Sensors

260 KiB

Open AccessArticle

Potentiometric Responses of Ion-Selective Electrodes Doped with Diureidocalix[4]arene towards Un-dissociated Benzoic Acid

by Agnieszka Krajewska, Pavel Lhotak and Hanna Radecka

Sensors 2007, 7(8), 1655-1666; https://doi.org/10.3390/s7081655 - 27 Aug 2007

Cited by 9 | Viewed by 8768

Abstract

Diureidocalix[4]arene have been applied as new ionophore in liquid membraneelectrode (ISE) sensitive towards un-dissociated benzoic acid. The electrode demonstratedresponse towards benzoic acid with the detection limit 2.0 x 10^-4 M which is sufficient forthe determination of benzoic acid added to beverages as [...] Read more.

Diureidocalix[4]arene have been applied as new ionophore in liquid membraneelectrode (ISE) sensitive towards un-dissociated benzoic acid. The electrode demonstratedresponse towards benzoic acid with the detection limit 2.0 x 10^-4 M which is sufficient forthe determination of benzoic acid added to beverages as preservative in milimolarconcentration. The selectivity coefficients measured by the matched potential method(MPM) showed its good selectivity against common anions present in drink samples. Allmeasurements were made in presence of 1.0 x 10^-2 M NaHSO₄ pH 3.0 in order to reducethe influence of OH^-. The applicability of diureidocalix[4]arene incorporated ISE has beenchecked by recovery test of benzoic acid in the presence of artificial drink matrix and bystandard addition method. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Conductive Polymers)

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1374 KiB

Open AccessArticle

Micro Machining of Injection Mold Inserts for Fluidic Channel of Polymeric Biochips

by Woo-Chul Jung, Young-Moo Heo, Gil-Sang Yoon, Kwang-Ho Shin, Sung-Ho Chang, Gun-Hee Kim and Myeong-Woo Cho

Sensors 2007, 7(8), 1643-1654; https://doi.org/10.3390/s7081643 - 27 Aug 2007

Cited by 36 | Viewed by 14952

Abstract

Recently, the polymeric micro-fluidic biochip, often called LOC (lab-on-a-chip), has been focused as a cheap, rapid and simplified method to replace the existing biochemical laboratory works. It becomes possible to form miniaturized lab functionalities on a chip with the development of MEMS technologies. [...] Read more.

Recently, the polymeric micro-fluidic biochip, often called LOC (lab-on-a-chip), has been focused as a cheap, rapid and simplified method to replace the existing biochemical laboratory works. It becomes possible to form miniaturized lab functionalities on a chip with the development of MEMS technologies. The micro-fluidic chips contain many micro-channels for the flow of sample and reagents, mixing, and detection tasks. Typical substrate materials for the chip are glass and polymers. Typical techniques for micro-fluidic chip fabrication are utilizing various micro pattern forming methods, such as wet-etching, micro-contact printing, and hot-embossing, micro injection molding, LIGA, and micro powder blasting processes, etc. In this study, to establish the basis of the micro pattern fabrication and mass production of polymeric micro-fluidic chips using injection molding process, micro machining method was applied to form micro-channels on the LOC molds. In the research, a series of machining experiments using micro end-mills were performed to determine optimum machining conditions to improve surface roughness and shape accuracy of designed simplified micro-channels. Obtained conditions were used to machine required mold inserts for micro-channels using micro end-mills. Test injection processes using machined molds and COC polymer were performed, and then the results were investigated. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)

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439 KiB

Open AccessArticle

Development of a Molecularly Imprinted Biomimetic Electrode

by Lisa M. Kindschy and Evangelyn C. Alocilja

Sensors 2007, 7(8), 1630-1642; https://doi.org/10.3390/s7081630 - 27 Aug 2007

Cited by 20 | Viewed by 10018

Abstract

The technique of molecular imprinting produces artificial receptor sites in apolymer that can be used in a biomimetic sensor. This research extends previous studies ofa molecularly imprinted polymer (MIP) biomimetic sensor for the small drug theophylline.The presence of theophylline in the biomimetic sensor [...] Read more.

