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1

WO 3 thick-film gas sensors  

Microsoft Academic Search

Tungsten trioxide is a promising material for NOx gas sensors. This paper describes the preparation of tungsten trioxide thick films by the use of the traditional screen-printing technology. We present the characterization of both their structural properties by means of XRD measurements and the film morphology by the SEM microscope studies, and the electrical response of the films of various

A. A. Tomchenko; V. V. Khatko; I. L. Emelianov

1998-01-01

2

Micromachined thin-film gas flow sensor for microchemical reactors  

E-print Network

by the emergence of MEMS (Micro Electro Mechanical Systems). Miniaturization of sensors has enabled many new sensors [5], micro heaters [5,8], micro pressure sensors [5], etc. As an early example of a MEMSMicromachined thin-film gas flow sensor for microchemical reactors W C Shin and R S Besser New

Besser, Ronald S.

3

Gas sensors based on nanoparticle WO3 thick films  

Microsoft Academic Search

The gas sensing properties of chemical sensors based on nanoparticle WO3 thick films, doped with indium and bismuth, are studied. Commercial WO3 nanopowder with spherical diameter up to 33.1 nm was mixed with either InCl3 or BiCl3. The sensing films of the sensors were prepared using three different concentrations of each doping metal (1.5 wt.%, 3.0 wt.% and 5.0 wt.%,

V. Khatko; R. Ionescu; E. Llobet; X. Vilanova; J. Brezmes; J. Hubalek; K. Malysz; X. Correig

2004-01-01

4

Nano and microsized metal oxide thin film gas sensors  

Microsoft Academic Search

Functional micro- and nanosized metal oxide thin film structures are very promising candidate for future gas-sensors. Their\\u000a reduced size offers an increased surface to volume ratio thus improving sensitivity and sensor performance. Whilst most experimental\\u000a nanostructures are produced using a bottom-up approach, a top-down sputtering technique for structuring nano-sized gas sensitive\\u000a metal oxide areas is presented in this letter. Oxidised

Stefan Palzer; Emmanuel Moretton; Francisco Hernandez Ramirez; Albert Romano-Rodriguez; Jürgen Wöllenstein

2008-01-01

5

Electron Beam Evaporation of Tungsten Oxide Films for Gas Sensors  

Microsoft Academic Search

Pure and iron incorporated nanostructured Tungsten Oxide (WO3) thin films were investigated for gas sensing applications using noise spectroscopy. The WO3 sensor was able to detect lower concentrations (1-10 ppm) of NH3, CO, CH4, and Acetaldehyde gases at operating temperatures between 100°C to 250°C. The iron-doped Tungsten Oxide sensor ( WO3:Fe) showed some response to Acetaldehyde gas at relatively higher

T. Tesfamichael

2010-01-01

6

New fabrication of zinc oxide nanostructure thin film gas sensors  

NASA Astrophysics Data System (ADS)

The copper doped zinc oxide thin films have been prepared by sol-gel spin coating method. The structural and morphology properties of the Cu doped films were characterized by X-ray diffraction and atomic force microscope. XRD studies confirm the chemical structure of the ZnO films. The optical spectra method were used to determined optical constants and dispersion energy parameters of Cu doped Zno thin films. The optical band gap of undoped ZnO was found to be 3.16 eV. The Eg values of the films were changed with Cu doping. The refractive index dispersion of Cu doped ZnO films obeys the single oscillator model. The dispersion energy and oscillator energy values of the ZnO films were changed with Cu doping. The Cu doped ZnO nanofiber-based NH3 gas sensors were fabricated. The sensor response of the sensors was from 464.98 to 484.61 when the concentration of NH3 is changed 6600-13,300 ppm. The obtained results indicate that the response of the ZnO film based ammonia gas sensors can be controlled by copper content.

Hendi, A. A.; Alorainy, R. H.

2014-02-01

7

Anatase titanium dioxide thin film based carbon monoxide gas sensor  

NASA Astrophysics Data System (ADS)

Gas sensors are finding increasing number of applications in home, industrial and automotive areas. Incomplete combustion in gas and coal fired electricity plants can generate harmful gases and pollutants. The purpose of the proposed research was to develop titanium dioxide (TiO2) thin film based materials for carbon monoxide (CO) gas sensing to detect a very low concentration (20--100 ppm) of CO gas. Anatase TiO2 thin films (100--1000 nm) have been developed using pulsed DC magnetron reactive sputtering technique on glass, Si(100) and sapphire substrates. Optimum deposition parameters were determined by studying the crystalline quality of the films using X-ray diffraction. The x-ray photo-emission (XPS) studies indicated a good stoichiometric TiO 2 surface with O to Ti ratio of 1.95 +/- 0.05. Film residual stress was measured using curvature measurements of the substrates before and after deposition of the films. The anatase TiO2 thin films on sapphire showed lower stress compared to glass and Si substrates. Raman spectroscopy measurements were further used to study the correlation between the residual stress and Raman shifts of characteristic peaks to obtain a calibration factor. Anatase TiO2 thin films showed n-type electrical conductivity indicating the presence of shallow electron donors caused by oxygen vacancies. The response of films was tested for 100 ppm of CO in 100 sccm of N2 gas flow as a function of temperature, film thickness, and the substrate. The films show the highest response at 200°C. The films grown on sapphire substrates show the highest response. The response is higher for a film with 1000 nm thickness than the 250 nm thickness film. The CO sensor was tested as a function of CO concentration and as well as under different environs: The films respond to very low concentration, 20--100 ppm, of CO gas, with good reversibility. The response and recovery time were from 2 min to 1 min as the concentration increased from 20 to 100 ppm. It can be completely regenerated by turn off the CO gas without exposing it to oxygen or air. The sensor showed sensitivity for CO with as high as 2000 PPM of O2 concentration. It has the same response in dry and in humid environments. Furthermore, the anatase TiO2 thin film with no doping showed to have higher response than the doped films with Cu or La at 300°C.

Al-Homoudi, Ibrahim Abdullah

8

Sensing characteristics of tin oxide thick film gas sensor  

Microsoft Academic Search

Thick film gas sensor of tin oxide based materials has been developed by screen printing method, and its sensing characteristics have been examined for some gases. To perform the method, tin oxide fine power with the size about 0.5 ?m in diameter was prepared through the fine crystallization in liquid phase, and was mixed with glass frits as a binder

Takashi Oyabu; Tetsuo Osawa; Toshiji Kurobe

1982-01-01

9

Electrostatic spray deposited zinc oxide films for gas sensor applications  

NASA Astrophysics Data System (ADS)

In this work, thin films of zinc oxide (ZnO) for gas-sensor applications were deposited on platinum coated alumina substrate, using electrostatic spray deposition (ESD) technique. As precursor solution zinc acetate in ethanol was used. Scanning electron microscopy (SEM) evaluation showed a porous and homogeneous film morphology and the energy dispersive X-ray analysis (EDX) confirmed the composition of the films with no presence of other impurities. The microstructure studied with X-ray diffraction (XRD) and Raman spectroscopy indicated that the ZnO oxide films are crystallized in a hexagonal wurtzite phase. The films showed good sensitivity to 1 ppm nitrogen dioxide (NO 2) at 300 °C while a much lower sensitivity to 12 ppm hydrogen sulphide (H 2S).

Ghimbeu, Camelia Matei; Schoonman, Joop; Lumbreras, Martine; Siadat, Maryam

2007-07-01

10

Thin-film Li-doped NiO for thermoelectric hydrogen gas sensor  

Microsoft Academic Search

A hydrogen gas sensor using thermoelectric (TE) Li-doped NiO thin film with platinum catalyst film on the half of its surface was fabricated and this thin-film sensor has strong adhesion on the substrate. When this sensor is exposed to air mixed with the hydrogen gas, catalytic reaction heats up the platinum-coated surface, and then TE voltage builds up along the

Masahiko Matsumiya; Fabin Qiu; Woosuck Shin; Noriya Izu; Norimitsu Murayama; Shuzo Kanzaki

2002-01-01

11

Single-Walled Carbon Nanotube Thin-Film Sensor for Ultrasensitive Gas Detection  

NASA Astrophysics Data System (ADS)

We demonstrated a gas sensor fabricated by growing a single-walled carbon nanotube (SWNT) thin film directly on a conventional sensor substrate. NO2 and Cl2 were detected down to the ppb level under room-temperature operation with a fast response. Using an electrical breakdown technique, gas response sensitivity was improved by an order of magnitude. The relationship between gas concentration and sensor response was derived based on the Langmuir adsorption isotherm, predicting a detection limit of 8 ppb for NO2. The SWNT thin-film gas sensor exhibits merits over other types of sensors by virtue of its simplicity in fabrication and feasible application.

Wongwiriyapan, Winadda; Honda, Shin-ichi; Konishi, Hirofumi; Mizuta, Tomoaki; Ikuno, Takashi; Ito, Tatsuya; Maekawa, Toru; Suzuki, Kengo; Ishikawa, Hiroshi; Oura, Kenjiro; Katayama, Mitsuhiro

2005-04-01

12

Evanescent-wave optical gas sensor with a porous thin-film coating  

NASA Astrophysics Data System (ADS)

In this paper, we present the analysis and numerical model of absorptive gas detection by an optical evanescent-wave sensor. We investigate the influence of sensor geometry and thin-film porosity on the attenuation of guided modes caused by their interaction with the gas. We show that film porosity is a critical parameter that should be carefully optimized for a chosen mode. These findings served as a basis for the design of an experimentally realizable sensor of carbon dioxide.

Raicevic, N.; Maluckov, A.; Petrovic, J.

2014-09-01

13

Formulation and characterization of ZnO:Sb thick-film gas sensors  

Microsoft Academic Search

ZnO:Sb based screen printed thick-film H2, CO and CH4 gas sensors were fabricated. Films were realized on an alumina substrate by mixing ZnO with lead borosilicate glass frits as a binder and Sb as a catalyst. It was observed that the ZnO:Sb based sensors were more sensitive to these gases than the pure ZnO sensors. The conductance of the sensor

N. Jayadev Dayan; S. R Sainkar; R. N Karekar; R. C Aiyer

1998-01-01

14

Single-Walled Carbon Nanotube Thin-Film Sensor for Ultrasensitive Gas Detection  

Microsoft Academic Search

We demonstrated a gas sensor fabricated by growing a single-walled carbon nanotube (SWNT) thin film directly on a conventional sensor substrate. NO2 and Cl2 were detected down to the ppb level under room-temperature operation with a fast response. Using an electrical breakdown technique, gas response sensitivity was improved by an order of magnitude. The relationship between gas concentration and sensor

Winadda Wongwiriyapan; Shin-ichi Honda; Hirofumi Konishi; Tomoaki Mizuta; Takashi Ikuno; Tatsuya Ito; Toru Maekawa; Kengo Suzuki; Hiroshi Ishikawa; Kenjiro Oura; Mitsuhiro Katayama

2005-01-01

15

MICRO-MACHINED THIN FILM HYDROGEN GAS SENSORS  

Microsoft Academic Search

The ability to detect gaseous hydrogen is of critical importance to acceptance and utilization of hydrogen as an energy carrier. Micro-machined gas sensors are a new generation of sensor technology combining existing integrated circuit fabrication technology with novel deposition and etching processing. This results in a new device structure, known as a \\

Frank DiMeo; Ing-Shin Chen; Philip Chen; Jeffrey Neuner Michele Stawasz; James Welch; A. Rohrl

16

Organic hydrogen gas sensor with palladium-coated ?-phase poly(vinylidene fluoride) thin films  

NASA Astrophysics Data System (ADS)

We have proposed an organic hydrogen gas sensor in which palladium (Pd)-coated ?-phase poly(vinylidene fluoride) (PVDF) films are utilized. Volume expansion of the Pd thin film caused by absorption of hydrogen gas is monitored by a piezoelectric thin film of PVDF attached to the Pd films. We have developed a simple method of synthesizing ?-phase PVDF films from ?-phase PVDF powder by using a wet process in which a mixture of acetone and hexamethylphosphoric triamide is used as the solvent for the PVDF powder. The sensor works by itself at room temperature without a power source.

Imai, Yuji; Kimura, Yasuo; Niwano, Michio

2012-10-01

17

Al doped ZnO thin films for gas sensor application  

Microsoft Academic Search

Highly textured pure and Al doped ZnO thin films have been produced by pulsed laser deposition for optical gas sensor application. The influence of the processing parameters such as substrate temperature and oxygen pressure applied during depositions, and dopant concentration on the structural, morphological, and optical properties of the films were investigated. All deposited films are textured along the (002)

I. G. Dimitrov; A. O. Dikovska; P. A. Atanasov; T. R. Stoyanchov; T. Vasilev

2008-01-01

18

Copper on-top-sputtering induced modification of tin dioxide thin film gas sensors  

Microsoft Academic Search

Thin film gas sensors based on pure tin dioxide were modified by sputtering of copper on the surface of the films. A gradual increase of an amount of the on-top-Cu produced increasing doping with uniform distribution of copper throughout entire tin oxide film. An increase of an amount of Cu caused continuous variation of the clean air resistance and the

A Galdikas; A Mironas; A Šetkus; W Göpel; K.-D Schierbaum

1999-01-01

19

Thermo-Resistive Platinum Thin Film Hydrogen Gas Sensor Fabricated by MEMS Techniques  

Microsoft Academic Search

Thermo-resistive platinum(Pt) thin film sensor was produced using Micro Electro Mechanical Systems (MEMS) fabrication techniques. The sensor design incorporated resistor elements that would facilitate the temperature-resistance characteristics and mechanisms of Pt based thin film thermo-resistors. The sensor was fabricated with lift-off process that allowed the dual sensing surface area. Furthermore, the dual sensing surfaces ensured faster response to hydrogen gas.

Daisuke Yamazaki; Lin Zhang; Joanna Pawlat; Toshitsugu Ueda

2008-01-01

20

Preparation of nickel oxide thin films for gas sensors applications  

Microsoft Academic Search

Nickel oxide (NiO) thin films were prepared by dc reactive magnetron sputtering from a nickel metal target in an Ar+O2 mixed atmosphere in two sputtering modes. The oxygen content in the gas mixture varied from 15% to 45%. The films prepared in the oxide-sputtering mode were amorphous while the films in metal-sputtering mode exhibited polycrystalline (fcc) NiO phase. In this

I Hotovy; J Huran; L Spiess; S Hascik; V Rehacek

1999-01-01

21

Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film.  

PubMed

Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H(2)]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd(0.91)Y(0.09) alloy ultrathin film have potential applications in hydrogen detection and measurement. PMID:23278019

Yi, Liu; You-Ping, Chen; Han, Song; Gang, Zhang

2012-12-01

22

Nano-structured thin-film Pt catalyst for thermoelectric hydrogen gas sensor  

Microsoft Academic Search

A hydrogen gas sensor using thermoelectric thin-film of nickel oxide with platinum catalyst thin-film on half of its surface Pt\\/NiO\\/alumina was fabricated and showed prominent selectivity for hydrogen gas. The platinum catalyst thin-film plays the most important role for its detection mechanism and its catalytic activity which depends both on surface morphology and thickness was investigated using Pt\\/Si. The surface

Masahiko Matsumiya; Woosuck Shin; Noriya Izu; Norimitsu Murayama

2003-01-01

23

Sensing characteristics of tin-doped ZnO thin films as NO 2 gas sensor  

Microsoft Academic Search

NO2 gas sensor was fabricated by successive ionic layer adsorption and reaction (SILAR) technique and rapid photothermal processing (RPP) of the Sn-doped ZnO film. The experimental results shows that tin doping of zinc oxide thin films improve the sensor element sensitivity to 1.5ppm NO2 in air and downshift the operating temperature. The influence of variation of Sn concentration in the

Sergiu T. Shishiyanu; Teodor S. Shishiyanu; Oleg I. Lupan

2005-01-01

24

Thermoelectric Thick-Film Hydrogen Gas Sensor Operating at Room Temperature  

Microsoft Academic Search

A sensor of thick film NiO doped with alkali ions was fabricated and coated with Pt as the catalyst on half of its surface. When this sensor was exposed to air mixed with hydrogen gas, the catalytic reaction heated up the Pt-coated surface, and then thermoelectric voltage appeared across the hot and cold region of the oxide film. At 22°C,

Woosuck Shin; Kiyohisa Imai; Noriya Izu; Norimitsu Murayama

2001-01-01

25

Planar zeolite film-based potentiometric gas sensors manufactured by a combined thick-film and electroplating technique.  

PubMed

Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers. PMID:22164042

Marr, Isabella; Reiss, Sebastian; Hagen, Gunter; Moos, Ralf

2011-01-01

26

Elaboration of ammonia gas sensors based on electrodeposited polypyrrole--cobalt phthalocyanine hybrid films.  

PubMed

The electrochemical incorporation of a sulfonated cobalt phthalocyanine (sCoPc) in conducting polypyrrole (PPy) was done, in the presence or absence of LiClO4, in order to use the resulting hybrid material for the sensing of ammonia. After electrochemical deposition, the morphological features and structural properties of polypyrrole/phthalocyanine hybrid films were investigated and compared to those of polypyrrole films. A gas sensor consisting in platinum microelectrodes arrays was fabricated using silicon microtechnologies, and the polypyrrole and polypyrrole/phthalocyanine films were electrochemically deposited on the platinum microelectrodes arrays of this gas sensor. When exposed to ammonia, polymer-based gas sensors exhibited a decrease in conductance due to the electron exchange between ammonia and sensitive polymer-based layer. The characteristics of the gas sensors (response time, response amplitude, reversibility) were studied for ammonia concentrations varying from 1 ppm to 100 ppm. Polypyrrole/phthalocyanine films exhibited a high sensitivity and low detection limit to ammonia as well as a fast and reproducible response at room temperature. The response to ammonia exposition of polypyrrole films was found to be strongly enhanced thanks to the incorporation of the phthalocyanine in the polypyrrole matrix. PMID:24209308

Patois, Tilia; Sanchez, Jean-Baptiste; Berger, Franck; Fievet, Patrick; Segut, Olivier; Moutarlier, Virginie; Bouvet, Marcel; Lakard, Boris

2013-12-15

27

Thin film transistors gas sensors based on reduced graphene oxide poly(3-hexylthiophene) bilayer film for nitrogen dioxide detection  

NASA Astrophysics Data System (ADS)

Reduced graphene oxide (RGO)/poly(3-hexylthiophene) (P3HT) bilayer films were firstly utilized as active layers in OTFT gas sensors for nitrogen dioxide (NO2) detection. The OTFT with RGO/P3HT bilayer film exhibited the typical transistor characteristics and better gas sensing properties at room temperature. The electrical parameters of OTFTs based on pure P3HT film and RGO/P3HT bilayer film were calculated. The threshold voltage of OTFT was positively shifted due to the high concentration carriers in RGO. The sensing properties of the sensor with RGO/P3HT bilayer film were also investigated. Moreover, the sensing mechanism was analyzed as well.

Xie, Tao; Xie, Guangzhong; Zhou, Yong; Huang, Junlong; Wu, Mei; Jiang, Yadong; Tai, Huiling

2014-10-01

28

Metal Oxide Nanowire and Thin-Film-Based Gas Sensors for Chemical Warfare Simulants Detection  

Microsoft Academic Search

This work concerns with metal oxide (MOX) gas sensors based on nanowires and thin films. We focus on chemical warfare agents (CWAs) detection to compare these materials from the functional point-of-view. We work with different chemicals including simulants for Sarin nerve agents, vescicant gases, cyanide agents, and analytes such as ethanol, acetone, ammonia, and carbon monoxide that can be produced

Andrea Ponzoni; Camilla Baratto; Sebastiano Bianchi; Elisabetta Comini; Matteo Ferroni; Matteo Pardo; Marco Vezzoli; Alberto Vomiero; Guido Faglia; Giorgio Sberveglieri

2008-01-01

29

Nanocrystalline SnO2:F Thin Films for Liquid Petroleum Gas Sensors  

PubMed Central

This paper reports the improvement in the sensing performance of nanocrystalline SnO2-based liquid petroleum gas (LPG) sensors by doping with fluorine (F). Un-doped and F-doped tin oxide films were prepared on glass substrates by the dip-coating technique using a layer-by-layer deposition cycle (alternating between dip-coating a thin layer followed by a drying in air after each new layer). The results showed that this technique is superior to the conventional technique for both improving the film thickness uniformity and film transparency. The effect of F concentration on the structural, surface morphological and LPG sensing properties of the SnO2 films was investigated. Atomic Force Microscopy (AFM) and X-ray diffraction pattern measurements showed that the obtained thin films are nanocrystalline SnO2 with nanoscale-textured surfaces. Gas sensing characteristics (sensor response and response/recovery time) of the SnO2:F sensors based on a planar interdigital structure were investigated at different operating temperatures and at different LPG concentrations. The addition of fluorine to SnO2 was found to be advantageous for efficient detection of LPG gases, e.g., F-doped sensors are more stable at a low operating temperature (300 °C) with higher sensor response and faster response/recovery time, compared to un-doped sensor materials. The sensors based on SnO2:F films could detect LPG even at a low level of 25% LEL, showing the possibility of using this transparent material for LPG leak detection. PMID:22164007

Chaisitsak, Sutichai

2011-01-01

30

Characterization of reactive sputtered TiO2 thin films for gas sensor applications  

NASA Astrophysics Data System (ADS)

The technology for preparing and characterisation of titanium dioxide (TiO2) thin films with properties appropriate for usage as gas sensors are discussed. For preparing the samples the methods of reactive radio frequency (RF) and direct current (DC) magnetron sputtering were used. The composition and microstructure of the films were studied by XPS, EPMA, XRD and Raman spectroscopy and the surface of the films was observed by high resolution SEM. Thorough profile analyses on the structure changes were performed by XPS. Interactions with the substrate and changes between the different modifications of the crystal structure also were investigated. For measuring the thickness and to identify the refractive indices of the films laser ellipsometry was used. The research was focused on the sensing behaviour of the sputtered TiO2 thin films. Films of various thickness were deposited on quartz resonators and the quartz crystal microbalance (QCM) method was used. This enables highly sensitive gas sensor capable of detecting changes in the molecular range to be constructed. Prototype QCM sensors with TiO2 sensitive films made in our laboratory, showed good sensitivity to ammonia at room temperature, and are currently being tested for sensitivity to other gasses.

Boyadzhiev, Stefan; Georgieva, Velichka; Rassovska, Milka

2010-11-01

31

Novel BN/Pd composite films for stable liquid petroleum gas sensor  

NASA Astrophysics Data System (ADS)

Composite films of BN/Pd were synthesized by depositing thin films of BN by pulsed laser deposition technique and evaporating a thin layer of palladium on top of it to form a bi-layer structure. This bi-layer structure was then subjected to rapid thermal annealing for the incorporation of Pd in BN. The films thus obtained were characterized by SEM, XRD and FTIR studies. Liquid petroleum gas (LPG) sensing properties were also investigated critically. Very stable and reproducible LPG sensing properties and comparatively at lower operating temperature of 460 K would make this material superior to prevalent oxide based sensors.

Ghosh, D.; Ghosh, B.; Hussain, S.; Chaudhuri, Subhajyoti; Bhar, R.; Pal, A. K.

2012-12-01

32

Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications  

SciTech Connect

Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman spectroscopy. Electrical and gas sensitivity measurements were conducted as well. The average grain size is 240 and 224 A for undoped ZnO and Al-doped ZnO films, respectively. We demonstrate that rapid photothermal processing is an efficient method for improving the quality of nanostructured ZnO films. Nanostructured ZnO films doped with Al showed a higher sensitivity to carbon dioxide than undoped ZnO films. The correlations between material compositions, microstructures of the films and the properties of the gas sensors are discussed.

Lupan, O. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States)], E-mail: lupanoleg@yahoo.com; Chow, L. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States); Shishiyanu, S. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Monaico, E. [National Center for Materials Study and Testing, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Shishiyanu, T.; Sontea, V. [Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, 168 Stefan cel Mare Blvd., MD-2004 Chisinau (Moldova, Republic of); Roldan Cuenya, B.; Naitabdi, A.; Park, S.; Schulte, A. [Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, FL 32816-2385 (United States)

2009-01-08

33

Thin-film-bulk-acoustic-resonator gas sensor for the detection of organophosphate vapor detection  

Microsoft Academic Search

A novel design of an organophosphate vapor sensor based on a thin film bulk acoustic resonator (TFBAR) is presented. The TFBAR device is consisted of an AlN piezoelectric stack and a Mo\\/AlN Bragg reflector. Poly (vinylidene fluoride) (PVDF) is coated on the surface of the piezoelectric stack as the special sensitive layer. The concentration of the target gas can be

Jing-jing Wang; Da Chen; Lu-yin Zhang; Yan Xu

2011-01-01

34

Gas Sensing Properties of Metal Doped WO3 Thin Film Sensors Prepared by Pulsed Laser Deposition and DC Sputtering Process  

Microsoft Academic Search

Tungsten trioxide (WO3) thin films gas sensors were prepared by the KrF excimer pulsed laser deposition (PLD) method. The films were prepared on the quartz glass, silicon and also on the Al2O3 sensor substrates with platinum interdigitated electrodes. The effect of doping of the platinum (Pt), palladium (Pd) or gold (Au) on the WO3 thin film was also investigated. These

Tsuyoshi Ueda; Tomoaki Ikegami; Kenji Ebihara

2006-01-01

35

Nanoparticle thin films for gas sensors prepared by matrix assisted pulsed laser evaporation.  

PubMed

The matrix assisted pulsed laser evaporation (MAPLE) technique has been used for the deposition of metal dioxide (TiO(2), SnO(2)) nanoparticle thin films for gas sensor applications. For this purpose, colloidal metal dioxide nanoparticles were diluted in volatile solvents, the solution was frozen at the liquid nitrogen temperature and irradiated with a pulsed excimer laser. The dioxide nanoparticles were deposited on Si and Al(2)O(3) substrates. A rather uniform distribution of TiO(2) nanoparticles with an average size of about 10 nm and of SnO(2) nanoparticles with an average size of about 3 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspections. Gas-sensing devices based on the resistive transduction mechanism were fabricated by depositing the nanoparticle thin films onto suitable rough alumina substrates equipped with interdigitated electrical contacts and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol and acetone are presented. PMID:22574039

Caricato, Anna Paola; Luches, Armando; Rella, Roberto

2009-01-01

36

Thin film temperature sensor  

NASA Technical Reports Server (NTRS)

Thin film surface temperature sensors were developed. The sensors were made of platinum-platinum/10 percent rhodium thermocouples with associated thin film-to-lead wire connections and sputtered on aluminum oxide coated simulated turbine blades for testing. Tests included exposure to vibration, low velocity hydrocarbon hot gas flow to 1250 K, and furnace calibrations. Thermal electromotive force was typically two percent below standard type S thermocouples. Mean time to failure was 42 hours at a hot gas flow temperature of 1250 K and an average of 15 cycles to room temperature. Failures were mainly due to separation of the platinum thin film from the aluminum oxide surface. Several techniques to improve the adhesion of the platinum are discussed.

Grant, H. P.; Przybyszewski, J. S.

1980-01-01

37

Doping effect of SnO 2 on gas sensing characteristics of sputtered ZnO thin film chemical sensor  

Microsoft Academic Search

The SnO2 content dependence of the sensitivity of sputtered SnO2-doped ZnO thin film chemical sensor is studied for various gases. It is found that the SnO2(78 wt%)-doped ZnO thin film chemical sensor exhibits a high sensitivity and good selectivity for C2H5OH gas. The sensitivity of the SnO2(78 wt%)-doped ZnO thin film chemical sensor responds to the freshness change of alcohols,

H. Nanto; T. Morita; H. Habara; K. Kondo; Y. Douguchi; T. Minami

1996-01-01

38

Detection of liquid petroleum gas using mixed nanosized tungsten oxide-based thick-film semiconductor sensor  

Microsoft Academic Search

The thick-film semiconductor sensor for liquid petroleum gas (LPG) detection was fabricated using a mixed WO3-based sensor. We present the characterization of both their structural properties by means of XRD measurements and the electrical characteristics by using gas-sensing properties. The sensing characteristics such as sensitivity, working range, cross-sensitivity and response time were studied by using nanosized WO3-based mixed with different

G. N. Chaudhari; A. M. Bende; A. B. Bodade; S. S. Patil; S. V. Manorama

2006-01-01

39

ZnO transparent thin films for gas sensor applications M. Suchea a,b,, S. Christoulakis a,b  

E-print Network

the target material and the plasma gas flow ratio (O2 to Ar) affect the morphology of dc sputtered ZnO thinZnO transparent thin films for gas sensor applications M. Suchea a,b,, S. Christoulakis a,b , K (AFM) and X-ray Diffraction (XRD) have shown a strong influence of deposition technique parameters

40

Gas Sensor Test Chip  

NASA Technical Reports Server (NTRS)

A new test chip is being developed to characterize conducting polymers used in gas sensors. The chip, a seven-layer cofired alumina substrate with gold electrodes, contains 11 comb and U- bend test structures. These structures are designed to measure the sheet resistance, conduction anisotropy, and peripheral conduction of spin-coated films that are not subsequently patterned.

Buehler, M.; Ryan, M.

1995-01-01

41

Nano and micro stripe based metal oxide thin film gas sensor  

Microsoft Academic Search

Functional metal oxide micro and nanostructures for the detection of gas are a very promising candidate for future gas-sensors. Due to reduced size and thus an increased surface to volume ratio nanosized sensitive structures offer a high potential for increasing sensitivity. A top down sputtering approach for gas sensors with nano-sized gas sensitive metal oxide areas is presented. Oxidised silicon

Stefan Palzer; Emmanuel Moretton; Francisco Hernandez Ramirez; Albert Romano-Rodriguez; Juan Ramon Morante; Jürgen Wöllenstein

2007-01-01

42

Fiber optic hydrogen sulfide gas sensor utilizing surface plasmon resonance of Cu/ZnO thin films  

NASA Astrophysics Data System (ADS)

We report a surface plasmon resonance based fiber optic hydrogen sulphide gas sensor using Cu/ZnO thin films. The sensor works on wavelength modulation scheme. The fiber optic probe was fabricated by removing the cladding of appropriate length from the fiber and depositing copper and ZnO thin films on the unclad core by thermal evaporation technique. The presence of hydrogen sulphide gas around the probe changes the dielectric function of zinc oxide and a dip is observed in transmitted spectrum. With the increase in the gas concentration shift in the resonance wavelength has been observed. The proposed sensor can be used for online monitoring and remote sensing of hydrogen sulphide gas in the environment.

Tabassum, Rana; Mishra, Satyendra K.; Gupta, Banshi D.

2013-05-01

43

Manganese doped Zinc oxide thin film hydrogen gas sensor at reduced operating temperature  

Microsoft Academic Search

During the pas t few decades, semiconductor metal oxide (SMO) gas sensors have become a prime technology in several domestic, commercial, and industrial gas sensing. The semiconductor properties of zinc oxide along with its dopant remain to be trapped fully in its application as gas sensor. With the advent of nanotechnology, miniaturization and high sensitivity happens to be a key

Anjali Chatterjee; Partha Bhattacharjee; P. kumbakar; Nirmal Kumar Roy

2011-01-01

44

Microfabricated gas sensor systems with sensitive nanocrystalline metal-oxide films  

Microsoft Academic Search

This article gives an overview on recent developments in metal-oxide-based gas sensor systems, in particular on nanocrystalline\\u000a oxide materials deposited on modern, state-of-the-art sensor platforms fabricated in microtechnology. First, metal-oxide-based\\u000a gas sensors are introduced, and the underlying principles and fundamentals of the gas sensing process are laid out. In the\\u000a second part, the different deposition methods, such as evaporation, sputtering,

M. Graf; A. Gurlo; N. Bârsan; U. Weimar; A. Hierlemann

2006-01-01

45

Quartz crystal microbalance (QCM) sensor for ammonia gas using clay\\/polyelectrolyte layer-by-layer self-assembly film  

Microsoft Academic Search

An ammonia gas sensor which has a high sensitivity in robust conditions has been investigated. A nanoporous thin film consisting of polyelectrolytes and sheet particulate ?-ZrP was assembled by a layer-by-layer self assembly method on the electrode of a quartz crystal microbalance (QCM). This QCM sensor showed an eight times higher sensitivity than that of QCM deposited with ?-ZrP by

Masashi Kikuchi; Katsuya Omori; Seimei Shiratori

2004-01-01

46

Properties of palladium doped tin oxide thin films for gas sensors grown by PLD method combined with sputtering process  

Microsoft Academic Search

The gas sensors based on tin dioxide (SnO2) thin films and doped with different amount of palladium (Pd) were synthesized by a new developed preparation system using the pulsed Nd:YAG (532 nm) laser deposition method combined with d.c. sputtering. The Pd-doped SnO2 (SnO2–Pd) thin films have been grown on Si (100) and alumina (Al2O3) substrates using SnO2 targets. The composition

Yoshiaki Suda; Hiroharu Kawasaki; Jun Namba; Keitarou Iwatsuji; Kazuya Doi; Kenji Wada

2003-01-01

47

Influence of humidity on CO sensing with p-type CuO thick film gas sensors  

Microsoft Academic Search

A model for the detection of CO in the presence of humidity is proposed for thick porous film gas sensors based on p-type CuO. The sensing mechanism is investigated by means of simultaneous DC electrical resistance and work function changes measurements combined with appropriate modeling of the conduction in the polycrystalline sensing film. The experiments were performed at 150°C in

M. Hübner; C. E. Simion; A. Tomescu-St?noiu; S. Pokhrel; N. Bârsan; U. Weimar

2011-01-01

48

Temperature Gradient Effect on Gas Discrimination Power of a Metal-Oxide Thin-Film Sensor Microarray  

Microsoft Academic Search

The paper presents results concerning the effect of spatial inhomogeneous operating temperature on the gas discrimination power of a gas-sensor microarray, with the latter based on a thin SnO2 film employed in the KAMINA electronic nose. Three different temperature distributions over the substrate are discussed: a nearly homogeneous one and two temperature gradients, equal to approx. 3.3 o C\\/mm and

Victor V. Sysoev; Ilya Kiselev; Markus Frietsch; Joachim Goschnick

2004-01-01

49

Chemiresistive gas sensors employing solution-processed metal oxide quantum dot films  

NASA Astrophysics Data System (ADS)

We report low-temperature chemiresistive gas sensors based on tin oxide colloidal quantum dots (CQDs), in which the benefits of CQDs such as extremely small crystal size, solution-processability, and tunable surface activity are exploited to enhance the gas-sensing effect. The sensor fabrication is simply employing spin-coating followed by a solid-state ligand exchange treatment at room temperature in air ambient. The optimal gas sensor exhibited rapid and significant decrease in resistance upon H2S gas exposure when operated at 70 °C, and it was fully recoverable upon gas release. We observed a power law correlation between the sensor response and H2S gas concentration, and the sensing mechanism was discussed using the completely depletion model with a flat band diagram.

Liu, Huan; Xu, Songman; Li, Min; Shao, Gang; Song, Huaibing; Zhang, Wenkai; Wei, Wendian; He, Mingze; Gao, Liang; Song, Haisheng; Tang, Jiang

2014-10-01

50

Temperature-independent resistive oxygen exhaust gas sensor for lean-burn engines in thick-film technology  

Microsoft Academic Search

Strontium titanate based materials (SrTi0.65Fe0.35O3??; STF or La0.05Sr0.95Ti0.65Fe0.35O3??; LSTF) are suggested in the literature as resistive oxygen gas sensors due to their temperature-independent but oxygen concentration-dependent resistance characteristic.This contribution reports on the difficulties that had to be overcome by trying to transfer the properties of the pure material to a real exhaust gas compatible thick-film sensor device. Two main problems

Ralf Moos; Frank Rettig; Armin Hürland; Carsten Plog

2003-01-01

51

SnO2/Pt thin film laser ablated gas sensor array.  

PubMed

A gas sensor array was developed in a 10 × 10 mm(2) space using Screen Printing and Pulse Laser Ablation Deposition (PLAD) techniques. Heater, electrode, and an insulator interlayer were printed using the screen printing method on an alumina substrate, while tin oxide and platinum films, as sensing and catalyst layers, were deposited on the electrode at room temperature using the PLAD method, respectively. To ablate SnO(2) and Pt targets, depositions were achieved by using a 1,064 nm Nd-YAG laser, with a power of 0.7 J/s, at different deposition times of 2, 5 and 10 min, in an atmosphere containing 0.04 mbar (4 kPa) of O(2). A range of spectroscopic diffraction and real space imaging techniques, SEM, EDX, XRD, and AFM were used in order to characterize the surface morphology, structure, and composition of the films. Measurement on the array shows sensitivity to some solvent and wood smoke can be achieved with short response and recovery times. PMID:22164041

Shahrokh Abadi, Mohammad Hadi; Hamidon, Mohd Nizar; Shaari, Abdul Halim; Abdullah, Norhafizah; Wagiran, Rahman

2011-01-01

52

Thin film hydrogen sensor  

DOEpatents

A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed. 6 figs.

