Sensors

605 KiB

Open AccessArticle

Stability, Nonlinearity and Reliability of Electrostatically Actuated MEMS Devices

by Wen-Ming Zhang, Guang Meng and Di Chen

Sensors 2007, 7(5), 760-796; https://doi.org/10.3390/s7050760 - 31 May 2007

Cited by 83 | Viewed by 18997

Electrostatic micro-electro-mechanical system (MEMS) is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity [...] Read more.

Electrostatic micro-electro-mechanical system (MEMS) is a special branch with a wide range of applications in sensing and actuating devices in MEMS. This paper provides a survey and analysis of the electrostatic force of importance in MEMS, its physical model, scaling effect, stability, nonlinearity and reliability in detail. It is necessary to understand the effects of electrostatic forces in MEMS and then many phenomena of practical importance, such as pull-in instability and the effects of effective stiffness, dielectric charging, stress gradient, temperature on the pull-in voltage, nonlinear dynamic effects and reliability due to electrostatic forces occurred in MEMS can be explained scientifically, and consequently the great potential of MEMS technology could be explored effectively and utilized optimally. A simplified parallel-plate capacitor model is proposed to investigate the resonance response, inherent nonlinearity, stiffness softened effect and coupled nonlinear effect of the typical electrostatically actuated MEMS devices. Many failure modes and mechanisms and various methods and techniques, including materials selection, reasonable design and extending the controllable travel range used to analyze and reduce the failures are discussed in the electrostatically actuated MEMS devices. Numerical simulations and discussions indicate that the effects of instability, nonlinear characteristics and reliability subjected to electrostatic forces cannot be ignored and are in need of further investigation. Full article

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

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537 KiB

Open AccessArticle

Multi-instrumental Investigation of Affecting of Early Somatic Embryos of Spruce by Cadmium(II) and Lead(II) Ions

by Veronika Supalkova, Jiri Petrek, Jiri Baloun, Vojtech Adam, Karel Bartusek, Libuse Trnkova, Miroslava Beklova, Vaclav Diopan, Ladislav Havel and René Kizek

Sensors 2007, 7(5), 743-759; https://doi.org/10.3390/s7050743 - 31 May 2007

Cited by 56 | Viewed by 10649

Abstract

The main aim of this work was to use multi-instrumental analytical apparatus toinvestigate the effects of treatment with cadmium(II) and/or lead(II) ions (50, 250 and 500μM) for twelve days on early somatic spruce embryos (ESEs). Primarily we used imageanalysis for estimation of growth [...] Read more.

The main aim of this work was to use multi-instrumental analytical apparatus toinvestigate the effects of treatment with cadmium(II) and/or lead(II) ions (50, 250 and 500μM) for twelve days on early somatic spruce embryos (ESEs). Primarily we used imageanalysis for estimation of growth and a fluorimetric sensor for enzymatic detection ofviability of the treated ESEs. It follows from the obtained results that Cd caused highertoxicity to ESEs than Pb. Besides this fundamental finding, we observed that ESEs grewand developed better in the presence of 500 μM of the metal ions than in the presence of250 μM. Based on the results obtained using nuclear magnetic resonance this phenomenonwas related to an increase of the area of ESE clusters by intensive uptake of water from thecultivation medium, due to dilution of the heavy metal concentration inside the cluster. Inaddition we studied the glutathione content in treated ESEs by the adsorptive transferstripping technique coupled with the differential pulse voltammetry Brdicka reaction. GSHcontents increased up to 148 ng/mg (clone 2/32) and 158 ng/mg (clone PE 14) after twelve day long treatment with Cd-EDTA ions. The GSH content was about 150 and 160 % higher in comparison with the ESEs treated with Pb-EDTA ions, respectively. The difference between GSH contents determined in ESEs treated with Pb-EDTA and Cd-EDTA ions correlates with the higher toxicity of cadmium(II) ions. Full article

(This article belongs to the Special Issue Utilization of Electrochemical Sensors and Biosensors in Biochemistry and Molecular Biology)

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308 KiB

Open AccessArticle

Optimized Self Organized Sensor Networks

by Sungyun Park, Kwangcheol Shin, Ajith Abraham and SangYong Han

Sensors 2007, 7(5), 730-742; https://doi.org/10.3390/s7050730 - 31 May 2007

Cited by 21 | Viewed by 9291

Abstract

Wireless sensor networks are composed of a huge number of sensor nodes, which have limited resources - energy, memory and computation power. Energies are directly related to the lifetime of sensor network. If sensor nodes can be grouped to clusters, cluster member sensor [...] Read more.

