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Sensors, Volume 7, Issue 4 (April 2007), Pages 420-627

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Research

Open AccessArticle Modifications of Poly(o-phenylenediamine) Permselective Layer on Pt-Ir for Biosensor Application in Neurochemical Monitoring
Sensors 2007, 7(4), 420-437; doi:10.3390/s7040420
Received: 27 March 2007 / Accepted: 10 April 2007 / Published: 12 April 2007
Cited by 36 | PDF Full-text (149 KB) | HTML Full-text | XML Full-text
Abstract
Reports that globular proteins could enhance the interference blocking ability ofthe PPD (poly(o-phenylenediamine) layer used as a permselective barrier in biosensordesign, prompted this study where a variety of modifying agents were incorporated into PPDduring its electrosynthesis on Pt-Ir electrodes. Trapped molecules, including fibrous
[...] Read more.
Reports that globular proteins could enhance the interference blocking ability ofthe PPD (poly(o-phenylenediamine) layer used as a permselective barrier in biosensordesign, prompted this study where a variety of modifying agents were incorporated into PPDduring its electrosynthesis on Pt-Ir electrodes. Trapped molecules, including fibrous proteinsand β-cyclodextrin, altered the polymer/modifier composite selectivity by affecting thesensitivity to both H2O2 (signal molecule in many enzyme-based biosensors) and thearchetypal interference species, ascorbic acid. A comparison of electrochemical properties ofPt and a Pt-Ir alloy suggests that the benefits of the latter, more rigid, metal can be exploitedin PPD-based biosensor design without significant loss of backward compatibility withstudies involving pure Pt. Full article
(This article belongs to the Special Issue Amperometric Sensors and Techniques for Neurochemical Monitoring)
Open AccessArticle Design of a Selective and Sensitive PVC-Membrane Potentiometric Sensor for Strontium Ion Based on 1,10-Diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dioneas a Neutral Ionophore
Sensors 2007, 7(4), 438-447; doi:10.3390/s7040438
Received: 6 February 2007 / Accepted: 16 March 2007 / Published: 12 April 2007
Cited by 13 | PDF Full-text (213 KB) | HTML Full-text | XML Full-text
Abstract
A novel PVC membrane sensor for the Sr2+ ion based on 1,10-diaza-5,6-benzo-4,7- dioxacyclohexadecane-2,9-dione has been prepared. The sensor possesses a Nernstian slope of 30.0 ± 0.6 mV decade-1 over a wide linear concentration range of 1.6 × 10-6-3.0 ×10
[...] Read more.
A novel PVC membrane sensor for the Sr2+ ion based on 1,10-diaza-5,6-benzo-4,7- dioxacyclohexadecane-2,9-dione has been prepared. The sensor possesses a Nernstian slope of 30.0 ± 0.6 mV decade-1 over a wide linear concentration range of 1.6 × 10-6-3.0 ×10-3 M with a detection limit of 6.3 ×10-7 M. It has a fast response time of less than 15 s and can be used for at least two months without any considerable divergence in potential. The potentiometric response is independent of the pH of test solution in the pH range 4.3-9.4. The proposed electrode shows good selectivities over a variety of alkali, alkaline earth, and transition metal ions. Full article
Open AccessArticle Flow Injection Technique for Biochemical Analysis with Chemiluminescence Detection in Acidic Media
Sensors 2007, 7(4), 448-458; doi:10.3390/s7040448
Received: 23 March 2007 / Accepted: 4 April 2007 / Published: 16 April 2007
Cited by 9 | PDF Full-text (117 KB) | HTML Full-text | XML Full-text
Abstract
A review with 90 references is presented to show the development of acidic chemiluminescence methods for biochemical analysis by use of flow injection technique in the last 10 years. A brief discussion of both the chemiluminescence and flow injection technique is given. The
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A review with 90 references is presented to show the development of acidic chemiluminescence methods for biochemical analysis by use of flow injection technique in the last 10 years. A brief discussion of both the chemiluminescence and flow injection technique is given. The proposed methods for biochemical analysis are described and compared according to the used chemiluminescence system. Full article
Open AccessArticle Step Prediction During Perturbed Standing Using Center Of Pressure Measurements
Sensors 2007, 7(4), 459-472; doi:10.3390/s7040459
Received: 23 February 2007 / Accepted: 13 April 2007 / Published: 18 April 2007
Cited by 2 | PDF Full-text (137 KB) | HTML Full-text | XML Full-text
Abstract
The development of a sensor that can measure balance during quiet standing and predict stepping response in the event of perturbation has many clinically relevant applica- tions, including closed-loop control of a neuroprothesis for standing. This study investigated the feasibility of an algorithm
[...] Read more.
