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Sensors, Volume 10, Issue 7 (July 2010), Pages 6275-7066

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Open AccessCommunication Two-channel Hyperspectral LiDAR with a Supercontinuum Laser Source
Sensors 2010, 10(7), 7057-7066; https://doi.org/10.3390/s100707057
Received: 18 June 2010 / Revised: 15 July 2010 / Accepted: 19 July 2010 / Published: 23 July 2010
Cited by 59 | Viewed by 5831 | PDF Full-text (391 KB) | HTML Full-text | XML Full-text
Abstract
Recent advances in nonlinear fiber optics and compact pulsed lasers have resulted in creation of broadband directional light sources. These supercontinuum laser sources produce directional broadband light using cascaded nonlinear optical interactions in an optical fibre framework. This system is used to simultaneously
[...] Read more.
Recent advances in nonlinear fiber optics and compact pulsed lasers have resulted in creation of broadband directional light sources. These supercontinuum laser sources produce directional broadband light using cascaded nonlinear optical interactions in an optical fibre framework. This system is used to simultaneously measure distance and reflectance to demonstrate a technique capable of distinguishing between a vegetation target and inorganic material using the Normalized Difference Vegetation Index (NDVI) parameters, while the range can be obtained from the waveform of the echoes. A two-channel, spectral range-finding system based on a supercontinuum laser source was used to determine its potential application of distinguishing the NDVI for Norway spruce, a coniferous tree, and its three-dimensional parameters at 600 nm and 800 nm. A prototype system was built using commercial components. Full article
(This article belongs to the Section Remote Sensors)
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Open AccessArticle Investigation of the Frequency Shift of a SAD Circuit Loop and the Internal Micro-Cantilever in a Gas Sensor
Sensors 2010, 10(7), 7044-7056; https://doi.org/10.3390/s100707044
Received: 15 June 2010 / Revised: 30 June 2010 / Accepted: 10 July 2010 / Published: 23 July 2010
Cited by 4 | Viewed by 5605 | PDF Full-text (426 KB) | HTML Full-text | XML Full-text
Abstract
Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts.
[...] Read more.
Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF) and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF). A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD) circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed.Micro-cantilever sensors for mass detection using resonance frequency have attracted considerable attention over the last decade in the field of gas sensing. For such a sensing system, an oscillator circuit loop is conventionally used to actuate the micro-cantilever, and trace the frequency shifts. In this paper, gas experiments are introduced to investigate the mechanical resonance frequency shifts of the micro-cantilever within the circuit loop(mechanical resonance frequency, MRF) and resonating frequency shifts of the electric signal in the oscillator circuit (system working frequency, SWF). A silicon beam with a piezoelectric zinc oxide layer is employed in the experiment, and a Self-Actuating-Detecting (SAD) circuit loop is built to drive the micro-cantilever and to follow the frequency shifts. The differences between the two resonating frequencies and their shifts are discussed and analyzed, and a coefficientrelated to the two frequency shifts is confirmed. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessReview Fluorescent Chemosensors for Toxic Organophosphorus Pesticides: A Review
Sensors 2010, 10(7), 7018-7043; https://doi.org/10.3390/s100707018
Received: 24 March 2010 / Revised: 12 April 2010 / Accepted: 24 June 2010 / Published: 21 July 2010
Cited by 66 | Viewed by 11031 | PDF Full-text (1408 KB) | HTML Full-text | XML Full-text
Abstract
Many organophosphorus (OP) based compounds are highly toxic and powerful inhibitors of cholinesterases that generate serious environmental and human health concerns. Organothiophosphates with a thiophosphoryl (P=S) functional group constitute a broad class of these widely used pesticides. They are related to the more
[...] Read more.
Many organophosphorus (OP) based compounds are highly toxic and powerful inhibitors of cholinesterases that generate serious environmental and human health concerns. Organothiophosphates with a thiophosphoryl (P=S) functional group constitute a broad class of these widely used pesticides. They are related to the more reactive phosphoryl (P=O) organophosphates, which include very lethal nerve agents and chemical warfare agents, such as, VX, Soman and Sarin. Unfortunately, widespread and frequent commercial use of OP-based compounds in agricultural lands has resulted in their presence as residues in crops, livestock, and poultry products and also led to their migration into aquifers. Thus, the design of new sensors with improved analyte selectivity and sensitivity is of paramount importance in this area. Herein, we review recent advances in the development of fluorescent chemosensors for toxic OP pesticides and related compounds. We also discuss challenges and progress towards the design of future chemosensors with dual modes for signal transduction. Full article
(This article belongs to the Special Issue Fluorescent Chemosensors)
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Open AccessArticle The Effects of the Location of Au Additives on Combustion-generated SnO2 Nanopowders for CO Gas Sensing
Sensors 2010, 10(7), 7002-7017; https://doi.org/10.3390/s100707002
Received: 9 June 2010 / Revised: 16 July 2010 / Accepted: 19 July 2010 / Published: 21 July 2010
Cited by 26 | Viewed by 5625 | PDF Full-text (1288 KB) | HTML Full-text | XML Full-text
Abstract
The current work presents the results of an experimental study of the effects of the location of gold additives on the performance of combustion-generated tin dioxide (SnO2) nanopowders in solid state gas sensors. The time response and sensor response
to 500
[...] Read more.