Lauf, R.J.; Hoffheins, B.S.; Fleming, P.H.

1994-11-22

53

Design of low cost gas sensor based on SrTiO3 and BaTiO3 films.  

PubMed

We have prepared SrTiO3/BaTiO3 multilayer film on alumina substrates by a sol-gel technique and investigated their response for sensing ethanol vapor. The surface morphology of the films were characterized by atomic force microscope (AFM) showing that the grain size of the films increase up to 40 nm as the annealing temperature increased to 1000 degrees C. The ethanol sensors based on SrTiO3/BaTiO3 thin films were fabricated by applying interdigitated gold electrodes by sputtering technique. The ethanol sensing characteristics of SrTiO3/BaTiO3 thin films were quantified by the change in resistance of the sensors when they were exposed to ethanol. The optimum operating tempearature of these sensors was found to be 350 degrees C. In addition, the film annealed at 1000 degrees C exhibited p-type gas sensing behavior with the best sensitivity of 30-100 for low ethanol concentration in the range of 100-1000 ppm. PMID:21137905

Hodak, Satreerat K; Supasai, Thidarat; Wisitsoraat, Anurat; Hodak, Jose H

2010-11-01

54

High sensitive formaldehyde graphene gas sensor modified by atomic layer deposition zinc oxide films  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) thin films with various thicknesses were fabricated by Atomic Layer Deposition on Chemical Vapor Deposition grown graphene films and their response to formaldehyde has been investigated. It was found that 0.5 nm ZnO films modified graphene sensors showed high response to formaldehyde with the resistance change up to 52% at the concentration of 9 parts-per-million (ppm) at room temperature. Meanwhile, the detection limit could reach 180 parts-per-billion (ppb) and fast response of 36 s was also obtained. The high sensitivity could be attributed to the combining effect from the highly reactive, top mounted ZnO thin films, and high conductive graphene base network. The dependence of ZnO films surface morphology and its sensitivity on the ZnO films thickness was also investigated.

Mu, Haichuan; Zhang, Zhiqiang; Zhao, Xiaojing; Liu, Feng; Wang, Keke; Xie, Haifen

2014-07-01

55

Study on TiO2-doped ZnO thick film gas sensors enhanced by UV light at room temperature  

Microsoft Academic Search

The gas-sensing properties of titanium oxide (TiO2)-doped zinc oxide (ZnO) thick film sensor specimens to typical ethanol vapor under UV light activation at room temperature have been investigated. Zinc nanoparticles were mixed with commercial TiO2 in various weight percentage (0%, 1%, 5%, and 10%) and sintered at 650°C for 2h to prepare the thick film sensors. The sensors exhibit better

Yanghai Gui; Shumian Li; Jiaqiang Xu; Chao Li

2008-01-01

56

Gas identification by modulating temperatures of SnO 2-based thick film sensors  

Microsoft Academic Search

A new method is presented to identify the presence of two gases in the ambient atmosphere. The method employs only one SnO2-based gas sensor in a sinusoidal temperature mode to perform the quantitative analysis of a binary gas mixture (CO\\/NO2) in air.

A. Heilig; N. Bârsan; U. Weimar; M. Schweizer-Berberich; J. W. Gardner; W. Göpel

1997-01-01

57

Low operating temperature of oxygen gas sensor based on undoped and Cr-doped ZnO films  

Microsoft Academic Search

Undoped and doped ZnO with 1at.% (atomic percentage) chromium (Cr) was synthesized by RF reactive co-sputtering for oxygen gas sensing applications. The prepared films showed a highly c-oriented phase with a dominant (002) peak at a Bragg angle of around 34.2°. The operating temperature of the prepared ZnO sensor was around 350°C and shifted to around 250°C for the doped

N. Al-Hardan; M. J. Abdullah; A. Abdul Aziz; H. Ahmad

2010-01-01

58

Novel Zinc Oxide Nanostructured thin Films for Volatile Organic Compaunds Gas Sensors  

Microsoft Academic Search

Novel zinc oxide nanostructured thin films have been obtained by chemical deposition technique and rapid photothermal processing (RPP). ZnO nanostructures were studied for the development of volatile organic compounds (VOC) sensors. The investigations results indicate that by RPP is possible to control the sensing properties and operating temperature. A correlation taking into account the nanostructure of the material, the effects

T. Shishiyanu; S. Shishiyanu; O. Lupan; V. Ontea; A. Bragorenco

2006-01-01

59

Dual SAW sensor technique for determining mass and modulus changes in thin silicate films during gas adsorption  

SciTech Connect

Surface acoustic wave (SAW) sensors, which are sensitive to a variety of surface changes, have been widely used for chemical and physical sensing. The ability to control or compensate for the many surface forces has been instrumental in collecting valid data. In cases where it is not possible to neglect certain effects, such as frequency drift with temperature, methods such as the dual sensor technique have been utilized. This paper describes a novel use of a dual sensor technique, using two sensor materials, Quartz and GaAs, to separate out the contributions of mass and modulus of the frequency change during gas adsorption experiments. The large modulus change in the film calculated using this technique, and predicted by the Gassmann equation, provide a greater understanding of the challenges of SAW sensing.

Hietala, S.L.; Hietala, V.M.; Brinker, C.J.

2000-01-10

60

Gas sensor  

SciTech Connect

An electro-chemical cell for quantitatively detecting an acidic or an alkaline gas, e.g. carbon dioxide, includes a sensing electrode which is connected to a top cap by a contact strip and is accessible to the gas to be tested through a hole. The electrode comprises an electro-chemical couple whose potential is pH-dependent (e.g. silver/silver oxide for carbon dioxide) the active material being supported by a nickel gauze to give good current collection. A counter electrode without significant gas access is immersed in an electrolyte whose pH is such that it will change following adsorption of the gas being tested for. A wicking separator ensures an electrolytic path between the two electrodes. The components are contained within a metal can, the top cap being held by folding over the rim. An insulating grommet is fitted between the two electrodes. When using silver/silver oxide for the sensing electrode, the counter electrode may be of the same material and the electrolyte may be potassium carbonate. The current flowing between the electrodes is a measure of the concentration of gas being detected. A reference electrode may also be included.

Tantram, A.D.S.; Finbow, J.R.; Hobbs, B.S.

1984-10-02

61

Microstructure and hydrogen gas sensitivity of amorphous (Ba,Sr)TiO 3 thin film sensors  

Microsoft Academic Search

Ferroelectric (Ba0.67Sr0.33)Ti1.02O3 thin films have been prepared by the sol–gel technology and characterized using TGA, DTA, XRD, TEM, dielectric characterizations, and gas sensing properties. The (Ba0.67Sr0.33)Ti1.02O3 thin film devices are made on Pt-coated Si substrate to detect hydrogen gas and to study gas sensing mechanism. Experimental results show that the diode I–V behavior appears in these Pd\\/amorphous (Ba,Sr)TiO3 (BST) thin

W. Zhu; O. K. Tan; Q. Yan; J. T. Oh

2000-01-01

62

Hydrogen-selective thermoelectric gas sensor  

Microsoft Academic Search

A thermoelectric (TE) hydrogen gas sensor was fabricated by depositing a platinum catalyst thin film on the half surface of nickel oxide thick film. When it was exposed to combustible gas diluted by synthetic air, the catalyst layer converts hydrogen and oxygen effectively to water vapor, and give out heat energy, resulting temperature difference across the sensor, and consequently voltage

Woosuck Shin; Masahiko Matsumiya; Noriya Izu; Norimitsu Murayama

2003-01-01

63

Nanonails structured ferric oxide thick film as room temperature liquefied petroleum gas (LPG) sensor  

NASA Astrophysics Data System (ADS)

In the present work, ferric oxide nanonails were prepared by screen printing method on borosilicate glass substrate and their electrical and LPG sensing properties were investigated. The structural and morphological characterizations of the material were analyzed by means of X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD pattern revealed crystalline ?-phase and rhombohedral crystal structure. SEM images show nanonails type of morphology throughout the surface. Optical characterization of the film was carried out by UV-visible spectrophotometer. By Tauc plot the estimated value of band gap of film was found 3.85 eV. The LPG sensing properties of the ferric oxide film were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the film were measured with the exposure of LPG as a function of time. The maximum values of sensitivity and sensor response factors were found 51 and 50 respectively for 2 vol.% of LPG. The activation energy calculated from Arrhenius plot was found 0.95 eV. The response and recovery time of sensing film were found ˜120 s and 150 s respectively. These experimental results show that nanonails structured ferric oxide is a promising material as LPG sensor.

Yadav, B. C.; Singh, Satyendra; Yadav, Anuradha

2011-01-01

64

Gas sensor based on nano ZSM-5 zeolite films for the nerve agent simulant dimethylmethylphosphonate detection  

NASA Astrophysics Data System (ADS)

The piezoelectric sensor device coated with nanosize ZSM-5 zeolite films has beem fabricated. The Nerve agent simulant Dimethylmethylphosphonate has been tested with this piezoelectric sensor devices. The frequency shifts to time at 1 ppm, 5ppm and 20ppm DMMP are examined respectively. The minimum detection concentration of 1ppm DMMP has been obtained in the N2 at 293K. 1 ppm is lower than the EC50 concentration value (where EC50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min). The frequency sensitivity was found to be about 60HZ / ppm. The effect of acetone on the ZSM-5 zeolite film was also investigated for the selectivity test. Using principle component analysis (PCA), we can qualify and quantify these testing gases.

Xie, Haifen; Ting, Yu; Sun, Xiaoxiang; Jia, Zhou; Huang, Yiping

2004-12-01

65

Qualitative and quantitative differentiation of gases using ZnO thin film gas sensors and pattern recognition analysis.  

PubMed

In the present work we have grown highly textured, ultra-thin, nano-crystalline zinc oxide thin films using a metal organic chemical vapor deposition technique and addressed their selectivity towards hydrogen, carbon dioxide and methane gas sensing. Structural and microstructural characteristics of the synthesized films were investigated utilizing X-ray diffraction and electron microscopy techniques respectively. Using a dynamic flow gas sensing measurement set up, the sensing characteristics of these films were investigated as a function of gas concentration (10-1660 ppm) and operating temperature (250-380 °C). ZnO thin film sensing elements were found to be sensitive to all of these gases. Thus at a sensor operating temperature of ~300 °C, the response% of the ZnO thin films were ~68, 59, and 52% for hydrogen, carbon monoxide and methane gases respectively. The data matrices extracted from first Fourier transform analyses (FFT) of the conductance transients were used as input parameters in a linear unsupervised principal component analysis (PCA) pattern recognition technique. We have demonstrated that FFT combined with PCA is an excellent tool for the differentiation of these reducing gases. PMID:24551870

Pati, Sumati; Maity, A; Banerji, P; Majumder, S B

2014-04-01

66

Thick film hydrogen sensor  

Microsoft Academic Search

A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors. 8 figs.

B. S. Hoffheins; R. J. Lauf

1995-01-01

67

Plasmonic nanocomposite thin film enabled fiber optic sensors for simultaneous gas and temperature sensing at extreme temperatures  

NASA Astrophysics Data System (ADS)

Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment.Embedded sensors capable of operation in extreme environments including high temperatures, high pressures, and highly reducing, oxidizing and/or corrosive environments can make a significant impact on enhanced efficiencies and reduced greenhouse gas emissions of current and future fossil-based power generation systems. Relevant technologies can also be leveraged in a wide range of other applications with similar needs including nuclear power generation, industrial process monitoring and control, and aviation/aerospace. Here we describe a novel approach to embedded sensing under extreme temperature conditions by integration of Au-nanoparticle based plasmonic nanocomposite thin films with optical fibers in an evanescent wave absorption spectroscopy configuration. Such sensors can potentially enable simultaneous temperature and gas sensing at temperatures approaching 900-1000 °C in a manner compatible with embedded and distributed sensing approaches. The approach is demonstrated using the Au/SiO2 system deposited on silica-based optical fibers. Stability of optical fibers under relevant high temperature conditions and interactions with changing ambient gas atmospheres is an area requiring additional investigation and development but the simplicity of the sensor design makes it potentially cost-effective and may offer a potential for widespread deployment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02891g

Ohodnicki, Paul R.; Buric, Michael P.; Brown, Thomas D.; Matranga, Christopher; Wang, Congjun; Baltrus, John; Andio, Mark

2013-09-01

68

Toxic gas sensors using thin film transistor platform at low temperature  

E-print Network

Semiconducting metal-oxides such as SnO?, TiO?, ZnO and WO? are commonly used for gas sensing in the form of thin film resistors (TFRs) given their high sensitivity to many vapor species, simple construction and capability ...

Jin, Yoonsil

2009-01-01

69

Fabrication of a gas sensor array with micro-wells for VOCs gas sensing based on polymer/carbon nanotube thin films  

NASA Astrophysics Data System (ADS)

In this paper, gas sensor array with micro-well was designed and prepared by Micro Electro-Mechanical Systems (MEMS) technology. The micro-well and interdigital electrodes of sensor array were prepared using photolithography process, reactive ion etching (RIE) process, wet etching and conventional vacuum evaporation. In the manufacture process of the gas sensor array, KOH wet etching process was mainly discussed. The optimum etching processing parameters were as follows: 30 wt% KOH solution at 80 °C, a cooling back-flow device and a magnetic stirrer. The multi-walled carbon nanotubes (MWCNTs)-polyethyleneoxide (PEO) and MWNTs-Polyvinylpyrrolidone (PVP) composite films were utilized as sensitive layers to test gas-sensing properties. Response performances of MWCNTs- PEO and MWNTs-PVP composite films to toluene vapor and methanol vapor at room temperature were investigated. The results revealed that the sensor array showed a larger sensitivity to toluene vapor than to methanol vapor. In addition, the sensing mechanisms were studied as well.

Xie, Guangzhong; Xie, Tao; Zhu, Tao; Jiang, Yadong; Tai, Huiling

2014-08-01

70

Fiber optic gas sensor  

NASA Technical Reports Server (NTRS)

A gas sensor includes an in-fiber resonant wavelength device provided in a fiber core at a first location. The fiber propagates a sensing light and a power light. A layer of a material is attached to the fiber at the first location. The material is able to absorb the gas at a temperature dependent gas absorption rate. The power light is used to heat the material and increases the gas absorption rate, thereby increasing sensor performance, especially at low temperatures. Further, a method is described of flash heating the gas sensor to absorb more of the gas, allowing the sensor to cool, thereby locking in the gas content of the sensor material, and taking the difference between the starting and ending resonant wavelengths as an indication of the concentration of the gas in the ambient atmosphere.

Chen, Peng (Inventor); Buric, Michael P. (Inventor); Swinehart, Philip R. (Inventor); Maklad, Mokhtar S. (Inventor)

2010-01-01

71

Characterization of thin MoO3 films formed by RF and DC-magnetron reactive sputtering for gas sensor applications  

NASA Astrophysics Data System (ADS)

The present work discusses a technology for deposition and characterization of thin molybdenum oxide (MoOx, MoO3) films studied for gas sensor applications. The samples were produced by reactive radio-frequency (RF) and direct current (DC) magnetron sputtering. The composition and microstructure of the films were studied by XPS, XRD and Raman spectroscopy, the morphology, using high resolution SEM. The research was focused on the sensing properties of the sputtered thin MoO3 films. Highly sensitive gas sensors were implemented by depositing films of various thicknesses on quartz resonators. Making use of the quartz crystal microbalance (QCM) method, these sensors were capable of detecting changes in the molecular range. Prototype QCM structures with thin MoO3 films were tested for sensitivity to NH3 and NO2. Even in as-deposited state and without heating the substrates, these films showed good sensitivity. Moreover, no additional thermal treatment is necessary, which makes the production of such QCM gas sensors simple and cost-effective, as it is fully compatible with the technology for producing the initial resonator. The films are sensitive at room temperature and can register concentrations as low as 50 ppm. The sorption is fully reversible, the films are stable and capable of long-term measurements.

Yordanov, R.; Boyadjiev, S.; Georgieva, V.; Vergov, L.

2014-05-01

72

Thin film hydrogen sensor  

DOEpatents

A thin film hydrogen sensor includes a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end. 5 figs.

Cheng, Y.T.; Poli, A.A.; Meltser, M.A.

1999-03-23

73

Thin film hydrogen sensor  

DOEpatents

A thin film hydrogen sensor, includes: a substantially flat ceramic substrate with first and second planar sides and a first substrate end opposite a second substrate end; a thin film temperature responsive resistor on the first planar side of the substrate proximate to the first substrate end; a thin film hydrogen responsive metal resistor on the first planar side of the substrate proximate to the fist substrate end and proximate to the temperature responsive resistor; and a heater on the second planar side of the substrate proximate to the first end.

Cheng, Yang-Tse (Rochester Hills, MI); Poli, Andrea A. (Livonia, MI); Meltser, Mark Alexander (Pittsford, NY)

1999-01-01

74

Semiconductor gas sensors based on nanostructured tungsten oxide  

Microsoft Academic Search

Semiconductor gas sensors based on nanocrystallline WO3 films were produced by two different methods. Advanced reactive gas evaporation was used in both cases either for a direct deposition of films (deposited films) or to produce ultra fine WO3 powder which was used for screen printing of thick films. The deposited films sintered at 480 °C and the screen-printed films sintered

J. L Solis; S Saukko; L Kish; C. G Granqvist; V Lantto

2001-01-01

75

Development of Oxide Semiconductor Thick Film Gas Sensor for the Detection of Total Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

After an amendment of Building Standards Law in 2003, the installation of the ventilator is compulsory in the newly built house. Because many persons suffer from indoor-air pollutants caused by the volatile organic compounds (VOCs). The final purpose of this research is to develop the gas sensor which can monitor the gross weight of VOC gases indoors and then to control the ventilator efficiently using the sensor. In order to develop the sensor which detects total VOC, the responses of 4 oxide semiconductor materials to 37 kinds of VOC gases were studied. Those materials showed small responses to halogenated and aliphatic hydrocarbon gases. As a result of improving the response to these gases, among 4 metal oxides examined, SnO2 and WO3 showed high sensitivities by the addition of Pd and Pt. The sensing properties of SnO2 for halogenated hydrocarbon gases were extremely improved by the addition of 0.5wt% Pd. Also, the sensing properties of SnO2 for aliphatic hydrocarbon gases were improved by the addition of 0.7wt% Pt. In addition, the doubly promoted element, Pt(0.5wt%)-Pd(0.5wt%)-SnO2, showed a large response to many kinds of VOC gases examined.

Kadosaki, Masahiro; Sakai, Yuichi; Tamura, Ikuo; Matsubara, Ichiro; Itoh, Toshio

76

Nanoparticle engineering for gas sensor optimisation: improved sol–gel fabricated nanocrystalline SnO 2 thick film gas sensor for NO 2 detection by calcination, catalytic metal introduction and grinding treatments  

Microsoft Academic Search

The control of the technological steps such as calcination temperature and introduction of catalytic additives are accepted to be key points in the obtaining of improved sol–gel fabricated SnO2 thick film gas sensors with different sensitivity to NO2 and CO. In this work, after proving that the undoped material calcined at 1000°C is optimum for NO2 detection, grinding is added

A. Diéguez; A. Romano-Rodr??guez; J. R. Morante; J. Kappler; N. Bârsan; W. Göpel

1999-01-01

77

Microfabricated Formaldehyde Gas Sensors  

PubMed Central

Formaldehyde is a volatile organic compound that is widely used in textiles, paper, wood composites, and household materials. Formaldehyde will continuously outgas from manufactured wood products such as furniture, with adverse health effects resulting from prolonged low-level exposure. New, microfabricated sensors for formaldehyde have been developed to meet the need for portable, low-power gas detection. This paper reviews recent work including silicon microhotplates for metal oxide-based detection, enzyme-based electrochemical sensors, and nanowire-based sensors. This paper also investigates the promise of polymer-based sensors for low-temperature, low-power operation. PMID:22291561

Flueckiger, Jonas; Ko, Frank K.; Cheung, Karen C.

2009-01-01

78

Response characteristics of a potentiometric CO2 gas sensor based on Li3PO4 solid electrolyte using Au film as the electrodes  

NASA Astrophysics Data System (ADS)

A potentiometric CO2 gas sensor based on Li3PO4 film with the thickness of 0.8 ?m prepared by thermal evaporation method was developed. Au thin film with the thickness of 400 nm deposited by sputtering method was used as the metal electrodes of the sensor. Li2CO3 and Li2TiO3 with 10 mol. % TiO2 were used as the sensing and reference electrodes by screen printing the materials on the Au thin film electrodes, respectively. Response characteristics of the sensor to CO2 in the range of 250 ppm to 5000 ppm at different working temperatures were investigated. The electromotive force (EMF) values of the sensor were linearly dependent on logarithm of CO2 partial pressure at the temperatures between 420 °C and 530 °C. Dependence of response and recovery time, initial EMF, ?EMF/dec on working temperature was presented. It can be found that the response time and recovery time reduced with the enhancement of working temperature and gradually reached to the limit when the temperature is above 500 °C. However, the maximum ?EMF/dec value was obtained at the temperature of 440 °C. The dependence of ?EMF/dec on working temperature was newly found and different from previous research. The results suggest potential use of thin film metal electrodes in solid electrolyte gas sensors for lower temperature and miniature applications.

Sun, Guoliang; Wang, Hairong; Li, Peng; Liu, Zhen; Jiang, Zhuangde

2014-03-01

79

Calorimetric gas sensor  

DOEpatents

A combustible gas sensor that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 .mu.m thick.times.10 .mu.m wide.times.100, 250, 500, or 1000 .mu.m-long polycrystalline Si; some are overcoated with a 0.25 .mu.m-thick protective CVD Si.sub.3 N.sub.4 layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac).sub.2 onto microfilaments resistively heated to approximately 500.degree. C.; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300.degree. C. (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H.sub.2 concentrations between 100 ppm and 1% in an 80/20 N.sub.2 /O.sub.2 mixture. Other catalytic materials can also be used.

Ricco, Antonio J. (Albuquerque, NM); Hughes, Robert C. (Cedar Crest, NM); Smith, James H. (Albuquerque, NM); Moreno, Daniel J. (Albuquerque, NM); Manginell, Ronald P. (Albuquerque, NM); Senturia, Stephen D. (Brookline, MA); Huber, Robert J. (Bountiful, UT)

1998-01-01

80

Calorimetric gas sensor  

DOEpatents

A combustible gas sensor is described that uses a resistively heated, noble metal-coated, micromachined polycrystalline Si filament to calorimetrically detect the presence and concentration of combustible gases. The filaments tested to date are 2 {micro}m thick {times} 10{micro}m wide {times} 100, 250, 500, or 1000 {micro}m-long polycrystalline Si; some are overcoated with a 0.25 {micro}m-thick protective CVD Si{sub 3}N{sub 4} layer. A thin catalytic Pt film was deposited by CVD from the precursor Pt(acac){sub 2} onto microfilaments resistively heated to approximately 500 C; Pt deposits only on the hot filament. Using a constant-resistance-mode feedback circuit, Pt-coated filaments operating at ca. 300 C (35 mW input power) respond linearly, in terms of the change in supply current required to maintain constant resistance (temperature), to H{sub 2} concentrations between 100 ppm and 1% in an 80/20 N{sub 2}/O{sub 2} mixture. Other catalytic materials can also be used. 11 figs.

Ricco, A.J.; Hughes, R.C.; Smith, J.H.; Moreno, D.J.; Manginell, R.P.; Senturia, S.D.; Huber, R.J.

1998-11-10

81

Thin film porous membranes for catalytic sensors  

SciTech Connect

This paper reports on new and surprising experimental data for catalytic film gas sensing resistors coated with nanoporous sol-gel films to impart selectivity and durability to the sensor structure. This work is the result of attempts to build selectivity and reactivity to the surface of a sensor by modifying it with a series of sol-gel layers. The initial sol-gel SiO{sub 2} layer applied to the sensor surprisingly showed enhanced O{sub 2} interaction with H{sub 2} and reduced susceptibility to poisons such as H{sub 2}S.

Hughes, R.C.; Boyle, T.J.; Gardner, T.J. [and others

1997-06-01

82

Supramolecular and polymeric structures for gas sensors  

Microsoft Academic Search

Molecular, supramolecular and polymeric compounds are particularly suitable for tailoring chemically sensitive coatings of thin-film gas sensors to monitor volatile organic compounds (VOC's). The molecular recognition occurs either by specific key\\/lock interactions in the first monolayer, or by incorporation in the bulk. The separation of surface reactions from bulk dissolution effects is deduced from the thickness dependence of sensor effects

Wolfgang Göpel

1995-01-01

83

Gas Sensors Based on Electrospun Nanofibers  

PubMed Central

Nanofibers fabricated via electrospinning have specific surface approximately one to two orders of the magnitude larger than flat films, making them excellent candidates for potential applications in sensors. This review is an attempt to give an overview on gas sensors using electrospun nanofibers comprising polyelectrolytes, conducting polymer composites, and semiconductors based on various sensing techniques such as acoustic wave, resistive, photoelectric, and optical techniques. The results of sensing experiments indicate that the nanofiber-based sensors showed much higher sensitivity and quicker responses to target gases, compared with sensors based on flat films. PMID:22573976

Ding, Bin; Wang, Moran; Yu, Jianyong; Sun, Gang

2009-01-01

84

Nanostructured zinc oxide films synthesized by successive chemical solution deposition for gas sensor applications  

E-print Network

synthesis D. Electrical properties A B S T R A C T Nanostructured ZnO thin films have been deposited using ZnO thin films [21,22,26]. The SCSD is a simple and flexible method which offers an easy way to dope be realized [25­27,9]. However, the SCSD synthesis of Al-doped ZnO (AZO) films and effect of post-grown rapid

Kik, Pieter

85

Nanocrystalline Cu-doped ZnO thin film gas sensor for CO  

Microsoft Academic Search

A Cu-doped ZnO (CZO) film was prepared on a glass substrate by co-sputtering using ZnO and Cu targets. The CZO film possessed a columnar structure consisting of small crystals with an average grain size of around 5nm. The CO-sensing properties of the CZO film were tested at operating temperatures of 150, 300, 350 and 400°C. It was found that CZO-based

H. Gong; J. Q. Hu; J. H. Wang; C. H. Ong; F. R. Zhu

2006-01-01

86

Highly sensitive SnO 2 thin film NO 2 gas sensor operating at low temperature  

Microsoft Academic Search

Thin films of pure nano-crystalline SnO2 and WO3-doped SnO2 in different concentrations (3wt.% and 5wt.%) are deposited using sol–gel spin coating technique on glass substrates. The structural and morphological properties of these films are investigated using XRD, TEM and AFM. The sensitivity and selectivity of these films are tested to different reducing and oxidizing gases such as SO2, NH3, NO2

Jaswinder Kaur; Somnath C. Roy; M. C. Bhatnagar

2007-01-01

87

Quartz crystal microbalance coated with sol–gel-derived indium–tin oxide thin films as gas sensor for NO detection  

Microsoft Academic Search

This paper presents the possibilities and properties of indium–tin oxide (ITO)-covered quartz crystal microbalances (QCM) as a NOx toxic gas sensors. The starting sol–gel solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol (0–20% by weight). The ITO thin films were deposited on the gold electrodes of quartz crystals by spin-coating and annealing

J Zhang; J Hu; Z. Q Zhu; H Gong; S. J O’Shea

2004-01-01

88

Preparation and gas-sensing properties of Ce-doped ZnO thin-film sensors by dip-coating  

Microsoft Academic Search

CeO2-doped ZnO thin-film gas sensors with different Ce\\/Zn ratios have been fabricated by dip-coating method, starting from zinc acetate dihydrate, cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and anhydrous ethanol. Each layer was fired at 180°C in a conventional oven for 30min and the final coatings were sintered at 500°C in a muffle furnace for 60min. The microstructure and morphology of the films

Chunqiao Ge; Changsheng Xie; Shuizhou Cai

2007-01-01

89

Thin film micro carbon dioxide sensor using MEMS process  

Microsoft Academic Search

Pt\\/Na+ ion conductive ceramic thin film\\/Pt\\/carbonate (Na2CO3:BaCO3=1:1.7mol) system CO2 micro gas sensor was fabricated and the sensing properties were investigated. The Na+ ion conductive thin film was prepared by RF magnetron sputtering method. The thin film micro carbon dioxide sensor was prepared by using silicon process combined with MEMS technology.A NASICON thin film (2000–2500Å) as main layer of the device

Yeung-Il Bang; Kap-Duk Song; Byung-Su Joo; Jeung-Soo Huh; Soon-Don Choi; Duk-Dong Lee

2004-01-01

90

Polypyrrole Thin Films as Sensors of Volatile Organic Compounds  

Microsoft Academic Search

Thin films of polypyrrole (PPY), doped with different counter-ions and prepared by in situ polymerization on conducting glass electrodes, are used for the development of gas sensors with fast response time. On exposure to a given vapor, each individual film exhibits a fast change of the fractional difference of its electrical resistivity, by adopting a sensor array composed of 4

José E. G. De Souza; Maria Virgínia B. Dos Santos; Francisco L. Dos Santos; Benício B. Neto; Clécio G. Dos Santos; Celso P. De Melo

2002-01-01

91

Gas-Sensing Properties of Doped In 2 O 3 Films as Sensors for NO 2 in Air  

Microsoft Academic Search

A number of sensing systems based on indium oxide doped with various metal oxides (In2O3 · WO3, In2O3 · ZnO, In2O3 · RuO2, In2O3 · Gd2O3, and In2O3 · Sm2O3) in amounts of no more than 3–5 mol % and also Au · In2O3 films were studied as sensors for detecting NO2 in air. The working temperature of sensors was

T. V. Belysheva; L. P. Bogovtseva; E. A. Kazachkov; N. V. Serebryakova

2003-01-01

92

MEMS-based hydrogen gas sensors  

Microsoft Academic Search

The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This paper reports the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a micro-electro-mechanical system (MEMS) structure known as a micro-hotplate. Micro-hotplate structures are fabricated via surface

Frank DiMeo; Ing-Shin Chen; Philip Chen; Jeffrey Neuner; Andreas Roerhl; James Welch

2006-01-01

93

Thin film oxygen partial pressure sensor  

NASA Technical Reports Server (NTRS)

The development is described of a laboratory model oxygen partial pressure sensor using a sputtered zinc oxide thin film. The film is operated at about 400 C through the use of a miniature silicon bar. Because of the unique resistance versus temperature relation of the silicon bar, control of the operational temperature is achieved by controlling the resistance. A circuit for accomplishing this is described. The response of sputtered zinc oxide films of various thicknesses to oxygen, nitrogen, argon, carbon dioxide, and water vapor caused a change in the film resistance. Over a large range, film conductance varied approximately as the square root of the oxygen partial pressure. The presence of water vapor in the gas stream caused a shift in the film conductance at a given oxygen partial pressure. A theoretical model is presented to explain the characteristic features of the zinc oxide response to oxygen.

Wortman, J. J.; Harrison, J. W.; Honbarrier, H. L.; Yen, J.

1972-01-01

94

Room-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide thin-film transistors  

NASA Astrophysics Data System (ADS)

An organic sensing layer is capped onto an amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction with the a-IGZO film. Oxidizing or reducing vapor molecules act like electron acceptors or electron donors to change the potential of the organic layer and the current of a-IGZO TFT. A sensitive and reversible response to 100 ppb ammonia and 100 ppb acetone is obtained at room temperature. This letter opens a route to develop low-cost large-area bio/chemical sensor arrays based on the emerging a-IGZO TFT technology.

Zan, Hsiao-Wen; Li, Chang-Hung; Yeh, Chun-Cheng; Dai, Ming-Zhi; Meng, Hsin-Fei; Tsai, Chuang-Chuang

2011-06-01

95

Tin, Niobium and Vanadium mixed oxide thin films based gas sensors for chemical warfare agent attacks prevention  

Microsoft Academic Search

In this work we have studied the synthesis and characterization SnO2 thin films with varying Nb and V content for Sarin detection. As target molecule we used dimethyl methylphosphonate (DMMP), a Sarin nerve agent simulant. Nb and V oxides have been used because of their well-known catalytic properties. Results highlight that the proposed approach is suitable to develop sensors of

A. Ponzoni; E. Comini; G. Sberveglieri; I. Alessandri; E. Bontempi; L. E. Depero

2007-01-01

96

Characterization of metal-modified and vertically-aligned carbon nanotube films for functionally enhanced gas sensor applications  

Microsoft Academic Search

Carbon nanotube (CNT) networked films have been grown by radiofrequency plasma enhanced chemical vapour deposition (RF–PECVD) technology onto low-cost alumina substrates, coated by nanosized Fe-catalyst for growing CNTs, to perform chemical detection of hazardous gases, at an operating sensor temperature in the range 25–150 °C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM),

M. Penza; R. Rossi; M. Alvisi; M. A. Signore; G. Cassano; D. Dimaio; R. Pentassuglia; E. Piscopiello; E. Serra; M. Falconieri

2009-01-01

97

Thin-film Sensors for Space Propulsion Technology  

NASA Technical Reports Server (NTRS)

SSME components such as the turbine blades of the high pressure fuel turbopump are subjected to rapid and extreme thermal transients that contribute to blade cracking and subsequent failure. The objective was to develop thin film sensors for SSME components. The technology established for aircraft gas turbine engines was adopted to the materials and environment encountered in the SSME. Specific goals are to expand the existing thin film sensor technology, to continue developing improved sensor processing techniques, and to test the durability of aircraft gas turbine engine technology in the SSME environment. A thin film sensor laboratory is being installed in a refurbished clean room, and new sputtering and photoresist exposure equipment is being acquired. Existing thin film thermocouple technology in an SSME environment are being tested. Various coatings and their insulating films are being investigated for use in sensor development.

Kim, W. S.; Englund, D. R.

1985-01-01

98

The effects of the particle size and crystallite size on the response time for resistive oxygen gas sensor using cerium oxide thick film  

Microsoft Academic Search

Resistive oxygen sensors based on porous thick CeO2 film (obtained by firing powder of various particle sizes made by mist pyrolysis at different temperatures), were fabricated and their response time was measured. The response times for the oxygen sensors were unaffected by particle size of thick film but clearly depended on its firing temperature. The response time for the sensor

Noriya Izu; Woosuck Shin; Ichiro Matsubara; Norimitsu Murayama

2003-01-01

99

Properties and sensor performance of zinc oxide thin films  

E-print Network

Reactively sputtered ZnO thin film gas sensors were fabricated onto Si wafers. The atmosphere dependent electrical response of the ZnO micro arrays was examined. The effects of processing conditions on the properties and ...

Min, Yongki, 1965-

2003-01-01

100

Improvement of H2S sensing properties of SnO2-based thick film gas sensors promoted with MoO3 and NiO.  

