

207 citations

Journal ArticleDOI
TL;DR: A nanodevice was developed that has achieved the resolution to decipher touch on a par with the human finger; this resolution is over an order of magnitude improvement on previous devices with a sensing area larger than 1 cm(2), and represents an important step towards the realization of artificial touch.
Abstract: Our sense of touch enables us to recognize texture and shape and to grasp objects. The challenge in making an electronic skin which can emulate touch for applications such as a humanoid robot or minimally invasive and remote surgery is both in mimicking the (passive) mechanical properties of the dermis and the characteristics of the sensing mechanism, especially the intrinsic digital nature of neurons. Significant progress has been made towards developing an electronic skin by using a variety of materials and physical concepts, but the challenge of emulating the sense of touch remains. Recently, a nanodevice was developed that has achieved the resolution to decipher touch on a par with the human finger; this resolution is over an order of magnitude improvement on previous devices with a sensing area larger than 1 cm(2). With its robust mechanical properties, this new system represents an important step towards the realization of artificial touch.

182 citations

Journal ArticleDOI
TL;DR: In this article, a novel C O M M U N IC A IO N (COMU N) pattern is created by nanoimprinting, and then used as a mask for metal film etching or metal lift-off process.
Abstract: Recent years have witnessed an expanding interest in the application of flexible polymer materials (e.g., polyimide, polyester, etc.) as the substrates for electronic and display devices. These applications include flexible organic light-emitting displays, thin film transistors, sensors, and polymer MEMS. The advantages of polymer-based materials are their mechanical flexibility, light weight, enhanced durability, and low cost compared with rigid materials (such as silicon and quartz). However, it can be difficult to integrate polymers into an integrated circuit (IC) microfabrication process due to their low thermal stability (low melting and low glass transition temperatures) and solvent susceptibility. In practice, conventional IC fabrication processes are subject to limitations, in that they are multi-step, involve high processing temperatures, caustic baths and strong solvents. In order to address the current problems of microfabrication on flexible substrate, many alternative approaches to conventional photolithography-based process have been introduced by a number of researchers. These include microcontact printing (lCP) combined with metal etching, electroless plating, electropolymerization, and direct metal layer transfer for the microscale metal patterning on flexible substrates. Stencil lithography was mainly applied for dielectric layer patterning on polymer substrates for the formation of electrical capacitors due to its limited resolution. Inkjet printing was used for a drop-on-demand patterning of conductive polymer PEDOT and gold layers for drain-source and gate electrodes. However, its best resolution is 20–50 lm limited by the nozzle diameter, the statistical variation of the droplet flight, and spreading on the substrate. Organic semiconducting materials are being widely used as semiconducting layers in flexible electronics due to their costeffectiveness, mechanical flexibility, and ease of application via specific chemical modification. However, further channel size down-scaling is essential for better performance of organic field effect transistor due to the lower carrier mobility of the organic semiconducting materials. While the abovementioned methods cannot achieve ultrafine features (a few lm’s down to ∼ 100 nm) in high aerial density and good reproducibility, nanoimprinting lithography (NIL) allows easy fabrication of precise nanoscale structures. NIL has been applied for nanopatterning in various fields such as biological nanostructures, nanophotonic devices, organic electronics, and the patterning of magnetic materials. Especially, metal nanopatterning via nanoimprinting is widely employed in nanoscale electronics and biosensing platforms. However, metal nanoimprinting has been typically an indirect process where a polymer (e.g., PMMA) pattern is first created by nanoimprinting, and then used as a mask for metal film etching or metal lift-off process. This involves multiple and expensive process steps and its chemistry is harsh for the flexible substrates. Furthermore, flexible substrates are not resistant to high temperature and pressure during the imprinting process. Recently, imprint resists based on monomer or copolymer have been developed and used for low pressure/low temperature nanoimprinting process. However, these are also indirect methods for metal nanopatterning. Very few direct metal nanoimprinting processes have been demonstrated so far due to the high melting temperature of metals. As an alternative to metal direct nanoimprinting, solid state embossing methods based upon plastic deformation of metal thin films have been introduced. These approaches involved either deformation of a metal film under very high pressure or deformation of a metal thin film/polymer multilayer under relatively lower pressure. Evidently, they are not compatible with flexible substrate since its mechanical strength is not sufficient for such processes. Additionally, these methods do not allow the fabrication of isolated, arbitrary features, and always leave unwanted residual layers. To alleviate the limitations described in the fabrication processes above, the authors have recently developed a novel C O M M U N IC A IO N