The current work presents the results of an experimental study of the effects of the location of gold additives on the performance of combustion-generated tin dioxide (SnO2) nanopowders in solid state gas sensors. The time response and sensor response
to 500 ppm carbon monoxide is reported for a range of gold additive/SnO2 film architectures including the use of colloidal, sputtered, and combustion-generated Au additives. The opportunities afforded by combustion synthesis to affect the SnO2/additive morphology are demonstrated. The best sensor performance in terms of sensor response (S) and time response (t) was observed when the Au additives were restricted to the outermost layer of the gas-sensing film. Further improvement was observed in the sensor response and time response when the Au additives were dispersed throughout the outermost layer of the film, where S = 11.3 and t = 51 s, as opposed to Au localized at the surface, where
S = 6.1 and t = 60 s. Full article
(This article belongs to the Special Issue Gas Sensors - 2010)
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Open AccessArticle L Band Brightness Temperature Observations over a Corn Canopy during the Entire Growth Cycle
Sensors 2010, 10(7), 6980-7001; https://doi.org/10.3390/s100706980
Received: 26 March 2010 / Revised: 11 June 2010 / Accepted: 11 June 2010 / Published: 20 July 2010
Cited by 4 | Viewed by 8620 | PDF Full-text (1196 KB) | HTML Full-text | XML Full-text
Abstract
During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (TB) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive
[...] Read more.
During a field campaign covering the 2002 corn growing season, a dual polarized tower mounted L-band (1.4 GHz) radiometer (LRAD) provided brightness temperature (TB) measurements at preset intervals, incidence and azimuth angles. These radiometer measurements were supported by an extensive characterization of land surface variables including soil moisture, soil temperature, vegetation biomass, and surface roughness. In the period May 22 to August 30, ten days of radiometer and ground measurements are available for a corn canopy with a vegetation water content (W) range of 0.0 to 4.3 kg m−2. Using this data set, the effects of corn vegetation on surface emissions are investigated by means of a semi-empirical radiative transfer model. Additionally, the impact of roughness on the surface emission is quantified using TB measurements over bare soil conditions. Subsequently, the estimated roughness parameters, ground measurements and horizontally OPEN ACCESS (H)-polarized TB are employed to invert the H-polarized transmissivity (γh) for the monitored corn growing season. Full article
(This article belongs to the Section Remote Sensors)
Open AccessArticle Exploiting the Autofluorescent Properties of Photosynthetic Pigments for Analysis of Pigmentation and Morphology in Live Fremyella diplosiphon Cells
Sensors 2010, 10(7), 6969-6979; https://doi.org/10.3390/s100706969
Received: 7 June 2010 / Revised: 12 July 2010 / Accepted: 16 July 2010 / Published: 19 July 2010
Cited by 18 | Viewed by 7767 | PDF Full-text (343 KB) | HTML Full-text | XML Full-text
Abstract
Fremyella diplosiphon is a freshwater, filamentous cyanobacterium that exhibits light-dependent regulation of photosynthetic pigment accumulation and cellular and filament morphologies in a well-known process known as complementary chromatic adaptation (CCA). One of the techniques used to investigate the molecular bases of distinct aspects
[...] Read more.
Fremyella diplosiphon is a freshwater, filamentous cyanobacterium that exhibits light-dependent regulation of photosynthetic pigment accumulation and cellular and filament morphologies in a well-known process known as complementary chromatic adaptation (CCA). One of the techniques used to investigate the molecular bases of distinct aspects of CCA is confocal laser scanning microscopy (CLSM). CLSM capitalizes on the autofluorescent properties of cyanobacterial phycobiliproteins and chlorophyll a. We employed CLSM to perform spectral scanning analyses of F. diplosiphon strains grown under distinct light conditions. We report optimized utilization of CLSM to elucidate the molecular basis of the photoregulation of pigment accumulation and morphological responses in F. diplosiphon. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessReview Wireless Sensor Networks for Oceanographic Monitoring: A Systematic Review
Sensors 2010, 10(7), 6948-6968; https://doi.org/10.3390/s100706948
Received: 11 June 2010 / Revised: 29 June 2010 / Accepted: 1 July 2010 / Published: 19 July 2010
Cited by 75 | Viewed by 10363 | PDF Full-text (858 KB) | HTML Full-text | XML Full-text
Abstract
Monitoring of the marine environment has come to be a field of scientific interest in the last ten years. The instruments used in this work have ranged from small-scale sensor networks to complex observation systems. Among small-scale networks, Wireless Sensor Networks (WSNs) are
[...] Read more.
Monitoring of the marine environment has come to be a field of scientific interest in the last ten years. The instruments used in this work have ranged from small-scale sensor networks to complex observation systems. Among small-scale networks, Wireless Sensor Networks (WSNs) are a highly attractive solution in that they are easy to deploy, operate and dismantle and are relatively inexpensive. The aim of this paper is to identify, appraise, select and synthesize all high quality research evidence relevant to the use of WSNs in oceanographic monitoring. The literature is systematically reviewed to offer an overview of the present state of this field of study and identify the principal resources that have been used to implement networks of this kind. Finally, this article details the challenges and difficulties that have to be overcome if these networks are to be successfully deployed. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Position and Speed Control of Brushless DC Motors Using Sensorless Techniques and Application Trends
Sensors 2010, 10(7), 6901-6947; https://doi.org/10.3390/s100706901
Received: 10 June 2010 / Revised: 30 June 2010 / Accepted: 5 July 2010 / Published: 19 July 2010
Cited by 82 | Viewed by 16633 | PDF Full-text (2283 KB) | HTML Full-text | XML Full-text
Abstract
This paper provides a technical review of position and speed sensorless methods for controlling Brushless Direct Current (BLDC) motor drives, including the background analysis using sensors, limitations and advances. The performance and reliability of BLDC motor drivers have been improved because the conventional
[...] Read more.