PubMed

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (<1 ppm). SnO2 sensors and SnO2-based thick-film gas sensors promoted with NiO, ZnO, MoO3, CuO or Fe2O3 were prepared, and their sensing properties were examined in a flow system. The SnO2 materials were prepared by calcining SnO2 at 600, 800, 1,000 and 1,200 °C to give materials identified as SnO2(600), SnO2(800), SnO2(1000), and SnO2(1200), respectively. The Sn(12)Mo5Ni3 sensor, which was prepared by physically mixing 5 wt% MoO3 (Mo5), 3 wt% NiO (Ni3) and SnO2(1200) with a large pore size of 312 nm, exhibited a high sensor response of approximately 75% for the detection of 1 ppm H2S at 350 °C with excellent recovery properties. Unlike the SnO2 sensors, its response was maintained during multiple cycles without deactivation. This was attributed to the promoter effect of MoO3. In particular, the Sn(12)Mo5Ni3 sensor developed in this study showed twice the response of the Sn(6)Mo5Ni3 sensor, which was prepared by SnO2(600) with the smaller pore size than SnO2(1200). The excellent sensor response and recovery properties of Sn(12)Mo5Ni3 are believed to be due to the combined promoter effects of MoO3 and NiO and the diffusion effect of H2S as a result of the large pore size of SnO2. PMID:23519347

Lee, Soo Chool; Kim, Seong Yeol; Hwang, Byung Wook; Jung, Suk Yong; Ragupathy, Dhanusuraman; Son, In Sung; Lee, Duk Dong; Kim, Jae Chang

2013-01-01

101

Improvement of H2S Sensing Properties of SnO2-Based Thick Film Gas Sensors Promoted with MoO3 and NiO  

PubMed Central

The effects of the SnO2 pore size and metal oxide promoters on the sensing properties of SnO2-based thick film gas sensors were investigated to improve the detection of very low H2S concentrations (<1 ppm). SnO2 sensors and SnO2-based thick-film gas sensors promoted with NiO, ZnO, MoO3, CuO or Fe2O3 were prepared, and their sensing properties were examined in a flow system. The SnO2 materials were prepared by calcining SnO2 at 600, 800, 1,000 and 1,200 °C to give materials identified as SnO2(600), SnO2(800), SnO2(1000), and SnO2(1200), respectively. The Sn(12)Mo5Ni3 sensor, which was prepared by physically mixing 5 wt% MoO3 (Mo5), 3 wt% NiO (Ni3) and SnO2(1200) with a large pore size of 312 nm, exhibited a high sensor response of approximately 75% for the detection of 1 ppm H2S at 350 °C with excellent recovery properties. Unlike the SnO2 sensors, its response was maintained during multiple cycles without deactivation. This was attributed to the promoter effect of MoO3. In particular, the Sn(12)Mo5Ni3 sensor developed in this study showed twice the response of the Sn(6)Mo5Ni3 sensor, which was prepared by SnO2(600) with the smaller pore size than SnO2(1200). The excellent sensor response and recovery properties of Sn(12)Mo5Ni3 are believed to be due to the combined promoter effects of MoO3 and NiO and the diffusion effect of H2S as a result of the large pore size of SnO2. PMID:23519347

Lee, Soo Chool; Kim, Seong Yeol; Hwang, Byung Wook; Jung, Suk Yong; Ragupathy, Dhanusuraman; Son, In Sung; Lee, Duk Dong; Kim, Jae Chang

2013-01-01

102

The effect of the addition of carbon black and the increase in film thickness on the sensing layers of ZnO / ZnFe 2O 4 in polymer thick film gas sensors  

NASA Astrophysics Data System (ADS)

The aim of this work is to investigate the effect of increasing the carbon black and the sensing layer thickness on the response of a sensor. Three sensors of 60/40 mol% ZnO/Fe 2O 3 with different percentages of carbon black (1.5, 2 and 2.5 wt%) were fabricated on alumina substrates and copper thin film electrodes. The base resistance of the 1.5 wt% carbon black sensor was 4 M? while for the 2 wt% carbon black sensors it was 25.50 k?. The lowest base resistance was recorded with the 2.5 wt% carbon black sensor to be 8.2 k?. The sensors were used to detect propanol in the concentration range 2500-5000 ppm, increasing with a step size of 500 ppm, at room temperature. The responses of the sensors were determined as ((R gas-R air)/R air)×100 while the sensitivity was calculated as the slope of the graphs. The sensitivity was increased as the amount of carbon black decreased. The sensitivities of the sensors to propanol at room temperature were 0.0105, 0.005 and 0.002%/ppm for the three sensors. On the other hand, four sensors have different thickness were fabricated used by the same manner. It was found that the response of the sensor increased relatively as the thicknesses of the sensing layer decreased. Results show that the one-layer sensor has the highest response, followed by a decrease in the responses for sensors with higher numbers of layers, 2, 3, 4 and 5 successively.

Arshak, K.; Gaidan, Ibrahim; Moore, E. G.; Cunniffe, C.

2007-07-01

103

TiO2 Based Nanocrystalline Thin Film Gas Sensors Prepared by Ion-assisted Electron beam Evaporation  

Microsoft Academic Search

In this work, we develop TiO2 based nanocrystalline thin films prepared by ion-assisted e-beam evaporation process. N-type and p-type TiO2 gas-sensing layers have been deposited by doping with various metal oxide materials including WO3, MoO3, and NiOx. Structural and morphological characterization by means of AFM, SEM, and XRD reveal the thin film is nanocrystalline structure with fine grain of 10-30

A. Wisitsoraat; E. Comini; G. Sberveglieri; W. Wlodarski; A. Tuantranont

2007-01-01

104

Thin Film Sensors for Surface Measurements  

NASA Technical Reports Server (NTRS)

Advanced thin film sensors that can provide accurate surface temperature, strain, and heat flux measurements have been developed at NASA Glenn Research Center. These sensors provide minimally intrusive characterization of advanced propulsion materials and components in hostile, high-temperature environments as well as validation of propulsion system design codes. The sensors are designed for applications on different material systems and engine components for testing in engine simulation facilities. Thin film thermocouples and strain gauges for the measurement of surface temperature and strain have been demonstrated on metals, ceramics and advanced ceramic-based composites of various component configurations. Test environments have included both air-breathing and space propulsion-based engine and burner rig environments at surface temperatures up to 1100 C and under high gas flow and pressure conditions. The technologies developed for these sensors as well as for a thin film heat flux gauge have been integrated into a single multifunctional gauge for the simultaneous real-time measurement of surface temperature, strain, and heat flux. This is the first step toward the development of smart sensors with integrated signal conditioning and high temperature electronics that would have the capability to provide feedback to the operating system in real-time. A description of the fabrication process for the thin film sensors and multifunctional gauge will be provided. In addition, the material systems on which the sensors have been demonstrated, the test facilities and the results of the tests to-date will be described. Finally, the results will be provided of the current effort to demonstrate the capabilities of the multifunctional gauge.

Martin, Lisa C.; Wrbanek, John D.; Fralick, Gustave C.

2001-01-01

105

Bimodular high temperature planar oxygen gas sensor.  

PubMed

A bimodular planar O2 sensor was fabricated using NiO nanoparticles (NPs) thin film coated yttria-stabilized zirconia (YSZ) substrate. The thin film was prepared by radio frequency (r.f.) magnetron sputtering of NiO on YSZ substrate, followed by high temperature sintering. The surface morphology of NiO NPs film was characterized by atomic force microscope (AFM) and scanning electron microscope (SEM). X-ray diffraction (XRD) patterns of NiO NPs thin film before and after high temperature O2 sensing demonstrated that the sensing material possesses a good chemical and structure stability. The oxygen detection experiments were performed at 500, 600, and 800°C using the as-prepared bimodular O2 sensor under both potentiometric and resistance modules. For the potentiometric module, a linear relationship between electromotive force (EMF) output of the sensor and the logarithm of O2 concentration was observed at each operating temperature, following the Nernst law. For the resistance module, the logarithm of electrical conductivity was proportional to the logarithm of oxygen concentration at each operating temperature, in good agreement with literature report. In addition, this bimodular sensor shows sensitive, reproducible and reversible response to oxygen under both sensing modules. Integration of two sensing modules into one sensor could greatly enrich the information output and would open a new venue in the development of high temperature gas sensors. PMID:25191652

Sun, Xiangcheng; Liu, Yixin; Gao, Haiyong; Gao, Pu-Xian; Lei, Yu

2014-01-01

106

Multiwall carbon nanotube gas sensor fabricated using thermomechanical structure  

Microsoft Academic Search

We address a multiwall carbon nanotube (MWCNT) gas sensor that has an enhanced reproducibility. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and an MWCNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature changes to modify the rates for desorption of gases on the sensing surface during sensor operation.

Woo-Sung Cho; Seung-Il Moon; Yang-Doo Lee; Yun-Hi Lee; Jung-Ho Park; Byeong Kwon Ju

2005-01-01

107

WO 3 and W?Ti?O thin-film gas sensors prepared by sol–gel dip-coating  

Microsoft Academic Search

The WO3 and W?Ti?O thin-films were prepared by sol–gel dip-coating on alumina substrate using tungsten chloride, 2,4-pentanedione (PTN), ethanol and water as sources and calcined at 400°C. The structure was characterized by XRD, Raman, SEM and TEM analyses. The effect of titanium doping on the structure was then discussed and related to the gas sensing properties. The results show that

J. Shieh; H. M. Feng; M. H. Hon; H. Y. Juang

2002-01-01

108

ZnO Thin Film Ga s Sensor for CO  

NASA Astrophysics Data System (ADS)

ZnO thin films were deposited onto corning glass substrates by rf magnetron sputtering system using ZnO targets. Films were deposited under rf power of 80 W at various deposition time. The distance between the target and substrate was held at 45 cm. A mixed Ar and O2 gas was introduced into the chamber at 4×10-2 Torr. The structure of the deposited ZnO films was investigated by Scanning electron miscroscopy. The gas sensing properties were evaluated at various operation temperatures by measuring the changes of resistance of the sensor in air and in CO gas respectively using the gas sensing characterization system. The grain size was increased as the film thickness was increased during deposition. The sensor with 233 nm film thickness exhibited the highest sensitivity for CO gas.

Manap, Y. A.; Ismail, B.; Yusuf, M. N. M.; Shamsuri, W. N. W.; Wahab, Y.; Othaman, Z.

2010-03-01

109

ZnO Thin Film Ga s Sensor for CO  

SciTech Connect

ZnO thin films were deposited onto corning glass substrates by rf magnetron sputtering system using ZnO targets. Films were deposited under rf power of 80 W at various deposition time. The distance between the target and substrate was held at 45 cm. A mixed Ar and O{sub 2} gas was introduced into the chamber at 4x10{sup -2} Torr. The structure of the deposited ZnO films was investigated by Scanning electron miscroscopy. The gas sensing properties were evaluated at various operation temperatures by measuring the changes of resistance of the sensor in air and in CO gas respectively using the gas sensing characterization system. The grain size was increased as the film thickness was increased during deposition. The sensor with 233 nm film thickness exhibited the highest sensitivity for CO gas.

Manap, Y. A.; Ismail, B.; Yusuf, M. N. M.; Shamsuri, W. N. W.; Wahab, Y.; Othaman, Z. [Department of Physics, Faculty of Science, University of Technology Malaysia, Skudai, Johor (Malaysia)

2010-03-11

110

A Rapid Process for Fabricating Gas Sensors  

PubMed Central

Zinc oxide (ZnO) is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for “green” usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD) was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (?R/R) of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost. PMID:25010696

Hsiao, Chun-Ching; Luo, Li-Siang

2014-01-01

111

New Gas Polarographic Hydrogen Sensor  

NASA Technical Reports Server (NTRS)

Polarography is the measurement of the current that flows in solution as a function of an applied voltage. The actual form of the observed polarographic current depends upon the manner in which the voltage is applied and on the characteristics of the working electrode. The new gas polarographic H2 sensor shows a current level increment with concentration of the gaseous H2 similar to those relating to metal ions in liquid electrolytes in well-known polarography. This phenomenon is caused by the fact that the diffusion of the gaseous H2 through a gas diffusion hole built in the sensor is a rate-determining step in the gaseous-hydrogen sensing mechanism. The diffusion hole artificially limits the diffusion of the gaseous H2 toward the electrode located at the sensor cavity. This gas polarographic H2 sensor. is actually an electrochemical-pumping cell since the gaseous H2 is in fact pumped via the electrochemical driving force generated between the electrodes. Gaseous H2 enters the diffusion hole and reaches the first electrode (anode) located in the sensor cavity to be transformed into an H+ ions or protons; H+ ions pass through the electrolyte and reach the second electrode (cathode) to be reformed to gaseous H2. Gas polarographic 02 sensors are commercially available; a gas polarographic 02 sensor was used to prove the feasibility of building a new gas polarographic H2 sensor.

Dominguez, Jesus A.; Barile, Ron

2004-01-01

112

Binary MEMS gas sensors  

NASA Astrophysics Data System (ADS)

A novel sensing mechanism for electrostatic MEMS that employs static bifurcation-based sensing and binary detection is demonstrated. It is implemented as an ethanol vapour sensor that exploits the static pull-in bifurcation. Sensor detection of 5 ppm of ethanol vapour in dry nitrogen, equivalent to a detectable mass of 165 pg, is experimentally demonstrated. Sensor robustness to external disturbances is also demonstrated. A closed-form expression for the sensitivity of statically detected electrostatic MEMS sensors is derived. It is shown that the sensitivity of static bifurcation-based binary electrostatic MEMS sensors represents an upper bound on the sensitivity of static detection for given sensor dimensions and material properties.

Khater, M. E.; Al-Ghamdi, M.; Park, S.; Stewart, K. M. E.; Abdel-Rahman, E. M.; Penlidis, A.; Nayfeh, A. H.; Abdel-Aziz, A. K. S.; Basha, M.

2014-06-01

113

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H(2) Gas Sensor.  

PubMed

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2-2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5-20 nm wide and 20-40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al(2)O(3) substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H(2)) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H(2) sensitivity of ?164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature. PMID:22399971

Tamaekong, Nittaya; Liewhiran, Chaikarn; Wisitsoraat, Anurat; Phanichphant, Sukon

2009-01-01

114

Sensing Characteristics of Flame-Spray-Made Pt/ZnO Thick Films as H2 Gas Sensor  

PubMed Central

Hydrogen sensing of thick films of nanoparticles of pristine, 0.2, 1.0 and 2.0 atomic percentage of Pt concentration doped ZnO were investigated. ZnO nanoparticles doped with 0.2–2.0 at.% Pt were successfully produced in a single step by flame spray pyrolysis (FSP) technique using zinc naphthenate and platinum(II) acetylacetonate as precursors dissolved in xylene. The particle properties were analyzed by XRD, BET, SEM and TEM. Under the 5/5 (precursor/oxygen) flame condition, ZnO nanoparticles and nanorods were observed. The crystallite sizes of ZnO spheroidal and hexagonal particles were found to be ranging from 5 to 20 nm while ZnO nanorods were seen to be 5–20 nm wide and 20–40 nm long. ZnO nanoparticles paste composed of ethyl cellulose and terpineol as binder and solvent respectively was coated on Al2O3 substrate interdigitated with gold electrodes to form thin films by spin coating technique. The thin film morphology was analyzed by SEM technique. The gas sensing properties toward hydrogen (H2) was found that the 0.2 at.% Pt/ZnO sensing film showed an optimum H2 sensitivity of ?164 at hydrogen concentration in air of 1 volume% at 300 °C and a low hydrogen detection limit of 50 ppm at 300 °C operating temperature. PMID:22399971

Tamaekong, Nittaya; Liewhiran, Chaikarn; Wisitsoraat, Anurat; Phanichphant, Sukon

2009-01-01

115

Investigation of a p-CuO/n-ZnO thin film heterojunction for H2 gas-sensor applications  

NASA Astrophysics Data System (ADS)

A p-CuO/n-ZnO thin film heterojunction is fabricated on a glass substrate by the sol-gel technique. The crystallinity of the junction materials and microstructure of the top p-layer are examined by an x-ray diffractometer (XRD) and scanning electron microscope (SEM). The current-voltage (I-V) characteristics of the p-n heterojunction and its temperature dependence have been investigated in air and H2 ambient. Although the junction possesses linear I-V characteristics from room temperature (RT) to 150 °C in air, at higher temperatures (200 °C to 300 °C), it shows nonlinear rectifying behaviour. The forward current is greatly increased with increasing temperature while the reverse current is increased slightly resulting in a IF/IR ratio as high as 485. The ideality factor (n) is 4.88 at a temperature of 300 °C. The forward current is highly increased by the introduction of H2 gas at 300 °C. However, a simultaneous increase in the reverse current makes the IF/IR ratio 8.4. It is observed that H2 sensitivity of the heterojunction is increased with the increase in temperature as well as the thickness of CuO film. A sensitivity value as high as 266.5 is observed at 300 °C when biased at 3 V in the presence of approximately 3000 ppm of H2.

Mridha, S.; Basak, D.

2006-07-01

116

Solid State Gas Sensor Research in Germany - a Status Report  

PubMed Central

This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor. PMID:22408529

Moos, Ralf; Sahner, Kathy; Fleischer, Maximilian; Guth, Ulrich; Barsan, Nicolae; Weimar, Udo

2009-01-01

117

Integrated Mirco-Machined Hydrogen Gas Sensors  

SciTech Connect

The widespread use of hydrogen as both an industrial process gas and an energy storage medium requires fast, selective detection of hydrogen gas. This report discusses the development of a new type of solid-state hydrogen gas sensor that couples novel metal hydride thin films with a MEMS (Micro-Electro-Mechanical System) structure known as a micro-hotplate. In this project, Micro-hotplate structures were overcoated with engineered multilayers that serve as the active hydrogen-sensing layer. The change in electrical resistance of these layers when exposed to hydrogen gas was the measured sensor output. This project focused on achieving the following objectives: (1) Demonstrating the capabilities of micro-machined H2 sensors; (2) Developing an understanding of their performance; (3) Critically evaluating the utility and viability of this technology for life safety and process monitoring applications. In order to efficiently achieve these objectives, the following four tasks were identified: (1) Sensor Design and Fabrication; (2) Short Term Response Testing; (3) Long Term Behavior Investigation; (4) Systems Development. Key findings in the project include: The demonstration of sub-second response times to hydrogen; measured sensitivity to hydrogen concentrations below 200 ppm; a dramatic improvement in the sensor fabrication process and increased understanding of the processing properties and performance relationships of the devices; the development of improved sensing multilayers; and the discovery of a novel strain based hydrogen detection mechanism. The results of this program suggest that this hydrogen sensor technology has exceptional potential to meet the stringent demands of life safety applications as hydrogen utilization and infrastructure becomes more prevalent.

Frank DiMeoJr. Ing--shin Chen

2005-12-15

118

Multifunctional Nanowire/film Composites based Bi-modular Sensors for In-situ and Real-time High Temperature Gas Detection  

SciTech Connect

This final report to the Department of Energy/National Energy Technology Laboratory for DE-FE0000870 covers the period from 2009 to June, 2013 and summarizes the main research accomplishments, which can be divided in sensing materials innovation, bimodular sensor demonstration, and new understanding and discoveries. As a matter of fact, we have successfully completed all the project tasks in June 1, 2013, and presented the final project review presentation on the 9th of July, 2013. Specifically, the major accomplishments achieved in this project include: 1) Successful development of a new class of high temperature stable gas sensor nanomaterials based on composite nano-array strategy in a 3D or 2D fashion using metal oxides and perovskite nanostructures. 2) Successful demonstration of bimodular nanosensors using 2D nanofibrous film and 3D composite nanowire arrays using electrical resistance mode and electrochemical electromotive force mode. 3) Series of new discoveries and understandings based on the new composite nanostructure platform toward enhancing nanosensor performance in terms of stability, selectivity, sensitivity and mass flux sensing. In this report, we highlight some results toward these accomplishments.

Gao, Pu-Xian; Lei, Yu

2013-06-01

119

Thin film deposition and characterization of pure and iron-doped electron-beam evaporated tungsten oxide for gas sensors  

Microsoft Academic Search

Pure tungsten oxide (WO3) and iron-doped (10at.%) tungsten oxide (WO3:Fe) nanostructured thin films were prepared using a dual crucible Electron Beam Evaporation (EBE) technique. The films were deposited at room temperature under high vacuum onto glass as well as alumina substrates and post-heat treated at 300°C for 1h. Using Raman spectroscopy the as-deposited WO3 and WO3:Fe films were found to

Tuquabo Tesfamichael; Masashi Arita; Thor Bostrom; John Bell

2010-01-01

120

Ethanol, acetone and ammonia gas room temperature operated sensor  

NASA Astrophysics Data System (ADS)

CuO nanocrystalline thick films were fabricated from powder synthesized by a sol-gel auto combustion route at different pH value of the precursor solution. The gas sensing response of thick film samples towards ethanol, acetone and ammonia gases has been tested and response has been found to be higher for ammonia gas. The sensor recovers its original state after ammonia exposure.

Singh, Iqbal; Bedi, R. K.

2013-06-01

121

Thin Hot-Film Sensors On Polyimide Film  

NASA Technical Reports Server (NTRS)

Array of closely spaced hot-film sensors with thickness well below critical reference height with regard to air-flow pattern nonintrusively detect laminar boundary-layer transitions with very high resolution. Method developed at NASA Langley Research Center to fabricate such sensors on polyimide films to detect boundary-layer transitions with resolution as high as 0.050 in. These films formed by combination of vacuum deposition and photolithography.

Hopson, Purnell

1993-01-01

122

Thin film porous membranes based on sol-gel chemistry for catalytic sensors  

Microsoft Academic Search

Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel

R. C. Hughes; S. V. Patel; M. W. Jenkins; T. J. Boyle; T. J. Gardner; C. J. Brinker

1998-01-01

123

Influence of microstructure of tungsten oxide thin films on their general performance as ozone and NOx gas sensors  

Microsoft Academic Search

Tungsten oxides thin films were obtained by electron beam deposition and annealed in the temperature range 350-800°C for 1-3 h. The structure, morphology and phase composition of the as-deposited and annealed films were characterized by X-ray diffraction and AFM. The electrical response towards NO2 and O3 was studied both experimentally and theoretically. In order to interprete the kinetic characteristics of

Olena Berger; Thomas Hoffmann; Wolf-Joachim Fischer; Valeri Melev

2003-01-01

124

Thickness dependence of sensor response for CO gas sensing by tin oxide films grown using atomic layer deposition  

Microsoft Academic Search

Ultrathin tin oxide films were deposited on flat hotplate templates using atomic layer deposition (ALD) techniques with SnCl4 and H2O2 as the reactants. The resistance of the SnOx ALD films across an electrode gap on the hotplate template was observed to oscillate and decrease versus the number of sequential SnCl4 and H2O2 reactions at 250°C. The resistance also varied with

X. Du; S. M. George

2008-01-01

125

Combustion Sensors: Gas Turbine Applications  

NASA Technical Reports Server (NTRS)

This report documents efforts to survey the current research directions in sensor technology for gas turbine systems. The work is driven by the current and future requirements on system performance and optimization. Accurate real time measurements of velocities, pressure, temperatures, and species concentrations will be required for objectives such as combustion instability attenuation, pollutant reduction, engine health management, exhaust profile control via active control, etc. Changing combustor conditions - engine aging, flow path slagging, or rapid maneuvering - will require adaptive responses; the effectiveness of such will be only as good as the dynamic information available for processing. All of these issues point toward the importance of continued sensor development. For adequate control of the combustion process, sensor data must include information about the above mentioned quantities along with equivalence ratios and radical concentrations, and also include both temporal and spatial velocity resolution. Ultimately these devices must transfer from the laboratory to field installations, and thus must become low weight and cost, reliable and maintainable. A primary conclusion from this study is that the optics-based sensor science will be the primary diagnostic in future gas turbine technologies.

Human, Mel

2002-01-01

126

Pd conductor for thick film hydrogen sensor  

SciTech Connect

Cooperation between a materials developer and sensor designers has resulted in a palladium conductor used ro design and build a new hydrogen sensor that has superior performance characteristics and is also inexpensive to manufacture. Material characteristics give it faster response time and greater thermal/mechanical stability. The thick film palladium conductor paste, which can be fired at 850{degrees}C-950{degrees}C, has provided device designers a practical conductor paste with which to produce the improved sensor. The conductor uses a high surface area Pd powder combined with a binder glass that is chemically very inert, which combination produces a porous conductor that has good adhesion and chemical resistance. The current sensor design consists of three or four thick film Layers. Because of the flexibility of thick film techniques, the sensor element can be configured to any desired size and shape for specific instrument needs.

Felten, J.J. [DuPont Electronics, Research Triangle Park, NC (United States); Hoffheins, B.S.; Lauf, R.J. [Oak Ridge National Lab., TN (United States)

1996-12-31

127

Multilayer Thin Film Sensors for Damage Diagnostics  

NASA Astrophysics Data System (ADS)

The new innovative approach to damage diagnostics within the production and maintenance/servicing procedures in industry is proposed. It is based on the real-time multiscale monitoring of the smart-designed multilayer thin film sensors of fatigue damage with the standard electrical input/output interfaces which can be connected to the embedded and on-board computers. The multilayer thin film sensors supply information about the actual unpredictable deformation damage, actual fatigue life, strain localization places, damage spreading, etc.

Protasov, A. G.; Gordienko, Y. G.; Zasimchuk, E. E.

2006-03-01

128

Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures  

PubMed Central

Recently, the hydrogen gas sensing properties of semiconductor oxide (SMO) nanostructures have been widely investigated. In this article, we provide a comprehensive review of the research progress in the last five years concerning hydrogen gas sensors based on SMO thin film and one-dimensional (1D) nanostructures. The hydrogen sensing mechanism of SMO nanostructures and some critical issues are discussed. Doping, noble metal-decoration, heterojunctions and size reduction have been investigated and proved to be effective methods for improving the sensing performance of SMO thin films and 1D nanostructures. The effect on the hydrogen response of SMO thin films and 1D nanostructures of grain boundary and crystal orientation, as well as the sensor architecture, including electrode size and nanojunctions have also been studied. Finally, we also discuss some challenges for the future applications of SMO nanostructured hydrogen sensors. PMID:22778599

Gu, Haoshuang; Wang, Zhao; Hu, Yongming

2012-01-01

129

Development of a hydrogen gas sensor using microfabrication technology  

NASA Technical Reports Server (NTRS)

Microfabrication and micromachining technologies are used to produce a hydrogen gas sensor based on a palladium-silver film. The sensor uses a heater that is fabricated by diffusing p-type borones into the substrate, forming a resistance heater. A diode for temperature measurement is produced using p-type boron and n-type phosphor diffused into the substrate. A thickness of the palladium-silver film is approximately 300 arcsec. The hydrogen gas sensor employs the proven palladium-silver diode structure and is surrounded by a phosphor doped resistance heater which can be heated up to a temperature of 250 C. Experimental results show that the sensor is capable of operating over a wide range of hydrogen concentration levels between 0-95 percent without any hysteresis effects.

Liu, Chung-Chiun; Wu, Qinghai; Stuczynski, Matthew; Madzsar, George C.

1992-01-01

130

Micro-sensor thin-film anemometer  

NASA Technical Reports Server (NTRS)

A device for measuring turbulence in high-speed flows is provided which includes a micro-sensor thin-film probe. The probe is formed from a single crystal of aluminum oxide having a 14.degree. half-wedge shaped portion. The tip of the half-wedge is rounded and has a thin-film sensor attached along the stagnation line. The bottom surface of the half-wedge is tilted upward to relieve shock induced disturbances created by the curved tip of the half-wedge. The sensor is applied using a microphotolithography technique.

Sheplak, Mark (Inventor); McGinley, Catherine B. (Inventor); Spina, Eric F. (Inventor); Stephens, Ralph M. (Inventor); Hopson, Jr., Purnell (Inventor); Cruz, Vincent B. (Inventor)

1996-01-01

131

Numerical analysis of response time for resistive oxygen gas sensors  

Microsoft Academic Search

The response time (t90) for resistive-type oxygen gas sensors based on thick films formed with cerium oxide (CeO2??) powder can be calculated as a function of the diffusion coefficient (DV), surface reaction coefficient (kV) and particle size (R). In the case of large particle size the kinetics of the sensors were controlled by diffusion, while in the case of small

Noriya Izu; Woosuck Shin; Norimitsu Murayama

2002-01-01

132

Micromachined polymer-based chemical gas sensor array  

Microsoft Academic Search

We have developed a miniature polymer-based chemical gas sensor array on silicon using micromachining technology. The sensors are polymer–carbon black composite films, which swell reversibly and cause a resistance change upon exposure to a wide variety of gases. We have fabricated two types of devices which can measure this resistance change using a “well” design. These “wells” contain the polymer–carbon

Frank Zee; Jack W. Judy

2001-01-01

133

Enhanced Sensing Characteristics in MEMS-based Formaldehyde Gas Sensor  

E-print Network

This study has successfully demonstrated a novel self-heating formaldehyde gas sensor based on a thin film of NiO sensing layer. A new fabrication process has been developed in which the Pt micro heater and electrodes are deposited directly on the substrate and the NiO thin film is deposited above on the micro heater to serve as sensing layer. Pt electrodes are formed below the sensing layer to measure the electrical conductivity changes caused by formaldehyde oxidation at the oxide surface. Furthermore, the upper sensing layer and NiO/Al2O3 co-sputtering significantly increases the sensitivity of the gas sensor, improves its detection limit capability. The microfabricated formaldehyde gas sensor presented in this study is suitable not only for industrial process monitoring, but also for the detection of formaldehyde concentrations in buildings in order to safeguard human health.

Wang, Yu-Hsiang; Lee, Chia-Yen; Ma, R -H; Chou, Po-Cheng

2008-01-01

134

Fast response of resistive-type oxygen gas sensors based on nano-sized ceria powder  

Microsoft Academic Search

The oxygen gas sensors based on cerium oxide porous thick film with the average particle size of 100nm were fabricated by screen-printing method on alumina substrate using the powder of 100nm prepared by mist pyrolysis. The sensor’s response to the oxygen partial pressure drop from 105 to 103Pa was compared with that of the sensors using films of larger particle

Noriya Izu; Woosuck Shin; Norimitsu Murayama

2003-01-01

135

Electrostatic thin film chemical and biological sensor  

DOEpatents

A chemical and biological agent sensor includes an electrostatic thin film supported by a substrate. The film includes an electrostatic charged surface to attract predetermined biological and chemical agents of interest. A charge collector associated with said electrostatic thin film collects charge associated with surface defects in the electrostatic film induced by the predetermined biological and chemical agents of interest. A preferred sensing system includes a charge based deep level transient spectroscopy system to read out charges from the film and match responses to data sets regarding the agents of interest. A method for sensing biological and chemical agents includes providing a thin sensing film having a predetermined electrostatic charge. The film is exposed to an environment suspected of containing the biological and chemical agents. Quantum surface effects on the film are measured. Biological and/or chemical agents can be detected, identified and quantified based on the measured quantum surface effects.

Prelas, Mark A. (Columbia, MO); Ghosh, Tushar K. (Columbia, MO); Tompson, Jr., Robert V. (Columbia, MO); Viswanath, Dabir (Columbia, MO); Loyalka, Sudarshan K. (Columbia, MO)

2010-01-19

136

Study of VHF-band QCM gas sensor  

Microsoft Academic Search

A VHF-band quartz crystal microbalance (QCM) gas sensor made up of a resonator with its thin quartz plate and a sensing film was studied to raise its sensitivity. The fundamental mode was used instead of the harmonic mode because of its high sensitivity. The sample flow system using a diffusion method was constructed and the experiment on the vapor exposure

T. Nakamoto; Y. Suzuki; T. Moriizumi

2002-01-01

137

Thin-film fiber optic hydrogen and temperature sensor system  

DOEpatents

The invention discloses a sensor probe device for monitoring of hydrogen gas concentrations and temperatures by the same sensor probe. The sensor probe is constructed using thin-film deposition methods for the placement of a multitude of layers of materials sensitive to hydrogen concentrations and temperature on the end of a light transparent lens located within the sensor probe. The end of the lens within the sensor probe contains a lens containing a layer of hydrogen permeable material which excludes other reactive gases, a layer of reflective metal material that forms a metal hydride upon absorbing hydrogen, and a layer of semi-conducting solid that is transparent above a temperature dependent minimum wavelength for temperature detection. The three layers of materials are located at the distal end of the lens located within the sensor probe. The lens focuses light generated by broad-band light generator and connected by fiber-optics to the sensor probe, onto a reflective metal material layer, which passes through the semi-conducting solid layer, onto two optical fibers located at the base of the sensor probe. The reflected light is transmitted over fiberoptic cables to a spectrometer and system controller. The absence of electrical signals and electrical wires in the sensor probe provides for an elimination of the potential for spark sources when monitoring in hydrogen rich environments, and provides a sensor free from electrical interferences.

Nave, Stanley E. (Evans, GA)

1998-01-01

138

Zinc oxide thin film acoustic sensor  

SciTech Connect

This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah [Department of Physics , College of Science, Al-Mustansiriyah University, Baghdad (Iraq); Mansour, Hazim Louis [Department of Physics , College of Education, Al-Mustansiriyah University, Baghdad (Iraq)

2013-12-16

139

Zinc oxide thin film acoustic sensor  

NASA Astrophysics Data System (ADS)

This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Mansour, Hazim Louis; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah

2013-12-01

140

Sensors and Actuators B 49 (1998) 258267 Pd/PVDF thin film hydrogen sensor based on  

E-print Network

Sensors and Actuators B 49 (1998) 258­267 Pd/PVDF thin film hydrogen sensor based on laser thin film coated on a polymeric membrane, optical reflectance and transmittance signals are generated polyvinilydene fluoride (PVDF) thin-film photopy- roelectric (PPE) sensors [1,2]. The PPE sensor exhibits

Mandelis, Andreas

141

Thin film porous membranes based on sol-gel chemistry for catalytic sensors  

SciTech Connect

Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel films have little effect on the sensing response to H{sub 2} alone. However, in the presence of other gases, the nanoporous film modifies the sensor behavior in several beneficial ways. (1) They have shown that the sol-gel coated sensors were only slightly poisoned by high concentrations of H{sub 2}S while uncoated sensors showed moderate to severe poisoning effects. (2) For a given partial pressure of H{sub 2}, the signal from the sensor is modified by the presence of O{sub 2} and other oxidizing gases.

Hughes, R.C.; Patel, S.V.; Jenkins, M.W.; Boyle, T.J.; Gardner, T.J.; Brinker, C.J.

1998-05-01

142

Platform for a Hydrocarbon Exhaust Gas Sensor Utilizing a Pumping Cell and a Conductometric Sensor  

PubMed Central

Very often, high-temperature operated gas sensors are cross-sensitive to oxygen and/or they cannot be operated in oxygen-deficient (rich) atmospheres. For instance, some metal oxides like Ga2O3 or doped SrTiO3 are excellent materials for conductometric hydrocarbon detection in the rough atmosphere of automotive exhausts, but have to be operated preferably at a constant oxygen concentration. We propose a modular sensor platform that combines a conductometric two-sensor-setup with an electrochemical pumping cell made of YSZ to establish a constant oxygen concentration in the ambient of the conductometric sensor film. In this paper, the platform is introduced, the two-sensor-setup is integrated into this new design, and sensing performance is characterized. Such a platform can be used for other sensor principles as well. PMID:22423212

Biskupski, Diana; Geupel, Andrea; Wiesner, Kerstin; Fleischer, Maximilian; Moos, Ralf

2009-01-01

143

Gas sensor with attenuated drift characteristic  

Microsoft Academic Search

A sensor with an attenuated drift characteristic, including a layer structure in which a sensing layer has a layer of diffusional barrier material on at least one of its faces. The sensor may for example be constituted as a hydrogen gas sensor including a palladium\\/yttrium layer structure formed on a micro-hotplate base, with a chromium barrier layer between the yttrium

Ing-Shin Chen; Dimeo Jr. Frank; Philip S. H. Chen; Jeffrey W. Neuner; James Welch; Bryan Hendrix

2008-01-01

144

A MultiParameter Platform For Gas Sensing Using Semiconducting Metal Oxide Films  

Microsoft Academic Search

A multi-parameter sensor platform for engineering gas responsive semiconducting metal oxide (SMO) materials and gas sensors is demonstrated. The platform combines a chemiresistor with a Metal Oxide Semiconductor (MOS) capacitor for the detection of oxidation-reduction reactions occurring in SMO films. With this platform, changes in resistance, work function, and capacitance of the SMO film can be simultaneously measured upon exposure

Guixiong Zhong; G. Bernhardt; R. Lad; S. Collins; R. Smith

2007-01-01

145

Development of high sensitivity tin oxide based sensors for gas\\/odour detection at room temperature  

Microsoft Academic Search

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases\\/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the

Roopali Srivastava; R Dwivedi; S. K Srivastava

1998-01-01

146

Advances in Thin Film Sensor Technologies for Engine Applications  

NASA Technical Reports Server (NTRS)

Advanced thin film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle Main Engine, High Speed Civil Transport, Advanced Subsonic Transports and General Aviation Aircraft) in hostile, high-temperature environments and for validation of design codes. This paper presents two advanced thin film sensor technologies: strain gauges and thermocouples. These sensors are sputter deposited directly onto the test articles and are only a few micrometers thick; the surface of the test article is not structurally altered and there is minimal disturbance of the gas flow over the surface. The strain gauges are palladium-13% chromium based and the thermocouples are platinum-13% rhodium vs. platinum. The fabrication techniques of these thin film sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, including superalloys, ceramics and advanced ceramic matrix composites, in several hostile, high-temperature test environments are discussed.

Lei, Jih-Fen; Martin, Lisa C.; Will, Herbert A.

1997-01-01

147

Chemical Gas Sensors Based On Nanowires  

Microsoft Academic Search

Chemical gas sensors based on nanowires can find a wide range of applications in clinical assaying, environmental emission control, explosive detection, agricultural storage and shipping, and workplace hazard monitoring. Sensors in the forms of nanowires are expected to have significantly enhanced performance due to high surface-volume ratio and quasi-one-dimensional confinement in nanowires. Indeed, chemical gas sensors based on nanowires with

Yaping Dan; Stephane Evoy; A. T. Charlie Johnson

2008-01-01

148

Toxic gas response of (In,Sn)O2\\/Pt nanowire sensors  

Microsoft Academic Search

Thin film gas sensors based on tin oxide are fabricated and its characteristics are examined. Target gases are dimethyl methylphosphonate(C3H9O3P, DMMP) as a simulant gas for nerve gas GA (Tabun) and acetonitrile (CH3CN) as a simulant gas for blood gas. Sensing materials are Pt\\/SnO2, where Pt layer (30 Å) is deposited on tin oxide film grown on alumina substrate, (Sn,In)O2\\/Pt

Gi-Hong Rue; Tae-Hyun Ban; Nak-Jin Choi; Jun-Hyuk Kwak; Yeon-Tae Lim; Duk-Dong Lee; Jeung-Soo Huh

2005-01-01

149

A Large Scale Virtual Gas Sensor Array  

NASA Astrophysics Data System (ADS)

This paper depicts a virtual sensor array that allows the user to generate gas sensor synthetic data while controlling a wide variety of the characteristics of the sensor array response: arbitrary number of sensors, support for multi-component gas mixtures and full control of the noise in the system such as sensor drift or sensor aging. The artificial sensor array response is inspired on the response of 17 polymeric sensors for three analytes during 7 month. The main trends in the synthetic gas sensor array, such as sensitivity, diversity, drift and sensor noise, are user controlled. Sensor sensitivity is modeled by an optionally linear or nonlinear method (spline based). The toolbox on data generation is implemented in open source R language for statistical computing and can be freely accessed as an educational resource or benchmarking reference. The software package permits the design of scenarios with a very large number of sensors (over 10000 sensels), which are employed in the test and benchmarking of neuromorphic models in the Bio-ICT European project NEUROCHEM.