The technique of molecular imprinting produces artificial receptor sites in apolymer that can be used in a biomimetic sensor. This research extends previous studies ofa molecularly imprinted polymer (MIP) biomimetic sensor for the small drug theophylline.The presence of theophylline in the biomimetic sensor was monitored by analyzing thepeak currents from cyclic voltammetry experiments. The functional working range of theMIP modified electrode was 2 - 4 mM theophylline. The concentration of theophyllinethat resulted in the best signal was 3 mM. The MIP sensor showed no response to thestructurally related molecule caffeine, and therefore was selective to the target analytetheophylline. This research will provide the foundation for future studies that will result indurable biomimetic sensors that can offer a viable alternative to current sensors. Full article

(This article belongs to the Special Issue Physiological Sensing)

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987 KiB

Open AccessArticle

Chemomechanical Polymers as Sensors and Actuators for Biological and Medicinal Applications

by Hans-Jörg Schneider, Kazuaki Kato and Robert M. Strongin

Sensors 2007, 7(8), 1578-1611; https://doi.org/10.3390/s7081578 - 27 Aug 2007

Cited by 59 | Viewed by 16426

Abstract

Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any [...] Read more.

Changes in the chemical environment can trigger large motions in chemomechanical polymers. The unique feature of such intelligent materials, mostly in the form of hydrogels, is therefore, that they serve as sensors and actuators at the same time, and do not require any measuring devices, transducers or power supplies. Until recently the most often used of these materials responded to changes in pH. Chemists are now increasingly using supramolecular recognition sites in materials, which are covalently bound to the polymer backbone. This allows one to use a nearly unlimited variety of guest (or effector) compounds in the environment for a selective response by automatically triggered size changes. This is illustrated with non-covalent interactions of effectors comprising of metal ions, isomeric organic compounds, including enantiomers, nucleotides, aminoacids, and peptides. Two different effector molecules can induce motions as functions of their concentration, thus representing a logical AND gate. This concept is particularly fruitful with effector compounds such as peptides, which only trigger size changes if, e.g. copper ions are present in the surroundings. Another principle relies on the fast formation of covalent bonds between an effector and the chemomechanical polymer. The most promising application is the selective interaction of covalently fixed boronic acid residues with glucose, which renders itself not only for sensing, but eventually also for delivery of drugs such as insulin. The speed of the responses can significantly increase by increasing the surface to volume ratio of the polymer particles. Of particular interest is the sensitivity increase which can be reached by downsizing the particle volume. Full article

(This article belongs to the Special Issue Physiological Sensing)

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446 KiB

Open AccessReview

An Overview of the "Triangle Method" for Estimating Surface Evapotranspiration and Soil Moisture from Satellite Imagery

by Toby Carlson

Sensors 2007, 7(8), 1612-1629; https://doi.org/10.3390/s7081612 - 24 Aug 2007

Cited by 602 | Viewed by 26548

Abstract

An overview of the ‘triangle’ method for estimating soil surface wetness and evapotranspiration fraction from satellite imagery is presented here. The method is insensitive to initial atmospheric and surface conditions, net radiation and atmospheric correction, yet can yield accuracies comparable to other methods. [...] Read more.

An overview of the ‘triangle’ method for estimating soil surface wetness and evapotranspiration fraction from satellite imagery is presented here. The method is insensitive to initial atmospheric and surface conditions, net radiation and atmospheric correction, yet can yield accuracies comparable to other methods. We describe the method first from the standpoint of the how the triangle is observed as obtained from aircraft and satellite image data and then show how the triangle can be created from a land surface model. By superimposing the model triangle over the observed one, pixel values from the image are determined for all points within the triangle. We further show how the stretched (or ‘universal’) triangle can be used to interpret pixel configurations within the triangle, showing how the temporal trajectories of points uniquely describe patterns of land use change. Finally, we conclude the paper with a brief assessment of the method’s limitations. Full article

(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)

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1816 KiB

Open AccessArticle

Airborne Laser Scanning of Forest Stem Volume in a Mountainous Environment

by Markus Hollaus, Wolfgang Wagner, Bernhard Maier and Klemens Schadauer

Sensors 2007, 7(8), 1559-1577; https://doi.org/10.3390/s7081559 - 17 Aug 2007

Cited by 96 | Viewed by 14672

Abstract

Airborne laser scanning (ALS) is an active remote sensing technique that uses the time-of-flight measurement principle to capture the three-dimensional structure of the earth’s surface with pulsed lasers that transmit nanosecond-long laser pulses with a high pulse repetition frequency. Over forested areas most [...] Read more.