This paper provides a technical review of position and speed sensorless methods for controlling Brushless Direct Current (BLDC) motor drives, including the background analysis using sensors, limitations and advances. The performance and reliability of BLDC motor drivers have been improved because the conventional control and sensing techniques have been improved through sensorless technology. Then, in this paper sensorless advances are reviewed and recent developments in this area are introduced with their inherent advantages and drawbacks, including the analysis of practical implementation issues and applications. The study includes a deep overview of state-of-the-art back-EMF sensing methods, which includes Terminal Voltage Sensing, Third Harmonic Voltage Integration, Terminal Current Sensing, Back-EMF Integration and PWM strategies. Also, the most relevant techniques based on estimation and models are briefly analysed, such as Sliding-mode Observer, Extended Kalman Filter, Model Reference Adaptive System, Adaptive observers (Full-order and Pseudoreduced-order) and Artificial Neural Networks. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Quantum Cascade Laser Absorption Spectroscopy as a Plasma Diagnostic Tool: An Overview
Sensors 2010, 10(7), 6861-6900; https://doi.org/10.3390/s100706861
Received: 8 June 2010 / Revised: 25 June 2010 / Accepted: 10 July 2010 / Published: 16 July 2010
Cited by 41 | Viewed by 9623 | PDF Full-text (1025 KB) | HTML Full-text | XML Full-text
Abstract
The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim
[...] Read more.
The recent availability of thermoelectrically cooled pulsed and continuous wave quantum and inter-band cascade lasers in the mid-infrared spectral region has led to significant improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarize the challenges which arise in the application of quantum cascade lasers in such environments, and, (ii) to provide an overview of recent spectroscopic results (encompassing cavity enhanced methods) obtained in different kinds of plasma used in both research and industry. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
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Open AccessArticle Study on a Two-Dimensional Scanning Micro-Mirror and Its Application in a MOEMS Target Detector
Sensors 2010, 10(7), 6848-6860; https://doi.org/10.3390/s100706848
Received: 23 June 2010 / Revised: 16 July 2010 / Accepted: 16 July 2010 / Published: 16 July 2010
Cited by 9 | Viewed by 5012 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
A two-dimensional (2D) scanning micro-mirror for target detection and measurement has been developed. This new micro-mirror is used in a MOEMS target detector to replace the conventional scanning detector. The micro-mirror is fabricated by MEMS process and actuated by a piezoelectric actuator. To
[...] Read more.
A two-dimensional (2D) scanning micro-mirror for target detection and measurement has been developed. This new micro-mirror is used in a MOEMS target detector to replace the conventional scanning detector. The micro-mirror is fabricated by MEMS process and actuated by a piezoelectric actuator. To achieve large deflection angles, the micro-mirror is excited in the resonance modes. It has two degrees of freedom and changes the direction of the emitted laser beam for a regional 2D scanning. For the deflection angles measurement, piezoresistors are integrated in the micro-mirror and the deflection angles of each direction can be detected independently and precisely. Based on the scanning micro-mirror and the phase-shift ranging technology, a MOEMS target detector has been developed in a size of 90 mm × 35 mm × 50 mm. The experiment shows that the target can be detected in the scanning field and the relative range and orientation can be measured by the MOEMS target detector. For the target distance up to 3 m with a field of view about 20º × 20º, the measurement resolution is about 10.2 cm in range, 0.15º in the horizontal direction and 0.22º in the vertical direction for orientation. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
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Open AccessArticle Optimization of Anodized-Aluminum Pressure-Sensitive Paint by Controlling Luminophore Concentration
Sensors 2010, 10(7), 6836-6847; https://doi.org/10.3390/s100706836
Received: 16 June 2010 / Revised: 8 July 2010 / Accepted: 13 July 2010 / Published: 16 July 2010
Cited by 11 | Viewed by 5232 | PDF Full-text (328 KB) | HTML Full-text | XML Full-text
Abstract
Anodized-aluminum pressure-sensitive paint (AA-PSP) has been used as a global pressure sensor for unsteady flow measurements. We use a dipping deposition method to apply a luminophore on a porous anodized-aluminum surface, controlling the luminophore concentration of the dipping method to optimize AA-PSP characteristics.
[...] Read more.
Anodized-aluminum pressure-sensitive paint (AA-PSP) has been used as a global pressure sensor for unsteady flow measurements. We use a dipping deposition method to apply a luminophore on a porous anodized-aluminum surface, controlling the luminophore concentration of the dipping method to optimize AA-PSP characteristics. The concentration is varied from 0.001 to 10 mM. Characterizations include the pressure sensitivity, the temperature dependency, and the signal level. The pressure sensitivity shows around 60 % at a lower concentration up to 0.1 mM. Above this concentration, the sensitivity reduces to a half. The temperature dependency becomes more than a half by setting the luminophore concentration from 0.001 to 10 mM. There is 3.6-fold change in the signal level by varying the concentration. To discuss an optimum concentration, a weight coefficient is introduced. We can arbitrarily change the coefficients to create an optimized AA-PSP for our sensing purposes. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Voltammetry under a Controlled Temperature Gradient
Sensors 2010, 10(7), 6821-6835; https://doi.org/10.3390/s100706821
Received: 30 May 2010 / Revised: 20 June 2010 / Accepted: 1 July 2010 / Published: 14 July 2010
Cited by 5 | Viewed by 5514 | PDF Full-text (572 KB) | HTML Full-text | XML Full-text
Abstract
Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient
[...] Read more.