Ziyatdinov, Andrey; Fernández-Diaz, Eduard; Chaudry, A.; Marco, Santiago; Persaud, Krishna; Perera, Alexandre

2011-09-01

150

Development of Sic Gas Sensor Systems  

NASA Technical Reports Server (NTRS)

Silicon carbide (SiC) based gas sensors have significant potential to address the gas sensing needs of aerospace applications such as emission monitoring, fuel leak detection, and fire detection. However, in order to reach that potential, a range of technical challenges must be overcome. These challenges go beyond the development of the basic sensor itself and include the need for viable enabling technologies to make a complete gas sensor system: electrical contacts, packaging, and transfer of information from the sensor to the outside world. This paper reviews the status at NASA Glenn Research Center of SiC Schottky diode gas sensor development as well as that of enabling technologies supporting SiC gas sensor system implementation. A vision of a complete high temperature microfabricated SiC gas sensor system is proposed. In the long-term, it is believed that improvements in the SiC semiconductor material itself could have a dramatic effect on the performance of SiC gas sensor systems.

Hunter, G. W.; Neudeck, P. G.; Okojie, R. S.; Beheim, G. M.; Thomas, V.; Chen, L.; Lukco, D.; Liu, C. C.; Ward, B.; Makel, D.

2002-01-01

151

Ionization Gas Sensor using Aligned Multiwalled Carbon Nanotubes Array  

SciTech Connect

The challenge with current conventional gas sensors which are operating using semiconducting oxides is their size. After the introduction of nanotechnology and in order to reduce the dimension and consequently the power consumption and cost, new materials such as carbon nanotubes (CNTs) are being introduced. From previous works and characterization results, it was proven that the CNTs based gas sensor has better sensitivity, selectivity and faster response time in compared with semiconducting oxides based gas sensors. As in this work, a fabrication and successful testing of an ionization-based gas sensor using aligned Multiwalled CNTs (MWCNTs) as sensing element is discussed, in which MWCNTs array and Al film are used as anode and cathode plates respectively with electrode separation ranging from 80 {mu}m to 140 {mu}m. Aligned MWCNTs array was incorporated into a sensor configuration in the gas chamber for testing of gases such as argon, air, and mixed gas of 2%H{sub 2} in air. Obtained results show that among the three gases, argon has the lowest breakdown voltage whilst air has the highest value and the breakdown voltage was found to decrease as the electrode spacing was reduced from 140 {mu}m to 80 {mu}m for all three gases.

Kermany, A. R. [Electrical and Electronics Engineering, 31750 Bandar Seri Iskandar, Tronoh, Perak (Malaysia); Mohamed, N. M.; Singh, B. S. M. [Fundamental and Applied Sciences Department Universiti Teknologi PETRONAS (UTP) 31750 Bandar Seri Iskandar, Tronoh, Perak (Malaysia)

2011-05-25

152

All thin film magnetoelectric magnetic field sensors.  

NASA Astrophysics Data System (ADS)

We have fabricated prototype ac magnetic field sensors operating at room temperature based on all thin film ME devices showing strong magnetoelectric (ME) coupling. The ME layers consist of a sol-gel derived Pb(Zr0.52Ti0.48)TiO3 (PZT) film and a dc magnetron sputter deposited magnetostrictive Fe70Ga30 (FeGa) film. The bilayer structures are prepared on micromachined Si wafers, and the laser cutting technique is used to release and isolate the cantilevers for optimization of the sensor performance. The PZT layer and the FeGa layer couple via the piezoelectric d31 mode and the corresponding ME coupling coefficient is as high as 2 V/(Oe cm) for a lateral dimension of 1 mm^2 device at the mechanical resonant frequency of 333 Hz of a Si cantilever. The soft magnetic FeGa film requires dc bias magnetic field of around 90 Oe to operate the thin film ME device. The coupling between the PZT and the FeGa films is remarkably improved by depositing a 40 nm thick Pt intermediate layer. The clamping effect on the ME coupling is dramatically reduced by back-etching the Si cantilever down to 35 ?m thick. The present work indicates presence of robust ME coupling in microfabricated multilayer thin film ME devices.

Zhao, Peng

2009-03-01

153

Nanostructured zinc oxide gas sensors by successive ionic layer adsorption and reaction method and rapid photothermal processing  

E-print Network

22 October 2007 Abstract Undoped and Sn, Ni-doped nanostructured ZnO thin films were deposited oxide thin films. © 2007 Elsevier B.V. All rights reserved. Keywords: ZnO; SILAR; RPP; Sensor, there appeared many publication on ZnO nanorod or thin film gas sensors using various synthesis techniques

Chow, Lee

154

Nerve gas sensor using film bulk acoustic resonator modified with a self-assembled Cu 2+\\/11-mercaptoundecanoic acid bilayer  

Microsoft Academic Search

We present an application of film bulk acoustic resonator for trace nerve gas sensing. The resonator consisted of a piezoelectric Au\\/AlN\\/Mo stack and a Bragg reflector has a working resonance near 2.35GHz and a high performance. A self-assembled composite layer of Cu2+\\/11-mercaptoundecanoic acid is modified on the Au electrode as a specific coating to capture organophosphorus compounds. The experimental results

Da Chen; Yan Xu; Jingjing Wang; Luyin Zhang

2010-01-01

155

Thin Film Sensors for Minimally-Intrusive Measurements in Harsh High Temperature Environment  

NASA Technical Reports Server (NTRS)

Advanced thin film sensors are being developed to provide accurate surface temperature, heat flux and strain measurements for components used in hostile propulsion environments. These sensors are sputter deposited and microfabricated directly onto the test articles with no additional bonding agent. The thickness of the sensors is only a few micrometers which creates minimal disturbance of the gas flow over the test surface. Thus thin film sensors have the advantage over conventional wire- based sensors by providing minimally intrusive measurement and having a faster response. These thin film sensors are being developed for characterization of advanced materials and structures in hostile, high-temperature environments, and for validation of design codes. This paper presents the advances of three high temperature thin film sensor technologies developed at NASA Lewis Research Center: thermocouples, heat-flux gages and strain gages. The fabrication techniques of these thin film sensors which include physical vapor deposition, photolithography patterning and lead Wire attachment are described. Sensors demonstrations on a variety of engine materials, including superalloys, ceramics and advanced ceramic matrix composites, in several hostile, high-temperature test environments are presented. The advantages and limitations of thin film sensor technology are also discussed.

Lei, Jih-Fen; Will, Herbert A.; Martin, Lisa C.

1998-01-01

156

Fiber loop ringdown gas flow sensors  

NASA Astrophysics Data System (ADS)

Fiber loop ringdown (FLRD) is a versatile sensing technique, which has been increasingly used for the development of high sensitivity, fast response FLRD chemical, physical, and biomedical sensors. In this paper, we report the first fiber loop ringdown gas flow sensor. The FLRD gas flow sensor is based on a micro-bending sensing mechanism, in which optical loss is induced when a gas flows through the sensor head and creates a physical deformation. The sensor was employed to determine airflow at various rates. Two different sensor head configurations were investigated. The results show that the sensor has a high upper measuring range of 5–22.5 standard liters per minute (slpm). Given the known airflow cross sections used, the corresponding airflow speeds measured in this work are within the range of 5.7–311.0 m s−1. A theoretical detection resolution limit (minimum detectable change) for the sensor is estimated to be 0.1 slpm using the best fiber loop ringdown baseline stability of 0.2%, while the experimentally measured resolution limit is 2.5 slpm (or 2.9 m s−1). The sensor demonstrated a fast response (<1 s) and excellent reproducibility and reversibility. Compared with other types of airflow fiber optic sensors, this new FLRD airflow sensor, besides its simplicity and low cost, offers the additional capability of measuring higher gas flow rates and a high potential for the fiber optic gas flow sensor network.

Alali, Haifa; Wang, Chuji

2014-11-01

157

Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors  

PubMed Central

One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed. PMID:25232915

Feng, Ping; Shao, Feng; Shi, Yi; Wan, Qing

2014-01-01

158

Piezoelectric Pb(Zrx, Ti1-x)O3 thin film cantilever and bridge acoustic sensors for miniaturized photoacoustic gas detectors  

NASA Astrophysics Data System (ADS)

Novel, highly sensitive piezoelectric acoustic sensors based on partially unclamped Pb(Zrx, Ti1-x)O3 (PZT) coated cantilever and bridge have been fabricated by silicon micromachining. High sensitivity at low frequencies (5-100 Hz) has been achieved by patterning very narrow slits (3 to 5 µm) around the structures. A typical response of 100 mV Pa-1 and a noise equivalent pressure of 1.6 mPa Hz1/2 at 20 Hz have been measured using a 10 pF charge amplifier. Stress compensation, dry etching and integration of high performance piezoelectric thin films were the key issues. PZT/Pt/SiO2 stacks have been patterned by reactive ion etching and stress compensation has been achieved by compensating the PZT film's tensile stress by adjusting the thickness of a thermal SiO2 layer. The integration of sol-gel PZT films with a transverse piezoelectric coefficient e31,f of -12.8 C m-2 has been realized without any degradation of the properties. The microphones were successfully integrated into a miniature photoacoustic detector and tested for CO2 detection. Concentrations down to 330 ppm could be measured with significant signals.

Ledermann, Nicolas; Muralt, Paul; Baborowski, Jacek; Forster, Martin; Pellaux, Jean-Paul

2004-12-01

159

Thin film mixed potential sensors  

DOEpatents

A mixed potential sensor for oxidizable or reducible gases and a method of making. A substrate is provided and two electrodes are formed on a first surface of the substrate, each electrode being formed of a different catalytic material selected to produce a differential voltage between the electrodes from electrochemical reactions of the gases catalyzed by the electrode materials. An electrolytic layer of an electrolyte is formed over the electrodes to cover a first portion of the electrodes from direct exposure to the gases with a second portion of the electrodes uncovered for direct exposure to the gases.

Garzon, Fernando H. (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM); Mukundan, Rangachary (Santa Fe, NM)

2007-09-04

160

Thin-film spectroscopic sensor  

DOEpatents

There is disclosed an integrated spectrometer for chemical analysis by evanescent electromagnetic radiation absorption in a reaction volume. The spectrometer comprises a noninteractive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device. There is further disclosed a chemical sensor to determine the pressure and concentration of a chemical species in a mixture comprising an interactive waveguide, a substrate, an entrance grating and an exit grating, an electromagnetic radiation source, and an electromagnetic radiation sensing device.

Burgess, Jr., Lloyd W. (Seattle, WA); Goldman, Don S. (Richland, WA)

1992-01-01

161

Solid state potentiometric oxygen gas sensors  

Microsoft Academic Search

Oxygen gas sensors, operating in the potentiometric (zero current) mode, based upon oxygen ion conducting solid electrolytes are reviewed. Detailed consideration is given to practical aspects of their composition, construction and operation.

W. C. Maskell; B. C. H. Steele

1986-01-01

162

Mechanical Drawing of Gas Sensors on Paper  

E-print Network

Pencil it in: Mechanical abrasion of compressed single-walled carbon nanotubes (SWCNTs) on the surface of paper produces sensors capable of detecting NH[subscript 3] gas at sub-ppm concentrations. This method of fabrication ...

Esser, Birgit

163

Developing Multilayer Thin Film Strain Sensors With High Thermal Stability  

NASA Technical Reports Server (NTRS)

A multilayer thin film strain sensor for large temperature range use is under development using a reactively-sputtered process. The sensor is capable of being fabricated in fine line widths utilizing the sacrificial-layer lift-off process that is used for micro-fabricated noble-metal sensors. Tantalum nitride films were optimized using reactive sputtering with an unbalanced magnetron source. A first approximation model of multilayer resistance and temperature coefficient of resistance was used to set the film thicknesses in the multilayer film sensor. Two multifunctional sensors were fabricated using multilayered films of tantalum nitride and palladium chromium, and tested for low temperature resistivity, TCR and strain response. The low temperature coefficient of resistance of the films will result in improved stability in thin film sensors for low to high temperature use.

Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M., III

2006-01-01

164

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films  

E-print Network

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films A dissertation presented Advisor Author Joost J. Vlassak Patrick J. McCluskey Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films Abstract Membrane-based thermal sensor arrays were developed for the high- throughput

165

Characterization of piezoelectric film sensors for tongue-computer interface  

Microsoft Academic Search

In this paper we examine the pressure detection quality and signal clarity for two types of piezoelectric film sen- sors. One sensor was coated with polydimethylsiloxane (PDMS) while the other remained uncoated. Our goal was to determine how coating the sensor with PDMS would affect sensor per- formance. Our long-term goal is to develop a tongue-computer interface using piezoelectric film

Lukash Monczak; Daniel Shapiro; Alexey Borisenko; Ovidiu Draghici; Miodrag Bolic

2011-01-01

166

Integrated Microfluidic Gas Sensors for Water Monitoring  

NASA Technical Reports Server (NTRS)

A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

2003-01-01

167

Hydrogen gas sensor and method of manufacture  

DOEpatents

A sensor for measuring the pressure of hydrogen gas in a nuclear reactor, and method of manufacturing the same. The sensor comprises an elongated tube of hydrogen permeable material which is connected to a pressure transducer through a feedthrough tube which passes through a wall at the boundary of the region in which hydrogen is present. The tube is pressurized and flushed with hydrogen gas at an elevated temperature during the manufacture of the sensor in order to remove all gasses other than hydrogen from the device.

McKee, John M. (Hinsdale, IL)

1991-01-01

168

Design and development of multiple sensor array based on SnO2 thin films for e-nose application  

NASA Astrophysics Data System (ADS)

Fabrication of a 2 × 4 multiple sensor array based on SnO2 thin films was demonstrated. SnO2 thin films were deposited on Al2O3 substrates and modified selectively using Au and CuO by sputtering. The sensor array was tested for its gas sensing characteristics towards H2S. The maximum sensor response (S=52) was observed in case of Au modified SnO2 thin films. By the surface modification using Au there is increase in the sensor response at all temperature. With the increase in temperature, sensor response decreases.

Sharma, P. K.; Ramgir, N.; Goyal, C. P.; Datta, N.; Kailasaganapathi, S.; Kaur, M.; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.

2013-06-01

169

Sensor array for toxic gas detection  

DOEpatents

A portable instrument for use in the field in detecting and identifying a hazardous component in air or other gas including an array of small sensors which upon exposure to the gas from a pattern of electrical responses, a source of standard response patterns characteristic of various components, and microprocessor means for comparing the sensor-formed response pattern with one or more standard patterns to thereby identify the component on a display. The number of responses may be increased beyond the number of sensors by changing the operating voltage, temperature or other condition associated with one or more sensors to provide a plurality of responses from each of one or more of the sensors. In one embodiment, the instrument is capable of identifying anyone of over 50-100 hazardous components.

Stetter, Joseph R. (Naperville, IL); Zaromb, Solomon (Hinsdale, IL); Penrose, William R. (Naperville, IL)

1987-01-01

170

Integrated Micro-Machined Hydrogen Gas Sensor. Final Report  

SciTech Connect

This report details our recent progress in developing novel MEMS (Micro-Electro-Mechanical Systems) based hydrogen gas sensors. These sensors couple novel thin films as the active layer on a device structure known as a Micro-HotPlate. This coupling has resulted in a gas sensor that has several unique advantages in terms of speed, sensitivity, stability and amenability to large scale manufacture. This Phase-I research effort was focused on achieving the following three objectives: (1) Investigation of sensor fabrication parameters and their effects on sensor performance. (2) Hydrogen response testing of these sensors in wet/dry and oxygen-containing/oxygen-deficient atmospheres. (3) Investigation of the long-term stability of these thin film materials and identification of limiting factors. We have made substantial progress toward achieving each of these objectives, and highlights of our phase I results include the demonstration of signal responses with and without oxygen present, as well as in air with a high level of humidity. We have measured response times of <0.5 s to 1% H{sub 2} in air, and shown the ability to detect concentrations of <200 ppm. These results are extremely encouraging and suggest that this technology has substantial potential for meeting the needs of a hydrogen based economy. These achievements demonstrate the feasibility of using micro-hotplates structures in conjunction with palladium+coated metal-hydride films for sensing hydrogen in many of the environments required by a hydrogen based energy economy. Based on these findings, they propose to continue and expand the development of this technology in Phase II.

Frank DiMeo, Jr.

2000-10-02

171

Sensitivity Analysis of Lateral Field Excited Acoustic Wave Gas Sensors with Finite Element Method  

NASA Astrophysics Data System (ADS)

In the last decade, there are increasing investigations on lateral field excited (LFE) acoustic wave sensors in biochemical liquid sensing applications due to their high sensitivity and simple fabrication. However, the research on this kind of sensor for gas detection is still awaited. This paper presents a theoretical modeling of the LFE acoustic wave gas sensor with a nanostrustured selective film for the first time. We developed this model by adopting a finite element software, COMSOL. Besides the eigenfrequency and frequency-response analyses, the sensitivities to the variations of mass density and electrical conductivity of the selective film caused from gas concentration were calculated. In the meantime, quartz crystal microbalance (QCM) sensors were also analyzed for comparison. Finally, the effect of geometry of the LFE gas sensor on the sensitivity was discussed. Results show that the LFE sensor exhibits larger sensing range and higher sensitivity to external electrical variation than the QCM sensor. This is because no shielding electrode exists on sensing surface of the LFE sensor, and hence the electric field can penetrate into the selective film. The simulation results provide useful guidelines for designing LFE acoustic wave gas sensors.

Chen, Yung-Yu; Liu, Chih-Chieh

2011-07-01

172

Effects of Palladium Loading on the Response of a Thick Film Flame-made ZnO Gas Sensor for Detection of Ethanol Vapor  

PubMed Central

ZnO nanoparticles doped with 0-5 mol% Pd were successfully produced in a single step by flame spray pyrolysis (FSP) using zinc naphthenate and palladium (II) acetylacetonate dissolved in toluene-acetonitrile (80:20 vol%) as precursors. The effect of Pd loading on the ethanol gas sensing performance of the ZnO nanoparticles and the crystalline sizes were investigated. The particle properties were analyzed by XRD, BET, AFM, SEM (EDS line scan mode), TEM, STEM, EDS, and CO-pulse chemisorption measurements. A trend of an increase in specific surface area of samples and a decrease in the dBET with increasing Pd concentrations was noted. ZnO nanoparticles were observed as particles presenting clear spheroidal, hexagonal and rod-like morphologies. The sizes of ZnO spheroidal and hexagonal particle crystallites were in the 10-20 nm range. ZnO nanorods were in the range of 10-20 nm in width and 20-50 nm in length. The size of Pd nanoparticles increased and Pd-dispersion% decreased with increasing Pd concentrations. The sensing films were produced by mixing the particles 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 film morphology was analyzed by SEM and EDS analyses. The gas sensing of ethanol (25-250 ppm) was studied in dry air at 400°C. The oxidation of ethanol on the sensing surface of the semiconductor was confirmed by MS. A well-dispersed of 1 mol%Pd/ZnO films showed the highest sensitivity and the fastest response time (within seconds).

Liewhiran, Chaikarn; Phanichphant, Sukon

2007-01-01

173

The study of structural properties of carbon nanotubes decorated with NiFe2O4 nanoparticles and application of nano-composite thin film as H2S gas sensor.  

PubMed

Nano-composite of multiwall carbon nanotube, decorated with NiFe2O4 nanoparticles (NiFe2O4-MWCNT), was synthesized using the sol-gel method. NiFe2O4-MWCNTs were characterized using different methods such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM). The average size of the crystallites is 23.93nm. The values of the saturation magnetization (MS), coercivity (HC) and retentivity (MR) of NiFe2O4-MWCNTs are obtained as 15emug(-1), 21Oe and 5emug(-1), respectively. In this research, NiFe2O4-MWCNT thin films were prepared with the spin-coating method. These thin films were used as the H2S gas sensor. The results suggest the possibility of the utilization of NiFe2O4-MWCNT nano-composite, as the H2S detector. The sensor shows appropriate response towards 100ppm of H2S at 300°C. PMID:25280723

Hajihashemi, R; Rashidi, Ali M; Alaie, M; Mohammadzadeh, R; Izadi, N

2014-11-01

174

Biomaterial based sulphur di oxide gas sensor  

NASA Astrophysics Data System (ADS)

Biomaterials are getting importance in the present research field of sensors. In this present paper performance of biomaterial based gas sensor made of gum Arabica and garlic extract had been studied. Extract of garlic clove with multiple medicinal and chemical utility can be proved to be useful in sensing Sulphur di Oxide gas. On exposure to Sulphur di Oxide gas the material under observation suffers some temporary structural change, which can be observed in form of amplified potentiometric change through simple electronic circuitry. Exploiting this very property a potentiometric gas sensor of faster response and recovery time can be designed. In this work sensing property of the said material has been studied through DC conductance, FTIR spectrum etc.

Ghosh, P. K.; Sarkar, A.

2013-06-01

175

Graphene Based Flexible Gas Sensors  

NASA Astrophysics Data System (ADS)

Graphene is a novel carbon material with great promise for a range of applications due to its electronic and mechanical properties. Its two-dimensional nature translates to a high sensitivity to surface chemical interactions thereby making it an ideal platform for sensors. Graphene's electronic properties are not degraded due to mechanical flexing or strain (Kim, K. S., et al. nature 07719, 2009) offering another advantage for flexible sensors integrated into numerous systems including fabrics, etc. We have demonstrated a graphene NO2 sensor on a solid substrate (100nm SiO2/heavily doped silicon). Three different methods were used to synthesize graphene and the sensor fabrication process was optimized accordingly. Water is used as a controllable p-type dopant in graphene to study the relationship between doping and graphene's response to NO2 . Experimental results show that interface water between graphene and the supporting SiO2 substrate induces higher p-doping in graphene, leading to a higher sensitivity to NO2, consistent with theoretical predications (Zhang, Y. et al., Nanotechnology 20(2009) 185504). We have also demonstrated a flexible and stretchable graphene-based sensor. Few layer graphene, grown on a Ni substrate, is etched and transferred to a highly stretchable polymer substrate (VHB from 3M) with preloaded stress, followed by metal contact formation to construct a flexible, stretchable sensor. With up to 500% deformation caused by compressive stress, graphene still shows stable electrical response to NO2. Our results suggest that higher compressive stress results in smaller sheet resistance and higher sensitivity to NO2. A possible molecular detection sensor utilizing Surface Enhanced Raman Spectrum (SERS) based on a graphene/gallium nanoparticles platform is also studied. By correlating the enhancement of the graphene Raman modes with metal coverage, we propose that the Ga transfers electrons to the graphene creating local regions of enhanced electron concentration modifying the Raman scattering in graphene.

Yi, Congwen

176

Exhaust Gas Sensor Based On Tin Dioxide For Automotive Application  

E-print Network

layer with gold electrodes. This gas sensor is able to detect both reducing and oxidizing gases lambda sensors, mixed potential type sensors [1] using a solid electrolyte (often yttria stabilizedµm. The sensors are tested in a bench which is able to submit sensors to high gas temperature (250°C

Paris-Sud XI, Université de

177

Study on Fiber-optic Hydrogen Sulfide Gas Sensor  

NASA Astrophysics Data System (ADS)

We describe a novel fiber-optic gas sensor which hydrogen Sulfide (H2S) gas can be detected by a silver coated fiber bragg grating (FBG). The H2S sensitive material Ag can be coated on the cladding surrounding surface of FBG by conventional silver mirror reaction. The scanning electron microscope (SEM) was applied to analysis the Ag film structure before and after the interaction with H2S gas. By conducting the experiment of Ag-coated optical sensor (AOS), the relation between the H2S gas concentration and absorption spectrum was built. Result shows that while the concentration alters from 0 to 9.32%, a linear response of AOS signal to H2S concentration was observed with the response sensitivity of 0.332 dBm/% and linearity R2=0.9966. Such H2S sensor is suitable for monitoring the H2S hazard as a one time disposable logging-while-drilling sensor.

Zhou, Hong; Wen, Jun-Qing; Zhang, Xiao-Zhen; Wang, Wei; Feng, De-Quan; Wang, Qi; Jia, Fei

178

Ultra-Low-Power MEMS Selective Gas Sensors  

NASA Technical Reports Server (NTRS)

This innovation is a system for gas sensing that includes an ultra-low-power MEMS (microelectromechanical system) gas sensor, combined with unique electronic circuitry and a proprietary algorithm for operating the sensor. The electronics were created from scratch, and represent a novel design capable of low-power operation of the proprietary MEMS gas sensor platform. The algorithm is used to identify a specific target gas in a gas mixture, making the sensor selective to that target gas.

Stetter, Joseph

2012-01-01

179

Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

Single-arm double-mode double-order optical waveguide interferometer utilizes interference between two propagating modes of different orders. Sensing effect results from the change in propagation conditions of the modes caused by the environment. The waveguide is made as an open asymmetric slab structure containing a dye-doped polymer film onto a fused quartz substrate. It is more sensitive to the change of environment than its conventional polarimetric analog using orthogonal modes (TE and TM) of the same order. The sensor still preserves the option of operating in polarimetric regime using a variety of mode combinations such as TE(sub 0)/TM(sub 0) (conventional), TE(sub 0)/TM(sub 1), TE(sub 1)/TM(sub 0), or TE(sub 1)/TM(sub 1) but can also work in nonpolarimetric regime using combinations TE(sub 0)/TM(sub 1) or TE(sub 0)/TM(sub 1). Utilization of different mode combinations simultaneously makes the device more versatile. Application of the sensor to gas sensing is based on doping polymer film with an organic indicator dye sensitive to a particular gas. Change of optical absorption spectrum of the dye caused by the gaseous pollutant results change of the reactive index of the dye-doped polymer film that can be detected by the sensor. As an indicator dyes, we utilize Bromocresol Purple doped into polymer poly(methyl) methacrylate, which shows a reversible growth of the absorption peak neat 600 nm after exposure to wet ammonia. We have built a breadboard prototype of the sensor with He-Ne laser as a light source and with a single mode fiber input and a multimode fiber output. The prototype showed sensitivity to temperature change of the order of 2 C per one full oscillation of the signal. The sensitivity of the sensor to the presence of wet ammonia is 200 ppm per one full oscillation of the signal. The further improvements include switching to a longer wavelength laser source (750-nm semiconductor laser), substitution of poly(methyl) methacrylate with hydrophilic high-temperature polyimide, and increase the doping rate of indicator dye. All these improvements are expected to bring sensitivity to 10 ppm of ammonia per one full oscillation of signal independent on the humidity of ambient air. The proposed sensor can be used as a robust and inexpensive stand-alone instrument for continuous environment pollution monitoring.

Sarkisov, S. S.; Diggs, D.; Curley, M.; Adamovsky, Grigory (Technical Monitor)

2001-01-01

180

Patterning of structures by e-beam lithography and ion etching for gas sensor applications  

NASA Astrophysics Data System (ADS)

This work deals with a method of preparation of nanometer structures for a gas detector based on e-beam lithography and ion etching of a thin TiO2 film. The aim was the fabrication of a gas sensor with meander or comb structures of nanometer dimensions. This is of importance since both the size of the contacts and the layer thickness affect the sensor's sensitivity.

Durina, P.; Bencurova, A.; Konecnikova, A.; Kostic, I.; Vutova, K.; Koleva, E.; Mladenov, G.; Kus, P.; Plecenik, A.

2014-05-01

181

Conduction Model of Metal Oxide Gas Sensors  

Microsoft Academic Search

Tin dioxide is a widely used sensitive material for gas sensors. Many research and development groups in academia and industry are contributing to the increase of (basic) knowledge\\/(applied) know-how. However, from a systematic point of view the knowledge gaining process seems not to be coherent. One reason is the lack of a general applicable model which combines the basic principles

Nicolae Barsan; Udo Weimar

2001-01-01

182

Colorimetric blood-gas monitoring sensors  

NASA Astrophysics Data System (ADS)

Colorimetric fiber optic sensors have been developed for measuring the pH and pCO2 of blood. These sensors are fabricated using a single 125 micrometers diameter optical fiber. Located at the distal end of the fiber is a capsule that contains a pH sensitive dye. The pCO2 sensor is fabricated from a pH sensor with the addition of a salt, bicarbonate, and the encapsulation with an ion impermeable gas permeable membrane. The distal end of the capsule is terminated with a reflective surface. The reflective surface can either be a polished metallic surface or, in this case, a TiO2 impregnated epoxy. The disposable sensor mates with an optical connector that contains two optical fibers of the same size as the disposable sensor. The two fibers within the optical cable provide a light path for both the antegrade and retrograde optical signals. These fibers are terminated at either the LED source or the detector. A prototype sensor assembly that incorporates the measurement of three physiological parameters (pH, pCO2, and sO2) has been demonstrated to fit within a standard 20 gauge arterial catheter, typically used for radial artery blood pressure monitoring, without significant damping of the blood pressure waveform. The pH sensor has a range of 6.9 - 7.8 with a precision of 0.01 pH units and the pCO2 sensor has a range of 15 - 95 mm Hg with a precision of 3 mm Hg. The long term drift pH drift is less than 0.01 pH unit per 8 hours and the pCO2 drift is less than 1 mm Hg per 8 hours. Sensor performance in the canine has demonstrated that the pH sensor is accurate to within +/- 0.03 pH units and the pCO2 sensor is accurate to within +/- 3 mm Hg when compared to a typical blood gas analyzer.

Proctor, Keith J.; Seifert, George P.

1993-05-01

183

Development of a thin film solid state gaseous HCl sensor  

NASA Technical Reports Server (NTRS)

The selection of materials to develop a thin film HCl sensor is discussed. Data were primarily concerned with chemical and physical properties of the film and with electrical properties which exhibit and enhance electrical response when HCl is absorbed on the film surface. Techniques investigated for enhancing electrical response include changing conditions for growing films, adding impurities to the film, changing ambient light intensity, and altering the ambient temperature of the sensing element.

1975-01-01

184

Test Structures for Rapid Prototyping of Gas and Pressure Sensors  

NASA Technical Reports Server (NTRS)

A multi-project ceramic substrate was used in developing a gas sensor and pressure sensor. The ceramic substrate cantained 36 chips with six variants including sensors, process control monitors, and an interconnect ship. Tha gas sensor is being developed as an air quality monitor and the pressure gauge as a barometer.

Buehler, M.; Cheng, L. J.; Martin, D.

1996-01-01

185

Thermal Enzyme Sensor Utilizing Temperature-Sensitive Magnetic Thin Film  

Microsoft Academic Search

An approach to the biomagnetics of the thermal enzyme sensor (TES) utilizing a temperature-sensitive magnetic thin film (TMF) as a micromagnetic transducer is described. When an enzyme is infused into a chemical substance or a metabolite, an exothermic reaction occurs and the sensor absorbs a minute amount of heat, which causes a change of magnetization. Therefore, the sensor is suitable

Yoshimitsu Yachi; Kiyotaka Ito; Shigeki Chiba; Hiroshi Osada; Keiichi Sasaki; Masao Takahashi; Tsuneo Kubota; Kyoshiro Seki

2002-01-01

186

PALLADIUM DOPED TIN OXIDE BASED HYDROGEN GAS SENSORS FOR SAFETY APPLICATIONS  

SciTech Connect

Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd) are preferred due to their compactness and fast response. They detect hydrogen by monitoring the changes to the electrical, mechanical or optical properties of the films. We report the development of Pd-doped tin-oxide based gas sensors prepared on thin ceramic substrates with screen printed platinum (Pt) contacts and integrated nicrome wire heaters. The sensors are tested for their performances using hydrogen-nitrogen gas mixtures to a maximum of 4%H{sub 2} in N{sub 2}. The sensors detect hydrogen and their response times are less than a few seconds. Also, the sensor performance is not altered by the presence of helium in the test gas mixtures. By the above desired performance characteristics, field trials of these sensors have been undertaken. The paper presents the details of the sensor fabrication, electronic circuits, experimental setup for evaluation and the test results.

Kasthurirengan, S.; Behera, Upendra; Nadig, D. S. [Centre for Cryogenic Technology, Indian Institute of Science, Bangalore 560012 (India)

2010-04-09

187

Palladium Doped Tin Oxide Based Hydrogen Gas Sensors for Safety Applications  

NASA Astrophysics Data System (ADS)

Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd) are preferred due to their compactness and fast response. They detect hydrogen by monitoring the changes to the electrical, mechanical or optical properties of the films. We report the development of Pd-doped tin-oxide based gas sensors prepared on thin ceramic substrates with screen printed platinum (Pt) contacts and integrated nicrome wire heaters. The sensors are tested for their performances using hydrogen—nitrogen gas mixtures to a maximum of 4% H2 in N2. The sensors detect hydrogen and their response times are less than a few seconds. Also, the sensor performance is not altered by the presence of helium in the test gas mixtures. By the above desired performance characteristics, field trials of these sensors have been undertaken. The paper presents the details of the sensor fabrication, electronic circuits, experimental setup for evaluation and the test results.

Kasthurirengan, S.; Behera, Upendra; Nadig, D. S.

2010-04-01

188

1708 IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013 Integration of Thin Film Strain Sensors Into Hard  

E-print Network

of piezoelectric thin-film sensing technology by incorporating ZnO strain sensors into a hard disk drive (HDD) and deploying the sensors in a high-sample-rate feedback controller to suppress vibrations. First, thin-film ZnO1708 IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013 Integration of Thin Film Strain Sensors

Horowitz, Roberto

189

Graphene-based microfiber gas sensor  

NASA Astrophysics Data System (ADS)

In this paper, a novel graphene-based microfiber sensor is proposed and demonstrated for detection of gas concentration for the first time. As the complex refractive index (CRI) of graphene can be modulated by gas molecules in the surrounding environment, the propagating light along the graphene layer coupled by the microfiber would be altered to induce the attenuation of polarization mode intensity. Based on such a unique TE-polarization mode attenuation feature of graphene, experimental results showed that the acetone concentration can be measured accurately and quickly. Such an approach could open a window for realization of a variety of highly sensitive and fast gas or liquid sensors based on graphene, for wide applications in biological, medical and chemical fields.

Yao, Bai-Cheng; Wu, Yu; Chen, Yang; Liu, Xiu-Ping; Gong, Yuan; Rao, Yun-Jiang

190

Gas-sensitive holographic sensors  

E-print Network

pressure and temperature. 7 1. Introduction Butane, propane and methane, for instance, are the main constituents of fuel gas for domestic uses or transportation. Structural isomers and derivatives of hydrocarbons such as alcohols, ketones and other VOCs... and the most abundant alkaline con- stituent of the atmosphere. It is widely used for the production of explosives, fertilizers, resins, nylon and semiconductors, for waste-water treatment plants, and as a refrigerant for industrial processes [48]. Ammonia...

Martínez Hurtado, Juan Leonardo

2013-04-16

191

Porous Semiconductors: Advanced Material for Gas Sensor Applications  

Microsoft Academic Search

The present review article is devoted to the analysis of the problems related to the design of gas sensors based on porous semiconductors (PS). The peculiarities of the semiconductor porosification by anodic etching and the principles of gas sensor design based on porous semiconductors, including gas sensor construction and main operating characteristics, are considered in the article. It is shown

G. Korotcenkov; B. K. Cho

2010-01-01

192

Free-grown polypyrrole thin films as aroma sensors  

Microsoft Academic Search

We describe the use of free-grown thin polypyrrole films as fast response sensors of volatile compounds. Using a variety of dopants, the polymeric films were prepared directly on conducting glass substrates. Ultraviolet-visible and near infrared regions absorbance measurements were used to investigate the deposition process and the doping level of the films. We identify the polymerization time as the fundamental

J. E. G de Souza; F. L dos Santos; B. B Neto; C. G dos Santos; M. V. B dos Santos; C. P de Melo

2003-01-01

193

Study on adhesion of thin film coatings of polypyrrole on glass substrate for mechanical durability of sensor devices  

NASA Astrophysics Data System (ADS)

Thin film coatings of polypyrrole have been extensively used as gas sensors in chemiresistors where the films are deposited on insulating substrates. These polypyrrole films have also been used as coatings to glass optical fiber as a chemo-chromic transducer for gas sensing. For long term mechanical durability of these sensing films, their adhesion to the substrate is very important. Adhesion between polypyrrole films and glass slide substrates is investigated for solution deposited polypyrrole films. The substrate surface is investigated in terms of addition of silane coupling agents and substrate surface roughness, for enhancement of the film substrate adhesion. The adhesion test is performed by the standard ASTM D - 4541 Pull-off Test Method. The films deposited on as-received slides are characterized for their electrical conductivity and optical transmission for their use in both chemiresistor and optical fiber sensor applications for nerve agent DMMP (di-methylmethylphosphonate) sensing.