Airborne laser scanning (ALS) is an active remote sensing technique that uses the time-of-flight measurement principle to capture the three-dimensional structure of the earth’s surface with pulsed lasers that transmit nanosecond-long laser pulses with a high pulse repetition frequency. Over forested areas most of the laser pulses are reflected by the leaves and branches of the trees, but a certain fraction of the laser pulses reaches the forest floor through small gaps in the canopy. Thus it is possible to reconstruct both the three-dimensional structure of the forest canopy and the terrain surface. For the retrieval of quantitative forest parameters such as stem volume or biomass it is necessary to use models that combine ALS with inventory data. One approach is to use multiplicative regression models that are trained with local inventory data. This method has been widely applied over boreal forest regions, but so far little experience exists with applying this method for mapping alpine forest. In this study the transferability of this approach to a 128 km2 large mountainous region in Vorarlberg, Austria, was evaluated. For the calibration of the model, inventory data as operationally collected by Austrian foresters were used. Despite these inventory data are based on variable sample plot sizes, they could be used for mapping stem volume for the entire alpine study area. The coefficient of determination R2 was 0.85 and the root mean square error (RMSE) 90.9 m3ha-1 (relative error of 21.4%) which is comparable to results of ALS studies conducted over topographically less complex environments. Due to the increasing availability, ALS data could become an operational part of Austrian’s forest inventories. Full article

(This article belongs to the Special Issue Remote Sensing of Land Surface Properties, Patterns and Processes)

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390 KiB

Open AccessArticle

A New Method to Retrieve the Data Requirements of the Remote Sensing Community – Exemplarily Demonstrated for Hyperspectral User NEEDS

by Jens Nieke and Ils Reusen

Sensors 2007, 7(8), 1545-1558; https://doi.org/10.3390/s7081545 - 17 Aug 2007

Cited by 7 | Viewed by 11014

Abstract

User-driven requirements for remote sensing data are difficult to define,especially details on geometric, spectral and radiometric parameters. Even more difficult isa decent assessment of the required degrees of processing and corresponding data quality. Itis therefore a real challenge to appropriately assess data costs [...] Read more.

User-driven requirements for remote sensing data are difficult to define,especially details on geometric, spectral and radiometric parameters. Even more difficult isa decent assessment of the required degrees of processing and corresponding data quality. Itis therefore a real challenge to appropriately assess data costs and services to be provided.In 2006, the HYRESSA project was initiated within the framework 6 programme of theEuropean Commission to analyze the user needs of the hyperspectral remote sensingcommunity. Special focus was given to finding an answer to the key question, “What arethe individual user requirements for hyperspectral imagery and its related data products?”.A Value-Benefit Analysis (VBA) was performed to retrieve user needs and address openitems accordingly. The VBA is an established tool for systematic problem solving bysupporting the possibility of comparing competing projects or solutions. It enablesevaluation on the basis of a multidimensional objective model and can be augmented withexpert’s preferences. After undergoing a VBA, the scaling method (e.g., Law ofComparative Judgment) was applied for achieving the desired ranking judgments. Theresult, which is the relative value of projects with respect to a well-defined main objective,can therefore be produced analytically using a VBA. A multidimensional objective modeladhering to VBA methodology was established. Thereafter, end users and experts wererequested to fill out a Questionnaire of User Needs (QUN) at the highest level of detail -the value indicator level. The end user was additionally requested to report personalpreferences for his particular research field. In the end, results from the experts’ evaluationand results from a sensor data survey can be compared in order to understand user needsand the drawbacks of existing data products. The investigation – focusing on the needs of the hyperspectral user community in Europe – showed that a VBA is a suitable method for analyzing the needs of hyperspectral data users and supporting the sensor/data specification-building process. The VBA has the advantage of being easy to handle, resulting in a comprehensive evaluation. The primary disadvantage is the large effort in realizing such an analysis because the level of detail is extremely high. Full article