Electrochemical measurements are generally done under isothermal conditions. Here we report on the application of a controlled temperature gradient between the working electrode surface and the solution. Using electrochemical sensors prepared on ceramic materials with extremely high specific heat conductivity, the temperature gradient between the electrode and solution was applied here as a second driving force. This application of the Soret phenomenon increases the mass transfer in the Nernst layer and enables more accurate control of the electrode response enhancement by a combination of diffusion and thermal diffusion. We have thus studied the effect of Soret phenomenon by cyclic voltammetry measurements in ferro/ferricyanide. The time dependence of sensor response disappears when applying the Soret phenomenon, and the complicated shape of the cyclic voltammogram is replaced by a simple exponential curve. We have derived the Cotrell-Soret equation describing the steady-state response with an applied temperature difference. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Intelligent Chiral Sensing Based on Supramolecular and Interfacial Concepts
Sensors 2010, 10(7), 6796-6820; https://doi.org/10.3390/s100706796
Received: 17 June 2010 / Revised: 7 July 2010 / Accepted: 8 July 2010 / Published: 13 July 2010
Cited by 40 | Viewed by 8026 | PDF Full-text (421 KB) | HTML Full-text | XML Full-text
Abstract
Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely
[...] Read more.
Of the known intelligently-operating systems, the majority can undoubtedly be classed as being of biological origin. One of the notable differences between biological and artificial systems is the important fact that biological materials consist mostly of chiral molecules. While most biochemical processes routinely discriminate chiral molecules, differentiation between chiral molecules in artificial systems is currently one of the challenging subjects in the field of molecular recognition. Therefore, one of the important challenges for intelligent man-made sensors is to prepare a sensing system that can discriminate chiral molecules. Because intermolecular interactions and detection at surfaces are respectively parts of supramolecular chemistry and interfacial science, chiral sensing based on supramolecular and interfacial concepts is a significant topic. In this review, we briefly summarize recent advances in these fields, including supramolecular hosts for color detection on chiral sensing, indicator-displacement assays, kinetic resolution in supramolecular reactions with analyses by mass spectrometry, use of chiral shape-defined polymers, such as dynamic helical polymers, molecular imprinting, thin films on surfaces of devices such as QCM, functional electrodes, FET, and SPR, the combined technique of magnetic resonance imaging and immunoassay, and chiral detection using scanning tunneling microscopy and cantilever technology. In addition, we will discuss novel concepts in recent research including the use of achiral reagents for chiral sensing with NMR, and mechanical control of chiral sensing. The importance of integration of chiral sensing systems with rapidly developing nanotechnology and nanomaterials is also emphasized. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle A Microring Resonator Sensor for Sensitive Detection of 1,3,5-Trinitrotoluene (TNT)
Sensors 2010, 10(7), 6788-6795; https://doi.org/10.3390/s100706788
Received: 6 April 2010 / Revised: 8 June 2010 / Accepted: 24 June 2010 / Published: 13 July 2010
Cited by 61 | Viewed by 8142 | PDF Full-text (378 KB) | HTML Full-text | XML Full-text
Abstract
A microring resonator sensor device for sensitive detection of the explosive 1,3,5-trinitrotoluene (TNT) is presented. It is based on the combination of a silicon microring resonator and tailored receptor molecules. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessReview Catalysts as Sensors—A Promising Novel Approach in Automotive Exhaust Gas Aftertreatment
Sensors 2010, 10(7), 6773-6787; https://doi.org/10.3390/s100706773
Received: 4 June 2010 / Revised: 7 July 2010 / Accepted: 9 July 2010 / Published: 13 July 2010
Cited by 50 | Viewed by 8925 | PDF Full-text (1292 KB) | HTML Full-text | XML Full-text
Abstract
Sensors that detect directly and in situ the status of automotive exhaust gas catalysts by monitoring the electrical properties of the catalyst coating itself are overviewed. Examples included in this review are the in-situ determination of the electrical impedance of three-way catalysts based
[...] Read more.
Sensors that detect directly and in situ the status of automotive exhaust gas catalysts by monitoring the electrical properties of the catalyst coating itself are overviewed. Examples included in this review are the in-situ determination of the electrical impedance of three-way catalysts based on ceria-zirconia solutions and of lean NOx traps of earth-alkaline based coatings, as well as approaches to determine the ammonia loading in Fe-SCR-zeolites with electrical ac measurements. Even more sophisticated approaches based on interactions with electromagnetic waves are also reviewed. For that purpose, metallic stick-like antennas are inserted into the exhaust pipe. The catalyst properties are measured in a contactless manner, directly indicating the catalyst status. The radio frequency probes gauge the oxygen loading degree of three-way catalysts, the NOx-loading of lean NOx traps, and the soot loading of Diesel particulate filters Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview “Smart” Continuous Glucose Monitoring Sensors: On-Line Signal Processing Issues
Sensors 2010, 10(7), 6751-6772; https://doi.org/10.3390/s100706751
Received: 30 May 2010 / Revised: 25 June 2010 / Accepted: 30 June 2010 / Published: 12 July 2010
Cited by 65 | Viewed by 8350 | PDF Full-text (499 KB) | HTML Full-text | XML Full-text
Abstract
The availability of continuous glucose monitoring (CGM) sensors allows development of new strategies for the treatment of diabetes. In particular, from an on-line perspective, CGM sensors can become “smart” by providing them with algorithms able to generate alerts when glucose concentration is predicted
[...] Read more.
