Sensors

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Online ISSN: 1424-8220

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Figure 2. Complete sensing part schematic.
Table 2 . Previous works comparison.
Figure 3. Charging circuitry explanation: On the left, the charge pump example circuit. On the right, transient signals for the charge pump.
Figure 4. Relevant circuital elements to analyze V BIAS stability issues.
Figure 5. Constituent blocks of the 65 nm thermal sensor.

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A 0.0016 mm2 0.64 nJ leakage-based CMOS temperature sensor
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September 2013

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604 Reads

Pablo Ituero

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This paper presents a CMOS temperature sensor based on the thermal dependencies of the leakage currents targeting the 65 nm node. To compensate for the effect of process fluctuations, the proposed sensor realizes the ratio of two measures of the time it takes a capacitor to discharge through a transistor in the subthreshold regime. Furthermore, a novel charging mechanism for the capacitor is proposed to further increase the robustness against fabrication variability. The sensor, including digitization and interfacing, occupies 0.0016 mm2 and has an energy consumption of 47.7-633 pJ per sample. The resolution of the sensor is 0.28 °C, and the 3σ inaccuracy over the range 40-110 °C is 1.17 °C.
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Micro Ethanol Sensors with a Heater Fabricated Using the Commercial 0.18 μm CMOS Process

October 2013

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1,051 Reads

The study investigates the fabrication and characterization of an ethanol microsensor equipped with a heater. The ethanol sensor is manufactured using the commercial 0.18 µm complementary metal oxide semiconductor (CMOS) process. The sensor consists of a sensitive film, a heater and interdigitated electrodes. The sensitive film is zinc oxide prepared by the sol-gel method, and it is coated on the interdigitated electrodes. The heater is located under the interdigitated electrodes, and it is used to supply a working temperature to the sensitive film. The sensor needs a post-processing step to remove the sacrificial oxide layer, and to coat zinc oxide on the interdigitated electrodes. When the sensitive film senses ethanol gas, the resistance of the sensor generates a change. An inverting amplifier circuit is utilized to convert the resistance variation of the sensor into the output voltage. Experiments show that the sensitivity of the ethanol sensor is 0.35 mV/ppm.

5A Zirconium Dioxide Ammonia Microsensor Integrated with a Readout Circuit Manufactured Using the 0.18 μm CMOS Process

March 2013

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772 Reads

The study presents an ammonia microsensor integrated with a readout circuit on-a-chip fabricated using the commercial 0.18 μm complementary metal oxide semiconductor (CMOS) process. The integrated sensor chip consists of a heater, an ammonia sensor and a readout circuit. The ammonia sensor is constructed by a sensitive film and the interdigitated electrodes. The sensitive film is zirconium dioxide that is coated on the interdigitated electrodes. The heater is used to provide a working temperature to the sensitive film. A post-process is employed to remove the sacrificial layer and to coat zirconium dioxide on the sensor. When the sensitive film adsorbs or desorbs ammonia gas, the sensor produces a change in resistance. The readout circuit converts the resistance variation of the sensor into the output voltage. The experiments show that the integrated ammonia sensor has a sensitivity of 4.1 mV/ppm.

Self-Assembled 3D ZnO Porous Structures with Exposed Reactive {0001} Facets and Their Enhanced Gas Sensitivity

July 2013

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488 Reads

Complex three-dimensional structures comprised of porous ZnO plates were synthesized in a controlled fashion by hydrothermal methods. Through subtle changes to reaction conditions, the ZnO structures could be self-assembled from 20 nm thick nanosheets into grass-like and flower-like structures which led to the exposure of high proportions of ZnO {0001} crystal facets for both these materials. The measured surface area of the flower-like and the grass, or platelet-like ZnO samples were 72.8 and 52.4 m2∙g-1, respectively. Gas sensing results demonstrated that the porous, flower-like ZnO structures exhibited enhanced sensing performance towards NO2 gas compared with either grass-like ZnO or commercially sourced ZnO nanoparticle samples. The porous, flower-like ZnO structures provided a high surface area which enhanced the ZnO gas sensor response. X-ray photoelectron spectroscopy characterization revealed that flower-like ZnO samples possessed a higher percentage of oxygen vacancies than the other ZnO sample-types, which also contributed to their excellent gas sensing performance.