(This article belongs to the Special Issue Remote Sensing of Natural Resources and the Environment)

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619 KiB

Open AccessArticle

Design of a Capacitive Flexible Weighing Sensor for Vehicle WIM System

by Lu Cheng, Hongjian Zhang and Qing Li

Sensors 2007, 7(8), 1530-1544; https://doi.org/10.3390/s7081530 - 17 Aug 2007

Cited by 34 | Viewed by 12446

Abstract

With the development of the Highway Transportation and Business Trade, vehicle weigh-in-motion (WIM) technology has become a key technology and trend of measuring traffic loads. In this paper, a novel capacitive flexible weighing sensor which is light weight, smaller volume and easy to [...] Read more.

With the development of the Highway Transportation and Business Trade, vehicle weigh-in-motion (WIM) technology has become a key technology and trend of measuring traffic loads. In this paper, a novel capacitive flexible weighing sensor which is light weight, smaller volume and easy to carry was applied in the vehicle WIM system. The dynamic behavior of the sensor is modeled using the Maxwell-Kelvin model because the materials of the sensor are rubbers which belong to viscoelasticity. A signal processing method based on the model is presented to overcome effects of rubber mechanical properties on the dynamic weight signal. The results showed that the measurement error is less than ±10%. All the theoretic analysis and numerical results demonstrated that appliance of this system to weigh in motion is feasible and convenient for traffic inspection. Full article

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350 KiB

Open AccessArticle

Self-Calibration and Optimal Response in Intelligent Sensors Design Based on Artificial Neural Networks

by José Rivera, Mariano Carrillo, Mario Chacón, Gilberto Herrera and Gilberto Bojorquez

Sensors 2007, 7(8), 1509-1529; https://doi.org/10.3390/s7081509 - 16 Aug 2007

Cited by 46 | Viewed by 13641

Abstract

The development of smart sensors involves the design of reconfigurable systemscapable of working with different input sensors. Reconfigurable systems ideally shouldspend the least possible amount of time in their calibration. An autocalibration algorithmfor intelligent sensors should be able to fix major problems such [...] Read more.

The development of smart sensors involves the design of reconfigurable systemscapable of working with different input sensors. Reconfigurable systems ideally shouldspend the least possible amount of time in their calibration. An autocalibration algorithmfor intelligent sensors should be able to fix major problems such as offset, variation of gainand lack of linearity, as accurately as possible. This paper describes a new autocalibrationmethodology for nonlinear intelligent sensors based on artificial neural networks, ANN.The methodology involves analysis of several network topologies and training algorithms.The proposed method was compared against the piecewise and polynomial linearizationmethods. Method comparison was achieved using different number of calibration points,and several nonlinear levels of the input signal. This paper also shows that the proposedmethod turned out to have a better overall accuracy than the other two methods. Besides,experimentation results and analysis of the complete study, the paper describes theimplementation of the ANN in a microcontroller unit, MCU. In order to illustrate themethod capability to build autocalibration and reconfigurable systems, a temperaturemeasurement system was designed and tested. The proposed method is an improvement over the classic autocalibration methodologies, because it impacts on the design process of intelligent sensors, autocalibration methodologies and their associated factors, like time and cost. Full article

(This article belongs to the Special Issue Intelligent Sensors)

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983 KiB

Open AccessArticle

Piezoelectric Sensor for Determination of Genetically Modified Soybean Roundup Ready (R) in Samples not Amplified by PCR

by Magdalena Stobiecka, Jarosław M. Cieśla, Beata Janowska, Barbara Tudek and Hanna Radecka

Sensors 2007, 7(8), 1462-1479; https://doi.org/10.3390/s7081462 - 14 Aug 2007

Cited by 47 | Viewed by 10352

Abstract

The chemically modified piezoelectrodes were utilized to develop relativelycheap and easy to use biosensor for determination of genetically modified Roundup Readysoybean (RR soybean). The biosensor relies on the immobilization onto goldpiezoelectrodes of the 21-mer single stranded oligonucleotide (probes) related to5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, [...] Read more.