Bansal, Lalitkumar; El-Sherif, Mahmoud

2004-09-01

194

A novel thick film sensor for simultaneous O 2 and NO monitoring in exhaust gases  

Microsoft Academic Search

A miniaturized two-electrode sensor for the simultaneous detection of oxygen and nitrogen monoxide in oxygen, nitrogen, NO gas mixtures has been developed by using thick film technology. The solid state electrochemical sensor, based on yttria-stabilized zirconia, operates in the amperometric mode. Oxygen concentrations ranging up to 5vol.% and NO concentrations ranging up to 2500ppm can be detected separately and simultaneously.

P Schmidt-Zhang; K.-P Sandow; F Adolf; W Göpel; U Guth

2000-01-01

195

Enhanced electrodes for solid state gas sensors  

DOEpatents

A solid state gas sensor generates an electrical potential between an equilibrium electrode and a second electrode indicative of a gas to be sensed. A solid electrolyte substrate has the second electrode mounted on a first portion of the electrolyte substrate and a composite equilibrium electrode including conterminous transition metal oxide and Pt components mounted on a second portion of the electrolyte substrate. The composite equilibrium electrode and the second electrode are electrically connected to generate an electrical potential indicative of the gas that is being sensed. In a particular embodiment of the present invention, the second electrode is a reference electrode that is exposed to a reference oxygen gas mixture so that the electrical potential is indicative of the oxygen in a gas stream.

Garzon, Fernando H. (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM)

2001-01-01

196

Sensor Array Devices Utilizing Nano-structured Metal-oxides for Hazardous Gas Detection  

NASA Astrophysics Data System (ADS)

Methane and carbon monoxide are two hazardous gases which require continuous monitoring by gas sensors in underground coal mines for explosion prevention and toxicity, respectively. This work explored implementing miniaturized gas sensors in this area to simultaneously detect both gases for benefits of increased portability and reduced power consumption of the chemiresistive gas sensor device. The focus of this research was to understand how the particle size, morphology, and microstructure of the metaloxide film affected the gas sensor performance to the two gases of interest on miniaturized gas sensor devices in the form of microhotplate platforms. This was done through three main research studies. The first was conducted by growing SnO2 nanowires from SnO 2 particles using an Au-catalyst. Growth conditions including temperature, time, and oxygen partial pressure were explored to determine the formation aspects of the SnO2 nanowires. Gas sensor studies were completed that provided evidence that the SnO2 nanowires increased detection to a fixed concentration of carbon monoxide compared to SnO2 particles without nano-structure formation. A second research study was performed to compare the gas sensor performance of SnO2 nanoparticles, hierarchical particles, and micron-size particles. The nanoparticles were developed into an ink and deposited via ink-jet printing on the microhotplate substrates to control the microstructure of the metal-oxide film. By preventing agglomeration of the nanoparticle film, the SnO2 nanoparticles displayed similar gas sensor performance to methane and carbon monoxide as the hierarchical particles. Both nano-structures had much higher gas sensor response than the micron-size particles which confirms the surface area of the metal-oxide film is critical for reaction of the analyte gas at the surface. The last research study presented in the dissertation describes an oxide nanoparticle array developed for detecting methane and carbon monoxide in the presence of one another. A design of experiments was constructed and principal component analysis was used for determining the optimum temperatures of the metal-oxide elements. A four element array was developed with the SnO 2 and TiO2 sensor elements able to detect methane concentrations of interest and the ZnO and NiO sensor elements able to detect the carbon monoxide concentrations. A linear based prediction model was developed and tested for accuracy and reproducibility of the model to a series of random gas concentrations.

Andio, Mark A.

197

Self-assembled thin film chemical sensors  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Current chemical sensors suffer from poor molecular specificity, sensitivity, and stability and seldom have the recovery properties needed for real-time monitoring applications. We have employed self-assembly techniques to covalently bond species- selective reagents directly to the surface of the transducer so that analyte/reagent chemistry occurs at the interface between the transducer and the media to be monitored. The use of self-assembling monolayer and -multilayer (SAM) techniques results in stable sensing elements with optimal specificity built in through the use of reagents that have been designed for molecular recognition. Moreover, self-assembly chemistry applied to oxide surfaces allows flexible means of transduction spanning optical, electrochemical, mass-loading, and conduction methods. The work conducted on this project focused on demonstration of the methodology and the application to selected organic vapors (aromatic compounds and halogenated hydrocarbons). We have been able to develop a series of surface acoustic wave (SAW) sensors that are specific for aromatic compounds and halogenated hydrocarbons based on self-assembled thin films of cyclodextrins and calixarenes. Monolayers of seven different cyclodextrins and clixarenes have been attached to SAW transducers and their response to several organic molecules in the vapor phase have been measured. This preliminary data confirms the efficacy of this approach for real- time monitoring of hydrocarbons.

Swanson, B.; Li, DeQuan

1996-11-01

198

Remote datalogger for thin film sensors  

SciTech Connect

Electrochemical galvanic microsensors have been developed by the US Navy for the detection and monitoring of corrosive environments. These microsensors are ideal for monitoring corrosion in inaccessible or inconvenient locations, such as under coatings, paints, and sealants; within airframes or double hulls; and even in lay-ups of graphite-polymer composite materials. Presently, galvanic microsensors are being used with a companion electronics package, the Current Monitoring Unit (CMU), that provides signal-conditioning, digitization, and data-logging functions. Though the microsensors and CMU have been successfully tested in the field, the CMU must be electrically connected to the sensors, is bulky, and can accommodate only a limited number of sensor channels. A more compact and versatile solution is required before the advantages of the galvanic microsensor technology can be realized for practical corrosion monitoring in naval applications. In this paper, the authors report on the development of a miniature and versatile corrosion measurement system for use with the electrochemical galvanic microsensors. The system is comprised of Intelligent Corrosion Sensors (ICS) and a Data Gathering Unit (DGU). The ICS units combine the sensitivity and small size of existing bi-metallic thin-film galvanic microsensors with advanced micro-electronic and radio-frequency (RF) communications technology. The DGU can be either a fixed-base station or a hand-held portable unit and is used to query the ICS units via low-frequency (approximately 100 KHz) radio waves. The system will enable accurate, portable, cable-free corrosivity determination in virtually any location that has limited access.

Zollars, B.; Salazar, N.; Gilbert, J.; Sanders, M. [Systems and Processes Engineering Corp., Austin, TX (United States)

1997-12-01

199

Electron transport mechanism of thermally oxidized ZnO gas sensors  

NASA Astrophysics Data System (ADS)

ZnO gas sensor was fabricated by thermal oxidation of metallic Zn at different time periods. The sensors were characterized by I- V measurement with DC voltage, ranging from -2 to 2 volts, in both normal air and H 2 gas with concentration from 40 to 160 ppm. The transport mechanism of the carriers was found to be due to thermionic process through both the grain boundaries and the metal-semiconductor junctions. Resistance of the ZnO sensing film is independent of applied voltage in the range 0.5 V< Va<2 V; however, it is dependent on gas concentration, which makes it useful for gas sensing application.

Al-Hardan, N. H.; Abdullah, M. J.; Abdul Aziz, A.

2010-11-01

200

Processing and Gas Barrier Behavior of Multilayer Thin Nanocomposite Films  

E-print Network

loadings, creating super gas barrier thin films on substrates normally exhibiting high gas permeability. Branched polyethylenimine (PEI) and poly (acrylic acid) (PAA) were deposited using LbL to create gas barrier films with varying pH combinations. Film...

Yang, You-Hao

2012-10-19

201

Gas mixing apparatus for automated gas sensor characterization  

NASA Astrophysics Data System (ADS)

We developed a computer-controlled gas mixing system that provides automated test procedures for the characterization of gas sensors. The focus is the generation of trace gases (e.g. VOCs like benzene or naphthalene) using permeation furnaces and pre-dilution of test gases. With these methods, the sensor reaction can be analyzed at very low gas concentrations in the ppb range (parts per billion) and even lower. The pre-dilution setup enables to cover a high concentration range (1:62?500) within one test procedure. Up to six test gases, humidity, oxygen content, total flow and their variation over time can be controlled via a LabVIEW-based user-interface.

Helwig, Nikolai; Schüler, Marco; Bur, Christian; Schütze, Andreas; Sauerwald, Tilman

2014-05-01

202

Sensor activity of thin polymer films containing lead nanoparticles  

Microsoft Academic Search

Thin poly(p-xylylene) films containing lead nanoparticles were prepared by vacuum deposition technique. The vapors of p-xylylene monomer and lead were condensed onto the surfaces cooled down to 80 K. Films thus obtained were characterized by electric conductivity measurements during film samples formation. Such metallopolymer films exhibit sensor activity in the presence of ammonia in the atmospheric air. The influence of

Vladimir E Bochenkov; Niels Stephan; Ludwig Brehmer; Vyacheslav V Zagorskii; Gleb B Sergeev

2002-01-01

203

Printable polythiophene gas sensor array for low-cost electronic noses  

NASA Astrophysics Data System (ADS)

A route for generating arrays of printable polythiophene-based gas sensor materials suitable for low-cost manufacturing is demonstrated. Materials with complementary sensor responses are synthesized by incorporating functional groups into the molecule, either along the polymer backbone or as end-capping groups. Using these materials as printable sensor inks, a functional, integrated gas sensor array chip is fabricated using additive deposition techniques. The sensor array shows sensitivity to a range of volatile organic compounds down to concentrations of 10ppm. A three-terminal thin film transistor structure is used, allowing the extraction of multiple parameters that help to elucidate the mechanisms responsible for sensor response and the role of the functional groups in this response.

Chang, Josephine B.; Liu, Vincent; Subramanian, Vivek; Sivula, Kevin; Luscombe, Christine; Murphy, Amanda; Liu, Jinsong; Fréchet, Jean M. J.

2006-07-01

204

A Thick-Film NO2 Sensor Fabricated Using Zn-Sn-Sb-O Composite Material  

NASA Astrophysics Data System (ADS)

Thick film NO2 sensors comprised of various Zn-Sn-Sb-O composite materials have been studied. The gas-sensing materials were prepared by sintering a mixture of ZnO, SnO2 and Sb2O3 powders at 800, 1000 and 1200°C. Thick films were fabricated on an Al2O3 substrate using a conventional screen-printing method. The atomic ratios of the fabricated films were confirmed by the results obtained from EPMA (Electron probe micro analysis). The dominant compositions of the sintered gas-sensing materials were characterized by XRD (X-ray diffraction). It was found that the composition of the gas-sensing material depended on the initial Sb/Zn atomic ratio, where the gas-sensing material shows almost single-phase ZnSb2O6 when Sb/Zn = 2.0, a mixture of ZnSb2O6 and SnO2 when Sb/Zn = 1.0 and a mixture of SnO2 and an unknown crystal when Sb/Zn = 0.5. The sensing film shows high sensitivity and excellent selectivity for ppm levels of NO2 gas because the film shows no sensitivity for i-C4H10 and CO gases. The capability for NO2 detection in a practical application was examined by using the sensor to monitor the gas which was emitted from a kerosene heater.

Yamada, Yasushi; Yamashita, Katsuji; Masuoka, Yumi; Ogita, Masami

2003-12-01

205

Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection.  

PubMed

Carbon nanoflake (CNFL) was obtained from graphite pencil by using the electrochemical method and the CNFL/SnO2 composite material assessed its potential as an ammonia gas sensor. A thin film resistive gas sensor using the composite material was manufactured by the drop casting method, and the sensor was evaluated to test in various ammonia concentrations and operating temperatures. Physical and chemical characteristics of the composite material were assessed using SEM, TEM, SAED, EDS and Raman spectroscopy. The composite material having 10% of SnO2 showed 3 times higher sensor response and better repeatability than the gas sensor using pristine SnO2 nano-particle at the optimal temperature of 350°C. PMID:24473403

Lee, Soo-Keun; Chang, Daeic; Kim, Sang Wook

2014-03-15

206

A Micro Gas Sensor Using TiO2 Nanotubes to Detect Volatile Organic Compounds  

NASA Astrophysics Data System (ADS)

To develop a portable gas sensor with low power consumption, we deposited a micro size sensing film (100×100 µm2) on a Si substrate with an integrated micro heater and electrodes constructed using micro-electro-mechanical system (MEMS) technology. TiO2 nanotubes ca. 500 nm long with a 50 nm diameter were used to sense and detect volatile organic compounds (VOCs). We demonstrate that the MEMS sensor responded well to ethanol and toluene in air at elevated temperatures, such as 500 °C, which suggests that it is a promising battery-operable micro gas sensor for detecting VOCs.

Kida, Tetsuya; Seo, Min-Hyun; Suematsu, Koichi; Yuasa, Masayoshi; Kanmura, Yuichi; Shimanoe, Kengo

2013-04-01

207

Platinum thin film resistors as accurate and stable temperature sensors  

NASA Technical Reports Server (NTRS)

The measurement characteristics of thin-Pt-film temperature sensors fabricated using advanced methods are discussed. The limitations of wound-wire Pt temperature sensors and the history of Pt-film development are outlined, and the commonly used film-deposition, structuring, and trimming methods are presented in a table. The development of a family of sputtered film resistors is described in detail and illustrated with photographs of the different types. The most commonly used tolerances are reported as + or - 0.3 C + 0.5 percent of the temperature measured.

Diehl, W.

1984-01-01

208

Tungsten-oxide thin films as novel materials with high sensitivity and selectivity to NO 2 , O 3 , and H 2 S. Part II: Application as gas sensors  

Microsoft Academic Search

The electrical response of tungsten-oxide thin films as-deposited by electron-beam deposition and annealed (at 350–800 °C for 1–3 h in O2) to NO2, O3 and H2S was studied both experimentally and theoretically. In order to interpret the kinetic characteristics of tungsten-oxide thin films on exposure to different gases, a model based on surface adsorption\\/desorption processes coupled with bulk diffusion was

O. Berger; T. Hoffmann; W.-J. Fischer; V. Melev

2004-01-01

209

Influence of Al, In, Cu, Fe and Sn dopants on the response of thin film ZnO gas sensor to ethanol vapour  

Microsoft Academic Search

A spray pyrolysis technique was used to obtain ZnO:X films doped with different elements, X=Al, In, Cu, Fe and Sn. X-Ray diffraction, transmission electron microscopy and scanning electron microscopy were used to study the microstructure and surface morphology of the films. From the microstructural analysis, we can conclude that the amount as well as the type of dopant modifies the

M. Miki-Yoshida; J. Morales; J. Solis

2000-01-01

210

Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection  

NASA Technical Reports Server (NTRS)

A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs) and metal oxides nanowires or nanobelts, on a pair of interdigitated electrodes (IDE) processed with a silicon based microfabrication and micromachining technique. The IDE fingers were fabricated using thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to hazardous gases and vapors, such as acetone, benzene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing in our sensor platform can be understood by electron modulation between the nanostructure engineered device and gas molecules. As a result of the electron modulation, the conductance of nanodevice will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost.

Li, Jing; Lu, Yijiang

2005-01-01

211

Gas Sensors Based on Ceramic p-n Heterocontacts  

SciTech Connect

Ceramic p-n heterocontacts based on CuO/ZnO were successfully synthesized and a systematic study of their hydrogen sensitivity was conducted. The sensitivity and response rates of CuO/ZnO sensors were studied utilizing current-voltage, current-time, and impedance spectroscopy measurements. The heterocontacts showed well-defined rectifying characteristics and were observed to detect hydrogen via both dc and ac measurements. Surface coverage data were derived from current-time measurements which were then fit to a two-site Langmuir adsorption model quite satisfactorily. The fit suggested that there should be two energetically different adsorption sites in the system. The heterocontacts were doped in an attempt to increase the sensitivity and the response rate of the sensor. First, the effects of doping the p-type (CuO) on the sensor characteristics were investigated. Doping the p-type CuO with both acceptor and isovalent dopants greatly improved the hydrogen sensitivity. The sensitivity of pure heterocontact observed via I-V measurements was increased from {approx}2.3 to {approx}9.4 with Ni doping. Dopants also enhanced the rectifying characteristics of the heterocontacts. Small amounts of Li addition were shown to decrease the reverse bias (saturation) current to 0.2 mA at a bias level of -5V. No unambiguous trends were observed between the sensitivity, the conductivity, and the density of the samples. Comparing the two phase microstructure to the single phase microstructure there was no dramatic increase in the sensitivity. Kinetic studies also confirmed the improved sensor characteristics with doping. The dopants decreased the response time of the sensor by decreasing the response time of one of the adsorption sites. The n-type ZnO was doped with both acceptor and donor dopants. Li doping resulted in the degradation of the p-n junction and the response time of the sensor. However, the current-voltage behavior of Ga-doped heterocontacts showed the best rectifying characteristics with very high forward currents. Ga doped heterocontacts showed the highest sensitivity observed during current-time measurements as well, even though the sensor response was rather slow. Finally, a possible synergistic effect of doping both p and n-sides was studied by utilizing current-time measurements for 1.5 mol% Ni-CuO/1.5 mol% Ga-ZnO heterocontact. A sensitivity value of {approx}5.1 was obtained with the fastest response among all the samples. The time needed to reach 90% coverage was lowered by a factor of 4 when compared to the pure heterocontact and the time needed to reach 70% coverage was just over one minute. Heterocontact gas sensors are promising candidates for high temperature sensor applications. Today, Si-based microelectromechanical system (MEMS) technology has shown great promise for developing novel devices such as pressure sensors, chemical sensors, and temperature sensors through complex designs. However, the harsh thermal, vibrational, and corrosive environments common to many aerospace applications impose severe limitations on their use. Sensors based on ceramic p-n heterocontacts are promising alternatives because of their inherent corrosion resistance and environmental stability. The other advantages include their inherent tuning ability to differentiate between different reducing gases and a possible cost efficient production of a wireless sensor. Being a capacitive type sensor, its output can be transformed into a passive wireless device by creating a tuned LC circuit. In this way, the sensor output (the capacitance) can be accessed remotely by measuring the resonant frequency. The relatively simple structure of heterocontacts makes it suitable for thick film fabrication techniques to make sensor packages.

Seymen Murat Aygun

2004-12-19

212

A novel thick-film ceramic humidity sensor  

Microsoft Academic Search

The paper describes the results of studies on the fabrication and characterisation of a thick-film humidity sensor based on the semiconducting metal oxide MnWO4. The sensor element possesses a novel ‘sandwich’-configuration with a 40 ?m porous MnWO4 ceramic layer sandwiched by two 10 ?m polarity-reversed, interdigitated metal films. Instead of traditional glass frits, LiCl powders are used as adhesion promoters

Wenmin Qu; Jörg-Uwe Meyer

1997-01-01

213

Development of a PVDF film sensor for infrastructure monitoring  

Microsoft Academic Search

Development of a health monitoring system is of vital importance for all civil infrastructures. However, this effort has been stymied in part by the lack of suitable low priced sensors and associated signal conditioning. Very often the requirement of a controlled stable power supply to the sensor itself poses another challenge. Piezoelectric polymer films offer an excellent alternative to the

Debashis Satpathi; J. P. Victor; Ming L. Wang; H. Y. Yang; C. C. Shih

1999-01-01

214

Gas sensing mechanism of TiO 2-based thin films  

Microsoft Academic Search

Two classes of thin film gas sensors have been studied: TiO2 doped with Cr or Nb and TiO2–SnO2 mixed systems. Thin films have been prepared by the reactive sputtering from mosaic targets. It is demonstrated that titanium dioxide doped with Nb and Cr should be considered as a bulk sensor. Its performance is governed by the diffusion of point defects,

K. Zakrzewska

2004-01-01

215

Low power consumption thermal gas-flow sensor based on thermopiles of highly effective thermoelectric materials  

Microsoft Academic Search

A thermal gas-flow sensor based on thermopiles made of thin films of Bi0.87Sb0.13 for the n-type legs and Sb for the p-type legs with a high thermoelectric figure of merit is presented. The micromachined sensor chip is mounted within a package, which is kept at a constant temperature of 22°C. Experimental data and the results of finite-element analysis calculations concerning

U Dillner; E Kessler; S Poser; V Baier; J Müller

1997-01-01

216

Understanding the response behavior of potentiometric gas sensors for non-equilibrium gas mixtures  

SciTech Connect

Many applications of gas sensors require concentration measurements of reactive gases in mixtures that are out of thermodynamic equilibrium. These applications include: hydrogen and hydrocarbon fuel gas sensors operating in ambient air for explosion hazard detection, carbon monoxide detection in ambient air for health protection, combustion efficiency sensors for stoichiometry control, and nitric oxide sensors for air pollution monitoring. Many potentiometric and amperometric electrochemical sensor technologies have been developed for these applications. A class of the potentiometric sensors developed for gas mixtures are the non-Nerstian sensors. This presentation defines a categorization and theoretical analysis of three distinct electrochemical processes that can produce a non-Nernstian sensor response.

Garzon, F. H. (Fernando H.); Mukundan, R. (Rangachary); Brosha, E. L. (Eric L.)

2002-01-01

217

Resistive oxygen gas sensors based on CeO 2 fine powder prepared using mist pyrolysis  

Microsoft Academic Search

Mist pyrolysis was used to prepare cerium oxide (CeO2) fine powder. The average particle size was 200nm. Using the powder, resistive oxygen gas sensors based on porous thick films were fabricated by screen printing and firing at 1473K for 2h in air. The microstructure of the fired thick film showed the neck growth and the random network structure of cerium

Noriya Izu; Woosuck Shin; Norimitsu Murayama; Shuzo Kanzaki

2002-01-01

218

Method of Forming Micro-Sensor Thin-Film Anemometer  

NASA Technical Reports Server (NTRS)

A device for measuring turbulence in high-speed flows is provided which includes a micro- sensor thin-film probe. The probe is formed from a single crystal of aluminum oxide having a 14 deg half-wedge shaped portion. The tip of the half-wedge is rounded and has a thin-film sensor attached along the stagnation line. The bottom surface of the half-wedge is tilted upward to relieve shock induced disturbances created by the curved tip of the half-wedge. The sensor is applied using a microphotolithography technique.

Sheplak, Mark (Inventor); McGinley, Catherine B. (Inventor); Spina, Eric F. (Inventor); Stephens, Ralph M. (Inventor); Hopson, Purnell, Jr. (Inventor); Cruz, Vincent B. (Inventor)

2000-01-01

219

Fuzzy logic in the improvement of semiconductor gas sensor performance  

NASA Astrophysics Data System (ADS)

The authors developed fuzzy logic procedure for the exact estimation of ozone concentration in air with variable humidity. The used sensor array consisted of thin film ozone sensor fabricated by the authors and commercial Keithley humidity sensor. Two-input fuzzy sensor model was elaborated using the known calibration data and developing the learning procedure based on genetic algorithms. The performance of the model was tested.

Pisarkiewicz, Tadeusz; Potempa, Przemyslaw; Habdank-Wojewodzki, Tadeusz; Stapinski, Tomasz; Wojcik, P.

1999-04-01

220

Thin film magnetostrictive sensor with on-chip readout  

Microsoft Academic Search

We report the first successful integration of magnetostrictive Metglas2605S2 (Fesb{78}Sisb9Bsb{13}) thin film sensor system on silicon with high resolution capacitive readout. A deposition process for Metglas thin film has been developed to allow easy control of thin film composition. An amorphous microstructure has been achieved over a wide temperature range, and in-situ magnetic domain alignment can be accomplished at room

Yong Lu

1997-01-01

221

Ellipsometric measurements for thin-film-based sensor systems  

NASA Astrophysics Data System (ADS)

The application of a highly birefringent fiber polarization modulation technique for ellipsometric measurements on sol-gel thin films is described. The ability of the system to determine the ellipsometric parameters of thin films is demonstrated. The system is then used to monitor the ellipsometric parameters of thin films on exposure to a perturbing environment of humidity and pressure. The potential of the system for application in chemical sensor systems is indicated and discussed.

Chitaree, Ratchapak; Murphy, V.; Weir, K.; Palmer, Andrew W.; Grattan, Kenneth T. V.; MacCraith, Brian D.

1995-09-01

222

Zinc oxide thin-film chemical sensors in conjunction with neural network pattern recognition for trimethylamine and dimethylamine gases  

Microsoft Academic Search

Transient response curves for exposure to several gases are observed using zinc oxide (ZnO) thin-film gas sensors. It is found that an aluminium-doped ZnO (ZnO::Al) sensor exhibits a high sensitivity and an excellent selectivity for amine gases. In order to discriminate between gas species such as trimethylamine (TMA), dimethylamine (DMA) and other gases pattern recognition analysis using a neural network

H. Nanto; S. Tsubakino; T. Kawai; M. Ikeda; S. Kitagawa; M. Habara

1994-01-01

223

Enhancement of gas sensor response of nanocrystalline zinc oxide for ammonia by plasma treatment  

NASA Astrophysics Data System (ADS)

The effect of oxygen plasma treatment on nanocrystalline ZnO thin film based gas sensor was investigated. ZnO thin films were synthesized on alkali-free glass substrates by a sol-gel process. ZnO thin films were treated with oxygen plasma to change the number of vacancies/defects in ZnO. The effect of oxygen plasma on the structural, electrical, optical and gas sensing properties was investigated as a function of plasma treatment time. The results suggest that the microstructure and the surface morphology can be tuned by oxygen plasma treatment. The optical transmission in the visible range varies after the oxygen plasma treatment. Moreover, it is found that the oxygen plasma has significant impact on the electrical properties of ZnO thin films indicating a variation of resistivity. The oxygen plasma treated ZnO thin film exhibits an enhanced sensing response towards NH3 in comparison with that of the as-deposited ZnO sensor. When compared with the as-deposited ZnO film, the sensing response was improved by 50% for the optimum oxygen plasma treatment time of 8 min. The selectivity of 8 min plasma treated ZnO sensor was also examined for an important industrial gas mixture of H2, CH4 and NH3.

Hou, Yue; Jayatissa, Ahalapitiya H.

2014-08-01

224

Carbon-Nanotube-Based Chemical Gas Sensor  

NASA Technical Reports Server (NTRS)

Conventional thermal conductivity gauges (e.g. Pirani gauges) lend themselves to applications such as leak detectors, or in gas chromatographs for identifying various gas species. However, these conventional gauges are physically large, operate at high power, and have a slow response time. A single-walled carbon-nanotube (SWNT)-based chemical sensing gauge relies on differences in thermal conductance of the respective gases surrounding the CNT as it is voltage-biased, as a means for chemical identification. Such a sensor provides benefits of significantly reduced size and compactness, fast response time, low-power operation, and inexpensive manufacturing since it can be batch-fabricated using Si integrated-circuit (IC) process technology.

Kaul, Arunpama B.

2010-01-01

225

Development of a detection sensor for lethal H2S gas.  

PubMed

The gas which may be lethal to human body with short-term exposure in common industrial fields or workplaces in LAB may paralyze the olfactory sense and impose severe damages to central nervous system and lung. This study is concerned with the gas sensor which allows individuals to avoid the toxic gas that may be generated in the space with residues of organic wastes under 50 degrees C or above. This study investigates response and selectivity of the sensor to hydrogen sulfide gas with operating temperatures and catalysts. The thick-film semiconductor sensor for hydrogen sulfide gas detection was fabricated WO3/SnO2 prepared by sol-gel and precipitation methods. The nanosized SnO2 powder mixed with the various metal oxides (WO3, TiO2, and ZnO) and doped with transition metals (Au, Ru, Pd Ag and In). Particle sizes, specific surface areas and phases of sensor materials were investigated by SEM, BET and XRD analyses. The metal-WO3/SnO2 thick films were prepared by screen-printing method. The measured response to hydrogen sulfide gas is defined as the ratio (Ra/R,) of the resistance of WO3ISnO2 film in air to the resistance of WO3/SnO2 film in a hydrogen sulfide gas. It was shown that the highest response and selectivity of the sensor for hydrogen sulfide by doping with 1 wt% Ru and 10 wt% WO3 to SnO2 at the optimum operating temperature of 200 degrees C. PMID:22966558

Park, Young-Ho; Kim, Yong-Jae; Lee, Chang-Seop

2012-07-01

226

Sensors and Actuators A 125 (2006) 170177 Thin film temperature sensor for real-time measurement  

E-print Network

protons, but too much water can lead to local flooding. With poor thermal management, short-term effectsSensors and Actuators A 125 (2006) 170­177 Thin film temperature sensor for real-time measurement; received in revised form 25 May 2005; accepted 25 May 2005 Available online 15 August 2005 Abstract

Mench, Matthew M.

227

Miniature infrared gas sensors using photonic crystals  

NASA Astrophysics Data System (ADS)

We present an optical gas sensor based on the classical nondispersive infrared technique using ultracompact photonic crystal gas cells. The ultracompact device is conceptually based on low group velocities inside a photonic crystal gas cell and low-reflectivity antireflection layers coupling light into the device. Experimentally, an enhancement of the CO2 infrared absorption by a factor of 2.6 to 3.5 as compared to an empty cell, due to slow light inside a 2D silicon photonic crystal gas cell, was observed; this is in excellent agreement with numerical simulations. We show that, theoretically, for an optimal design enhancement factors of up to 60 are possible in the region of slow light. However, the overall transmission of bulk photonic crystals, and thus the performance of the device, is limited by fluctuations of the pore diameter. Numerical estimates suggest that the positional variations and pore diameter fluctuations have to be well below 0.5% to allow for a reasonable transmission of a 1 mm device.

Pergande, Daniel; Geppert, Torsten M.; Rhein, Andreas von; Schweizer, Stefan L.; Wehrspohn, Ralf B.; Moretton, Susanne; Lambrecht, Armin

2011-04-01

228

Cr2O3-modified ZnO thick film resistors as LPG sensors.  

PubMed

Thick films of pure ZnO were obtained by screen-printing technique. Surface functionalized ZnO thick films by Cr(2)O(3) were obtained by dipping pure ZnO thick films into 0.01M aqueous solution of chromium trioxide (CrO(3)). The dipped films were fired at 500 degrees C for 30 min. Upon firing, the CrO(3) would reduce to Cr(2)O(3). Cr(2)O(3)-activated (0.47 mass%) ZnO thick films resulted in LPG sensor. Upon exposure to 100 ppm LPG, the barrier height between Cr(2)O(3) and ZnO grains decreases markedly, leading to a drastic decrease in resistance. The sensor was found to sense LPG at 350 degrees C and no cross sensitivity was observed to other hazardous, polluting and inflammable gases. The quick response ( approximately 18s) and fast recovery ( approximately 42s) are the main features of this sensor. The effects of microstructures and dopant concentrations on the gas sensing performance of the sensor were studied and discussed. PMID:19084657

Patil, D R; Patil, L A

2009-02-15

229

Gas sensing properties of WO 3 doped rutile TiO 2 thick film at high operating temperature  

Microsoft Academic Search

A semiconductor gas sensor based on WO3 doped TiO2 having a rutile phase was fabricated on an Al2O3 substrate. The sensing film of the sensor was deposited by using screen printing. In order to enhance the sensitivity of the sensor, the sensing film was fabricated with a porous shape by high temperature heat treatment and the TiO2 layer was doped

Sung-Eun Jo; Byeong-Geun Kang; Sungmoo Heo; Soonho Song; Yong-Jun Kim

2009-01-01

230

Selectivity enhancement of SnO 2 gas sensors: simultaneous monitoring of resistances and temperatures  

Microsoft Academic Search

We present results obtained with microstructured tin dioxide-based gas sensors. Thick films with controlled nanocrystallite sizes were deposited on micromachined substrates. Discrimination between CO, CH4, and C2H5OH, and between CO, CH4 and H2 in changing humidity conditions was achieved by simultaneously measuring temperature and resistance changes upon gas exposure. These results make it possible to fulfil the American and European

A Heilig; N Barsan; U Weimar; W Göpel

1999-01-01

231

Sensoring hydrogen gas concentration using electrolyte made of proton  

SciTech Connect

Hydrogen gas promises to be a major clean fuel in the near future. Thus, sensors that can measure the concentrations of hydrogen gas over a wide dynamic range (e.g., 1 99.9%) are in demand for the production, storage, and utilization of hydrogen gas. However, it is difficult to directly measure hydrogen gas concentrations greater than 10% using conventional sensor [1 11]. We report a simple sensor using an electrolyte made of proton conductive manganese dioxide that enables in situmeasurements of hydrogen gas concentration over a wide range of 0.1 99.9% at room temperature.

Ueda, Yoshikatsu [Kyoto University, Japan; Kolesnikov, Alexander I [ORNL; Koyanaka, Hideki [Kyoto University, Japan

2011-01-01

232

Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers  

PubMed Central

Numerous medical studies show that tumor growth is accompanied by protein changes that may lead to the peroxidation of the cell membrane with consequent emission of volatile organic compounds (VOCs) by breath or intestinal gases that should be seen as biomarkers for colorectal cancer (CRC). The analysis of VOCs represents a non-invasive and potentially inexpensive preliminary screening technique. An array of chemoresistive gas sensors based on screen-printed metal oxide semiconducting films has been selected to discriminate gases of oncological interest, e.g., 1-iodononane and benzene, widely assumed to be biomarkers of colorectal cancer, from those of interference in the gut, such as methane and nitric oxide. PMID:25313496

Malagù, Cesare; Fabbri, Barbara; Gherardi, Sandro; Giberti, Alessio; Guidi, Vincenzo; Landini, Nicolò; Zonta, Giulia

2014-01-01

233

Thin Film Ceramic Strain Sensor Development for High Temperature Environments  

NASA Technical Reports Server (NTRS)

The need for sensors to operate in harsh environments is illustrated by the need for measurements in the turbine engine hot section. The degradation and damage that develops over time in hot section components can lead to catastrophic failure. At present, the degradation processes that occur in the harsh hot section environment are poorly characterized, which hinders development of more durable components, and since it is so difficult to model turbine blade temperatures, strains, etc, actual measurements are needed. The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in harsh environments. The effort at the NASA Glenn Research Center (GRC) to develop high temperature thin film ceramic static strain gauges for application in turbine engines is described, first in the fan and compressor modules, and then in the hot section. The near-term goal of this research effort was to identify candidate thin film ceramic sensor materials and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. A thorough literature search was conducted for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible with the NASA GRCs microfabrication procedures and substrate materials. Test results are given for tantalum, titanium and zirconium-based nitride and oxynitride ceramic films.

Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M.; Laster, Kimala L.

2008-01-01

234

A sensitivity enhanced gas sensor based on carbon nanotubes around microfiber  

NASA Astrophysics Data System (ADS)

In this paper, a carbon nanotubes (CNTs) films around microfiber gas sensor is reported. The CNTs films are deposited uniformly on the surface of microfiber with Langmuir-Blodgett(LB) coating technology. The CNTs which are rank tightly perform as cladding of microfiber and show the well absorption characteristic when they are used for gas sensing. The experimental results have shown the variations of intensity of transmitting light while the concentration of acetone and xylene around CNTs films based microfiber are different, The changes of light intensity are 3.1dB and 9.5dB respectively, when acetone and xylene concentrations reached 1200ppm. As the gas vaporizing freely, the results also show the fine characteristic with real-time response. The results demonstrate that this type of CNTs films around microfiber structure has great potential applied in trace gases detecting in micro-scale.

Jia, Lan; Wu, Yu; Yao, Baicheng; Yang, Feiya; Rao, Yunjiang

2012-02-01

235

Gas sensor arrays for quantitative analysis and alarm generation  

Microsoft Academic Search

The use of different approaches for analysing the response of a small sensor array based on artificial neural networks is presented. In one case the quantification of all compounds in a three component mixture is discussed. Based on the same gas sensor array (and data) an approach for extracting safety information directly from the sensor array response is illustrated. Carbon

G. Huyberechts; P. M. Szecowka; B. W. Licznerski

1997-01-01

236

Fabrication of clinical gas sensor using MEMS process  

Microsoft Academic Search

The polyaniline (PANi) micro gas sensor was developed for medical application using the silicon process in order to detect ammonia odor of stomach inside. Fabricated sensor can be applied to medical purpose if it can detect the variation of ammonia concentration that is generated by Helicobacter pylori (H. pylori) living in stomach. Today, there are many ammonia sensors for various

Yun-Su Lee; Kap-Duk Song; Jeung-Soo Huh; Wan-Young Chung; Duk-Dong Lee

2005-01-01

237

Porous silicon layers used for gas sensor applications  

Microsoft Academic Search

In this communication we report on the elaboration of porous silicon layers for gas sensor applications. We describe our test system for gas sensors, and we investigate the electric characteristics of porous silicon layers (p type) under different gases and levels of humidity. © 1997 Elsevier Science S.A.