A 1,000 Frames/s Programmable Vision Chip with Variable Resolution and Row-Pixel-Mixed Parallel Image Processors

August 2009

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6,854 Reads

Qingyu Lin

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Wei Miao

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A programmable vision chip with variable resolution and row-pixel-mixed parallel image processors is presented. The chip consists of a CMOS sensor array, with row-parallel 6-bit Algorithmic ADCs, row-parallel gray-scale image processors, pixel-parallel SIMD Processing Element (PE) array, and instruction controller. The resolution of the image in the chip is variable: high resolution for a focused area and low resolution for general view. It implements gray-scale and binary mathematical morphology algorithms in series to carry out low-level and mid-level image processing and sends out features of the image for various applications. It can perform image processing at over 1,000 frames/s (fps). A prototype chip with 64 × 64 pixels resolution and 6-bit gray-scale image is fabricated in 0.18 μm Standard CMOS process. The area size of chip is 1.5 mm × 3.5 mm. Each pixel size is 9.5 μm × 9.5 μm and each processing element size is 23 μm × 29 μm. The experiment results demonstrate that the chip can perform low-level and mid-level image processing and it can be applied in the real-time vision applications, such as high speed target tracking.

Diagrams comparing the conventional low field NMR instrument in (a) to the single sided instrument in (b). The primary difference between these two geometries is that applied rf interacts with the entire sample in (a) and only a fraction of the sample in (b) as shown by the shaded gray area.
Modified saturation recovery pulse sequence that incorporates a ±75 kHz frequency sweep into the saturation pulse. The CPMG backend is required to observe a signal because of the large inhomogeneous static field and rf circuit ring down. The variable frequency rf pulse more efficiently saturates the magnetization in single sided mode in comparison to the conventional rf pulse train used for sample-in-the-coil geometries.
Comparison of sterile (open circles) to unsterile (solid circles) T1 values as a function of room temperature exposure time. The 95% confidence intervals corresponding to averaging over 15 samples are included in the plot.
Example 1H NMR spectra obtained with the single sided coil magnet for a 100 mL tomato paste sample without (a) and enclosed in (b) the aluminum lined tote material.
Towards Using NMR to Screen for Spoiled Tomatoes Stored in 1,000 L, Aseptically Sealed, Metal-Lined Totes

March 2014

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375 Reads

Nuclear magnetic resonance (NMR) spectroscopy is used to track factory relevant tomato paste spoilage. It was found that spoilage in tomato paste test samples leads to longer spin lattice relaxation times T1 using a conventional low magnetic field NMR system. The increase in T1 value for contaminated samples over a five day room temperature exposure period prompted the work to be extended to the study of industry standard, 1,000 L, non-ferrous, metal-lined totes. NMR signals and T1 values were recovered from a large format container with a single-sided NMR sensor. The results of this work suggest that a handheld NMR device can be used to study tomato paste spoilage in factory process environments.

A Signal Normalization Technique for Illumination-Based Synchronization of 1,000-fps Real-Time Vision Sensors in Dynamic Scenes

September 2010

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391 Reads

To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. In this paper, an illumination-based synchronization derived from the phase-locked loop (PLL) mechanism based on the signal normalization method is proposed and evaluated. To eliminate the system dependency due to the amplitude fluctuation of the reference illumination, which may be caused by the moving objects or relative positional distance change between the light source and the observed objects, the fluctuant amplitude of the reference signal is normalized framely by the estimated maximum amplitude between the reference signal and its quadrature counterpart to generate a stable synchronization in highly dynamic scenes. Both simulated results and real world experimental results demonstrated successful synchronization result that 1,000-Hz frame rate vision sensors can be successfully synchronized to a LED illumination or its reflected light with satisfactory stability and only 28-μs jitters.