The development of a sensor that can measure balance during quiet standing and predict stepping response in the event of perturbation has many clinically relevant applica- tions, including closed-loop control of a neuroprothesis for standing. This study investigated the feasibility of an algorithm that can predict in real-time when an able-bodied individual who is quietly standing will have to make a step to compensate for an external perturbation. Anterior and posterior perturbations were performed on 16 able-bodied subjects using a pul- ley system with a dropped weight. A linear relationship was found between the peak center of pressure (COP) velocity and the peak COP displacement caused by the perturbation. This result suggests that one can predict when a person will have to make a step based on COP velocity measurements alone. Another important feature of this finding is that the peak COP velocity occurs considerably before the peak COP displacement. As a result, one can predict if a subject will have to make a step in response to a perturbation sufficiently ahead of the time when the subject is actually forced to make the step. The proposed instability detection algorithm will be implemented in a sensor system using insole sheets in shoes with minitur- ized pressure sensors by which the COPv can be continuously measured. The sensor system will be integrated in a closed-loop feedback system with a neuroprosthesis for standing in the near future. Full article
(This article belongs to the Special Issue Physiological Sensing)
Open AccessArticle Design and Development of a Flexible Strain Sensor for Textile Structures Based on a Conductive Polymer Composite
Sensors 2007, 7(4), 473-492; doi:10.3390/s7040473
Received: 13 March 2007 / Accepted: 17 April 2007 / Published: 18 April 2007
Cited by 122 | PDF Full-text (226 KB) | HTML Full-text | XML Full-text
Abstract
The aim of this work is to develop a smart flexible sensor adapted to textile structures, able to measure their strain deformations. The sensors are “smart” because of their capacity to adapt to the specific mechanical properties of textile structures that are lightweight,
[...] Read more.
The aim of this work is to develop a smart flexible sensor adapted to textile structures, able to measure their strain deformations. The sensors are “smart” because of their capacity to adapt to the specific mechanical properties of textile structures that are lightweight, highly flexible, stretchable, elastic, etc. Because of these properties, textile structures are continuously in movement and easily deformed, even under very low stresses. It is therefore important that the integration of a sensor does not modify their general behavior. The material used for the sensor is based on a thermoplastic elastomer (Evoprene)/carbon black nanoparticle composite, and presents general mechanical properties strongly compatible with the textile substrate. Two preparation techniques are investigated: the conventional melt-mixing process, and the solvent process which is found to be more adapted for this particular application. The preparation procedure is fully described, namely the optimization of the process in terms of filler concentration in which the percolation theory aspects have to be considered. The sensor is then integrated on a thin, lightweight Nylon fabric, and the electromechanical characterization is performed to demonstrate the adaptability and the correct functioning of the sensor as a strain gauge on the fabric. A normalized relative resistance is defined in order to characterize the electrical response of the sensor. Finally, the influence of environmental factors, such as temperature and atmospheric humidity, on the sensor performance is investigated. The results show that the sensor’s electrical resistance is particularly affected by humidity. This behavior is discussed in terms of the sensitivity of the carbon black filler particles to the presence of water. Full article
(This article belongs to the Special Issue Intelligent Sensors)
Open AccessArticle Fabrication and Characterization of PZT Thick Films for Sensing and Actuation
Sensors 2007, 7(4), 493-507; doi:10.3390/s7040493
Received: 16 February 2007 / Accepted: 4 April 2007 / Published: 18 April 2007
Cited by 11 | PDF Full-text (776 KB) | HTML Full-text | XML Full-text
Abstract
Lead Zirconate Titanate oxide (PZT) thick films with thicknesses of up to 10 μmwere developed using a modified sol-gel technique. Usually, the film thickness is less than1 μm by conventional sol-gel processing, while the electrical charge accumulation whichreveals the direct effect of piezoelectricity
[...] Read more.