The availability of continuous glucose monitoring (CGM) sensors allows development of new strategies for the treatment of diabetes. In particular, from an on-line perspective, CGM sensors can become “smart” by providing them with algorithms able to generate alerts when glucose concentration is predicted to exceed the normal range thresholds. To do so, at least four important aspects have to be considered and dealt with on-line. First, the CGM data must be accurately calibrated. Then, CGM data need to be filtered in order to enhance their signal-to-noise ratio (SNR). Thirdly, predictions of future glucose concentration should be generated with suitable modeling methodologies. Finally, generation of alerts should be done by minimizing the risk of detecting false and missing true events. For these four challenges, several techniques, with various degrees of sophistication, have been proposed in the literature and are critically reviewed in this paper. Full article
(This article belongs to the Special Issue Glucose Sensors)
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Open AccessArticle Computational Methodology for Absolute Calibration Curves for Microfluidic Optical Analyses
Sensors 2010, 10(7), 6730-6750; https://doi.org/10.3390/s100706730
Received: 10 May 2010 / Revised: 12 July 2010 / Accepted: 12 July 2010 / Published: 12 July 2010
Cited by 1 | Viewed by 5115 | PDF Full-text (325 KB) | HTML Full-text | XML Full-text
Abstract
Optical fluorescence and absorption are two of the primary techniques used for analytical microfluidics. We provide a thorough yet tractable method for computing the performance of diverse optical micro-analytical systems. Sample sizes range from nano- to many micro-liters and concentrations from nano- to
[...] Read more.
Optical fluorescence and absorption are two of the primary techniques used for analytical microfluidics. We provide a thorough yet tractable method for computing the performance of diverse optical micro-analytical systems. Sample sizes range from nano- to many micro-liters and concentrations from nano- to milli-molar. Equations are provided to trace quantitatively the flow of the fundamental entities, namely photons and electrons, and the conversion of energy from the source, through optical components, samples and spectral-selective components, to the detectors and beyond. The equations permit facile computations of calibration curves that relate the concentrations or numbers of molecules measured to the absolute signals from the system. This methodology provides the basis for both detailed understanding and improved design of microfluidic optical analytical systems. It saves prototype turn-around time, and is much simpler and faster to use than ray tracing programs. Over two thousand spreadsheet computations were performed during this study. We found that some design variations produce higher signal levels and, for constant noise levels, lower minimum detection limits. Improvements of more than a factor of 1,000 were realized. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Electromagnet Weight Reduction in a Magnetic Levitation System for Contactless Delivery Applications
Sensors 2010, 10(7), 6718-6729; https://doi.org/10.3390/s100706718
Received: 1 June 2010 / Revised: 2 July 2010 / Accepted: 7 July 2010 / Published: 9 July 2010
Cited by 5 | Viewed by 5332 | PDF Full-text (849 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents an optimum design of a lightweight vehicle levitation electromagnet, which also provides a passive guide force in a magnetic levitation system for contactless delivery applications. The split alignment of C-shaped electromagnets about C-shaped rails has a bad effect on the
[...] Read more.
This paper presents an optimum design of a lightweight vehicle levitation electromagnet, which also provides a passive guide force in a magnetic levitation system for contactless delivery applications. The split alignment of C-shaped electromagnets about C-shaped rails has a bad effect on the lateral deviation force, therefore, no-split positioning of electromagnets is better for lateral performance. This is verified by simulations and experiments. This paper presents a statistically optimized design with a high number of the design variables to reduce the weight of the electromagnet under the constraint of normal force using response surface methodology (RSM) and the kriging interpolation method. 2D and 3D magnetostatic analysis of the electromagnet are performed using ANSYS. The most effective design variables are extracted by a Pareto chart. The most desirable set is determined and the influence of each design variable on the objective function can be obtained. The generalized reduced gradient (GRG) algorithm is adopted in the kriging model. This paper’s procedure is validated by a comparison between experimental and calculation results, which shows that the predicted performance of the electromagnet designed by RSM is in good agreement with the simulation results. Full article
Open AccessArticle Wireless Multimedia Sensor Networks: Current Trends and Future Directions
Sensors 2010, 10(7), 6662-6717; https://doi.org/10.3390/s100706662
Received: 27 May 2010 / Revised: 20 June 2010 / Accepted: 25 June 2010 / Published: 9 July 2010
Cited by 154 | Viewed by 11246 | PDF Full-text (10305 KB) | HTML Full-text | XML Full-text
Abstract
Wireless Multimedia Sensor Networks (WMSNs) have emerged and shifted the focus from the typical scalar wireless sensor networks to networks with multimedia devices that are capable to retrieve video, audio, images, as well as scalar sensor data. WMSNs are able to deliver multimedia
[...] Read more.
Wireless Multimedia Sensor Networks (WMSNs) have emerged and shifted the focus from the typical scalar wireless sensor networks to networks with multimedia devices that are capable to retrieve video, audio, images, as well as scalar sensor data. WMSNs are able to deliver multimedia content due to the availability of inexpensive CMOS cameras and microphones coupled with the significant progress in distributed signal processing and multimedia source coding techniques. In this paper, we outline the design challenges of WMSNs, give a comprehensive discussion of the proposed architectures, algorithms and protocols for the different layers of the communication protocol stack for WMSNs, and evaluate the existing WMSN hardware and testbeds. The paper will give the reader a clear view of the state of the art at all aspects of this research area, and shed the light on its main current challenges and future trends. We also hope it will foster discussions and new research ideas among its researchers. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessReview Microfluidic Systems for Biosensing
Sensors 2010, 10(7), 6623-6661; https://doi.org/10.3390/s100706623
Received: 1 June 2010 / Revised: 20 June 2010 / Accepted: 30 June 2010 / Published: 9 July 2010
Cited by 63 | Viewed by 10025 | PDF Full-text (2493 KB) | HTML Full-text | XML Full-text
Abstract
In the past two decades, Micro Fluidic Systems (MFS) have emerged as a powerful tool for biosensing, particularly in enriching and purifying molecules and cells in biological samples. Compared with conventional sensing techniques, distinctive advantages of using MFS for biomedicine include ultra-high sensitivity,
[...] Read more.