Antenna Systems and Electronic Warfare Applications.Edited by Richard A. Poisel, Artech House, 2012; 1036 pages. Price: £129.00, ISBN 978-1-60807-484-6

January 2013

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1,694 Reads

This comprehensive book serves as a one-stop resource for practical EW antenna system know-how. Supported with over 700 illustrations and nearly 1,700 equations, this authoritative reference offers you detailed explanations of all the important foundations and aspects of this technology. Moreover, you get an in-depth treatment of a wide range of antenna system applications.

Long-Term Monitoring of Fresco Paintings in the Cathedral of Valencia (Spain) through Humidity and Temperature Sensors in Various Locations for Preventive Conservation (vol 11, pg 8685, 2011)

April 2013

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138 Reads

A typo has been found in our paper [1]. It is stated on page 8698 that the range of acceptable temperature for the conservation of frescoes is 6-25 °C while in the case of RH, this range is 45%-60%, according to the Italian Standard UNI 10829 (1999). These recommended ranges of temperature (6-25 °C) and RH (45%-60%) correspond to the Standard DM 10/2001 [2], not to UNI 10829. The authors would like to apologize for any inconvenience this may have caused to the readers of this journal.




Retraction: Eldefrawy, M.H.; Khan, M.K.; Alghathbar, K.; Tolba, A.S.; Kim, K.J. Authenticated Key Agreement with Rekeying for Secured Body Sensor Networks. Sensors 2011, 11, 5835–5849.

December 2011

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135 Reads

It has been brought to our attention by a reader of Sensors that substantial portions of this article [1] have been copied from an earlier publication [2] without credit. After confirming this case with the authors, we have determined that indeed this manuscript clearly violates our policy on originality of all material submitted for publication and the generally accepted ethics of scientific publication. Consequently, the Editorial Team and Publisher have determined that it should be retracted. We apologize for any inconvenience this may cause.


Development of a New Surface Acoustic Wave Based Gyroscope on a X-112°Y LiTaO3 Substrate

December 2011

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336 Reads

A new micro gyroscope based on the surface acoustic wave (SAW) gyroscopic effect was developed. The SAW gyroscopic effect is investigated by applying the surface effective permittivity method in the regime of small ratios of the rotation velocity and the frequency of the SAW. The theoretical analysis indicates that the larger velocity shift was observed from the rotated X-112°Y LiTaO3 substrate. Then, two SAW delay lines with reverse direction and an operation frequency of 160 MHz are fabricated on a same X-112°Y LiTaO3 chip as the feedback of two SAW oscillators, which act as the sensor element. The single-phase unidirectional transducer (SPUDT) and combed transducers were used to structure the delay lines to improve the frequency stability of the oscillator. The rotation of a piezoelectric medium gives rise to a shift of the propagation velocity of SAW due to the Coriolis force, resulting in the frequency shift of the SAW device, and hence, the evaluation of the sensor performance. Meanwhile, the differential structure was performed to double the sensitivity and compensate for the temperature effects. Using a precise rate table, the performance of the fabricated SAW gyroscope was evaluated experimentally. A sensitivity of 1.332 Hz deg(-1) s at angular rates of up to 1,000 deg s(-1) and good linearity are observed.

Introduction to Modern EW Systems. Edited by Andrea De Martino, Artech House, 2012; 417 pages. Price: £119.00, ISBN 978-1-60807-207-1

January 2013

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2,991 Reads

Master the latest electronic warfare (EW) techniques and technologies related to on-board military platforms with this authoritative resource. You gain expert design guidance on technologies and equipment used to detect and identify emitter threats, giving you an advantage in the never-ending chess game between sensor guided weapons and EW systems. This unique book offers you deeper insight into EW systems principles of operation and their mathematical descriptions, arming you with better knowledge for your specific design applications.