Wireless sensor networks are composed of a huge number of sensor nodes, which have limited resources - energy, memory and computation power. Energies are directly related to the lifetime of sensor network. If sensor nodes can be grouped to clusters, cluster member sensor nodes only need to communicate with cluster center (head) and this leads to energy conservation of the member sensors. So, how to compose clusters with minimal number of cluster heads, while including each node in a cluster is an important research issue. We propose a new advanced optimization algorithm for sensor network clustering. Using the proposed optimization algorithm, redundant cluster heads are eliminated, and unnecessarily overlapped clusters are merged. Optimization algorithm can be used as a clustering algorithm by itself and also manage the dynamic changes like node addition or die-out, while the network is even on the working state. We tested the proposed method as a clustering algorithm and compared it with two other recent sensor network clustering algorithms, Algorithm for Cluster Establishment (ACE) and Self Organizing Sensor network algorithm (SOS). The experiments results not only illustrate that the proposed algorithm could result in clusters with smaller number of cluster heads than others with any density of sensor networks, but also that the performance is more stable, which is also verified through repeated experiments. Full article

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3862 KiB

Open AccessArticle

Horseradish Peroxidase (HRP) Immobilized Poly(aniline-co-m-aminophenol) Film Electrodes–fabrication and Evaluation as Hydrogen Peroxide Sensor

by Kang-Deuk Seo, Kwang-Pill Lee, Anantha Iyengar Gopalan, Sang J. Chung, Yong Taik Lim and Seong-Ho Choi

Sensors 2007, 7(5), 719-729; https://doi.org/10.3390/s7050719 - 31 May 2007

Cited by 23 | Viewed by 10628

Abstract

Enzyme modified electrodes were fabricated with poly(aniline-co-m-aminophenol). Electrochemical polymerization of aniline and m-aminophenol wasperformed to get the film of copolymer on the surface of gold electrode. Modifiedelectrodes were fabricated by two methods, physical entrapment and covalent cross-linking.In one of the method, gold nanoparticles [...] Read more.

Enzyme modified electrodes were fabricated with poly(aniline-co-m-aminophenol). Electrochemical polymerization of aniline and m-aminophenol wasperformed to get the film of copolymer on the surface of gold electrode. Modifiedelectrodes were fabricated by two methods, physical entrapment and covalent cross-linking.In one of the method, gold nanoparticles were loaded into the copolymer film andhorseradish peroxidase (HRP) was immobilized into the Au nanoparticle loaded copolymerfilm through physical entrapment. In the other method, the amino and -OH groups in thecopolymer are utilized to form covalent functionalization with HRP via glutaric dialdehydeas cross-linker/mediator. The conducting copolymer/enzyme modified electrodes preparedby physical entrapment/covalent functionalization of enzyme were tested forelectrocatalytic activities towards sensing of H₂O₂. Amperometric results indicate thatenzyme modified electrode via physical entrapment possesses better electrocatalyticperformance over covalent functionalized enzyme electrode. Full article

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881 KiB

Open AccessArticle

Preparation of Silver Nanoparticle and Its Application to the Determination of ct-DNA

by Chunhua Liu, Xiupei Yang, Hongyan Yuan, Zaide Zhou and Dan Xiao

Sensors 2007, 7(5), 708-718; https://doi.org/10.3390/s7050708 - 31 May 2007

Cited by 89 | Viewed by 16156

Abstract

A new method to prepare silver nanoparticles was reported in this paper, whichbased on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. Theproposed method is effective, rapid, and convenient. Transmission electron microscope(TEM) and X-ray diffraction (XRD) were used to characterize the [...] Read more.

A new method to prepare silver nanoparticles was reported in this paper, whichbased on aqueous-gaseous phase reaction of silver nitrate solution and ammonia gas. Theproposed method is effective, rapid, and convenient. Transmission electron microscope(TEM) and X-ray diffraction (XRD) were used to characterize the structure of the particles,respectively. It was found that the average diameter of the particles was about 10 nm and theshape was spherical. And the strong fluorescence signal of the silver nanoparticles solutioncan be quenched after the adding of the calf thymus DNA (ct-DNA) solution. Thequenched fluorescence intensity was linear with the concentration of ct-DNA in the range of0.5 to 5.0 × 10⁴ ng mL^-1 with a detection limit of 0.3 ng mL^-1. Full article

(This article belongs to the Special Issue Optical Biosensors)

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774 KiB

Open AccessArticle

An Experimental Study on the Fabrication of Glass-based Acceleration Sensor Body Using Micro Powder Blasting Method

by Dong-Sam Park, Dae-Jin Yun, Myeong-Woo Cho and Bong-Cheol Shin

Sensors 2007, 7(5), 697-707; https://doi.org/10.3390/s7050697 - 24 May 2007

Cited by 8 | Viewed by 11923

Abstract

This study investigated the feasibility of the micro powder blasting technique for the micro fabrication of sensor structures using the Pyrex glass to replace the existing silicon-based acceleration sensor fabrication processes. As the preliminary experiments, the effects of the blasting pressure, the mass [...] Read more.