In the past two decades, Micro Fluidic Systems (MFS) have emerged as a powerful tool for biosensing, particularly in enriching and purifying molecules and cells in biological samples. Compared with conventional sensing techniques, distinctive advantages of using MFS for biomedicine include ultra-high sensitivity, higher throughput, in-situ monitoring and lower cost. This review aims to summarize the recent advancements in two major types of micro fluidic systems, continuous and discrete MFS, as well as their biomedical applications. The state-of-the-art of active and passive mechanisms of fluid manipulation for mixing, separation, purification and concentration will also be elaborated. Future trends of using MFS in detection at molecular or cellular level, especially in stem cell therapy, tissue engineering and regenerative medicine, are also prospected. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in the UK)
Open AccessArticle An Efficient and Compact Difference-Frequency-Generation Spectrometer and Its Application to 12CH3D/12CH4 Isotope Ratio Measurements
Sensors 2010, 10(7), 6612-6622; https://doi.org/10.3390/s100706612
Received: 4 February 2010 / Revised: 28 April 2010 / Accepted: 7 June 2010 / Published: 9 July 2010
Cited by 4 | Viewed by 4828 | PDF Full-text (314 KB) | HTML Full-text | XML Full-text
Abstract
We have developed an efficient and compact 3.4 μm difference-frequency-generation spectrometer using a 1.55 μm distributed feedback (DFB) laser diode, a 1.06 μm DFB laser diode, and a ridge-waveguide periodically poled lithium niobate. It is continuously tunable in the 30 cm–1 span
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We have developed an efficient and compact 3.4 μm difference-frequency-generation spectrometer using a 1.55 μm distributed feedback (DFB) laser diode, a 1.06 μm DFB laser diode, and a ridge-waveguide periodically poled lithium niobate. It is continuously tunable in the 30 cm–1 span and is applied to 12CH3D/12CH4 isotope ratio measurements. The suitable pair of 12CH3D n4 pP(7,6) and 12CH4 ν24 R(6) F1(1) lines enabled us to determine their isotope ratio with a precision repeatability of 0.8‰ using a sample and a working standard of pure methane with an effective signal averaging time of 100 ms. Full article
(This article belongs to the Special Issue Laser Spectroscopy and Sensing)
Open AccessArticle Design and Characterization of a High Resolution Microfluidic Heat Flux Sensor with Thermal Modulation
Sensors 2010, 10(7), 6594-6611; https://doi.org/10.3390/s100706594
Received: 22 April 2010 / Revised: 31 May 2010 / Accepted: 24 May 2010 / Published: 9 July 2010
Cited by 9 | Viewed by 5539 | PDF Full-text (1273 KB) | HTML Full-text | XML Full-text
Abstract
A complementary metal-oxide semiconductor-compatible process was used in the design and fabrication of a suspended membrane microfluidic heat flux sensor with a thermopile for the purpose of measuring the heat flow rate. The combination of a thirty-junction gold and nickel thermoelectric sensor with
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A complementary metal-oxide semiconductor-compatible process was used in the design and fabrication of a suspended membrane microfluidic heat flux sensor with a thermopile for the purpose of measuring the heat flow rate. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, a low pass filter, and a lock-in amplifier can yield a resolution 20 nW with a sensitivity of 461 V/W. The thermal modulation method is used to eliminate low-frequency noise from the sensor output, and various amounts of fluidic heat were applied to the sensor to investigate its suitability for microfluidic applications. For sensor design and analysis of signal output, a method of modeling and simulating electro-thermal behavior in a microfluidic heat flux sensor with an integrated electronic circuit is presented and validated. The electro-thermal domain model was constructed by using system dynamics, particularly the bond graph. The electro-thermal domain system model in which the thermal and the electrical domains are coupled expresses the heat generation of samples and converts thermal input to electrical output. The proposed electro-thermal domain system model is in good agreement with the measured output voltage response in both the transient and the steady state. Full article
(This article belongs to the Special Issue Bio-devices and Materials)
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Open AccessArticle Error Analysis and Measurement Uncertainty for a Fiber Grating Strain-Temperature Sensor
Sensors 2010, 10(7), 6582-6593; https://doi.org/10.3390/s100706582
Received: 20 April 2010 / Revised: 17 June 2010 / Accepted: 2 July 2010 / Published: 9 July 2010
Cited by 9 | Viewed by 5983 | PDF Full-text (677 KB) | HTML Full-text | XML Full-text
Abstract
A fiber grating sensor capable of distinguishing between temperature and strain, using a reference and a dual-wavelength fiber Bragg grating, is presented. Error analysis and measurement uncertainty for this sensor are studied theoretically and experimentally. The measured root mean squared errors for temperature
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A fiber grating sensor capable of distinguishing between temperature and strain, using a reference and a dual-wavelength fiber Bragg grating, is presented. Error analysis and measurement uncertainty for this sensor are studied theoretically and experimentally. The measured root mean squared errors for temperature T and strain ε were estimated to be 0.13 °C and 6 με, respectively. The maximum errors for temperature and strain were calculated as 0.00155 T + 2.90 × 106 ε and 3.59 × 105 ε + 0.01887 T, respectively. Using the estimation of expanded uncertainty at 95% confidence level with a coverage factor of k = 2.205, temperature and strain measurement uncertainties were evaluated as 2.60 °C and 32.05 με, respectively. For the first time, to our knowledge, we have demonstrated the feasibility of estimating the measurement uncertainty for simultaneous strain-temperature sensing with such a fiber grating sensor. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessReview Prospects of Nanotechnology in Clinical Immunodiagnostics