The chemically modified piezoelectrodes were utilized to develop relativelycheap and easy to use biosensor for determination of genetically modified Roundup Readysoybean (RR soybean). The biosensor relies on the immobilization onto goldpiezoelectrodes of the 21-mer single stranded oligonucleotide (probes) related to5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene, which is an active componentof an insert integrated into RR soybean genome. The hybridization reaction between theprobe and the target complementary sequence in solution was monitored. The system wasoptimized using synthetic oligonucleotides, which were applied for EPSPS gene detectionin DNA samples extracted from animal feed containing 30% RR soybean amplified by thePCR and nonamplified by PCR. The detection limit for genomic DNA was in the range of4.7·10⁵ numbers of genom copies contained EPSPS gene in the QCM cell. The propertiessuch as sensitivity and selectivity of piezoelectric senor presented here indicated that it could be applied for the direct determination of genetically modified RR soybean in the samples non-amplified by PCR. Full article

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403 KiB

Open AccessArticle

Differentiation of Toxic Molds via Headspace SPME-GC/MS and Canine Detection

by Robert T. Griffith, Krishnaswamy Jayachandran, William Whitstine and Kenneth G. Furton

Sensors 2007, 7(8), 1496-1508; https://doi.org/10.3390/s7081496 - 13 Aug 2007

Cited by 16 | Viewed by 9463

Abstract

Indoor mold growth has recently become a concern in the legal world in regards to insurance litigation. Hazardous mold exposure to humans has been linked to many acute and chronic adverse health effects including death. As it grows, mold produces several types of [...] Read more.

Indoor mold growth has recently become a concern in the legal world in regards to insurance litigation. Hazardous mold exposure to humans has been linked to many acute and chronic adverse health effects including death. As it grows, mold produces several types of primary and secondary metabolites, including microbial volatile organic compounds (MVOCs). Microbial volatile organic compound emission may be used as a preliminary indication of a mold infestation that is invisible to the unaided eye. The objective of the study is to identify the unique odor signatures of three species of molds, Aspergillus versicolor, Penicillium chrysogenum, and Stachybotrys chartarum by SPME-GC/MS analysis. Determining the compounds that are emitted by the selected species has made it possible to conduct validation studies of canine detection of these mold species through a series of field tests. Full article

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248 KiB

Open AccessArticle

Using LOTOS for FormalisingWireless Sensor Network Applications

by Nelson Souto Rosa and Paulo Roberto Freire Cunha

Sensors 2007, 7(8), 1447-1461; https://doi.org/10.3390/s7081447 - 13 Aug 2007

Cited by 4 | Viewed by 8271

Abstract

The number of wireless sensor network (WSN) applications is rapidly increasingand becoming an integral part of sensor nodes. These applications have been widely devel-oped on TinyOS operating system using the nesC programming language. However, due tothe tight integration to physical world, limited node [...] Read more.

The number of wireless sensor network (WSN) applications is rapidly increasingand becoming an integral part of sensor nodes. These applications have been widely devel-oped on TinyOS operating system using the nesC programming language. However, due tothe tight integration to physical world, limited node power and resources (CPU and memory)and complexity of combining components into an application, to build such applications isnot a trivial task. In this context, we present an approach for treating with this complexityadopting a formal description technique, namely LOTOS, for formalising the WSN applica-tions‘ behaviour. The formalisation has three main benefits: better understanding on how theapplication actually works, checking of desired properties of the application‘s behaviour, andsimulation facilities. In order to illustrate the proposed approach, we apply it to two nesCtraditional applications, namely BLink and Sense. Full article

(This article belongs to the Special Issue Energy Efficiency and Intelligent Signal Processing for Wireless Sensing)

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1854 KiB

Open AccessArticle

Detection of Salmonella by Surface Plasmon Resonance

by Benjamin Barlen, Saikat Datta Mazumdar, Olga Lezrich, Peter Kämpfer and Michael Keusgen

Sensors 2007, 7(8), 1427-1446; https://doi.org/10.3390/s7081427 - 7 Aug 2007

Cited by 55 | Viewed by 12486

Abstract

This study explores the possibility of simultaneous and specific detection ofSalmonella serovars by surface plasmon resonance (SPR). The Plasmonic^® SPR device wasused to develop this rapid assay. The sandwich immunoassay involves the use of apolyclonal anti-Salmonella antibody to simultaneous capture multiple Salmonella [...] Read more.