Lead Zirconate Titanate oxide (PZT) thick films with thicknesses of up to 10 μmwere developed using a modified sol-gel technique. Usually, the film thickness is less than1 μm by conventional sol-gel processing, while the electrical charge accumulation whichreveals the direct effect of piezoelectricity is proportional to the film thickness and thereforerestricted. Two approaches were adopted to conventional sol-gel processing – precursorconcentration modulation and rapid thermal annealing. A 10 μm thick film was successfullyfabricated by coating 16 times via this technique. The thickness of each coating layer wasabout 0.6 μm and the morphology of the film was dense with a crack-free area as large as 16mm2. In addition, the structure, surface morphology and physical properties werecharacterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomicforce microscopy (AFM) and electrical performance. The dielectric constant and hysteresisloops were measured as electric characteristics. This study investigates the actuation andsensing performance of the vibrating structures with the piezoelectric thick film. Theactuation tests demonstrated that a 4 mm x 4 mm x 6.5 μm PZT film drove a 40 mm x 7 mmx 0.5 mm silicon beam as an actuator. Additionally, it generated an electrical signal of 60mVpp as a sensor, while vibration was input by a shaker. The frequencies of the first twomodes of the beam were compared with the theoretical values obtained by Euler-Bernoullibeam theory. The linearity of the actuation and sensing tests were also examined. Full article
Open AccessArticle Guided-Wave Optical Biosensors
Sensors 2007, 7(4), 508-536; doi:10.3390/s7040508
Received: 23 March 2007 / Accepted: 24 April 2007 / Published: 25 April 2007
Cited by 68 | PDF Full-text (579 KB) | HTML Full-text | XML Full-text
Abstract
Guided-wave optical biosensors are reviewed in this paper. Advantages related to optical technologies are presented and integrated architectures are investigated in detail. Main classes of bio receptors and the most attractive optical transduction mechanisms are discussed. The possibility to use Mach-Zehnder and Young
[...] Read more.
Guided-wave optical biosensors are reviewed in this paper. Advantages related to optical technologies are presented and integrated architectures are investigated in detail. Main classes of bio receptors and the most attractive optical transduction mechanisms are discussed. The possibility to use Mach-Zehnder and Young interferometers, microdisk and microring resonators, surface plasmon resonance, hollow and antiresonant waveguides, and Bragg gratings to realize very sensitive and selective, ultra-compact and fast biosensors is discussed. Finally, CMOS-compatible technologies are proved to be the most attractive for fabrication of guided-wave photonic biosensors. Full article
(This article belongs to the Special Issue Optical Biosensors)
Open AccessArticle Send-On-Delta Sensor Data Transmission With A Linear Predictor
Sensors 2007, 7(4), 537-547; doi:10.3390/s7040437
Received: 3 April 2007 / Accepted: 24 April 2007 / Published: 26 April 2007
Cited by 34 | PDF Full-text (143 KB) | HTML Full-text | XML Full-text
Abstract
This paper is concerned with sensor data transmission strategy. The main focus of the paper is how to reduce the number of sensor data transmission while maintaining the dif- ference between the estimated sensor value and the real sensor value. The proposed method
[...] Read more.
This paper is concerned with sensor data transmission strategy. The main focus of the paper is how to reduce the number of sensor data transmission while maintaining the dif- ference between the estimated sensor value and the real sensor value. The proposed method could be used in sensor networks and networked control systems, where number of transmis- sion should be minimal. A linear predictor is used to predict sensor values and sensor data are transmitted if the difference between the predicted sensor value and the real sensor value exceeds the specified limit. An analytic upper bound of the mean rate of messages is pro- vided. Through simulation, it is shown that the number of transmission could be significantly reduced compared with the periodic sampling and the conventional send-on-delta method. Full article
(This article belongs to the Special Issue Intelligent Sensors)
Open AccessArticle Simulated Effects of Soil Temperature and Salinity on Capacitance Sensor Measurements
Sensors 2007, 7(4), 548-577; doi:10.3390/s7040548
Received: 28 February 2007 / Accepted: 23 April 2007 / Published: 26 April 2007
Cited by 22 | PDF Full-text (1083 KB) | HTML Full-text | XML Full-text
Abstract
Dielectric measurement techniques are used widely for estimation of water contentin environmental media. However, factors such as temperature and salinity affecting thereadings require further quantitative investigation and explanation. Theoretical sensitivities ofcapacitance sensors to liquid salinity and temperature of porous media were derived andcomputed
[...] Read more.