Microscope image of RGB OLED on android screen for Smartphone HTC Desire. Approximate dimensions of each pixel are shown.
Optical spectra showing the emission from individual RGB OLED and the total spectra when all are activated.
Images obtained using the Smartphone as optical source: (a) Optical image of hollow shell using all RGB components; (b) Optical image using just the blue component and (c) fluorescent image obtained by excitation with the blue and transmitting green only.
SEM images of a regular sphere surface and edge of fracture showing dense hexagonal close packing of the structure. A very thin surface layer shows marked porosity over the interior and may partially explain the observed green fluorescence intensity at the edges in Figure 3(c)
Measurement of Fluorescence in a Rhodamine-123 Doped Self-Assembled “Giant” Mesostructured Silica Sphere Using a Smartphone as Optical Hardware

December 2011

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569 Reads

The blue OLED emission from a mobile phone was characterised, revealing a sharp emission band centred at λ = 445 nm with a 3dB bandwidth Δλ ∼ 20 nm. It was used to excite Rhodamine 123 doped within a "giant" mesostructured silica sphere during fabrication through evaporative self-assembly of silica nanoparticles. Fluorescence was able to be detected using a standard optical microscope fitted with a green transmission pass filter and cooled CCD and with 1 ms exposure time demonstrating the potential of mobile platforms as the basis for portable diagnostics in the field.

Wireless Prototype Based on Pressure and Bending Sensors for Measuring Gait Quality (vol 13, pg 9679, 2013)

November 2013

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79 Reads

In [1], we would like to change "Gate" to "Gait" in the title, which should read "Prototype Based on Pressure and Bending Sensors for Measuring Gait Quality". In Figure 7 we would like to change the analog inputs. The measurements should be between the sensor and the resistance, and not after the resistance. The revised figure is shown below.


Table 3 . Summary of the clustering of selected genes (wavebands), the number of genes, spectral range, means wavelength location and standard deviation.
The spectral emissivity profiles of the six plant species in the mid-wave and thermal infrared domain.
Performance of different sized chromosomes (number of bands in the chromosome) for the classification of 13 vegetation species.
The graphical representation of gene convergence, the frequency (count of genes selected in the population) clustered around certain wavebands as the number of generations increases.
The vertical bars represent the number of winning genes at a certain wavelength region for all 40 runs. The horizontal bar at the top shows the spread (mean and standard deviation) of the spectral regions from which the winning bands are selected.
Using a Genetic Algorithm as an Optimal Band Selector in the Mid and Thermal Infrared (2.5–14 μm) to Discriminate Vegetation Species

December 2012

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265 Reads

Genetic variation between various plant species determines differences in their physio-chemical makeup and ultimately in their hyperspectral emissivity signatures. The hyperspectral emissivity signatures, on the one hand, account for the subtle physio-chemical changes in the vegetation, but on the other hand, highlight the problem of high dimensionality. The aim of this paper is to investigate the performance of genetic algorithms coupled with the spectral angle mapper (SAM) to identify a meaningful subset of wavebands sensitive enough to discriminate thirteen broadleaved vegetation species from the laboratory measured hyperspectral emissivities. The performance was evaluated using an overall classification accuracy and Jeffries Matusita distance. For the multiple plant species, the targeted bands based on genetic algorithms resulted in a high overall classification accuracy (90%). Concentrating on the pairwise comparison results, the selected wavebands based on genetic algorithms resulted in higher Jeffries Matusita (J-M) distances than randomly selected wavebands did. This study concludes that targeted wavebands from leaf emissivity spectra are able to discriminate vegetation species.

Figure 5. ( a ) The pulse-echo signal A 44 , ( b ) the pitch-catch signal A 45 , and ( c ) the 
Figure 6. The pitch-catch signal A 12 of the target point (0, 30 nm). 
Figure 7. TFM images of (a) 8-elements FUT array (element size: 10 mm × 2 mm, gap: 1 mm) and (b) 7-elements FUT array (element size: 9 mm ×2 mm, gap: 0.5 mm) inspecting an Al alloy block of 30 mm thickness with a SDH of φ3 mm at the middle at 150 °C. Dashed circle: SDH.
Applications of Flexible Ultrasonic Transducer Array for Defect Detection at 150 °C