167 citations

10 Oct 2007
TL;DR: In this article, a novel C O M M U N IC A IO N (COMU N) pattern is created by nanoimprinting, and then used as a mask for metal film etching or metal lift-off process.
Abstract: Recent years have witnessed an expanding interest in the application of flexible polymer materials (e.g., polyimide, polyester, etc.) as the substrates for electronic and display devices. These applications include flexible organic light-emitting displays, thin film transistors, sensors, and polymer MEMS. The advantages of polymer-based materials are their mechanical flexibility, light weight, enhanced durability, and low cost compared with rigid materials (such as silicon and quartz). However, it can be difficult to integrate polymers into an integrated circuit (IC) microfabrication process due to their low thermal stability (low melting and low glass transition temperatures) and solvent susceptibility. In practice, conventional IC fabrication processes are subject to limitations, in that they are multi-step, involve high processing temperatures, caustic baths and strong solvents. In order to address the current problems of microfabrication on flexible substrate, many alternative approaches to conventional photolithography-based process have been introduced by a number of researchers. These include microcontact printing (lCP) combined with metal etching, electroless plating, electropolymerization, and direct metal layer transfer for the microscale metal patterning on flexible substrates. Stencil lithography was mainly applied for dielectric layer patterning on polymer substrates for the formation of electrical capacitors due to its limited resolution. Inkjet printing was used for a drop-on-demand patterning of conductive polymer PEDOT and gold layers for drain-source and gate electrodes. However, its best resolution is 20–50 lm limited by the nozzle diameter, the statistical variation of the droplet flight, and spreading on the substrate. Organic semiconducting materials are being widely used as semiconducting layers in flexible electronics due to their costeffectiveness, mechanical flexibility, and ease of application via specific chemical modification. However, further channel size down-scaling is essential for better performance of organic field effect transistor due to the lower carrier mobility of the organic semiconducting materials. While the abovementioned methods cannot achieve ultrafine features (a few lm’s down to ∼ 100 nm) in high aerial density and good reproducibility, nanoimprinting lithography (NIL) allows easy fabrication of precise nanoscale structures. NIL has been applied for nanopatterning in various fields such as biological nanostructures, nanophotonic devices, organic electronics, and the patterning of magnetic materials. Especially, metal nanopatterning via nanoimprinting is widely employed in nanoscale electronics and biosensing platforms. However, metal nanoimprinting has been typically an indirect process where a polymer (e.g., PMMA) pattern is first created by nanoimprinting, and then used as a mask for metal film etching or metal lift-off process. This involves multiple and expensive process steps and its chemistry is harsh for the flexible substrates. Furthermore, flexible substrates are not resistant to high temperature and pressure during the imprinting process. Recently, imprint resists based on monomer or copolymer have been developed and used for low pressure/low temperature nanoimprinting process. However, these are also indirect methods for metal nanopatterning. Very few direct metal nanoimprinting processes have been demonstrated so far due to the high melting temperature of metals. As an alternative to metal direct nanoimprinting, solid state embossing methods based upon plastic deformation of metal thin films have been introduced. These approaches involved either deformation of a metal film under very high pressure or deformation of a metal thin film/polymer multilayer under relatively lower pressure. Evidently, they are not compatible with flexible substrate since its mechanical strength is not sufficient for such processes. Additionally, these methods do not allow the fabrication of isolated, arbitrary features, and always leave unwanted residual layers. To alleviate the limitations described in the fabrication processes above, the authors have recently developed a novel C O M M U N IC A IO N

159 citations