Sensors 2010, 10(7), 6535-6581; https://doi.org/10.3390/s100706535
Received: 30 May 2010 / Revised: 12 June 2010 / Published: 7 July 2010
Cited by 25 | Viewed by 9346 | PDF Full-text (748 KB) | HTML Full-text | XML Full-text
Abstract
Nanostructured materials are promising compounds that offer new opportunities as sensing platforms for the detection of biomolecules. Having micrometer-scale length and nanometer-scale diameters, nanomaterials can be manipulated with current nanofabrication methods, as well as self-assembly techniques, to fabricate nanoscale bio-sensing devices. Nanostructured materials
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Nanostructured materials are promising compounds that offer new opportunities as sensing platforms for the detection of biomolecules. Having micrometer-scale length and nanometer-scale diameters, nanomaterials can be manipulated with current nanofabrication methods, as well as self-assembly techniques, to fabricate nanoscale bio-sensing devices. Nanostructured materials possess extraordinary physical, mechanical, electrical, thermal and multifunctional properties. Such unique properties advocate their use as biomimetic membranes to immobilize and modify biomolecules on the surface of nanoparticles. Alignment, uniform dispersion, selective growth and diameter control are general parameters which play critical roles in the successful integration of nanostructures for the fabrication of bioelectronic sensing devices. In this review, we focus on different types and aspects of nanomaterials, including their synthesis, properties, conjugation with biomolecules and their application in the construction of immunosensing devices. Some key results from each cited article are summarized by relating the concept and mechanism behind each sensor, experimental conditions and the behavior of the sensor under different conditions, etc. The variety of nanomaterial-based bioelectronic devices exhibiting novel functions proves the unique properties of nanomaterials in such sensing devices, which will surely continue to expand in the future. Such nanomaterial based devices are expected to have a major impact in clinical immunodiagnostics, environmental monitoring, security surveillance and for ensuring food safety. Full article
(This article belongs to the Special Issue Immunosensors)
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Open AccessArticle Bathymetry Determination via X-Band Radar Data: A New Strategy and Numerical Results
Sensors 2010, 10(7), 6522-6534; https://doi.org/10.3390/s100706522
Received: 27 May 2010 / Revised: 15 June 2010 / Accepted: 25 June 2010 / Published: 6 July 2010
Cited by 27 | Viewed by 6675 | PDF Full-text (885 KB) | HTML Full-text | XML Full-text
Abstract
This work deals with the question of sea state monitoring using marine X-band radar images and focuses its attention on the problem of sea depth estimation. We present and discuss a technique to estimate bathymetry by exploiting the dispersion relation for surface gravity
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This work deals with the question of sea state monitoring using marine X-band radar images and focuses its attention on the problem of sea depth estimation. We present and discuss a technique to estimate bathymetry by exploiting the dispersion relation for surface gravity waves. This estimation technique is based on the correlation between the measured and the theoretical sea wave spectra and a simple analysis of the approach is performed through test cases with synthetic data. More in detail, the reliability of the estimate technique is verified through simulated data sets that are concerned with different values of bathymetry and surface currents for two types of sea spectrum: JONSWAP and Pierson-Moskowitz. The results show how the estimated bathymetry is fairly accurate for low depth values, while the estimate is less accurate as the bathymetry increases, due to a less significant role of the bathymetry on the sea surface waves as the water depth increases. Full article
(This article belongs to the Special Issue Intelligent Sensors - 2010)
Open AccessArticle Effects of High-Humidity Aging on Platinum, Palladium, and Gold Loaded Tin Oxide—Volatile Organic Compound Sensors
Sensors 2010, 10(7), 6513-6521; https://doi.org/10.3390/s100706513
Received: 29 May 2010 / Revised: 15 June 2010 / Accepted: 25 June 2010 / Published: 6 July 2010
Cited by 26 | Viewed by 6319 | PDF Full-text (314 KB) | HTML Full-text | XML Full-text
Abstract
This study is an investigation of high-humidity aging effects on the total volatile organic compound (T–VOC) gas-sensing properties of platinum, palladium, and gold-loaded tin oxide (Pt,Pd,Au/SnO2) thick films. The sensor responses of the high-humidity aged Pt,Pd,Au/SnO2, a non-aged Pt,Pd,Au/SnO
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This study is an investigation of high-humidity aging effects on the total volatile organic compound (T–VOC) gas-sensing properties of platinum, palladium, and gold-loaded tin oxide (Pt,Pd,Au/SnO2) thick films. The sensor responses of the high-humidity aged Pt,Pd,Au/SnO2, a non-aged Pt,Pd,Au/SnO2, and a high-humidity aged Pt/SnO2 to T–VOC test gas have been measured. The high-humidity aging is an effective treatment for resistance to humidity change for the Pt,Pd,Au/SnO2 but not effective for the Pt/SnO2. The mechanism of the high-humidity aging effects is discussed based on the change of surface state of the SnO2 particles. Full article
(This article belongs to the Section Chemical Sensors)
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Open AccessArticle Optimal Configuration of Redundant Inertial Sensors for Navigation and FDI Performance
Sensors 2010, 10(7), 6497-6512; https://doi.org/10.3390/s100706497
Received: 20 May 2010 / Revised: 10 June 2010 / Accepted: 20 June 2010 / Published: 2 July 2010
Cited by 35 | Viewed by 4574 | PDF Full-text (427 KB) | HTML Full-text | XML Full-text
Abstract