This study explores the possibility of simultaneous and specific detection ofSalmonella serovars by surface plasmon resonance (SPR). The Plasmonic^® SPR device wasused to develop this rapid assay. The sandwich immunoassay involves the use of apolyclonal anti-Salmonella antibody to simultaneous capture multiple Salmonella serovarspresent in a sample. This is followed by specific detection of the captured serovars usingO-specific anti-Salmonella antibodies. Milk spiked with Salmonella Typhimurium andSalmonella Enteritidis was used as a model system to establish the assay. The assay wasfurther extended to sequentially differentiate between the two Salmonella serovars on asingle SPR chip in a single channel. The assay was proved to work without any additionaldilution or clean-up steps. The sample volume requirement for the assay is only 10 μL. Thelower limits of detection for Salmonella Typhimurium and Salmonella Enteritidis were2.50×10⁵ cells mL^-1 and 2.50×10⁸ cells mL^-1, respectively. Full article

(This article belongs to the Special Issue Optical Biosensors)

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893 KiB

Open AccessArticle

Development and Electrochemical Investigations of an EIS- (Electrolyte-Insulator-Semiconductor) based Biosensor for Cyanide Detection

by Monika Turek, Lothar Ketterer, Melanie Claßen, Heinz K. Berndt, Gereon Elbers, Peter Krüger, Michael Keusgen and Michael J. Schöning

Sensors 2007, 7(8), 1415-1426; https://doi.org/10.3390/s7081415 - 3 Aug 2007

Cited by 18 | Viewed by 11246

Abstract

A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulator-semiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at thelaboratory scale. The immobilisation of the cyanidase is performed in two distinct steps:first, the covalent coupling of cyanidase to an N-hydroxysuccinimide- (NHS) activatedSepharose^TM [...] Read more.

A cyanide biosensor based on a pH-sensitive p-doped electrolyte-insulator-semiconductor (EIS) structure with an immobilised enzyme (cyanidase) is realised at thelaboratory scale. The immobilisation of the cyanidase is performed in two distinct steps:first, the covalent coupling of cyanidase to an N-hydroxysuccinimide- (NHS) activatedSepharose^TM gel and then, the physical entrapment of NHS-activated Sepharose^TM with theimmobilised cyanidase in a dialysis membrane onto the EIS structure. The immobilisationof the cyanidase to the NHS-activated Sepharose^TM is studied by means of gelelectrophoresis measurements and investigations using an ammonia- (NH₃) selectiveelectrode. For the electrochemical characterisation of the cyanide biosensor,capacitance/voltage and constant capacitance measurements, respectively, have beencarried out. A differential measurement procedure is presented to evaluate the cyanideconcentration-dependent biosensor signals. Full article

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1542 KiB

Open AccessArticle

Investigations of Slip Effect on the Performance of Micro Gas Bearings and Stability of Micro Rotor-Bearing Systems

by Hai Huang, Guang Meng and Jieyu Chen

Sensors 2007, 7(8), 1399-1414; https://doi.org/10.3390/s7081399 - 3 Aug 2007

Cited by 14 | Viewed by 9628

Abstract

Incorporating the velocity slip effect of the gas flow at the solid boundary, theperformance and dynamic response of a micro gas-bearing-rotor system are investigated inthis paper. For the characteristic length scale of the micro gas bearing, the gas flow in thebearing resides in [...] Read more.