This study investigated the feasibility of the micro powder blasting technique for the micro fabrication of sensor structures using the Pyrex glass to replace the existing silicon-based acceleration sensor fabrication processes. As the preliminary experiments, the effects of the blasting pressure, the mass flow rate of abrasive and the number of nozzle scanning times on erosion depth of the Pyrex and the soda lime glasses were examined. From the experimental results, optimal blasting conditions were selected for the Pyrex glass machining. The dimensions of the designed glass sensor was 1.7×1.7×0.6mm for the vibrating mass, and 2.9×0.7×0.2mm for the cantilever beam. The machining results showed that the dimensional errors of the machined glass sensor ranged from 3 μm in minimum to 20 μm in maximum. These results imply that the micro powder blasting method can be applied for the micromachining of glass-based acceleration sensors to replace the exiting method. Full article

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

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195 KiB

Open AccessArticle

Simulation of Optical Microfiber Loop Resonators for Ambient Refractive Index Sensing

by Lei Shi, Yonghao Xu, Wei Tan and Xianfeng Chen

Sensors 2007, 7(5), 689-696; https://doi.org/10.3390/s7050689 - 24 May 2007

Cited by 60 | Viewed by 11518

Abstract

Based on theoretical modeling and optimization, we exploit the application ofoptical microfiber loop resonators in ambient refractive index sensing. We set up a reliabletheoretical model and optimize the structural parameters of microfiber loop resonatorsincluding the radius of the microrfiber, the radius of the [...] Read more.

Based on theoretical modeling and optimization, we exploit the application ofoptical microfiber loop resonators in ambient refractive index sensing. We set up a reliabletheoretical model and optimize the structural parameters of microfiber loop resonatorsincluding the radius of the microrfiber, the radius of the loop and the length of the couplingregion for higher sensitivity, wider dynamic measurement range, and lower detection limit.To show the convincible and realizable sensing ability we perform the simulation ofsensing an extreme small variation of ambient refractive index by employing a set ofexperimental data as the parameters in the expression of intensity transmission coefficient,and the detection limit reaches to a variation of ambient refractive index of 10^-5 refractiveindex unit (RIU). This has superiority over the existing evanescent field-basedsubwavelength-diameter optical fiber refractive index sensor. Full article

(This article belongs to the Special Issue Optical Biosensors)

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1688 KiB

Open AccessArticle

Behavior of Random Hole Optical Fibers under Gamma Ray Irradiation and Its Potential Use in Radiation Sensing Applications

by Bassam Alfeeli, Gary Pickrell, Marc A. Garland and Anbo Wang

Sensors 2007, 7(5), 676-688; https://doi.org/10.3390/s7050676 - 24 May 2007

Cited by 17 | Viewed by 12291

Abstract

Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF) called the random hole opticalfiber (RHOF) has been recently developed. The RHOFs can [...] Read more.

Effects of radiation on sensing and data transmission components are of greatinterest in many applications including homeland security, nuclear power generation, andmilitary. A new type of microstructured optical fiber (MOF) called the random hole opticalfiber (RHOF) has been recently developed. The RHOFs can be made in many differentforms by varying the core size and the size and extent of porosity in the cladding region.The fibers used in this study possessed an outer diameter of 110 μm and a core ofapproximately 20 μm. The fiber structure contains thousands of air holes surrounding thecore with sizes ranging from less than 100 nm to a few μm. We present the first study ofthe behavior of RHOF under gamma irradiation. We also propose, for the first time to ourknowledge, an ionizing radiation sensor system based on scintillation light from ascintillator phosphor embedded within a holey optical fiber structure. The RHOF radiationresponse was compared to normal single mode and multimode commercial fibers(germanium doped core, pure silica cladding) and to those of radiation resistant fibers (puresilica core with fluorine doped cladding fibers). The comparison was done by measuringradiation-induced absorption (RIA) in all fiber samples at the 1550 nm wavelength window(1545 ± 25 nm). The study was carried out under a high-intensity gamma ray field from a⁶⁰Co source (with an exposure rate of 4x10⁴ rad/hr) at an Oak Ridge National Laboratory gamma ray irradiation facility. Linear behavior, at dose values less than 10⁶ rad, was observed in all fiber samples except in the pure silica core fluorine doped cladding fiber which showed RIA saturation at 0.01 dB. RHOF samples demonstrated low RIA (0.02 and 0.005 dB) compared to standard germanium doped core pure silica cladding (SMF and MMF) fibers. Results also showed the possibility of post-fabrication treatment to improve the radiation resistance of the RHOF fibers. Full article