A. Foucaran; F Pascal-Delannoy; A Giani; A Sackda; P Combette; A Boyer

1997-01-01

238

Frequency counting interrogation techniques applied to gas sensor arrays  

Microsoft Academic Search

This paper presents a simple, elegant interrogation technique for conducting polymer gas sensor arrays which takes advantage of their resistive and capacitive properties. To accomplish this, a four-channel Wien bridge oscillator system has been designed and constructed in which the conducting polymer sensor forms one of the arms of the bridge circuit. As gas or odour molecules adsorb and desorb

M. E. H. Amrani; P. A. Payne; R. M. Dowdeswell; A. D. Hoffman

1999-01-01

239

Nanostructured Tin Dioxide Materials for Gas Sensor Applications  

E-print Network

CHAPTER 30 Nanostructured Tin Dioxide Materials for Gas Sensor Applications T. A. Miller, S. D) levels for some species. Tin dioxide (also called stannic oxide or tin oxide) semi- conductor gas sensors undergone extensive research and development. Tin dioxide (SnO2) is the most important material for use

Wooldridge, Margaret S.

240

Characterisation of porosity and sensor response times of sol–gel-derived thin films for oxygen sensor applications  

Microsoft Academic Search

In recent years, sol–gel-derived films have played a significant role in optical sensor development. This paper focuses on the characterisation of oxygen-sensitive tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS)-based films. Film porosity and sensor response times are reported for a range of films fabricated under different conditions. Porosity data are correlated with predicted film behaviour and also with previous characterisation studies. Oxygen

C. McDonagh; P. Bowe; K. Mongey; B. D. MacCraith

2002-01-01

241

Preparation of the spacer for narrow electrode gap configuration in ionization-based gas sensor  

SciTech Connect

Carbon nanotubes (CNTs) have started to be developed as the sensing element for ionization-based gas sensors due to the demand for improved sensitivity, selectivity, stability and other sensing properties beyond what can be offered by the conventional ones. Although these limitations have been overcome, the problems still remain with the conventional ionization-based gas sensors in that they are bulky and operating with large breakdown voltage and high temperature. Recent studies have shown that the breakdown voltage can be reduced by using nanostructured electrodes and narrow electrode gap. Nanostructured electrode in the form of aligned CNTs array with evenly distributed nanotips can enhance the linear electric field significantly. The later is attributed to the shorter conductivity path through narrow electrode gap. The paper presents the study on the design consideration in order to realize ionization based gas sensor using aligned carbon nanotubes array in an optimum sensor configuration with narrow electrode gap. Several deposition techniques were studied to deposit the spacer, the key component that can control the electrode gap. Plasma spray deposition, electron beam deposition and dry oxidation method were employed to obtain minimum film thickness around 32 {mu}m. For plasma spray method, sand blasting process is required in order to produce rough surface for strong bonding of the deposited film onto the surface. Film thickness, typically about 39 {mu}m can be obtained. For the electron beam deposition and dry oxidation, the film thickness is in the range of nanometers and thus unsuitable to produce the spacer. The deposited multilayer film consisting of copper, alumina and ferum on which CNTs array will be grown was found to be removed during the etching process. This is attributed to the high etching rate on the thin film which can be prevented by reducing the rate and having a thicker conductive copper film.

Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif [Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Fundamental and Applied Science, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia); Electrical and Electronic Engineering, Universiti Teknologi PETRONAS, Seri Iskandar, Tronoh, Perak. (Malaysia)

2012-09-26

242

Preparation of the spacer for narrow electrode gap configuration in ionization-based gas sensor  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) have started to be developed as the sensing element for ionization-based gas sensors due to the demand for improved sensitivity, selectivity, stability and other sensing properties beyond what can be offered by the conventional ones. Although these limitations have been overcome, the problems still remain with the conventional ionization-based gas sensors in that they are bulky and operating with large breakdown voltage and high temperature. Recent studies have shown that the breakdown voltage can be reduced by using nanostructured electrodes and narrow electrode gap. Nanostructured electrode in the form of aligned CNTs array with evenly distributed nanotips can enhance the linear electric field significantly. The later is attributed to the shorter conductivity path through narrow electrode gap. The paper presents the study on the design consideration in order to realize ionization based gas sensor using aligned carbon nanotubes array in an optimum sensor configuration with narrow electrode gap. Several deposition techniques were studied to deposit the spacer, the key component that can control the electrode gap. Plasma spray deposition, electron beam deposition and dry oxidation method were employed to obtain minimum film thickness around 32 ?m. For plasma spray method, sand blasting process is required in order to produce rough surface for strong bonding of the deposited film onto the surface. Film thickness, typically about 39 ?m can be obtained. For the electron beam deposition and dry oxidation, the film thickness is in the range of nanometers and thus unsuitable to produce the spacer. The deposited multilayer film consisting of copper, alumina and ferum on which CNTs array will be grown was found to be removed during the etching process. This is attributed to the high etching rate on the thin film which can be prevented by reducing the rate and having a thicker conductive copper film.

Saheed, Mohamed Shuaib Mohamed; Mohamed, Norani Muti; Burhanudin, Zainal Arif

2012-09-01

243

Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications  

NASA Technical Reports Server (NTRS)

Aerospace applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. In particular, factors such as minimal sensor size, weight, and power consumption are particularly important. Development areas which have potential aerospace applications include launch vehicle leak detection, engine health monitoring, and fire detection. Sensor development for these applications is based on progress in three types of technology: 1) Micromachining and microfabrication (Microsystem) technology to fabricate miniaturized sensors; 2) The use of nanocrystalline materials to develop sensors with improved stability combined with higher sensitivity; 3) The development of high temperature semiconductors, especially silicon carbide. This presentation discusses the needs of space applications as well as the point-contact sensor technology and sensor arrays being developed to address these needs. Sensors to measure hydrogen, hydrocarbons, nitrogen oxides (NO,), carbon monoxide, oxygen, and carbon dioxide are being developed as well as arrays for leak, fire, and emissions detection. Demonstrations of the technology will also be discussed. It is concluded that microfabricated sensor technology has significant potential for use in a range of aerospace applications.

Hunter, Gary W.

2005-01-01

244

Thick-film humidity sensor based on porous ? material  

Microsoft Academic Search

A new compact, robust, yet fast and highly sensitive ceramic humidity sensor based on the semiconducting metal oxide 0957-0233\\/8\\/6\\/002\\/img2 has been developed using thick-film technology. The sensor element possesses a novel `sandwich' configuration with a 0957-0233\\/8\\/6\\/002\\/img3 porous 0957-0233\\/8\\/6\\/002\\/img2 ceramic layer sandwiched by two 0957-0233\\/8\\/6\\/002\\/img5 polarity-reversed interdigitated metal films. Instead of traditional glass frits, LiCl powders were used as adhesion promoters.

Wenmin Qu; Jörg-Uwe Meyer

1997-01-01

245

Flight evaluation of a stagnation detection hot-film sensor  

NASA Technical Reports Server (NTRS)

Results are presented of flight evaluation tests of a stagnation detection hot-film sensor. Experiments were conducted at steady level-flight conditions over a range of altitudes, angles of attack, and air speeds, as well as quasi-steady conditions during level-flight velocity acceleration and deceleration maneuvers. The results demonstrate the ability of a hot-film sensor to provide an accurate, reliable, and relatively nonintrusive measurement of the stagnation region in a flight environment. Stagnation could be identified within 0.1 inches.

Scott, Michael A.; Strain, Natale A.; Lee, Cynthia C.

1992-01-01

246

Development of a PVDF film sensor for infrastructure monitoring  

NASA Astrophysics Data System (ADS)

Development of a health monitoring system is of vital importance for all civil infrastructures. However, this effort has been stymied in part by the lack of suitable low priced sensors and associated signal conditioning. Very often the requirement of a controlled stable power supply to the sensor itself poses another challenge. Piezoelectric polymer films offer an excellent alternative to the ubiquitous strain gage technology. The PVDF film generates an electrical charge when mechanically deformed. The PVDF film is typically a high impedance source with a capacitance in the nanofarad range and measurement of low frequency event can pose a challenge. The authors have utilized a charge mode amplification scheme for measuring quasi-static processes. The processed signal can be transmitted to a data acquisition system via a RF microelectronic circuit. The PVDF film as a transducer can be cut to very small size and are very affordable at around 50 cents per sensor. The whole circuitry can be integrated into one single unit. It would require very low power to function and could be embedded in the structure for a large number of remote applications. In this article the authors have reported the result of the various characterization test that have been carried out to determine the suitability of the basic film as the core of an autoadaptive sensor system to be designed for infrastructure monitoring.

Satpathi, Debashis; Victor, J. P.; Wang, Ming L.; Yang, H. Y.; Shih, C. C.

1999-05-01

247

Thick-film densification for pyroelectric sensors  

Microsoft Academic Search

Densification and adherence of thick films are usually achieved by the addition of a glass frit in the screen printing ink. However, the glass may have a detrimental effect on the electrical properties of the active component as a ferroelectric. The addition of a new step - the application of a uniaxial or isostatic pressure on the dry film -

C. Lucat; F. Menil; R. Von Der Mühll

1997-01-01

248

A thick-film hydrogen sensor based on a ZnO:MoO3 formulation  

NASA Astrophysics Data System (ADS)

A highly selective ZnO:0957-0233/9/3/008/img8 based thick-film hydrogen sensor has been developed. The surface morphological studies indicate that the average grain size increases with higher amounts of 0957-0233/9/3/008/img8 in ZnO. It is observed that the sensitivity increases with the grain size. A possible working model for the sensor is postulated. 0957-0233/9/3/008/img8 was mixed in ZnO in various weight percentages. These mixtures were screen printed on alumina substrate. The sensors operate at an operating temperature of 0957-0233/9/3/008/img11C and their conductance increases linearly with the square root of the concentration of 0957-0233/9/3/008/img12 gas in ambient air. The response time of these sensors is around 20 s.

Jayadev Dayan, N.; Sainkar, S. R.; Karekar, R. N.; Aiyer, R. C.

1998-03-01

249

Flush mounting of thin film sensors  

NASA Technical Reports Server (NTRS)

Flush mounting of a sensor on a surface is provided by first forming a recessed area on the surface. Next, an adhesive bonding mixture is introduced into the recessed area. The adhesive bonding mixture is chosen to provide thermal expansion matching with the surface surrounding the recessed area. A strip of high performance polymeric tape is provided, with the sensor attached to the underside thereof, and the tape is positioned over the recessed area so that it acts as a carrier of the sensor. A shim having flexibility so that it will conform to the surface surrounding the recessed area is placed over the tape, and a vacuum pad is placed over the shim. The area above the surface is then evacuated while holding the sensor flush with the surface during curing of the adhesive bonding mixture. After such curing, the pad, shim, and tape are removed from the sensor, electrical connections for the sensor are provided, after which the remaining space in the recessed area is filled with a polymeric foam.

Moore, Thomas C., Sr. (inventor)

1992-01-01

250

Thin film micro carbon oxide sensor using MEMS process  

Microsoft Academic Search

Pt\\/Na+ ion conductive ceramics thin film\\/Pt\\/carbonate a2CO3:BaCO3=1:1.7 mol) structure micro CO2 sensors were prepared and their sensing properties were investigated. The thin film Na+ ion conductors formed by using RF magnetron sputtering technique. The chemical composition of thin film Nae6>\\/e6> ion conductor was found to be same as that of NASICON(x=2). The nernst slope of 57 mV\\/decade or CO2 concentration

Yeung-Il Bang; Kap-Duk Song; Jeung-Soo Huh; Soon-Don oi; Duk-Dong Lee

2003-01-01

251

Fiber-Optic Sensor Would Monitor Growth of Polymer Film  

NASA Technical Reports Server (NTRS)

A proposed optoelectronic sensor system would measure the increase in thickness of a film of parylene (a thermoplastic polymer made from para-xylene) during growth of the film in a vapor deposition process. By enabling real-time monitoring of film thickness, the system would make it possible to identify process conditions favorable for growth and to tailor the final thickness of the film with greater precision than is now possible. The heart of the sensor would be a pair of fiber-optic Fabry-Perot interferometers, depicted schematically in the figure. (In principle, a single such interferometer would suffice. The proposal calls for the use of two interferometers for protective redundancy and increased accuracy.) Each interferometer would include a light source, a fiber-optic coupler, and photodetectors in a control box outside the deposition chamber. A single-mode optical fiber for each interferometer would run from inside the control box to a fused-silica faceplate in a sensor head. The sensory tips of the optical fibers would be polished flush with the free surface of the faceplate. In preparation for use, the sensor head would be mounted with a hermetic seal in a feed-through port in the deposition chamber, such that free face of the faceplate and the sensory tips of the optical fibers would be exposed to the deposition environment. During operation, light would travel along each optical fiber from the control box to the sensor head. A small portion of the light would be reflected toward the control box from the end face of each fiber. Once growth of the parylene film started, a small portion of the light would also be reflected toward the control box from the outer surface of the film. In the control box, the two reflected portions of the light beam would interfere in one of the photodetectors. The difference between the phases of the interfering reflected portions of the light beam would vary in proportion to the increasing thickness of the film and the known index of refraction of the film, causing the photodetector reading to vary in proportion to a known sinusoidal function of film thickness. Electronic means of monitoring this variation and the corresponding variation in phase and thickness are well established in the art of interferometry. Hence, by tracking the cumulative change in phase difference from the beginning of deposition, one could track the growing thickness of the film to within a small fraction of a wavelength of light.

Beamesderfer, Michael

2005-01-01

252

Thin film devices used as oxygen partial pressure sensors  

NASA Technical Reports Server (NTRS)

Electrical conductivity of zinc oxide films to be used in an oxygen partial pressure sensor is measured as a function of temperature, oxygen partial pressure, and other atmospheric constituents. Time response following partial pressure changes is studied as a function of temperature and environmental changes.

Canady, K. S.; Wortman, J. J.

1970-01-01

253

Flexible PZT thin film tactile sensor for biomedical monitoring.  

PubMed

This paper presents the development of tactile sensors using the sol-gel process to deposit a PZT thin-film from 250 nm to 1 ?m on a flexible stainless steel substrate. The PZT thin-film tactile sensor can be used to measure human pulses from several areas, including carotid, brachial, finger, ankle, radial artery, and the apical region. Flexible PZT tactile sensors can overcome the diverse topology of various human regions and sense the corresponding signals from human bodies. The measured arterial pulse waveform can be used to diagnose hypertension and cardiac failure in patients. The proposed sensors have several advantages, such as flexibility, reliability, high strain, low cost, simple fabrication, and low temperature processing. The PZT thin-film deposition process includes a pyrolysis process at 150 °C/500 °C for 10/5 min, followed by an annealing process at 650 °C for 10 min. Finally, the consistent pulse wave velocity (PWV) was demonstrated based on human pulse measurements from apical to radial, brachial to radial, and radial to ankle. It is characterized that the sensitivity of our PZT-based tactile sensor was approximately 0.798 mV/g. PMID:23698262

Tseng, Hong-Jie; Tian, Wei-Cheng; Wu, Wen-Jong

2013-01-01

254

Thin Film Ceramic Strain Sensor Development for Harsh Environments  

NASA Technical Reports Server (NTRS)

The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in propulsion system applications. In order to have a more passive method of negating changes of resistance due to temperature, an effort is underway at NASA GRC to develop high temperature thin film ceramic static strain gauges for application in turbine engines, specifically in the fan and compressor modules on blades. Other applications include on aircraft hot section structures and on thermal protection systems. The near-term interim goal of this research effort was to identify candidate thin film ceramic sensor materials to test for viability and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. This goal was achieved by conducting a thorough literature search for ceramics that have the potential for application as high temperature thin film strain gauges chemically and physically compatible and selecting potential candidate materials for with NASA GRC's microfabrication procedures and substrates.

Wrbanek, John D.; Fralick, Gustave

2007-01-01

255

Gas-sensitive properties of thin tin dioxide films under the influence of hydrogen sulfide  

NASA Astrophysics Data System (ADS)

In order to develop sensors for selective detection of hydrogen sulfide in the air, the characteristics of thin SnO2 films with various additives (Au, Pt) in the volume and deposited catalysts (Pt / Pd, Au) are studied. The films were obtained by magnetron sputtering. The sensor response to H2S (the ratio of the sensor conductivity G1 in the presence of hydrogen sulfide in the gas to the conductivity G0 in the clean air) is studied as a function of the operating temperature and gas concentration in the range 0.1-70 ppm. It is shown that the sensors with the addition of gold in the volume can be used to detect maximum permissible concentrations (7 ppm) of hydrogen sulfide in the working area after stabilization of the characteristics during long-term tests.

Sevast'yanov, E. Yu.; Maksimova, N. K.; Chernikov, E. V.; Firsov, A. A.

2012-11-01

256

Ultralow drift in organic thin-film transistor chemical sensors by pulsed gating  

E-print Network

Ultralow drift in organic thin-film transistor chemical sensors by pulsed gating Richard D. Yang the baseline stability of organic thin-film transistor OTFT chemical sensors. Trap states in the organic films of Physics. DOI: 10.1063/1.2767633 I. INTRODUCTION Organic thin-film transistors OTFTs have been investi

Kummel, Andrew C.

257

Resistive humidity sensor based on vanadium complex films  

NASA Astrophysics Data System (ADS)

A resistive-type relative humidity (RH) sensor based on vanadium complex (VO2(3-fl)) film is reported in this study. Gold electrodes were deposited on the glass substrates in a co-planar structure. A thin film of vanadium complex was coated as a humidity-sensing material on the top of the pre-patterned electrodes. The humidity-sensing principle of the sensor was based on the conductivity change of coated sensing element upon adsorption/desorption of water vapor. The resistance of the humidity sensor measured at 1 kHz decreased linearly with increasing the humidity in the range of 35%–70% RH. The overall resistance of the sensor decreases 11 times. An equivalent circuit for the VO2(3-fl) based resistive-type humidity sensor was developed. The properties of the sensor studied in this work make it beneficial for use in the instruments for environmental monitoring of humidity.

Karimov, Kh. S.; Saleem, M.; Mahroof-Tahir, M.; Akram, R.; Saeed Chanee, M. T.; Niaz, A. K.

2014-09-01

258

Transient hot-film sensor response in a shock tube  

NASA Technical Reports Server (NTRS)

Shock tube experiments were performed to determine the response of a hot-film sensor, mounted flush on the side wall of a shock tube, to unsteady flow behind a normal shock wave. The present experiments attempt to isolate the response of the anemometer due only to the change in convective heat transfer at the hot-film surface. The experiments, performed at low supersonic shock speeds in air, are described along with the data acquisition procedure. The change in convective heat transfer is deduced from the data and the results are compared with those from transient boundary layer theory and another set of experimental results. Finally, a transient local heat transfer coefficient is formulated for use as the forcing function in a hot-film sensor instrument model simulation.

Roberts, A. S., Jr.; Ortgies, K. R.; Gartenberg, E.

1989-01-01

259

Temperature-modulated direct thermoelectric gas sensors: thermal modeling and results for fast hydrocarbon sensors  

NASA Astrophysics Data System (ADS)

Direct thermoelectric gas sensors are a promising alternative to conductometric gas sensors. For accurate results, a temperature modulation technique in combination with a regression analysis is advantageous. However, the thermal time constant of screen-printed sensors is quite large. As a result, up to now the temperature modulation frequency (20 mHz) has been too low and the corresponding principle-related response time (50 s) has been too high for many applications. With a special design, respecting the physical properties of thermal waves and the use of signal processing similar to a lock-in-amplifier, it is possible to achieve response times of about 1 s. As a result, direct thermoelectric gas sensors with SnO2 as a gas-sensitive material respond fast and are reproducible to the propane concentration in the ambient atmosphere. Due to the path-independent behavior of the thermovoltage and the temperature, the measured thermopower of two sensors is almost identical.

Rettig, Frank; Moos, Ralf

2009-06-01

260

Volatile organic compound gas sensor based on aluminum-doped zinc oxide with nanoparticle.  

PubMed

Thick film semiconductor gas sensors based on aluminum-doped zinc oxide (AZO) with nanoparticle size were fabricated to detect volatile organic compound (VOC) existed in building, especially, formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. The sensing materials for screen printing were prepared using roll milling process with binder. The crystallite sizes of prepared materials were about 15 nm through X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Gas response characteristics were examined for formaldehyde (HCHO), benzene, carbon monoxide, carbon dioxide gas existing in building. In particular, the sensors showed responses to HCHO gas at sub ppm as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repeativity, selectivity, and response time of sensor. The transients were very sharp, taking less than 2 s for 90% response. The sensor has shown very stable response at 350 degrees C and followed a very good behavior and showed 60% response in 50 ppb HCHO concentration at 350 degrees C operating temperatures. PMID:23882782

Choi, Nak-Jin; Lee, Hyung-Kun; Moon, Seung Eon; Yang, Woo Seok; Kim, Jongdae

2013-08-01

261

Design and Experimentation with Sandwich Microstructure for Catalytic Combustion-Type Gas Sensors  

PubMed Central

The traditional handmade catalytic combustion gas sensor has some problems such as a pairing difficulty, poor consistency, high power consumption, and not being interchangeable. To address these issues, integrated double catalytic combustion of alcohol gas sensor was designed and manufactured using silicon micro-electro-mechanical systems (MEMS) technology. The temperature field of the sensor is analyzed using the ANSYS finite element analysis method. In this work, the silicon oxide-PECVD-oxidation technique is used to manufacture a SiO2-Si3N2-SiO2 microstructure carrier with a sandwich structure, while wet etching silicon is used to form a beam structure to reduce the heat consumption. Thin-film technology is adopted to manufacture the platinum-film sensitive resistance. Nano Al2O3-ZrO-ThO is coated to format the sensor carrier, and the sensitive unit is dipped in a Pt-Pd catalyst solution to form the catalytic sensitive bridge arm. Meanwhile the uncoated catalyst carrier is considered as the reference unit, realizing an integrated chip based on a micro double bridge and forming sensors. The lines of the Pt thin-film resistance have been observed with an electronic microscope. The compensation of the sensitive material carriers and compensation materials have been analyzed using an energy spectrum. The results show that the alcohol sensor can detect a volume fraction between 0 and 4,500 × 10?6 and has good linear output characteristic. The temperature ranges from ?20 to +40 °C. The humidity ranges from 30% to 85% RH. The zero output of the sensor is less than ±2.0% FS. The power consumption is ?0.2 W, and both the response and recovery time are approximately 20 s. PMID:24625742

Gu, Jun-Tao; Zhang, Yong-De; Jiang, Jin-Gang

2014-01-01

262

Design and experimentation with sandwich microstructure for catalytic combustion-type gas sensors.  

PubMed

The traditional handmade catalytic combustion gas sensor has some problems such as a pairing difficulty, poor consistency, high power consumption, and not being interchangeable. To address these issues, integrated double catalytic combustion of alcohol gas sensor was designed and manufactured using silicon micro-electro-mechanical systems (MEMS) technology. The temperature field of the sensor is analyzed using the ANSYS finite element analysis method. In this work, the silicon oxide-PECVD-oxidation technique is used to manufacture a SiO2-Si3N2-SiO2 microstructure carrier with a sandwich structure, while wet etching silicon is used to form a beam structure to reduce the heat consumption. Thin-film technology is adopted to manufacture the platinum-film sensitive resistance. Nano Al2O3-ZrO-ThO is coated to format the sensor carrier, and the sensitive unit is dipped in a Pt-Pd catalyst solution to form the catalytic sensitive bridge arm. Meanwhile the uncoated catalyst carrier is considered as the reference unit, realizing an integrated chip based on a micro double bridge and forming sensors. The lines of the Pt thin-film resistance have been observed with an electronic microscope. The compensation of the sensitive material carriers and compensation materials have been analyzed using an energy spectrum. The results show that the alcohol sensor can detect a volume fraction between 0 and 4,500 × 10(-6) and has good linear output characteristic. The temperature ranges from -20 to +40 °C. The humidity ranges from 30% to 85% RH. The zero output of the sensor is less than ±2.0% FS. The power consumption is ?0.2 W, and both the response and recovery time are approximately 20 s. PMID:24625742

Gu, Jun-Tao; Zhang, Yong-De; Jiang, Jin-Gang

2014-01-01

263

Dispersive-infrared gas sensor system design and operation manual  

SciTech Connect

The objective of this project was to develop nondispersive infrared (IR) gas sensor capable of detecting and quantifying gaseous HCl emitted during the launch of rockets using solid propellants. To satisfy the practical requirements of this application, the sensor must be capable of unmanned field operation, remotely addressable, field calibratable, and able to measure low concentrations (1 ppm) of HCl at relatively rapid rates.

Kulp, T.J.; McRae, T.G.; Kennedy, R.; Garvis, D.

1991-10-01

264

Metal Oxide Semiconductor Nanoparticles for Chemical Gas Sensors  

Microsoft Academic Search

During the recent years, it has been widely recognized that the use of semiconductor nanoparticles for the fabrication of chemical gas sensors by screen-printing technology definitely improves the sensor performance. In this paper, we review the possibilities offered by Fourier transform infrared (FTIR) spectroscopy for the study of semiconductor nanoparticles. Thanks to FTIR spectroscopy, it is possible to identify the

Marie-Isabelle Baraton

2006-01-01

265

A Thin Film Multifunction Sensor for Harsh Environments  

NASA Technical Reports Server (NTRS)

The status of work at NASA Glenn Research Center to develop a minimally intrusive integrated sensor to provide realtime measurement of strain, heat flux and flow in high temperature environments is presented in this paper. The sensor can be beneficial as a single package to characterize multiple stress and strain modes simultaneously on materials and components during engine development and validation. A major technical challenge is to take existing individual gauge designs and modify them into one integrated thin film sensor. Ultimately, the goal is to develop the ability to deposit the sensors directly onto internal engine parts or on a small thin substrate that can be attached to engine components. Several prototype sensors constructed of platinum, platinum-rhodium alloy, and alumina on constant-strain alumina beams have been built and bench-tested. The technical challenges of the design. construction, and testing are discussed. Data from the preliminary testing of the sensor array is presented. The future direction for the sensor development is discussed as well.

Wrbanek, John D.; Fralick, Gustave C.; Martin, Lisa C.; Blaha, Charles A.

2001-01-01

266

Enhanced Mass Sensitivity of Carbon Nanotube Multilayer Measured by QCM-Based Gas Sensors  

Microsoft Academic Search

\\u000a A Quartz Crystal Microbalance (QCM) gas sensor coated with carbon nanotubes (CNTs) layered films as chemically interactive\\u000a nanomaterial is described. A QCM resonator integrated on AT-cut quartz substrate has been functionally characterized as oscillator\\u000a at the resonant frequency of 10 MHz. The CNTs have been grown by chemical vapor deposition (CVD) system onto alumina substrates,\\u000a coated with 2.5 nm thick Fe catalyst,

M. Penza; P. Aversa; R. Rossi; M. Alvisi; G. Cassano; D. Suriano; E. Serra

267

Catalytic combustion type hydrogen gas sensor using TiO 2 and UV-LED  

Microsoft Academic Search

A thick film catalytic gas sensor operable at a temperature of 82°C in the presence of UV-LED (ultra violet-light emitting diode) has been developed to measure hydrogen concentration in the range of 0.5–5%. The sensing material as a combustion catalyst consists of TiO2 (5wt%) and Pd\\/Pt (20wt%) supported on ?-Al2O3 powder. The reference material to compensate the heat capacity of

Chi-Hwan Han; Dae-Woong Hong; Sang-Do Han; Jihye Gwak; Krishan C. Singh

2007-01-01

268

Dopants in Tin Oxide Gas Sensor for Enhancing Detection of Alcohol  

Microsoft Academic Search

SnO2 films were prepared from sol-gel by spinning on substrate, with various dopants at 0.5-4 mole%. The dopants included Al, La, Nd, Mn, Ni, Cu, Sb, In, Pd, Pt, Nb, Si and Fe. The effects of these dopants towards the alcohol sensitivity of SnO2 gas sensor were investigated. Only four dopants , Al, Pt ,Pd and Si, have shown the

Paisan Setasuwon

269

Multifunctional sensing film used for fiber optic cholesterol sensor  

NASA Astrophysics Data System (ADS)

In this paper, by using ethyl silicate, ethanol and fluorescence indicator as the precursors, the multifunctional optic biosensing (MOBS) film containing cholesterol oxidase and the fluorescence indicator was prepared by sol-gel method. This biosensing film has both the function of biocatalyst and oxygen biosensing and can be used as the effective biosensing materials for fiber optic cholesterol sensor. The fiber optical cholesterol sensor based on fluorescence quenching was designed and fabricated using lock-in amplifying technology to realize the detection of cholesterol concentration. The experimental results showed that the best precursor proportion in volume ratio is: ethyl silicate: ethanol: 0.01 M HCl = 5: 8: 1.6. The drying rate of the sol could be controlled by using formamide as the controlling drier. When 16% of formamide were added in the mixing system, the cracks of the film could be reduced greatly and the immobilization of cholesterol oxidase and the fluorescence indicator could be improved effectively. A linear relationship between phase delay ? and the cholesterol concentration was observed in the range of 100 to 500 mg/dL. Since the cholesterol concentration is in the range of 140 to 200 mg/dL in the blood of healthy people, it will be possible for the sensor to be used in clinical detection. The biosensor with MOBS film has the response time of about 30 s, which is rather fast for a biosensor, and the relative deviation of +/-5.03%. This biosensor also has good stability.

Wang, Bin; Huang, Jun; Li, Mingtian; Zhou, Xuan

2008-12-01

270

Effect of deposition times on structure of Ga-doped ZnO thin films as humidity sensor  

NASA Astrophysics Data System (ADS)

Gallium doped zinc oxide (GZO) has good electrical property. It is widely used as transparent electrode in photovoltaic devices, and sensing element in gas and pressure sensors. GZO thin film was prepared using magnetron sputtering. Film deposition times were set at 10, 15, 20, 25 and 30 minutes to get samples of different thickness. X-ray diffraction (XRD) was used to determine the structure of GZO thin films. Structure for GZO thin film is hexagonal wurtzite structure. Morphology and thickness of GZO thin films was observed from FESEM micrographs. Grain size and thickness of thin films improved with increasing deposition times. However, increasing the thickness of thin films occur below 25 minutes only. Electrical properties of GZO thin films were studied using a four-point probe technique. The changes in the structure of the thin films lead to the changed of their electrical properties resulting in the reduction of the film resistance. These thin films properties significantly implying the potential application of the sample as a humidity sensor.

Khalid, Faridzatul Shahira; Awang, Rozidawati

2014-09-01

271

Turbine Blade Temperature Measurements Using Thin Film Temperature Sensors  

NASA Technical Reports Server (NTRS)

The development of thin film temperature sensors is discussed. The technology for sputtering 2 micron thin film platinum versus platinum 10 percent rhodium thermocouples on alumina forming coatings was improved and extended to applications on actual turbine blades. Good adherence was found to depend upon achieving a proper morphology of the alumina surface. Problems of adapting fabrication procedures to turbine blades were uncovered, and improvements were recommended. Testing at 1250 K at one atmosphere pressure was then extended to a higher Mach No. (0.5) in combustor flow for 60 hours and 71 thermal cycles. The mean time to failure was 47 hours accumulated during 1 hour exposures in the combustor. Calibration drift was about 0.1 percent per hour, attributable to oxidation of the rhodium in the thin films. An increase in film thickness and application of a protective overcoat are recommended to reduce drift in actual engine testing.

Grant, H. P.; Przybyszewski, J. S.; Claing, R. G.

1981-01-01

272

Ion-Conducting Polymer Films as Chemical Sensors  

SciTech Connect

Solid Polymer Electrolytes (SPE) are widely used in batteries and fuel cells because of the high ionic conductivity that can be achieved at room temperature. The ions are usually Li or protons, although other ions can be shown to conduct in these polymer films. There has been very little work on using these films as chemical sensors. We have found that thin films of polymers like polyethyleneoxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCS) like common solvents. We will present impedance spectroscopy of PEO films in the frequency range 0.01 Hz to 1 MHz for different concentrations of VOCS. We find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and parasitic capacitances.

Hughes, R.C.; Patel, S.V.; Pfeifer, K.B.; Yelton, W.G.

1999-05-03

273

Thermal balance analysis of a micro-thermoelectric gas sensor using catalytic combustion of hydrogen.  

PubMed

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Q(catalyst) required for 1 mV of ?V(gas) was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Q(catalyst) for 200 and 1,000 ppm H? was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

274

Properties of thin films for high temperature flow sensors  

NASA Technical Reports Server (NTRS)

Requirements of material parameters of high temperature flow sensors are identified. Refractory metal silicides offer high temperature sensitivity and high frequency response and are stable up to 1000 C. Intrinsic semiconductors of high band gap are also considered as sensor elements. SiC and diamond are identified. Combined with substrates of low thermal and electrical conductivity, such as quartz or Al2O3, these materials meet several requirements of high sensitivity and frequency response. Film deposition and patterning techniques suitable for these materials are identified.

Albin, Sacharia

1991-01-01

275

Sensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas Detection  

E-print Network

(SAW) sensor [9], an optical fiber sensor [lo] and a piezo- electric crystal detector [ll reported. Furthermore, a variety of other hydrogen sensors have been developed: a surface acoustic waveSensors and Actuators B, 2 (1990) 19-81 79 Photopyroelectric (P'E) Sensor for Trace Hydrogen Gas

Mandelis, Andreas

276

Nanoporous thin film platform for biophotonic sensors  

NASA Astrophysics Data System (ADS)

A Nanoporous glass matrix is developed to encapsulate molecular probes for monitoring important biological parameters such as DO. The hydrophobic nanoporous host matrix is designed and fabricated using room temperature sol gel technique. The doped sol gel is then coated on biocompatible self adhesive patches or directly coated on the biocontainers. We demonstrate the application of this technique in non-invasive monitoring DO as well as oxygen partial pressure in a closed fermentation process as well as in a cell culture plate during bacterial growth. Dynamic response of sensor, sensitivity and accuracy is also demonstrated in this paper.

Alla, Suresh; Solanki, Rina; Mattley, Yvette D.; Dabhi, Harish; Shahriari, Mahmoud R.

2009-02-01

277

Surface and gas sensing properties of nanocrystalline nickel oxide thin films  

NASA Astrophysics Data System (ADS)

Preparation of nanocrystalline nickel oxide thin films and their applications for gas sensors were investigated. Nickel oxide thin films were deposited on a glass substrate by a sol-gel process. The microstructure and surface properties of the prepared sample were studied using X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The prepared nickel oxide films had a nanocrystalline NiO phase with the average grain size of 16 nm. Electronic property measurements indicated that the nickel oxide films had p-type conductivity with the activation energy of electrical conductivity around 0.42 eV. Gas sensing characteristics of NiO films were measured for different reducing gases, such as H2, CH4, NH3 and mixtures of these gases. The gas sensor response as well as response and recovery time was analyzed to understand sensing mechanism, selectivity and optimal sensing conditions. The cross sensitivity data suggested that this sensor could be used to detect gas molecules selectively in ambient conditions with high repeatability.

Soleimanpour, Amir M.; Jayatissa, Ahalapitiya H.; Sumanasekera, Gamini

2013-07-01

278

Correlation between XPS, Raman and TEM measurements and the gas sensitivity of Pt and Pd doped SnO2 based gas sensors  

Microsoft Academic Search

Nanocrystalline thick-film SnO2 sensors with different dopants were fabricated by an optimized screen printing process and subsequent annealing. Powders\\u000a were used as starting materials which were prepared by a wet chemical process from SnCl4. Microanalysis was performed of both, the precursors and the final sensor materials with their different annealing conditions.\\u000a Gas sensing tests with CO, CH4 and NO2 in

J. Kappler; N. Bârsan; U. Weimar; A. Dièguez; J. L. Alay; A. Romano-Rodriguez; J. R. Morante; W. Göpel

1998-01-01

279

Use of conducting polypyrrole blends as gas sensors  

Microsoft Academic Search

We discuss the use of polymeric blends formed by the controlled growth of doped polypyrrole chains in the interior of films of different dielectric polymers as sensors of the presence of representative examples of volatile organic compounds. The dielectric films (of either (poly(caprolactone), poly(ethylene oxide), poly(methyl-methacrylate), poly(vinyl alcohol), or poly(vinyl-acetate)) containing an appropriate oxidizing agent were prepared atop a conducting

C. P. de Melo; B. B. Neto; E. G. de Lima; L. F. B. de Lira; J. E. G. de Souza

2005-01-01

280

Off gas film cooler cleaner  

SciTech Connect

An apparatus is described for cleaning depositions of particulate matter from the inside of tubular piping while the piping is in use. The apparatus is remotely controlled in order to operate in hazardous environments. A housing containing brush and shaft assemblies is mounted on top of the tubular piping. Pneumatic cylinders provide linear motion. A roller nut bearing provides rotary motion. The combined motion causes the brush assembly to rotate as it travels along the tube dislodging particulate matter. The main application for this invention is to clean the off gas cooler of a radioactive waste vitrification unit.