Incorporating the velocity slip effect of the gas flow at the solid boundary, theperformance and dynamic response of a micro gas-bearing-rotor system are investigated inthis paper. For the characteristic length scale of the micro gas bearing, the gas flow in thebearing resides in the slip regime rather than in the continuum regime. The modifiedReynolds equations of different slip models are presented. Gas pressure distribution and loadcarrying capacity are obtained by solving the Reynolds equations with finite differentmethod (FDM). Comparing results from different models, it is found that the second orderslip model agrees reasonably well with the benchmarked solutions obtained from thelinearized Boltzmann equation. Therefore, dynamic coefficients derived from the secondorder slip model are employed to evaluate the linear dynamic stability and vibrationcharacteristics of the system. Compared with the continuum flow model, the slip effectreduces dynamic coefficients of the micro gas bearing, and the threshold speed for stableoperation is consequently raised. Also, dynamic analysis shows that the system responseschange with variation of the operating parameters including the eccentricity ratio, therotational speed, and the unbalance ratio. Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)

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484 KiB

Open AccessArticle

Formation and Characterization of Self-Assembled Phenylboronic Acid Derivative Monolayers toward Developing Monosaccaride Sensing-Interface

by Hongxia Chen, Minsu Lee, Jaebeom Lee, Jae-Ho Kim, Yeong-Soon Gal, Yoon-Hwae Hwang, Won Gun An and Kwangnak Koh

Sensors 2007, 7(8), 1480-1495; https://doi.org/10.3390/s7081480 - 1 Aug 2007

Cited by 29 | Viewed by 11588

Abstract

We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing [...] Read more.

We designed and synthesized phenylboronic acid as a molecular recognitionmodel system for saccharide detection. The phenylboronic acid derivatives that haveboronic acid moiety are well known to interact with saccharides in aqueous solution; thus,they can be applied to a functional interface of saccharide sensing through the formation ofself-assembled monolayer (SAM). In this study, self-assembled phenylboronic acidderivative monolayers were formed on Au surface and carefully characterized by atomicforce microscopy (AFM), Fourier transform infrared reflection absorption spectroscopy(FTIR-RAS), surface enhanced Raman spectroscopy (SERS), and surface electrochemicalmeasurements. The saccharide sensing application was investigated using surface plasmonresonance (SPR) spectroscopy. The phenylboronic acid monolayers showed goodsensitivity of monosaccharide sensing even at the low concentration range (1.0 × 10^-12 M).The SPR angle shift derived from interaction between phenylboronic acid andmonosaccharide was increased with increasing the alkyl spacer length of synthesizedphenylboronic acid derivatives. Full article

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7464 KiB

Open AccessArticle

Integrated Inductors for RF Transmitters in CMOS/MEMS Smart Microsensor Systems

by Jong-Wan Kim, Hidekuni Takao, Kazuaki Sawada and Makoto Ishida

Sensors 2007, 7(8), 1387-1398; https://doi.org/10.3390/s7081387 - 31 Jul 2007

Cited by 46 | Viewed by 13290

Abstract

This paper presents the integration of an inductor by complementary metal-oxide-semiconductor (CMOS) compatible processes for integrated smart microsensorsystems that have been developed to monitor the motion and vital signs of humans invarious environments. Integration of radio frequency transmitter (RF) technology withcomplementary metal-oxide-semiconductor/micro electro [...] Read more.

This paper presents the integration of an inductor by complementary metal-oxide-semiconductor (CMOS) compatible processes for integrated smart microsensorsystems that have been developed to monitor the motion and vital signs of humans invarious environments. Integration of radio frequency transmitter (RF) technology withcomplementary metal-oxide-semiconductor/micro electro mechanical systems (CMOS/MEMS) microsensors is required to realize the wireless smart microsensors system. Theessential RF components such as a voltage controlled RF-CMOS oscillator (VCO), spiralinductors for an LC resonator and an integrated antenna have been fabricated and evaluatedexperimentally. The fabricated RF transmitter and integrated antenna were packaged withsubminiature series A (SMA) connectors, respectively. For the impedance (50 ) matching,a bonding wire type inductor was developed. In this paper, the design and fabrication of thebonding wire inductor for impedance matching is described. Integrated techniques for theRF transmitter by CMOS compatible processes have been successfully developed. Aftermatching by inserting the bonding wire inductor between the on-chip integrated antennaand the VCO output, the measured emission power at distance of 5 m from RF transmitterwas -37 dBm (0.2 μW). Full article