This paper considers the optimal sensor configuration for inertial navigation systems which have redundant inertial sensors such as gyroscopes and accelerometers. We suggest a method to determine the optimal sensor configuration which considers both the navigation and FDI performance. Monte Carlo simulations are
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This paper considers the optimal sensor configuration for inertial navigation systems which have redundant inertial sensors such as gyroscopes and accelerometers. We suggest a method to determine the optimal sensor configuration which considers both the navigation and FDI performance. Monte Carlo simulations are performed to show the performance of the suggested optimal sensor configuration method. Full article
(This article belongs to the Section Chemical Sensors)
Open AccessArticle Semiconducting Polymer Photodetectors with Electron and Hole Blocking Layers: High Detectivity in the Near-Infrared
Sensors 2010, 10(7), 6488-6496; https://doi.org/10.3390/s100706488
Received: 22 April 2010 / Revised: 11 May 2010 / Accepted: 30 June 2010 / Published: 1 July 2010
Cited by 55 | Viewed by 8460 | PDF Full-text (260 KB) | HTML Full-text | XML Full-text
Abstract
Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Photodetectors with broad spectral response, from 300 nm to 1,100 nm, were fabricated using a narrow-band gap semiconducting polymer blended with a fullerene derivative. By using
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Sensing from the ultraviolet-visible to the infrared is critical for a variety of industrial and scientific applications. Photodetectors with broad spectral response, from 300 nm to 1,100 nm, were fabricated using a narrow-band gap semiconducting polymer blended with a fullerene derivative. By using both an electron-blocking layer and a hole-blocking layer, the polymer photodetectors, operating at room temperature, exhibited calculated detectivities greater than 1013 cm Hz1/2/W over entire spectral range with linear dynamic range approximately 130 dB. The performance is comparable to or even better than Si photodetectors. Full article
(This article belongs to the Special Issue Photodetectors and Imaging Technologies)
Open AccessArticle Fabrication of Localized Surface Plasmon Resonance Fiber Probes Using Ionic Self-Assembled Gold Nanoparticles
Sensors 2010, 10(7), 6477-6487; https://doi.org/10.3390/s100706477
Received: 11 May 2010 / Revised: 8 June 2010 / Accepted: 21 June 2010 / Published: 1 July 2010
Cited by 12 | Viewed by 5048 | PDF Full-text (704 KB) | HTML Full-text | XML Full-text
Abstract
An nm-thickness composite gold thin film consisting of gold nanoparticles and polyelectrolytes is fabricated through ionic self-assembled multilayers (ISAM) technique and is deposited on end-faces of optical fibers to construct localized surface plasmon resonance (LSPR) fiber probes. We demonstrate that the LSPR spectrum
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An nm-thickness composite gold thin film consisting of gold nanoparticles and polyelectrolytes is fabricated through ionic self-assembled multilayers (ISAM) technique and is deposited on end-faces of optical fibers to construct localized surface plasmon resonance (LSPR) fiber probes. We demonstrate that the LSPR spectrum induced by ISAM gold films can be fine-tuned through the ISAM procedure. We investigate variations of reflection spectra of the probe with respect to the layer-by-layer adsorption of ISAMs onto end-faces of fibers, and study the spectral variation mechanism. Finally, we demonstrated using this fiber probe to detect the biotin-streptavidin bioconjugate pair. ISAM adsorbed on optical fibers potentially provides a simple, fast, robust, and low-cost, platform for LSPR biosensing applications. Full article
(This article belongs to the Section Biosensors)
Open AccessArticle A Colorimetric Sensor for Qualitative Discrimination and Quantitative Detection of Volatile Amines
Sensors 2010, 10(7), 6463-6476; https://doi.org/10.3390/s100706463
Received: 23 May 2010 / Revised: 26 June 2010 / Accepted: 29 June 2010 / Published: 30 June 2010
Cited by 25 | Viewed by 6215 | PDF Full-text (264 KB) | HTML Full-text | XML Full-text
Abstract
We have developed a novel colorimetric sensor based on a digital camera and white LED illumination. Colorimetric sensor arrays (CSAs) were made from a set of six chemically responsive dyes impregnated on an inert substrate plate by solution casting. Six common amine aqueous
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We have developed a novel colorimetric sensor based on a digital camera and white LED illumination. Colorimetric sensor arrays (CSAs) were made from a set of six chemically responsive dyes impregnated on an inert substrate plate by solution casting. Six common amine aqueous solutions, including dimethylamine, triethylamine, diisopropyl-amine, aniline, cyclohexylamine, and pyridine vaporized at 25 °C and six health-related trimethylamine (TMA) concentrations including 170 ppm, 51 ppm, 8 ppm, 2 ppm, 125 ppb and 50 ppb were analyzed by the sensor to test its ability for the qualitative discrimination and quantitative detection of volatile amines. We extracted the feature vectors of the CSA's response to the analytes from a fusional color space, which was obtained by conducting a joint search algorithm of sequential forward selection and sequential backward selection (SFS&SBS) based on the linear discriminant criteria (LDC) in a mixed color space composed of six common color spaces. The principle component analysis (PCA) followed by the hierarchical cluser analysis (HCA) were utilized to discriminate 12 analytes. Results showed that the colorimetric sensor grouped the six amine vapors and five TMA concentrations correctly, while TMA concentrations of 125 ppb and 50 ppb were indiscriminable from each other. The limitation of detection (LOD) of the sensor for TMA was found to be lower than 50 ppb. The CSAs were reusable for TMA concentrations below 8 ppm. Full article
(This article belongs to the Section Chemical Sensors)
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