Dhingra, H.S.; Koch, W.C.; Burns, D.C.

1995-12-31

281

Theory for a gas composition sensor based on acoustic properties  

NASA Technical Reports Server (NTRS)

Sound travelling through a gas propagates at different speeds and its intensity attenuates to different degrees depending upon the composition of the gas. Theoretically, a real-time gaseous composition sensor could be based on measuring the sound speed and the acoustic attenuation. To this end, the speed of sound was modelled using standard relations, and the acoustic attenuation was modelled using the theory for vibrational relaxation of gas molecules. The concept for a gas composition sensor is demonstrated theoretically for nitrogen-methane-water and hydrogen-oxygen-water mixtures. For a three-component gas mixture, the measured sound speed and acoustic attenuation each define separate lines in the composition plane of two of the gases. The intersection of the two lines defines the gas composition. It should also be possible to use the concept for mixtures of more than three components, if the nature of the gas composition is known to some extent.

Phillips, Scott; Dain, Yefim; Lueptow, Richard M.

2003-01-01

282

High-performance sensors based on molybdenum disulfide thin films.  

PubMed

High-performance sensors based on molybdenum disulfide (MoS2 ) grown by sulfurization of sputtered molybdenum layers are presented. Using a simple integration scheme, it is found that the electrical conductivity of MoS2 films is highly sensitive to NH3 adsorption, consistent with n-type semiconducting behavior. A sensitivity of 300 ppb at room temperature is achieved, showing the high potential of 2D transition metal-dichalcogenides for sensing. PMID:24027114

Lee, Kangho; Gatensby, Riley; McEvoy, Niall; Hallam, Toby; Duesberg, Georg S

2013-12-10

283

Recent Progress in Electrochemical Gas Sensors Based on Solid Electrolytes  

NASA Astrophysics Data System (ADS)

In recent years, highly sensitive and selective detection of various gases has become increasingly important especially for the purpose of emission control and atmospheric environmental monitoring. Up to date, various electrochemical gas sensors based on solid electrolytes have been developed or proposed. The importance of solid electrolyte sensors was strongly recognized at an early stage when potentiometric zirconia-based oxygen sensors were used as a key device for emission control systems of automobiles. The solid electrolyte sensors are classified into three main groups based on the gas detection principles, i.e., equilibrium potential, electrochemical pumping current and mixed potential. Among them, the group of the devices based on mixed-potential gas-sensing principle has been paid special attention due to its attractive performances as well as unique working mechanism. These devices, if designed properly, can exhibit high sensitivity and selectivity to redox gases in oxygen containing atmospheres even at high temperature, showing promise of being applied for combustion exhaust monitoring. In this presentation, the recent progress in electrochemical gas sensors, especially the mixed-potential type gas sensors, will be reviewed. Particular attention is focused on our original works about the zirconia-based sensors using oxide electrodes for detecting various gases, such as CO and NOx, at high temperatures. [References] 1) N. Miura et al., J. Electrochem. Soc., 143, L33 (1996). 2) N. Miura et al., Sensors Update, 6, 191 (2000). 3) N. Miura et al., Solid State Ionics, 136/137, 533 (2000). 4) N. Miura et al., Sensors and Actuators B, in press.

Miura, Norio

2002-03-01

284

A Noninvasive Thin Film Sensor for Monitoring Oxygen Tension during in Vitro Cell Culture  

E-print Network

A Noninvasive Thin Film Sensor for Monitoring Oxygen Tension during in Vitro Cell Culture Peter C measurement of dissolved oxygen in real time remains difficult. We report a new noninvasive sensor that can) thin films. Response of the sensor in the pres- ence of oxygen can be characterized by the linear Stern

Raghavan, Srinivasa

285

A Multifunctional Tactile Sensor Based on PVDF Films for Identification of Materials  

Microsoft Academic Search

A new multifunctional tactile sensor based on polyvinylidene fluoride (PVDF) films has been developed for material identification. In the sensor, the voltages induced by the electrostatic and piezoelectric effects (contact voltages) at the contact between the sensor and a sample are measured by a PVDF film. The voltage induced by the electrostatic effect is measured by the front electrode of

Akira Kimoto; Naoki Sugitani; Shintarou Fujisaki

2010-01-01

286

Thick-film gas and humidity sensing array based on semiconducting metal oxides  

Microsoft Academic Search

There is considerable interest in the use of sensor array devices (SADs) in instruments both to analyse gas mixtures and to recognise complex odours from foodstuffs and beverages. This paper describes the results of studies on material processing, fabrication and characterisation of a new low-cost, solid state IC 24-pin gas and humidity sensing array based on thick-film technology. The array

Wenmin QUI; A. Haeusler; Joerg-Uwe Meyer; W. Wlodarski

1998-01-01

287

Tailoring the gas sensing properties of ZnO thin films through oxygen nonstoichiometry  

Microsoft Academic Search

A comparative study of the gas sensing properties of n- and p-type ZnO films was performed. The carrier type and concentration tailored by varying the sputtering Ar\\/O2 mixture were examined by Hall effect measurements. The gas sensing properties were studied by monitoring changes in the dc resistance upon exposure to hydrogen or oxygen. The selectivity of ZnO sensors to these

V. Kobrinsky; A. Rothschild; V. Lumelsky; Y. Komem; Y. Lifshitz

2008-01-01

288

Combinatorial libraries of semiconductor gas sensors as inorganic electronic noses  

E-print Network

- cal applications.6­9 The gas sensing mechanism of semiconducting metal oxide thin films involves, such as grain size, grain boundaries, and the film thickness of the semiconductors are known to strongly affect characteristics of a number of other metal oxides, including In2O3 , ZnO, and WO3 , have also been previously

Rubloff, Gary W.

289

High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated  

NASA Technical Reports Server (NTRS)

The ability to measure emissions from aeronautic engines and in commercial applications such as automotive emission control and chemical process monitoring is a necessary first step if one is going to actively control those emissions. One single sensor will not give all the information necessary to determine the chemical composition of a high-temperature, harsh environment. Rather, an array of gas sensor arrays--in effect, a high-temperature electronic "nose"--is necessary to characterize the chemical constituents of a diverse, high-temperature environment, such as an emissions stream. The signals produced by this nose could be analyzed to determine the constituents of the emission stream. Although commercial electronic noses for near-room temperature applications exist, they often depend significantly on lower temperature materials or only one sensor type. A separate development effort necessary for a high-temperature electronic nose is being undertaken by the NASA Glenn Research Center, Case Western Reserve University, Ohio State University, and Makel Engineering, Inc. The sensors are specially designed for hightemperature environments. A first-generation high-temperature electronic nose has been demonstrated on a modified automotive engine. This nose sensor array was composed of sensors designed for hightemperature environments fabricated using microelectromechanical-systems- (MEMS-) based technology. The array included a tin-oxide-based sensor doped for nitrogen oxide (NOx) sensitivity, a SiC-based hydrocarbon (CxHy) sensor, and an oxygen sensor (O2). These sensors operate on different principles--resistor, diode, and electrochemical cell, respectively--and each sensor has very different responses to the individual gases in the environment. A picture showing the sensor head for the array is shown in the photograph on the left and the sensors installed in the engine are shown in the photograph on the right. Electronics are interfaced with the sensors for temperature control and signal conditioning, and packaging designed for high temperatures is necessary for the array to survive the engine environment.

Hunter, Gary W.

2002-01-01

290

Compact Laser Multi-gas Spectral Sensors for Spacecraft Systems  

NASA Technical Reports Server (NTRS)

The objective of this research effort has been the development of a new gas sensor technology to meet NASA requirements for spacecraft and space station human life support systems for sensitive selective and real time detection of trace gas species in the mid-infrared spectral region.

Tittel, Frank K.

1997-01-01

291

Mixed Ionic and Electronic Conduction in Li3PO4 Electrolyte for a CO2 Gas Sensor  

E-print Network

equilib- rium potential types, are most promising for CO2 monitoring among the solid-state and Measurements, The Ohio State University, Columbus, Ohio 43210, USA An electrochemical CO2 gas sensor using Li2. Because Li3PO4 electrolyte has been fabricated as a Lipon glass thin film in battery applications,14

Dutta, Prabir K.

292

Photoacoustic photonic crystal fiber gas sensor  

E-print Network

Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, ...

Chen, Raymond, M. Eng. Massachusetts Institute of Technology

2007-01-01

293

Multi-walled carbon nanotube-doped tungsten oxide thin films for hydrogen gas sensing.  

PubMed

In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO(3)) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO(3) thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO(3) hydrogen sensor prepared by the E-beam method. PMID:22163623

Wongchoosuk, Chatchawal; Wisitsoraat, Anurat; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Kerdcharoen, Teerakiat

2010-01-01

294

Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films  

NASA Astrophysics Data System (ADS)

Membrane-based thermal sensor arrays were developed for the high-throughput analysis of the thermophysical properties of thin films. The continuous growth of integrated circuits and microelectromechanical systems, as well as the development of functional materials and the optimization of materials properties, have produced the need for instruments capable of fast materials screening and analysis at reduced length scales. Two instruments were developed based on a similar architecture, one to measure thermal transport properties and the other to perform calorimetry measurements. Both have the capability to accelerate the pace of materials development and understanding using combinatorial measurement methods. The shared architecture of the instruments consists of a silicon-based micromachined array of thermal sensors. Each sensor consists of a SiN X membrane and a W heating element that also serves as a temperature gauge. The array design allows the simultaneous creation of a library of thin film samples by various deposition techniques while systematically varying a parameter of interest across the device. The membrane-based sensors have little thermal mass making them extremely sensitive to changes in thermal energy. The nano-thermal transport array has an array of sensors optimized for sensitivity to heat loss. The heat loss is determined from the temperature response of the sensor to an applied current. An analytical model is used with a linear regression analysis to fit the thermal properties of the samples to the temperature response. The assumptions of the analytical model are validated with a finite element model. Measured thermal properties include specific heat, thermal effusivity, thermal conductivity, and emissivity. The technique is demonstrated by measuring the thermal transport properties of sputter deposited Cu multilayers with a total film thickness from 15 to 470 nm. The experimental results compare well to a theory based on electronic thermal transport. The parallel nano-scanning calorimeter (PnSC) has an array of sensors optimized to sense changes in enthalpy. In this case heat loss sensitivity is minimized with sensor geometry and a reference measurement scheme. The minimal heat loss and small addendum result in sensitivity on the order of 10 nJ/K at heating rates on the order of 104 K/s. The sensitivity is demonstrated by measuring the characteristics of the melting transformation of a 25 nm In film. The combinatorial capabilities of the device are demonstrated by creating and analyzing a library of thin-film (290 nm) Ni-Ti-Zr samples with in-plane composition gradients. The Ni-Ti-Zr films are crystallized in-situ by local heating and the temperature dependence of the martensite transformation on Zr content is detected. Further analysis of the Ni-Ti-Zr samples reveals that the as-deposited amorphous samples crystallize in a multi-stage process that is a function of composition. The features of the calorimetry traces are identified with the help of x-ray diffraction measurements of the crystallized samples. Crystallization at these fast heating rates results in suppression of structural relaxation, increased crystallization temperature (allowing the detection of the glass transition), and an ultra-fine nanocrystalline grain structure with non-equilibrium phases. The characteristics of the martensite-austenite phase transformation are investigated by PnSC to determine the effects of high-temperature (900°C) heat treatments and low-temperature (450°C) thermal cycling. Heat treatments produce precipitates that vary with Zr content and alter the transformation temperature. Thermal cycling results in the accumulation of plastic deformation, which relaxes internal stresses and reduces the transformation temperature. This effect, known as thermal fatigue, is reduced in these samples due to the ultra-fine grain structure, which suppresses dislocation mobility.

McCluskey, Patrick James

295

Alpha-Particle Gas-Pressure Sensor  

NASA Technical Reports Server (NTRS)

An approximate model was developed to establish design curves for the saturation region and a more complete model developed to characterize the current-voltage curves for an alpha-particle pressure sensor. A simple two-parameter current-voltage expression was developed to describe the dependence of the ion current on pressure. The parameters are the saturation-current pressure coefficient and mu/D, the ion mobility/diffusion coefficient. The sensor is useful in the pressure range between 0.1 and 1000 mb using a 1 - mu Ci(241) Am source. Experimental results, taken between 1 and up to 200 mb, show the sensor operates with an anode voltage of 5 V and a sensitivity of 20 fA/mb in nitrogen.

Buehler, M. C.; Bell, L. D.; Hecht, M. H.

1996-01-01

296

Smart chemical sensors using ZnO semiconducting thin films for freshness detection of foods and beverages  

NASA Astrophysics Data System (ADS)

The sensitivity of the chemical sensor, based on the resistance change of Al2O3-doped and SnO2-doped ZnO (ZnO:Al and ZnO:SnO2) thin film, is studied for exposure to various gases. It is found that the ZnO:Al and ZnO:Sn thin film chemical sensor has a high sensitivity and excellent selectivity for amine (TMA and DMA) gas and ethanol gas, respectively. The ZnO:Al (5.0 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to odors from rotten sea foods, such as salmon, sea bream, oyster, squid and sardine, responds to the freshness change of these sea foods. The ZnO:SnO2 (78 wt%) thin film chemical sensor which exhibit a high sensitivity for exposure to aroma from alcohols, such as wine, Japanese sake, and whisky, responds to the freshness change of these alcohols.

Nanto, Hidehito; Kobayashi, Toshiki; Dougami, Naganori; Habara, Masaaki; Yamamoto, Hajime; Kusano, Eiji; Kinbara, Akira; Douguchi, Yoshiteru

1998-07-01

297

Experimental investigation of film cooling effectiveness on gas turbine blades  

E-print Network

high temperature and high pressure blades as an active cooling scheme. In this study, the film cooling effectiveness in different regions of gas turbine blades was investigated with various film hole/slot configurations and mainstream flow conditions...

Gao, Zhihong

2009-05-15

298

MEMS device for mass market gas and chemical sensors  

NASA Astrophysics Data System (ADS)

Gas and chemical sensors are used in many applications. Industrial health and safety monitors allow companies to meet OSHA requirements by detecting harmful levels of toxic or combustible gases. Vehicle emissions are tested during annual inspections. Blood alcohol breathalizers are used by law enforcement. Refrigerant leak detection ensures that the Earth's ozone layer is not being compromised. Industrial combustion emissions are also monitored to minimize pollution. Heating and ventilation systems watch for high levels of carbon dioxide (CO2) to trigger an increase in fresh air exchange. Carbon monoxide detectors are used in homes to prevent poisoning from poor combustion ventilation. Anesthesia gases are monitored during a patients operation. The current economic reality is that two groups of gas sensor technologies are competing in two distinct existing market segments - affordable (less reliable) chemical reaction sensors for consumer markets and reliable (expensive) infrared (IR) spectroscopic sensors for industrial, laboratory, and medical instrumentation markets. Presently high volume mass-market applications are limited to CO detectros and on-board automotive emissions sensors. Due to reliability problems with electrochemical sensor-based CO detectors there is a hesitancy to apply these sensors in other high volume applications. Applications such as: natural gas leak detection, non-invasive blood glucose monitoring, home indoor air quality, personal/portable air quality monitors, home fire/burnt cooking detector, and home food spoilage detectors need a sensor that is a small, efficient, accurate, sensitive, reliable, and inexpensive. Connecting an array of these next generation gas sensors to wireless networks that are starting to proliferate today creates many other applications. Asthmatics could preview the air quality of their destinations as they venture out into the day. HVAC systems could determine if fresh air intake was actually better than the air in the house. Internet grocery delivery services could check for spoiled foods in their clients' refrigerators. City emissions regulators could monitor the various emissions sources throughout the area from their desk to predict how many pollution vouchers they will need to trade in the next week. We describe a new component architecture for mass-market sensors based on silicon microelectromechanical systems (MEMS) technology. MEMS are micrometer-scale devices that can be fabricated as discrete devices or large arrays, using the technology of integrated circuit manufacturing. These new photonic bandgap and MEMS fabricataion technologies will simplify the component technology to provide high-quality gas and chemical sensors at consumer prices.

Kinkade, Brian R.; Daly, James T.; Johnson, Edward A.

2000-08-01

299

Thin Film Heat Flux Sensor Development for Ceramic Matrix Composite (CMC) Systems  

NASA Technical Reports Server (NTRS)

The NASA Glenn Research Center (GRC) has an on-going effort for developing high temperature thin film sensors for advanced turbine engine components. Stable, high temperature thin film ceramic thermocouples have been demonstrated in the lab, and novel methods of fabricating sensors have been developed. To fabricate thin film heat flux sensors for Ceramic Matrix Composite (CMC) systems, the rough and porous nature of the CMC system posed a significant challenge for patterning the fine features required. The status of the effort to develop thin film heat flux sensors specifically for use on silicon carbide (SiC) CMC systems with these new technologies is described.

Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.; Zhu, Dongming; Laster, Kimala L.; Gonzalez, Jose M.; Gregory, Otto J.

2010-01-01

300

Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays  

PubMed Central

This paper presents a new pattern recognition approach for enhancing the selectivity of gas sensor arrays for clustering intelligent odor detection. The aim of this approach was to accurately classify an odor using pattern recognition in order to enhance the selectivity of gas sensor arrays. This was achieved using an odor monitoring system with a newly developed neural-genetic classification algorithm (NGCA). The system shows the enhancement in the sensitivity of the detected gas. Experiments showed that the proposed NGCA delivered better performance than the previous genetic algorithm (GA) and artificial neural networks (ANN) methods. We also used PCA for data visualization. Our proposed system can enhance the reproducibility, reliability, and selectivity of odor sensor output, so it is expected to be applicable to diverse environmental problems including air pollution, and monitor the air quality of clean-air required buildings such as a kindergartens and hospitals. PMID:23443378

Kim, Eungyeong; Lee, Seok; Kim, Jae Hun; Kim, Chulki; Byun, Young Tae; Kim, Hyung Seok; Lee, Taikjin

2012-01-01

301

Thermal Balance Analysis of a Micro-Thermoelectric Gas Sensor Using Catalytic Combustion of Hydrogen  

PubMed Central

A thermoelectric gas sensor (TGS) with a combustion catalyst is a calorimetric sensor that changes the small heat of catalytic combustion into a signal voltage. We analyzed the thermal balance of a TGS to quantitatively estimate the sensor parameters. The voltage signal of a TGS was simulated, and the heat balance was calculated at two sections across the thermoelectric film of a TGS. The thermal resistances in the two sections were estimated from the thermal time constants of the experimental signal curves of the TGS. The catalytic combustion heat Qcatalyst required for 1 mV of ?Vgas was calculated to be 46.1 ?W. Using these parameters, we find from simulations for the device performance that the expected Qcatalyst for 200 and 1,000 ppm H2 was 3.69 ?W and 11.7 ?W, respectively. PMID:24451468

Nagai, Daisuke; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

2014-01-01

302

Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

All the goals of the research effort for the first year were met by the accomplishments. Additional efforts were done to speed up the process of development and construction of the experimental gas chamber which will be completed by the end of 1997. This chamber incorporates vacuum sealed multimode optical fiber lines which connect the sensor to the remote light source and signal processing equipment. This optical fiber line is a prototype of actual optical communication links connecting real sensors to a control unit within an aircraft or spacecraft. An important problem which we are planning to focus on during the second year is coupling of optical fiber line to the sensor. Currently this problem is solved using focusing optics and prism couplers. More reliable solutions are planned to be investigated.

Sarkisov, Sergey S.

1997-01-01

303

Drift Invariant Gas Recognition Technique for On Chip Tin Oxide Gas Sensor Array  

Microsoft Academic Search

The purpose of this paper is the study of the robustness of a new low complexity recognition method based on the measurement issued from an on chip 4times4 Tin oxide gas sensor array. The recognition system is based on a vector angle similarity measure between the query gas and the representatives of the different gas classes. The latter are obtained

Farid Flitti; Aicha Far; Bin Guo; Amine Bermak

2008-01-01

304

Fiber optic gas sensor with nanocrystalline ZnO  

NASA Astrophysics Data System (ADS)

A fiber optic gas sensor with a PMMA fiber whose clad is modified with chemically sensitive nano-crystalline zinc oxide has been developed and investigated to detect acetone, isopropyl alcohol and benzene gases. The spectral characteristics of the sensor were recorded for different concentrations ranging from (0-500 ppm) for these gases both with as-prepared and annealed nanocrystalline ZnO, and the influence of annealing on the gas sensing has been studied.The response time and recovery time were found to be 48 min. and 42 min. respectively for 500 ppm concentration.

Renganathan, B.; Ganesan, A. R.

2014-01-01

305

Optical control and diagnostics sensors for gas turbine machinery  

NASA Astrophysics Data System (ADS)

There exists a vast range of optical techniques that have been under development for solving complex measurement problems related to gas-turbine machinery and phenomena. For instance, several optical techniques are ideally suited for studying fundamental combustion phenomena in laboratory environments. Yet other techniques hold significant promise for use as either on-line gas turbine control sensors, or as health monitoring diagnostics sensors. In this paper, we briefly summarize these and discuss, in more detail, some of the latter class of techniques, including phosphor thermometry, hyperspectral imaging and low coherence interferometry, which are particularly suited for control and diagnostics sensing on hot section components with ceramic thermal barrier coatings (TBCs).

Trolinger, James D.; Jenkins, Thomas P.; Heeg, Bauke

2012-10-01

306

Optical corrosion sensor based on fiber Bragg grating electroplated with Fe-C film  

NASA Astrophysics Data System (ADS)

An optical fiber corrosion sensor (OFCS) based on iron-carbon (Fe-C) film was researched. OFCS was formed by electroplating a Fe-C film on fiber Bragg grating (FBG) metalized with silver film by magnetron sputtering. There was a more than 430-pm change of FBG wavelength when Fe-C film was seriously corroded. Compared to electrochemical method, the optical fiber sensor shows dominance in long-lasting monitoring of corrosion. The electric signal was broken off after the 20-h corrosion of Fe-C film, while the optical fiber sensor's monitoring lasted more than 40 days.

Zheng, Xing; Hu, Wenbin; Zhang, Ning; Gao, Min

2014-07-01

307

Piezotronic Effect on ZnO Nanowire Film Based Temperature Sensor Limin Zhang,,  

E-print Network

Piezotronic Effect on ZnO Nanowire Film Based Temperature Sensor Fei Xue,,§ Limin Zhang,,§ Wei Tang ZnO nanowire (NW) film. The film was synthesized by the wet chemical deposition method, the traditional thin- film based processing is quite mature, which has been used successfully in semiconductor

Wang, Zhong L.

308

Electrodes for solid state gas sensor  

DOEpatents

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

Mukundan, Rangachary (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM); Garzon, Fernando (Santa Fe, NM)

2007-05-08

309

Electrodes for solid state gas sensor  

DOEpatents

A mixed potential electrochemical sensor for the detection of gases has a ceria-based electrolyte with a surface for exposing to the gases to be detected, and with a reference wire electrode and a sensing wire electrode extending through the surface and fixed within the electrolyte as the electrolyte is compressed and sintered. The electrochemical sensor is formed by placing a wire reference electrode and a wire sensing electrode in a die, where each electrode has a first compressed planar section and a second section depending from the first section with the second section of each electrode extending axially within the die. The die is filled with an oxide-electrolyte powder and the powder is pressed within the die with the wire electrodes. The wire-electrodes and the pressed oxide-electrolyte powder are sintered to form a ceramic electrolyte base with a reference wire electrode and a sensing wire electrode depending therefrom.

Mukundan, Rangachary (Santa Fe, NM); Brosha, Eric L. (Los Alamos, NM); Garzon, Fernando (Santa Fe, NM)

2003-08-12

310

Field emission model of carbon nanotubes to simulate gas breakdown in ionization gas sensor  

NASA Astrophysics Data System (ADS)

A new field emission model of carbon nanotubes (CNTs) to simulate gas detection mechanism in CNT based ionization gas sensor has been developed. The new model consists of three modules which are combined together and embedded in the standard particle-in-cell/Monte Carlo collision codes. The functionality of the enhanced model is checked by varying the gas pressure and gap spacing in the simulations. From the results, around one order of magnitude decrease in the breakdown voltages and two orders of magnitude faster response time is observed. The lowest breakdown voltages are observed when intertube spacing is equal to height of the nanotube. The field enhancement factor ? is calculated from our model and compared with the ? of the well established model. The closeness among the values of ? validates the performance of our field emission model. Furthermore, the ? of our model is compared with the ? of the existing ionization gas sensors. It was found that the ? of our sensor is around 3 times better than the ? of the gold nanowire based ionization gas sensor and 28 times better than the ? of the other CNT based ionization gas sensor. These results suggest that by properly controlling the growth of CNT structures, an optimized CNT based ionization gas sensor can be realized.

Mahmood, Salman; Arif Burhanudin, Zainal; Salman, Aysha

2013-01-01

311

Examining graphene field effect sensors for ferroelectric thin film studies.  

PubMed

We examine a prototype graphene field effect sensor for the study of the dielectric constant, pyroelectric coefficient, and ferroelectric polarization of 100-300 nm epitaxial (Ba,Sr)TiO3 thin films. Ferroelectric switching induces hysteresis in the resistivity and carrier density of n-layer graphene (n = 1-5) below 100 K, which competes with an antihysteresis behavior activated by the combined effects of electric field and temperature. We also discuss how the polarization asymmetry and interface charge dynamics affect the electronic properties of graphene. PMID:23924380

Rajapitamahuni, A; Hoffman, J; Ahn, C H; Hong, X

2013-09-11

312

New potentiomentric dissolved oxygen sensors in thick film technology  

Microsoft Academic Search

New designed dissolved oxygen potentiometric sensors in thick film technology based in the use of RuO2 as active material and TiO2 or polyisoftalamide diphenylsulphone (PIDS) as membranes have been developed. TiO2-coated RuO2 electrodes showed a linear response as a function of the logarithm of the dissolved oxygen concentration in the 0.5–8ppm range (log[O2], ?4.82 to ?3.60; concentration of O2 in

Ramón Mart??nez-Máñez; Juan Soto; Josefa Lizondo-Sabater; Eduardo Garc??a-Breijo; Luis Gil; Javier Ibáñez; Isabel Alcaina; Silvia Alvarez

2004-01-01

313

Surface plasmonic polaritonic sensor using a dielectric columnar thin film  

NASA Astrophysics Data System (ADS)

The propagation of a surface plasmon polariton (SPP) wave can be guided by the interface of a metal and a columnar thin film (CTF). Theory predicts that the angle of incidence on the prism/metal interface in the Turbadar-Kretschmann-Raether prism-coupled configuration required to excite the SPP wave shifts upon infiltration of the CTF by a fluid. Otherwise identical CTFs of different thicknesses were partnered with dense thin films of aluminum in optical experiments. The angle of incidence for exciting the SPP wave was found to shift to a higher value each time the CTF was infiltrated by a fluid of refractive index of increasing value. Experimental data indicated that the sensor offers a state-of-research sensitivity, thereby proving that a CTF can be a useful platform for SPP-wave-based optical sensing.

Swiontek, Stephen E.; Faryad, Muhammad; Lakhtakia, Akhlesh

2014-01-01

314

Film Sensor Device Fabricated by a Piezoelectric Poly(L-lactic acid) Film  

NASA Astrophysics Data System (ADS)

Synthetic piezoelectric polymer films produced from petroleum feedstock have long been used as thin-film sensors and actuators. However, the fossil fuel requirements for synthetic polymer production and carbon dioxide emission from its combustion have raised concern about the environmental impact of its continued use. Eco-friendly biomass polymers, such as poly(L-lactic acid) (PLLA), are made from plant-based (vegetable starch) plastics and, thus, have a much smaller carbon footprint. Additionally, PLLA does not exhibit pyroelectricity or unnecessary poling. This suggests the usefulness of PLLA films for the human-machine interface (HMI). As an example of a new HMI, we have produced a TV remote control using a PLLA film. The intuitive operation provided by this PLLA device suggests that it is useful for the elderly or handicapped.

Ando, Masamichi; Kawamura, Hideki; Kageyama, Keisuke; Tajitsu, Yoshiro

2012-09-01

315

Investigation of thiol derivatized gold nanoparticle sensors for gas analysis  

NASA Astrophysics Data System (ADS)

Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

Stephens, Jared S.

316

Acoustoelectric Effect on the Responses of SAW Sensors Coated with Electrospun ZnO Nanostructured Thin Film  

PubMed Central

In this study, zinc oxide (ZnO) was a very good candidate for improving the sensitivity of gas sensor technology. The preparation of an electrospun ZnO nanostructured thin film on a 433 MHz Rayleigh wave based Surface Acoustic Wave (SAW) sensor and the investigation of the acoustoelectric effect on the responses of the SAW sensor are reported. We prepared an electrospun ZnO nanostructured thin film on the SAW devices by using an electrospray technique. To investigate the dependency of the sensor response on the structure and the number of the ZnO nanoparticles, SAW sensors were prepared with different coating loads. The coating frequency shifts were adjusted to fall between 100 kHz and 2.4 MHz. The sensor measurements were performed against VOCs such as acetone, trichloroethylene, chloroform, ethanol, n-propanol and methanol vapor. The sensor responses of n-propanol have opposite characteristics to the other VOCs, and we attributed these characteristics to the elastic effect/acoustoelectric effect.

Tasaltin, Cihat; Ebeoglu, Mehmet Ali; Ozturk, Zafer Ziya

2012-01-01

317

CO gas sensing by ultrathin tin oxide films grown by atomic layer deposition using transmission FTIR spectroscopy.  

PubMed

Ultrathin tin oxide films were deposited on SiO2 nanoparticles using atomic layer deposition (ALD) techniques with SnCl4 and H2O2 as the reactants. These SnO(x) films were then exposed to O2 and CO gas pressure at 300 degrees C to measure and understand their ability to serve as CO gas sensors. In situ transmission Fourier transform infrared (FTIR) spectroscopy was used to monitor both the charge conduction in the SnO(x) films and the gas-phase species. The background infrared absorbance measured the electrical conductivity of the SnO(x) films based on Drude-Zener theory. O2 pressure was observed to decrease the SnO(x) film conductivity. Addition of CO pressure then increased the SnO(x) film conductivity. Static experiments also monitored the buildup of gas-phase CO2 reaction products as the CO reacted with oxygen species. These results were consistent with both ionosorption and oxygen-vacancy models for chemiresistant semiconductor gas sensors. Additional experiments demonstrated that O2 pressure was not necessary for the SnO(x) films to detect CO pressure. The background infrared absorbance increased with CO pressure in the absence of O2 pressure. These results indicate that CO can produce oxygen vacancies on the SnO(x) surface that ionize and release electrons that increase the SnO(x) film conductivity, as suggested by the oxygen-vacancy model. The time scale of the response of the SnO(x) films to O2 and CO pressure was also measured by using transient experiments. The ultrathin SnO(x) ALD films with a thickness of approximately 10 A were able to respond to O2 within approximately 100 s and to CO within approximately 10 s. These in situ transmission FTIR spectroscopy help confirm the mechanisms for chemiresistant semiconductor gas sensors. PMID:18710189

Du, X; Du, Y; George, S M

2008-10-01

318

Design of micro-sensor-array detector for toxic gas  

NASA Astrophysics Data System (ADS)

To quickly measure the trace concentration of the single component toxic gas (e.g. sarin), a micro-array toxic gas detector is designed. A 3 x 3 gas sensor array with metalloporphyrins as sensitive materials is introduced. A micro-capsule that can be easy to be loaded and unloaded is designed for the gas reaction. A fiber-array optical path is designed, which is based on the principle that gas sensors will show different colors after reaction with the toxic gas. The tricolor information about the concentration of gas is collected by the color liner CCD. A control handling system with C8051F021 MCU as the core is implemented and embedded into the detector to perform the functions of gas sampling, data collection and analysis calculation. Data acquisition experimental results show that the proposed scheme can effectively collect the color information after gas reaction. Moreover, the system has many important advantages, such as small size, compact structure, high degree of automation, fast detection speed and high performance-cost ratio, etc.

Liao, Hai-yang; Tian, Peng

2010-08-01

319

Harmful gas recognition exploiting a CTL sensor array.  

PubMed

In this paper, a novel cataluminescence (CTL)-based sensor array consisting of nine types of catalytic materials is developed for the recognition of several harmful gases, namely carbon monoxide, acetone, chloroform and toluene. First, the experimental setup is constructed by using sensing nanomaterials, a heating plate, a pneumatic pump, a gas flow meter, a digital temperature device, a camera and a BPCL Ultra Weak Chemiluminescence Analyzer. Then, unique CTL patterns for the four types of harmful gas are obtained from the sensor array. The harmful gases are successful recognized by the PCA method. The optimal conditions are also investigated. Finally, experimental results show high sensitivity, long-term stability and good linearity of the sensor array, which combined with simplicity, make our system a promising application in this field. PMID:24113681

Wang, Qihui; Xie, Lijun; Zhu, Bo; Zheng, Yao; Cao, Shihua

2013-01-01

320

Thin-film sensors for reusable space propulsion systems  

NASA Technical Reports Server (NTRS)

Thin-film thermocouples (TFTCs) were developed for aircraft gas turbine engines and are in use for temperature measurement on turbine blades up to 1800 F. Established aircraft engine gas turbine technology is currently being adapted to turbine engine blade materials and the environment encountered in the Space Shuttle Main Engine (SSME)-severe thermal shock from cryogenic fuel to combustion temperatures. Initial results with coupons of MAR M-246 (+Hf) and PWA 1480 were followed by fabrication of TFTC on SSME turbine blades. Current efforts are focused on preparation for testing in the Turbine Blade Tester at NASA Marshall Space Flight Center.

Hepp, Aloysius F.; Kim, Walter S.

1989-01-01

321

EXPERIENCES USING GAS SENSORS ON AN AUTONOMOUS MOBILE ROBOT  

Microsoft Academic Search

This paper reports on experiences concerning the de- ployment of gas sensors on an autonomous mobile robot. It particularly addresses the suitability of the developed system to localize a distant odour source. First experi- ments were undertaken in which the robot was ordered to move along different weakly ventilated corridors, while keeping track of its center (framing a '1D' scenario).

Achim Lilienthal; Andreas Zell; Michael Wandel; Udo Weimar

2001-01-01

322

On Optimization of Sensor Selection for Aircraft Gas  

E-print Network

1 On Optimization of Sensor Selection for Aircraft Gas Turbine Engines Ramgopal Mushini Dan Simon temperature 6. HPC exit temperature 7. Bypass duct pressure 8. HPC exit pressure 9. LPT (low pressure turbine) blade temperature 10. LPT exit temperature 11. LPT exit pressure #12;7 Background ­ Health parameters 1

Simon, Dan

323

Odour plume tracking robot using semiconductor gas sensors  

Microsoft Academic Search

This paper reports on the development of a mobile robot equipped with semiconductor gas sensors which has been designed to track odour plumes in the natural environment to locate their sources. One principal application could be the automatic location of explosives and analogies can be made with animal behaviour, particularly dogs, which can track both objects and persons using smell.