(This article belongs to the Special Issue Photonic Sensors for Chemical, Biological, and Nuclear Agent Detection)

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663 KiB

Open AccessArticle

Improvement of Flame-made ZnO Nanoparticulate Thick Film Morphology for Ethanol Sensing

by Chaikarn Liewhiran and Sukon Phanichphant

Sensors 2007, 7(5), 650-675; https://doi.org/10.3390/s7050650 - 15 May 2007

Cited by 48 | Viewed by 12424

Abstract

ZnO nanoparticles were produced by flame spray pyrolysis using zinc naphthenate as a precursor dissolved in toluene/acetonitrile (80/20 vol%). The particles properties were analyzed by XRD, BET. The ZnO particle size and morphology was observed by SEM and HR-TEM revealing spheroidal, hexagonal, and [...] Read more.

ZnO nanoparticles were produced by flame spray pyrolysis using zinc naphthenate as a precursor dissolved in toluene/acetonitrile (80/20 vol%). The particles properties were analyzed by XRD, BET. The ZnO particle size and morphology was observed by SEM and HR-TEM revealing spheroidal, hexagonal, and rod-like morphologies. The crystallite sizes of ZnO spheroidal and hexagonal particles ranged from 10-20 nm. ZnO nanorods were ranged from 10-20 nm in width and 20-50 nm in length. Sensing films were produced by mixing the nanoparticles into an organic paste composed of terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed onto Al2O3 substrates interdigitated with Au electrodes. The morphology of the sensing films was analyzed by optical microscopy and SEM analysis. Cracking of the sensing films during annealing process was improved by varying the heating conditions. The gas sensing of ethanol (25-250 ppm) was studied at 400 °C in dry air containing SiC as the fluidized particles. The oxidation of ethanol on the surface of the semiconductor was confirmed by mass spectroscopy (MS). The effect of micro-cracks was quantitatively accounted for as a provider of extra exposed edges. The sensitivity decreased notably with increasing crack of sensing films. It can be observed that crack widths were reduced with decreasing heating rates. Crack-free of thick (5 μm) ZnO films evidently showed higher sensor signal and faster response times (within seconds) than cracked sensor. The sensor signal increased and the response time decreased with increasing ethanol concentration. Full article

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72 KiB

Open AccessEditorial

Sensors Makes Sense

by Matthias Burkhalter

Sensors 2007, 7(5), 649; https://doi.org/10.3390/s7050649 - 11 May 2007

Viewed by 4878

Abstract

During my varied professional experience in different industries I have previously edited a number of trade magazines and newsletters.[...] Full article

403 KiB

Open AccessArticle

Distributed Particle Swarm Optimization and Simulated Annealing for Energy-efficient Coverage in Wireless Sensor Networks

by Xue Wang, Jun-Jie Ma, Sheng Wang and Dao-Wei Bi

Sensors 2007, 7(5), 628-648; https://doi.org/10.3390/s7050628 - 10 May 2007

Cited by 74 | Viewed by 13705

Abstract

The limited energy supply of wireless sensor networks poses a great challenge for the deployment of wireless sensor nodes. In this paper, we focus on energy-efficient coverage with distributed particle swarm optimization and simulated annealing. First, the energy-efficient coverage problem is formulated with [...] Read more.

The limited energy supply of wireless sensor networks poses a great challenge for the deployment of wireless sensor nodes. In this paper, we focus on energy-efficient coverage with distributed particle swarm optimization and simulated annealing. First, the energy-efficient coverage problem is formulated with sensing coverage and energy consumption models. We consider the network composed of stationary and mobile nodes. Second, coverage and energy metrics are presented to evaluate the coverage rate and energy consumption of a wireless sensor network, where a grid exclusion algorithm extracts the coverage state and Dijkstra’s algorithm calculates the lowest cost path for communication. Then, a hybrid algorithm optimizes the energy consumption, in which particle swarm optimization and simulated annealing are combined to find the optimal deployment solution in a distributed manner. Simulated annealing is performed on multiple wireless sensor nodes, results of which are employed to correct the local and global best solution of particle swarm optimization. Simulations of wireless sensor node deployment verify that coverage performance can be guaranteed, energy consumption of communication is conserved after deployment optimization and the optimization performance is boosted by the distributed algorithm. Moreover, it is demonstrated that energy efficiency of wireless sensor networks is enhanced by the proposed optimization algorithm in target tracking applications. Full article

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

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Sensors, Volume 7, Issue 5 (May 2007) – 11 articles , Pages 628-796

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