Dielectric measurement techniques are used widely for estimation of water contentin environmental media. However, factors such as temperature and salinity affecting thereadings require further quantitative investigation and explanation. Theoretical sensitivities ofcapacitance sensors to liquid salinity and temperature of porous media were derived andcomputed using a revised electrical circuit analogue model in conjunction with a dielectricmixing model and a finite element model of Maxwell’s equation to compute electrical fielddistributions. The mixing model estimates the bulk effective complex permittivities of solid-water-air media. The real part of the permittivity values were used in electric field simulations,from which different components of capacitance were calculated via numerical integration forinput to the electrical circuit analogue. Circuit resistances representing the dielectric losses werecalculated from the complex permittivity of the bulk soil and from the modeled fields. Resonantfrequencies from the circuit analogue were used to update frequency-dependent variables in aniterative manner. Simulated resonant frequencies of the capacitance sensor display sensitivitiesto both temperature and salinity. The gradients in normalized frequency with temperatureranged from negative to positive values as salinity increased from 0 to 10 g L-1. The modeldevelopment and analyses improved our understanding of processes affecting the temperatureand salinity sensitivities of capacitance sensors in general. This study provides a foundation forfurther work on inference of soil water content under field conditions. Full article
Open AccessArticle A Sensitive Chemiluminescence Method for Determination of Hydroquinone and Catechol
Sensors 2007, 7(4), 578-588; doi:10.3390/s7040578
Published: 26 April 2007
Cited by 31 | PDF Full-text (301 KB) | HTML Full-text | XML Full-text
Abstract
A novel flow-injection chemiluminescence(CL)method has been developedfor the determination of hydroquinone (HQ) and catechol (CT), based on their inhibition ofthe chemiluminescence reaction of luminol–KMnO4–β-cyclodextrin (β-CD). It was foundthat β-cyclodextrin could effectively enhance the chemiluminescence produced from thereaction of luminol with KMnO
[...] Read more.
A novel flow-injection chemiluminescence(CL)method has been developedfor the determination of hydroquinone (HQ) and catechol (CT), based on their inhibition ofthe chemiluminescence reaction of luminol–KMnO4–β-cyclodextrin (β-CD). It was foundthat β-cyclodextrin could effectively enhance the chemiluminescence produced from thereaction of luminol with KMnO4 in basic media. The proposed method is simple, rapid,convenient and sensitive, has a linear range of 1–20 ng/mL for catechol with a detectionlimit of 0.4 ng/mL, and 1–10 ng/mL for hydroquinone with a detection limit of 0.1 ng/mL,respectively. The possible mechanism of the CL reaction is also discussed Full article
Open AccessArticle Biosensors and Bio-Bar Code Assays Based on Biofunctionalized Magnetic Microbeads
Sensors 2007, 7(4), 589-614; doi:10.3390/s7040589
Received: 5 March 2007 / Accepted: 10 April 2007 / Published: 30 April 2007
Cited by 78 | PDF Full-text (356 KB) | HTML Full-text | XML Full-text
Abstract
This review paper reports the applications of magnetic microbeads in biosensors and bio-bar code assays. Affinity biosensors are presented through different types of transducing systems: electrochemical, piezo electric or magnetic ones, applied to immunodetection and genodetection. Enzymatic biosensors are based on biofunctionalization through
[...] Read more.
This review paper reports the applications of magnetic microbeads in biosensors and bio-bar code assays. Affinity biosensors are presented through different types of transducing systems: electrochemical, piezo electric or magnetic ones, applied to immunodetection and genodetection. Enzymatic biosensors are based on biofunctionalization through magnetic microbeads of a transducer, more often amperometric, potentiometric or conductimetric. The bio-bar code assays relie on a sandwich structure based on specific biological interaction of a magnetic microbead and a nanoparticle with a defined biological molecule. The magnetic particle allows the separation of the reacted target molecules from unreacted ones. The nanoparticles aim at the amplification and the detection of the target molecule. The bio-bar code assays allow the detection at very low concentration of biological molecules, similar to PCR sensitivity. Full article
Open AccessArticle Electrochemical Oxidation and Determination of Oxalic Acid at an Exfoliated Graphite-Polystyrene Composite Electrode
Sensors 2007, 7(4), 615-627; doi:10.3390/s7040615
Received: 13 April 2007 / Accepted: 30 April 2007 / Published: 30 April 2007
Cited by 23 | PDF Full-text (1865 KB) | HTML Full-text | XML Full-text
Abstract
An exfoliated graphite-polystyrene composite electrode was evaluated as analternative electrode in the oxidation and the determination of oxalic acid in 0.1 M Na2SO4supporting electrolyte. Using CV, LSV, CA procedures, linear dependences I vs. C wereobtained in the concentrations range
[...] Read more.
An exfoliated graphite-polystyrene composite electrode was evaluated as analternative electrode in the oxidation and the determination of oxalic acid in 0.1 M Na2SO4supporting electrolyte. Using CV, LSV, CA procedures, linear dependences I vs. C wereobtained in the concentrations range of oxalic acid between 0.5 to 3 mM, with LOD =0.05mM, and recovery degree of 98%, without need of surface renewing between successiveruns. The accuracy of the methods was evaluated as excellent comparing the detection resultswith that obtained using conventional KMnO4 titration method. In addition, the apparentdiffusion coefficient of oxalic acid D was found to be around 2.89 · 10-8 cm2·s-1 by CA andCV. Full article

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