January 2013

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906 Reads

In this study, the feasibility of using a one dimensional 16-element flexible ultrasonic transducer (FUT) array for nondestructive testing at 150 °C is demonstrated. The FUT arrays were made by a sol-gel sprayed piezoelectric film technology; a PZT composite film was sprayed on a titanium foil of 75 µm thickness. Since the FUT array is flexible, it was attached to a steel pipe with an outer diameter of 89 mm and a wall thickness of 6.5 mm at 150 °C. Using the ultrasonic pulse-echo mode, pipe thickness measurements could be performed. Moreover, using the ultrasonic pulse-echo and pitch-catch modes of each element of FUT array, the defect detection was performed on an Al alloy block of 30 mm thickness with a side-drilled hole (SDH) of f3 mm at 150 °C. In addition, a post-processing algorithm based on the total focusing method was used to process the full matrix of these A-scan signals of each single transmitter and multi-receivers, and then the phase-array image was obtained to indicate this defect- SDH. Both results show the capability of FUT array being operated at 150 °C for the corrosion and defect detections.

Table 1 . The typical protocol of on-chip CLIA tests using the microfluidic microarray device.
Chip layout of 1536-chamber microfluidic microarray (Top) Inlet and outlet ports, chambers, and the calibration area of 1536-chamber chip were diagramed in the middle. (Bottom right) The detection principle of sandwich-type CLIA was shown at the bottom right corner. (Bottom left) A photo of the chip prototype was shown at the bottom left corner.
The flow diagram of surface modification processing on the microfluidic microarray.
Quantitative detection assays on the microfluidic microarrays. (a) The calibration curve of TNF-α; (b) Comparison plot for FSH concentration of 42 clinical samples by using both the SMP chips and traditional ELISA method; (c) Comparison plot for the concentrations of LH measured in 42 clinical samples using both the SMP chips and traditional ELISA method; (d) Comparison of the R.L.U. value in the CLIA tests for TNF-α. Three kinds of SMP chips, the complete SMP chips, the semi-manufactured SMP chips and the roughcast chips without surface treatment, were employed. The standard solution here was the TNF-α solution of 1.25 × 10−12 mol·L−1; the concentration of TNF-α in the clinical sample here was about 1.07 × 10−12 mol·L−1; (e) All correlation coefficient factors of 16 comparison plots for corresponding biomarkers in the 42 clinical samples by using both the SMP chips and traditional ELISA method.
Design and Fabrication of Low-Cost 1536-Chamber Microfluidic Microarrays for Mood-Disorders-Related Serological Studies

November 2013

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365 Reads

Mood disorders are common mental diseases, but physiological diagnostic methods are still lacking. Since much evidence has implied a relationship between mood disorders and the protein composition of blood sera, it is conceivable to develop a serological criterion for assisting diagnosis of mood disorders, based on a correlative database with enough capacity and high quality. In this pilot study, a low-cost microfluidic microarray device for quantifying at most 384 serological biomarkers at the same time was designed for the data acquisition of the serological study. The 1,536-chamber microfluidic device was modeled on a 1,536-well microtiter plate in order to employ a common microplate reader as the detection module for measuring the chemiluminescent immunoassay tests on the chips. The microfluidic microarrays were rapidly fabricated on polymethylmethacrylate slides using carbon dioxide laser ablation, followed by effective surface treatment processing. Sixteen types of different capture antibodies were immobilized on the chips to test the corresponding hormones and cytokines. The preliminary tests indicated that the signal-to-noise ratio and the limit of detection of microfluidic microarrays have reached the level of standard ELISA tests, whereas the operation time of microfluidic microarrays was sharply reduced.

Absorption Measurements of Periodically Poled Potassium Titanyl Phosphate (PPKTP) at 775 nm and 1550 nm

January 2013

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199 Reads

The efficient generation of second-harmonic light and squeezed light requires non-linear crystals that have low absorption at the fundamental and harmonic wavelengths. In this work the photo-thermal self-phase modulation technique is exploited to measure the absorption coefficient of periodically poled potassium titanyl phosphate (PPKTP) at 1,550 nm and 775 nm. Themeasurement results are (84±40) ppm/cmand (127±24) ppm/cm, respectively. We conclude that the performance of state-of-the-art frequency doubling and squeezed light generation in PPKTP is not limited by absorption.


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