(This article belongs to the Special Issue Modeling, Testing and Reliability Issues in MEMS Engineering)

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557 KiB

Open AccessArticle

Agent Collaborative Target Localization and Classification in Wireless Sensor Networks

by Xue Wang, Dao-wei Bi, Liang Ding and Sheng Wang

Sensors 2007, 7(8), 1359-1386; https://doi.org/10.3390/s7081359 - 30 Jul 2007

Cited by 33 | Viewed by 10989

Abstract

Wireless sensor networks (WSNs) are autonomous networks that have beenfrequently deployed to collaboratively perform target localization and classification tasks.Their autonomous and collaborative features resemble the characteristics of agents. Suchsimilarities inspire the development of heterogeneous agent architecture for WSN in thispaper. The proposed agent [...] Read more.

Wireless sensor networks (WSNs) are autonomous networks that have beenfrequently deployed to collaboratively perform target localization and classification tasks.Their autonomous and collaborative features resemble the characteristics of agents. Suchsimilarities inspire the development of heterogeneous agent architecture for WSN in thispaper. The proposed agent architecture views WSN as multi-agent systems and mobileagents are employed to reduce in-network communication. According to the architecture,an energy based acoustic localization algorithm is proposed. In localization, estimate oftarget location is obtained by steepest descent search. The search algorithm adapts tomeasurement environments by dynamically adjusting its termination condition. With theagent architecture, target classification is accomplished by distributed support vectormachine (SVM). Mobile agents are employed for feature extraction and distributed SVMlearning to reduce communication load. Desirable learning performance is guaranteed bycombining support vectors and convex hull vectors. Fusion algorithms are designed tomerge SVM classification decisions made from various modalities. Real world experimentswith MICAz sensor nodes are conducted for vehicle localization and classification.Experimental results show the proposed agent architecture remarkably facilitates WSNdesigns and algorithm implementation. The localization and classification algorithms alsoprove to be accurate and energy efficient. Full article

(This article belongs to the Special Issue Energy Efficiency and Intelligent Signal Processing for Wireless Sensing)

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388 KiB

Open AccessReview

Raman Spectroscopy Cell-based Biosensors

by Ioan Notingher

Sensors 2007, 7(8), 1343-1358; https://doi.org/10.3390/s7081343 - 26 Jul 2007

Cited by 290 | Viewed by 19494

Abstract

One of the main challenges faced by biodetection systems is the ability to detectand identify a large range of toxins at low concentrations and in short times. Cell-basedbiosensors rely on detecting changes in cell behaviour, metabolism, or induction of celldeath following exposure of [...] Read more.

One of the main challenges faced by biodetection systems is the ability to detectand identify a large range of toxins at low concentrations and in short times. Cell-basedbiosensors rely on detecting changes in cell behaviour, metabolism, or induction of celldeath following exposure of live cells to toxic agents. Raman spectroscopy is a powerfultechnique for studying cellular biochemistry. Different toxic chemicals have differenteffects on living cells and induce different time-dependent biochemical changes related tocell death mechanisms. Cellular changes start with membrane receptor signalling leading tocytoplasmic shrinkage and nuclear fragmentation. The potential advantage of Ramanspectroscopy cell-based systems is that they are not engineered to respond specifically to asingle toxic agent but are free to react to many biologically active compounds. Ramanspectroscopy biosensors can also provide additional information from the time-dependentchanges of cellular biochemistry. Since no cell labelling or staining is required, the specifictime dependent biochemical changes in the living cells can be used for the identificationand quantification of the toxic agents. Thus, detection of biochemical changes of cells byRaman spectroscopy could overcome the limitations of other biosensor techniques, withrespect to detection and discrimination of a large range of toxic agents. Furtherdevelopments of this technique may also include integration of cellular microarrays forhigh throughput in vitro toxicological testing of pharmaceuticals and in situ monitoring ofthe growth of engineered tissues. Full article

(This article belongs to the Special Issue Optical Biosensors)

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Sensors, Volume 7, Issue 8 (August 2007) – 19 articles , Pages 1343-1666

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