Montep Kiatweerasakul; T. J. Stonham

2002-01-01

324

Functionalised zinc oxide nanowire gas sensors: Enhanced NO2 gas sensor response by chemical modification of nanowire surfaces  

PubMed Central

Summary Surface coating with an organic self-assembled monolayer (SAM) can enhance surface reactions or the absorption of specific gases and hence improve the response of a metal oxide (MOx) sensor toward particular target gases in the environment. In this study the effect of an adsorbed organic layer on the dynamic response of zinc oxide nanowire gas sensors was investigated. The effect of ZnO surface functionalisation by two different organic molecules, tris(hydroxymethyl)aminomethane (THMA) and dodecanethiol (DT), was studied. The response towards ammonia, nitrous oxide and nitrogen dioxide was investigated for three sensor configurations, namely pure ZnO nanowires, organic-coated ZnO nanowires and ZnO nanowires covered with a sparse layer of organic-coated ZnO nanoparticles. Exposure of the nanowire sensors to the oxidising gas NO2 produced a significant and reproducible response. ZnO and THMA-coated ZnO nanowire sensors both readily detected NO2 down to a concentration in the very low ppm range. Notably, the THMA-coated nanowires consistently displayed a small, enhanced response to NO2 compared to uncoated ZnO nanowire sensors. At the lower concentration levels tested, ZnO nanowire sensors that were coated with THMA-capped ZnO nanoparticles were found to exhibit the greatest enhanced response. ?R/R was two times greater than that for the as-prepared ZnO nanowire sensors. It is proposed that the ?R/R enhancement in this case originates from the changes induced in the depletion-layer width of the ZnO nanoparticles that bridge ZnO nanowires resulting from THMA ligand binding to the surface of the particle coating. The heightened response and selectivity to the NO2 target are positive results arising from the coating of these ZnO nanowire sensors with organic-SAM-functionalised ZnO nanoparticles. PMID:23016141

Chang, Jin; Ponzoni, Andrea; Concina, Isabella; Zappa, Dario; Comini, Elisabetta; Motta, Nunzio; Faglia, Guido; Sberveglieri, Giorgio

2012-01-01

325

Chemical warfare agent sensor using MEMS structure and thick film fabrication method  

Microsoft Academic Search

Recently, many researchers have been attempted to reduce the power consumption in the sensor system and to increase the sensitivity for toxic gases. Most metal oxide sensing films are deposited on an alumina substrate which is easy process but needs high power consumption. Moreover, thin film sensor deposited on the Si substrate shows low sensitivity. Accordingly, this study investigated the

Nak-Jin Choi; Yun-Su Lee; Jun-Hyuk Kwak; Joon-Shik Park; Kwang-Bum Park; Kyu-Sik Shin; Hyo-Derk Park; Jae-Chang Kim; Jeung-Soo Huh; Duk-Dong Lee

2005-01-01

326

Measuring muscle movements for human interfaces using a flexible piezoelectric thin film sensor  

Microsoft Academic Search

This paper proposes a novel method to measure muscle movements for human interfaces. During muscle movements, cross-sectional muscle area changes, and this can be detected at the skin surface. In this study, a flexible piezoelectric thin film sensor is used to measure the morphological change of the skin surface. This sensor is made of oriented aluminum nitride (AlN) thin film,

Nan Bu; Junpei Tsukamoto; Naohiro Ueno; Keisuke Shima; Toshio Tsuji

2008-01-01

327

Electrocatalytic cermet gas detector/sensor  

DOEpatents

An electrocatalytic device for sensing gases. The gas sensing device includes a substrate layer, a reference electrode disposed on the substrate layer comprised of a nonstoichiometric chemical compound enabling oxygen diffusion therethrough, a lower reference electrode coupled to the reference electrode, a solid electrolyte coupled to the lower reference electrode and an upper catalytically active electrode coupled to the solid electrolyte.

Vogt, Michael C. (Westmont, IL); Shoemarker, Erika L. (Westmont, IL); Fraioli, deceased, Anthony V. (late of Bristol, VT)

1995-01-01

328

Study on distributed optic fiber gas sensors  

Microsoft Academic Search

Online detection of gas concentrations is important research topic recently. Based on the analysis of near infrared spectral absorption of acetylene, ammonia and carbon monoxide, a system using absorption type optic fiber for high sensitivity distributed detection of gases with wideband light source is demonstrated. Light source modulation harmonic measurement is presented in this paper. Wavelength modulation is realized by

Jin Liu; Haima Yang; Yan Yue

2009-01-01

329

Thin Film Ceramic Strain Sensor Development for Harsh Environments: Identification of Candidate Thin Film Ceramics to Test for Viability for Static Strain Sensor Development  

NASA Technical Reports Server (NTRS)

The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in propulsion system applications. In order to have a more passive method of negating changes of resistance due to temperature, an effort is underway at NASA GRC to develop high temperature thin film ceramic static strain gauges for application in turbine engines, specifically in the fan and compressor modules on blades. Other applications include on aircraft hot section structures and on thermal protection systems. The near-term interim goal of this research effort was to identify candidate thin film ceramic sensor materials to test for viability and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. This goal was achieved by a thorough literature search for ceramics that have the potential for application as high temperature thin film strain gauges, reviewing potential candidate materials for chemical & physical compatibility with NASA GRC's microfabrication procedures and substrates.

Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.

2006-01-01

330

Thin Film Physical Sensor Instrumentation Research and Development at NASA Glenn Research Center  

NASA Technical Reports Server (NTRS)

A range of thin film sensor technology has been demonstrated enabling measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Multiple techniques exist for refractory thin film fabrication, fabrication and integration on complex surfaces and multilayered thin film insulation. Leveraging expertise in thin films and high temperature materials, investigations for the applications of thin film ceramic sensors has begun. The current challenges of instrumentation technology are to further develop systems packaging and component testing of specialized sensors, further develop instrumentation techniques on complex surfaces, improve sensor durability, and to address needs for extreme temperature applications. The technology research and development ongoing at NASA Glenn for applications to future launch vehicles, space vehicles, and ground systems is outlined.

Wrbanek, John D.; Fralick, Gustave C.

2006-01-01

331

Methods for gas detection using stationary hyperspectral imaging sensors  

DOEpatents

According to one embodiment, a method comprises producing a first hyperspectral imaging (HSI) data cube of a location at a first time using data from a HSI sensor; producing a second HSI data cube of the same location at a second time using data from the HSI sensor; subtracting on a pixel-by-pixel basis the second HSI data cube from the first HSI data cube to produce a raw difference cube; calibrating the raw difference cube to produce a calibrated raw difference cube; selecting at least one desired spectral band based on a gas of interest; producing a detection image based on the at least one selected spectral band and the calibrated raw difference cube; examining the detection image to determine presence of the gas of interest; and outputting a result of the examination. Other methods, systems, and computer program products for detecting the presence of a gas are also described.

Conger, James L. (San Ramon, CA); Henderson, John R. (Castro Valley, CA)

2012-04-24

332

The Dynamic Properties of Annular Gas Squeeze Film Dampers  

Microsoft Academic Search

The step jump method is used to characterize the stiffness and damping of flat-faced gas lubricated squeeze film dampers. Analytic solution of a linearized form of the isothermal and compressible Reynolds equation yields closed form expressions for the step and frequency responses of the gas film. Results from the step jump method obtained both analytically and numerically are shown to

Brad A. Miller; Itzhak Green

2000-01-01

333

Electrocatalytic cermet gas detector/sensor  

DOEpatents

An electrocatalytic device for sensing gases is described. The gas sensing device includes a substrate layer, a reference electrode disposed on the substrate layer comprised of a nonstoichiometric chemical compound enabling oxygen diffusion therethrough, a lower reference electrode coupled to the reference electrode, a solid electrolyte coupled to the lower reference electrode and an upper catalytically active electrode coupled to the solid electrolyte. 41 figs.

Vogt, M.C.; Shoemarker, E.L.; Fraioli, A.V.

1995-07-04

334

Preparation of nanostructured PbS thin films as sensing element for NO2 gas  

NASA Astrophysics Data System (ADS)

In this work, we demonstrate that semiconducting films of AIVBVI compounds, in particular, of nanostructured lead sulfide (PbS) which prepared by chemical bath deposition (CBD), can be used as a sensing element for nitrogen dioxide (NO2) gas. The CBD method is versatile, simple in implementation and gives homogeneous semiconductor structures. We have prepared PbS nanocrystalline thin film at different reaction baths and temperatures. In the course of deposition, variable amounts of additives, such as organic substances among them, were introduced into the baths. The energy dispersive analysis (EDX) confirms the chemical composition of PbS films. A current-voltage (I-V) characterization of Pd/nc-PbS/a-SiC:H pSi(100)/Al Schottky diode structures were studied in the presence of NO2 gas. The gas sensing behavior showed that the synthesized PbS nanocrystalline thin films were influenced by NO2 gas at room temperature. The results can be used for developing an experimental sensing element based on chemically deposited nanostructured PbS films which can be applicable in gas sensors.

Kaci, S.; Keffous, A.; Hakoum, S.; Trari, M.; Mansri, O.; Menari, H.

2014-06-01

335

A novel nanometric DNA thin film as a sensor for alpha radiation  

E-print Network

be one of promising candidates for the development of online radiation sensors. T he Fukushima nuclearA novel nanometric DNA thin film as a sensor for alpha radiation Atul Kulkarni1,2,3 *, Byeonghoon radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require

Cai, Long

336

Enhanced gas sensing of Au nanocluster-doped or -coated zinc oxide thin films  

Microsoft Academic Search

We demonstrated that doping or covering with Au nanoclusters boosts gas sensing effectiveness of optical metal oxide sensors. The sensing response of pulsed laser deposited ZnO films as sensing element was tested by m-line technique for low concentration (1000 ppm) of butane in environmental N2. The optical interrogation was performed for three types of coatings: undoped ZnO, undoped ZnO structures

G. Socol; E. Axente; C. Ristoscu; F. Sima; A. Popescu; N. Stefan; I. N. Mihailescu; L. Escoubas; J. Ferreira; S. Bakalova; A. Szekeres

2007-01-01

337

Acoustic-Wave Piezoelectric and Pyroelectric Sensors Based on PZT Thick Films  

Microsoft Academic Search

The operating principles, design and manufacturing in thick-film technology (TFT) of sensors based on the piezoelectric and\\u000a pyroelectric properties of lead zirconate titanate (PZT) thick films are described. In particular, the attention is focused\\u000a on acoustic-wave piezoelectric sensors for physical and chemical quantities, and on pyroelectric sensors and arrays for light\\u000a spot position measurement.\\u000a \\u000a Keywords: piezoelectric sensor, pyroelectric sensor, acoustic-wave

Vittorio Ferrari

338

Annealed Ce Doped ZnO Coated Fiber Optic Gas Sensor  

Microsoft Academic Search

Fiber optic sensor based on cladding modification method for detecting various gas emissions such as ammonia methanol, and ethanol is proposed. The Ce doped ZnO annealed at 500 and 1200 °C are used as a gas sensing material. The spectral characteristics of the gas sensor are studied for different concentrations (0-500 ppm) of gases. The sensor exhibits a linear variation

B. Renganathan; D. Sastikumar; G. Gobi; N. Rajeswari Yogamalar; A. Chandra Bose

2011-01-01

339

Physical mechanism of reectance inversion in hydrogen gas sensor with Pd/PVDF structures  

E-print Network

Physical mechanism of re¯ectance inversion in hydrogen gas sensor with Pd/PVDF structures Chinhua to hydrogen gas has been investigated. Based on experimental observations using sensors with or without and safe hydrogen-gas sensors becomes of great importance. Among a wide variety of Pd-based hydrogen

Mandelis, Andreas

340

Purely thermal wave based nonchemical photopyroelectric gas sensor: Application to hydrogen  

E-print Network

Purely thermal wave based nonchemical photopyroelectric gas sensor: Application to hydrogen, leading to considerable research efforts towards the development of hydrogen gas sensors. Most in this laboratory, in developing a new photopyroelectric hydrogen gas sensors using Pd-coated pyroelectric thin

Mandelis, Andreas

341

Optical Sensors Based on Single on Arm Thin Film Waveguide Interferometer  

NASA Technical Reports Server (NTRS)

Single-arm dual-mode optical waveguide interferometer utilizes interference between two modes of different order. Sensing effect results from the change in propagation conditions of the modes caused by the environment. The waveguide is made as an open asymmetric structure containing a dye-doped polymer film onto a quartz substrate. It is more sensitive to the change of environment than its conventional polarimetric analog using orthogonal modes (TE and TM) of the same order. The sensor still preserves the option of operating in polarimetric regime using a variety of mode combinations such as TE(sub 0)/TM(sub 0) (conventional) TE(sub 0)/TM(sub 1), TE(sub 1)/TM(sub 0), or TE(sub 1)/TM(sub 1) but can also work in nonpolarimetric regime using combinations TE(sub 0)/TE(sub 1) or TM(sub 0)/TM(sub 1). Utilization of different mode combinations simultaneously makes the device more versatile. Application of the sensor to gas sensing is based on doping polymer film with an organic indicator dye targeting a particular gaseous reagent. Change of the optical absorption spectrum of the dye caused by the gaseous pollutant results in change of the reactive index of the dye-doped polymer film that can be detected by the sensor. As indicator dyes we utilize Bromocresol Purple doped into polymer poly(methyl) methacrylate that is sensitive to small concentrations of ammonia. The indicator dye demonstrated an irreversible increase in optical absorption near the peak at 350 nm being exposed to 5% ammonia in pure nitrogen at 600 Torr. The dye also showed reversible growth of the absorption peak near 600 nm after exposure to a vapor of standard medical ammonia spirit (65% alcohol). We have built a breadboard prototype of the sensor with He-Ne laser as a light source and with a single mode fiber input and a multimode fiber output. The prototype showed a sensitivity to temperature change of the order of 2 C per 2pi phase shift. The sensitivity of the sensor to the presence of dTy ammonia is not less than 300 ppm per 2pi phase shift. The proposed sensor can be used as a robust stand-alone instrument for continuous environment pollution monitoring.

Sarkisov, S. S.; Diggs, D.; Curley, M.; Adamovsky, Grigory (Technical Monitor)

2000-01-01

342

TiO{sub 2}/PANI And MWNT/PANI Composites Thin Films For Hydrogen Gas Sensing  

SciTech Connect

The MWNT and TiO{sub 2} doped Polyaniline (PANI) composites were synthesized by In-situ chemical oxidative polymerization method at low temperature. The MWNT/PANI and TiO{sub 2}/PANI composite thin films were prepared using spin coating method onto finger type interdigited electrodes to develop the chemiresistor type gas sensor for hydrogen gas sensing application. It was observed that the MWNT and TiO{sub 2} doped PANI composite thin films show a higher response in comparision to neat PANI. The structural and morphological properties of these composite films were characterized by X-Ray differaction (XRD) pattern and sccaning electrone microscopy (SEM) respectively.

Srivastava, Subodh; Kumar, Sumit; Agrawal, Shweta; Saxena, Arpita; Choudhary, B. L.; Mathur, Shubhra; Singh, M.; Vijay, Y. K. [Department of Physics, University of Rajasthan, Jaipur-302004 (India)

2010-12-01

343

Robust Design of SAW Gas Sensors by Taguchi Dynamic Method.  

PubMed

This paper adopts Taguchi's signal-to-noise ratio analysis to optimize the dynamic characteristics of a SAW gas sensor system whose output response is linearly related to the input signal. The goal of the present dynamic characteristics study is to increase the sensitivity of the measurement system while simultaneously reducing its variability. A time- and cost-efficient finite element analysis method is utilized to investigate the effects of the deposited mass upon the resonant frequency output of the SAW biosensor. The results show that the proposed methodology not only reduces the design cost but also promotes the performance of the sensors. PMID:22573961

Tsai, Hsun-Heng; Wu, Der Ho; Chiang, Ting-Lung; Chen, Hsin Hua

2009-01-01

344

Engineered doped and codoped polyaniline gas sensors synthesized in N,N,dimethylformamide media  

NASA Astrophysics Data System (ADS)

Conducting Polyaniline films (Pani) on Corning glass substrates, produced using either an in-situ doping process or a co-doping process, were prepared by the oxidative polymerization of aniline in N,N,dimethylformamide. Bicyclic aliphatic camphorsulfonic acid (CSA), aromatic toluenesulfonic acid (TSA) and carboxylic trifluoroacetic acid (TFA) were employed as doping agents, and CSA mixed with TSA and CSA mixed with TFA were employed as the co-doping materials. The topography of the Pani films was analyzed by atomic-force microscopy (AFM), and their doping and oxidizing states were characterized by Fourier-transform infrared (FT-IR) spectroscopy and optical (UV-Vis) spectroscopy. Flower-like clusters, microfibers, and nanofibers were obtained by doping with CSA, TSA, and the mix of both (CSATSA), respectively. The flower-like morphology limits the conductivity of the film while the microfiber morphology leads to a highly conductive film. The conductivity of the films increases with the doping level, coil-like conformation of the chain and the protonation of the imine in quinoid units. The codoped process reduces the roughness of the CSA-doped films by 50%, but the conductivity depends on the acid type used for this process (TSA or TFA). The optical gas sensor response of the films is related to both the morphology and the degree of protonation. In this study, Pani with a microfiber morphology obtained from TSA-doping is the most sensitive to ammonia gas sensing, and Pani with flower-like morphology is the least sensitive.

Arenas, M. C.; Sánchez, Gabriela; Nicho, M. E.; Elizalde-Torres, Josefina; Castaño, V. M.

2012-03-01

345

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry.  

PubMed

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

346

Chemical Discrimination in Turbulent Gas Mixtures with MOX Sensors Validated by Gas Chromatography-Mass Spectrometry  

PubMed Central

Chemical detection systems based on chemo-resistive sensors usually include a gas chamber to control the sample air flow and to minimize turbulence. However, such a kind of experimental setup does not reproduce the gas concentration fluctuations observed in natural environments and destroys the spatio-temporal information contained in gas plumes. Aiming at reproducing more realistic environments, we utilize a wind tunnel with two independent gas sources that get naturally mixed along a turbulent flow. For the first time, chemo-resistive gas sensors are exposed to dynamic gas mixtures generated with several concentration levels at the sources. Moreover, the ground truth of gas concentrations at the sensor location was estimated by means of gas chromatography-mass spectrometry. We used a support vector machine as a tool to show that chemo-resistive transduction can be utilized to reliably identify chemical components in dynamic turbulent mixtures, as long as sufficient gas concentration coverage is used. We show that in open sampling systems, training the classifiers only on high concentrations of gases produces less effective classification and that it is important to calibrate the classification method with data at low gas concentrations to achieve optimal performance. PMID:25325339

Fonollosa, Jordi; Rodríguez-Luján, Irene; Trincavelli, Marco; Vergara, Alexander; Huerta, Ramón

2014-01-01

347

A poly(vinylidene fluoride)-coated ZnO film bulk acoustic resonator for nerve gas detection  

NASA Astrophysics Data System (ADS)

We apply the film bulk acoustic resonator for the detection of nerve gas. The resonator is consisted of a ZnO piezoelectric stack and a W/SiO2 Bragg reflector. Poly(vinylidene fluoride) (PVDF) is used as the sensing coating to adsorb the analyte under test. The testing results show that our proposed sensor can yield a sensitive, reversible and reproducible response to nerve gas. The relationship between the frequency shifts and the concentrations of the nerve gas exhibits a perfect linear correlation in the range of 10-50 ppm. The gas sensitivity of the proposed sensor is 718 kHz ppm-1, which is several orders of magnitude higher than that of a quartz crystal microbalance with the same sensitive coating. This study proves that it is feasible to use the PVDF-coated thin film bulk acoustic resonator for the detection of the traced nerve gas.

Chen, Da; Wang, Jingjing; Li, Dehua; Liu, Yijian; Song, Hongwei; Liu, Qixin

2011-08-01

348

DEVELOPMENT OF NOVEL CERAMIC NANOFILM-FIBER INTEGRATED OPTICAL SENSORS FOR RAPID DETECTION OF COAL DERIVED SYNTHESIS GAS  

SciTech Connect

The overall goal of this project is to conduct fundamental studies on advanced ceramic materials and fiber optic devices for developing new types of high temperature (>500{degree}C) fiber optic chemical sensors (FOCS) for monitoring fossil (mainly coal) and biomass derived gases in power plants. The primary technical objective is to investigate and demonstrate the nanocrystalline doped-ceramic thin film enabled FOCS that possess desired stability, sensitivity and selectivity for in-situ, rapid gas detection in the syngas streams from gasification and combustion flue gases. This report summarizes research works of two integrated parts: (1) development of metal oxide solid thin films as sensing materials for detection and measurement of important gas components relevant to the coal- and biomass-derived syngas and combustion gas streams at high temperatures; and (2) development of fiber optic devices that are potentially useful for constructing FOCS in combination with the solid oxide thin films identified in this program.

Junhang Dong; Hai Xiao; Xiling Tang; Hongmin Jiang; Kurtis Remmel; Amardeep Kaur

2012-09-30

349

Corrosion properties of sputter-deposited steel thin film for electrical resistance sensor material  

Microsoft Academic Search

Steel thin films for an electrical resistance sensor were prepared by sputter deposition. It was revealed that the electrochemical properties of the thin films were influenced by the surface roughness. Using an Al2O3 substrate with high surface roughness, it was possible to obtain a steel thin film with corrosion characteristics similar to bulk steel. The corrosion rate of the thin

Sungwon Jung; SeonYeob Li; Young-Geun Kim

2006-01-01

350

Final report for EMP instrumentation project DNA IACRO 75-815: magnetic thin film sensors  

Microsoft Academic Search

The magnetic thin film current sensor\\/recorder is a passive device which ; responds to the peak current and pulse shape of a transient event. The transient ; current information becomes a permanent record on the film. The thin film device ; is small, low mass and reusable. It has been proven to be fast (less than 1\\/2 ; nanosecond response),

E. J. Hsieh; D. E. Miller; K. E. Vindelov; T. G. Brown

1975-01-01

351

Varying potential silicon carbide gas sensor  

NASA Technical Reports Server (NTRS)

A hydrocarbon gas detection device operates by dissociating or electro-chemically oxidizing hydrocarbons adsorbed to a silicon carbide detection layer. Dissociation or oxidation are driven by a varying potential applied to the detection layer. Different hydrocarbon species undergo reaction at different applied potentials so that the device is able to discriminate among various hydrocarbon species. The device can operate at temperatures between 100.degree. C. and at least 650.degree. C., allowing hydrocarbon detection in hot exhaust gases. The dissociation reaction is detected either as a change in a capacitor or, preferably, as a change of current flow through an FET which incorporates the silicon carbide detection layers. The silicon carbide detection layer can be augmented with a pad of catalytic material which provides a signal without an applied potential. Comparisons between the catalytically produced signal and the varying potential produced signal may further help identify the hydrocarbon present.

Shields, Virgil B. (Inventor); Ryan, Margaret A. (Inventor); Williams, Roger M. (Inventor)

1997-01-01

352

Portable electronic nose system with gas sensor array and artificial neural network  

Microsoft Academic Search

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and artificial neural network. The sensor array consists of such thick-film oxide semiconductor sensing materials as Pd-doped WO3, Pt-doped SnO2, TiO2–Sb2O5–Pd-doped SnO2, TiO2–Sb2O5–Pd-doped SnO2+Pd-coated layer, Al2O3-doped ZnO and PdCl2-doped SnO2. The portable electronic nose system consists of an Intel 80c196kc as CPU, an

Hyung-Ki Hong; Chul Han Kwon; Seung-Ryeol Kim; Dong Hyun Yun; Kyuchung Lee; Yung Kwon Sung

2000-01-01

353

Polysilicon sacrificial layer etching using ClF 3 for thin film encapsulation of silicon acceleration sensors with high aspect ratio  

Microsoft Academic Search

We present a new thin film encapsulation technique for surface micromachined sensors using a polysilicon multilayer process. The main feature of the encapsulation process is that both the sacrificial layer above the silicon sensor structure and the cap layer consist of epitaxial polysilicon. The sacrificial layer is removed by chlorine trifluoride (ClF3) plasmaless gas-phase etching through vents within the cap

Lars Metzger; Frank Fischer; Wilfried Mokwa

2007-01-01

354

High performance surface inspection method for thin-film sensors  

NASA Astrophysics Data System (ADS)

Thin-film sensors for use in automotive or aeronautic applications must conform to very high quality standards. Due to defects that cannot be addressed by conventional electronic measurements, an accurate optical inspection is imperative to ensure long-term quality aspects of the produced thin-film sensor. In this particular case, resolutions of 1 ?m per pixel are necessary to meet the required high quality standards. Furthermore, it has to be guaranteed that defects are detected robustly with high reliability. In this paper, a new method is proposed that solves the problem of handling local deformations due to production variabilities without having to use computational intensive local image registration operations. The main idea of this method is based on a combination of efficient morphological preprocessing and a multi-step comparison strategy based on logical implication. The main advantage of this approach is that the neighborhood operations that care for the robustness of the image comparison can be computed in advance and stored in a modified reference image. By virtue of this approach, no further neighborhood operations have to be carried out on the acquired test image during inspection time. A systematic, experimental study shows that this method is superior to existing approaches concerning reliability, robustness, and computational efficiency. As a result, the requirements of high-resolution inspection and high-performance throughput while accounting for local deformations are met very well by the implemented inspection system. The work is substantiated with theoretical arguments and a comprehensive analysis of the obtained performance and practical usability in the above-mentioned, challenging industrial environment.

Wieser, Volkmar; Larndorfer, Stefan; Moser, Bernhard

2007-02-01

355

Laser optical gas sensor by photoexcitation effect on refractive index.  

PubMed

Laser optical gas sensors are fabricated by using the crystalline silicon carbide polytype 6H-SiC, which is a wide-bandgap semiconductor, and tested at high temperatures up to 650 degrees C. The sensor operates on the principle of semiconductor optics involving both the semiconductor and optical properties of the material. It is fabricated by doping 6H-SiC with an appropriate dopant such that the dopant energy level matches the quantum of energy of the characteristic radiation emitted by the combustion gas of interest. This radiation changes the electron density in the semiconductor by photoexcitation and, thereby, alters the refractive index of the sensor. The variation in the refractive index can be determined from an interference pattern. Such patterns are obtained for the reflected power of a He-Ne laser of wavelength 632.8 nm as a function of temperature. SiC sensors have been fabricated by doping two quadrants of a 6H-SiC chip with Ga and Al of dopant energy levels E(V)+0.29 eV and E(V)+0.23 eV, respectively. These doped regions exhibit distinct changes in the refractive index of SiC in the presence of carbon dioxide (CO(2)) and nitrogen monoxide (NO) gases respectively. Therefore Ga- and Al-doped 6H-SiC can be used for sensing CO(2) and NO gases at high temperatures, respectively. PMID:20300151

Lim, Geunsik; DeSilva, Upul P; Quick, Nathaniel R; Kar, Aravinda

2010-03-20

356

NiO thin film fabricated by electrophoretic deposition and formaldehyde gas sensing property thereof.  

PubMed

In the present work, nanostructured NiO thin films were prepared from a facile method based on electrophoretic deposition (EPD) using NiOOH sols as the starting material. The scanning electron microscope (SEM) and atomic force microscopy (AFM) observations revealed that the films were comprised of 40-80 nm particles with a thickness of about 100 nm. When using the obtained NiO film as formaldehyde gas sensor, it was found that such kind of nanostructured films have contributed and modified remarkably the sensing properties such as shorter response and recovery time (approximately 10 s and 5 s), higher sensitivity (approximately 3/10 ppm) at lower working temperature (approximately 300 degrees C). PMID:19441521

Han, Ning; Tian, Yajun; Wei, Lianqi; Wang, Chen; Chen, Yunfa

2009-02-01

357

Development of a film sensor for static and dynamic force measurement  

NASA Astrophysics Data System (ADS)

In this work an innovative double-layer film sensor for the measurement of forces is presented. The sensor is a thin film (thickness below 1 mm) based on a "sandwich" structure composed of two sensing elements glued together: one layer is a capacitive film and the other is a piezoelectric film. Both the layers are sensitive to compression loads, but they are suitable for working in different frequency ranges. In fact, while the capacitive element is capable of measuring from dc up to about 400 Hz, on the contrary the piezoelectric film works in the high frequency range. The output signals of both the sensors are acquired and then filtered and processed in order to achieve a single output signal. The piezocapacitive sensor has been developed in order to synthesize, in a small and cheap device, the capability to measure compression forces in a wide range of frequencies. The sensor is very small and has many potential applications, such as in the field of modal analysis. In particular, the very small thickness allows to insert it into a composite material to measure actual loads and excitations, as well as on the surface or between different components of a more complex system in order to obtain a smart structure. This article describes the realization of the sensor and the adopted signal processing strategies. The metrological characterization procedure is discussed and results are shown for both static and dynamic calibration of the film sensor. Finally, a simple application, that highlights the benefits of the sensor, is presented.

Castellini, P.; Montanini, R.; Revel, G. M.

2002-09-01

358

Percolation transition in the gas-induced conductance of nanograin metal oxide films with defects  

NASA Astrophysics Data System (ADS)

We use Monte-Carlo Simulations to study the conductance switching generated by gas-induced electron trapping/-releasing in films of sintered metal oxide nanoparticles by using a site-bond percolation model. We explore the possibilities of gas sensors based on these mechanisms. In our study, we model films of different thicknesses where the conductance values of the grains (sites) and of the contacts (bonds) between these grains depend on the surface density Nr of adsorbed gas molecules from the ambient atmosphere. Below a critical density Nr=Nr ,c, the system is insulating due to the interruption of current flow, either through the connecting bonds or through the grain interior. This leads to two competing critical gas covering thresholds Nr,c(bond) and Nr,c(site), respectively, that separate the insulating from the conducting phase. For Nr,c(site)>Nr,c(bond), the characteristic curve of monodisperse sensors shows a noticeable jump from zero to a finite conductance at Nr=Nr,c(site), while for polydisperse sensors site percolation effects modify the jump into a steep increase of the characteristic curve and thus lead to an enhanced sensitivity. For Nr,c(site)

Dräger, Julia; Russ, Stefanie; Sauerwald, Tilman; Kohl, Claus-Dieter; Bunde, Armin

2013-06-01

359

Thin-film chemical sensors based on electron tunneling  

NASA Technical Reports Server (NTRS)

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

Khanna, S. K.; Lambe, J.; Leduc, H. G.; Thakoor, A. P.

1985-01-01

360

Pseudorandom binary sequence interrogation technique for gas sensors  

Microsoft Academic Search

Electrically conducting organic polymers are widely used as a means of gas, odour or aroma analysis using multi-element array techniques coupled with direct current (d.c.) interrogation techniques. Recently, it has been established that the use of alternating current (a.c.) interrogation gives rise to improved performance. In addition, the need to use multi-element arrays is much reduced since a single sensor

M. E. H Amrani; R. M Dowdeswell; P. A Payne; K. C Persaud

1998-01-01

361

Laser Raman sensor for measurement of trace-hydrogen gas  

NASA Technical Reports Server (NTRS)

A new optical hydrogen sensor based on spontaneous Raman scattering of laser light has been designed and constructed for rugged field use. It provides good sensitivity, rapid response, and the inherent Raman characteristics of linearity and background gas independence of the signal. Efficient light collection and discrimination by using fast optics and a bandpass interference filter compensate for the inefficiency of the Raman-scattering process. A multipass optical cavity with a Herriott-type configuration provides intense illumination from an air-cooled CW gas laser. The observed performance is in good agreement with the theoretical signal and noise level predictions.

Adler-Golden, Steven M.; Goldstein, Neil; Bien, Fritz; Matthew, Michael W.; Gersh, Michael E.; Cheng, Wai K.; Adams, Frederick W.

1992-01-01

362

Sensitive ammonia gas sensors fabricated using biologically assembled copper sulfide  

NASA Astrophysics Data System (ADS)

Copper sulfide-based ammonia (NH3) gas sensors were assembled using a genetically modified viral template. Glutamic acid residues on the filament-shaped bioscaffold surface facilitated the synthesis of nanocrystalline Cu1.8S. Each device comprised a network of biological materials decorated with a nonstoichiometric semiconductor. These chemiresistive devices had high sensitivity to NH3 concentrations from 10 to 80 ppm under room-temperature operation. Response times greater than 15 min were observed. These results demonstrate the potential of biotemplated materials for sensitive gas detection at room temperature.

Shahriar Zaman, Mohammed; Moon, Chung Hee; Haberer, Elaine D.

2014-11-01

363

A novel microelectronic gas sensor utilizing carbon nanotubes for hydrogen gas detection  

Microsoft Academic Search

A novel microelectronic gas sensor utilizing carbon nanotubes (CNTs) in a thin-layered Pd\\/CNTs\\/n+-Si structure for hydrogen detection has been achieved. The sensor is fabricated on an n-type silicon wafer, which is needed as an ohmic supporting substrate. Multiwalled CNTs were grown selectively on the substrate via catalytic activation with microwave plasma enhanced chemical vapor deposition. The I–V characteristics of the

Y. M. Wong; W. P. Kang; J. L. Davidson; A. Wisitsora-at; K. L. Soh

2003-01-01

364

Optical Breath Gas Sensor for Extravehicular Activity Application  

NASA Technical Reports Server (NTRS)

The function of the infrared gas transducer used during extravehicular activity in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation portable life support system (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Space Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode spectrometer based on wavelength modulation spectroscopy is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode-based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen channel using a vertical cavity surface emitting laser. Both prototypes are controlled digitally with a field-programmable gate array/microcontroller architecture. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU.

Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S.; Chullen, Cinda; Falconi, Eric A.; McMillin, Summer

2013-01-01

365

Flammable and noxious gas sensing using a microtripolar electrode sensor with diameter and chirality sorted single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report on the utilization of densely packed (˜10 SWCNTs µm-1), well-aligned arrays of single-chirality single-walled carbon nanotubes (SWCNTs) as an effective thin-film for integration into a gas sensor with a microtripolar electrode, based on field ionization by dielectrophoretic assembly from a monodisperse SWCNTs solution obtained by polymer-mediated sorting. The sensor is characterized as a field ionization electrode with sorted SWCNTs acting as both the sensing material and transducer gas concentrated directly into an electrical signal, an extractor serving to improve electric field uniformity and a collector electrode completing the current path. The gas sensing properties toward flammable and noxious gases, such as CO and H2, were investigated at room temperature. Besides the high sensitivity, the as-fabricated sensor exhibited attractive behaviors in terms of both the detection limit and a fast response, suggesting that our sensor could be used to partly circumvent the low sensing selectivity, long recovery time or irreversibility and allow for a preferential identification of the selected flammable and noxious analytes. Interestingly, the excellent sensing behaviors of the sensors based on the field ionization effect derive directly from the combined effects of the high-quality, low defect SWCNTs arrays, which leads to a small device-to-device variation in the properties and the optimization of electrode fabrication, highlighting the sensor as an appealing candidate in view of nanotube electronics.

Cai, Shengbing; Duan, Zhe min; Zhang, Yong

2013-08-01

366

Dependence of NO 2 gas sensitivity of WO 3 sputtered films on film density  

Microsoft Academic Search

Pure WO3 films and WO3 films doped with noble metals such as Au, Pt, and Ru were deposited on quartz substrates by dc reactive magnetron sputtering to investigate the NO2 gas sensitivity. The temperature of the substrate and the pressure of the discharge gas were changed. The film structures were studied by X-ray diffraction, atomic force microscopy, and density measurements.

Cheng-Ji Jin; Toshinari Yamazaki; Yashuyoshi Shirai; Toshio Yoshizawa; Toshio Kikuta; Noriyuki Nakatani; Humio Takeda

2005-01-01

367

Low-Cost Gas Sensors Produced by the Graphite Line-Patterning Technique Applied to Monitoring Banana Ripeness  

PubMed Central

A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness. PMID:22163963

Manzoli, Alexandra; Steffens, Clarice; Paschoalin, Rafaella T.; Correa, Alessandra A.; Alves, William F.; Leite, Fabio L.; Herrmann, Paulo S. P.

2011-01-01

368

Low-cost gas sensors produced by the graphite line-patterning technique applied to monitoring banana ripeness.  

PubMed

A low-cost sensor array system for banana ripeness monitoring is presented. The sensors are constructed by employing a graphite line-patterning technique (LPT) to print interdigitated graphite electrodes on tracing paper and then coating the printed area with a thin film of polyaniline (PANI) by in-situ polymerization as the gas-sensitive layer. The PANI layers were used for the detection of volatile organic compounds (VOCs), including ethylene, emitted during ripening. The influence of the various acid dopants, hydrochloric acid (HCl), methanesulfonic acid (MSA), p-toluenesulfonic acid (TSA) and camphorsulfonic acid (CSA), on the electrical properties of the thin film of PANI adsorbed on the electrodes was also studied. The extent of doping of the films was investigated by UV-Vis absorption spectroscopy and tests showed that the type of dopant plays an important role in the performance of these low-cost sensors. The array of three sensors, without the PANI-HCl sensor, was able to produce a distinct pattern of signals, taken as a signature (fingerprint) that can be used to characterize bananas ripeness. PMID:22163963

Manzoli, Alexandra; Steffens, Clarice; Paschoalin, Rafaella T; Correa, Alessandra A; Alves, William F; Leite, Fábio L; Herrmann, Paulo S P

2011-01-01

369

Nano particle porous alumina based thin film parallel plate capacitive humidity sensor  

NASA Astrophysics Data System (ADS)

A Relative humidity sensor was fabricated based on porous thin film of ?-Al2O3 formed between the parallel Pd/Ag electrodes working on capacitive technique. The film was fabricated by dip coating of sol solution obtained from the sol-gel method. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. The sensor so obtained is found to be sensitive in 10 to 90% RH. The response time of the sensor is very low around 24 seconds and recovery time 40 seconds.

Kumar, Shailesh

2014-04-01

370

An investigation of response time of TiO 2 thin-film oxygen sensors  

Microsoft Academic Search

TiO2 thin-film oxygen sensors have been made by a sol-gel process. The TiO2 thin film is formed on an alumina rod by dip-coating of a titania sol derived from titanium butanol alkoxide solution in ethanol. The dependence of the resistance (R) of the TiO2 film on the oxygen partial pressure (PO2) and temperature (T) has been determined. The TiO2 thin-film

Maoqing Li; Yufeng Chen

1996-01-01

371

Failure study of SnO2 room temperature gas sensors fabricated on nanospike substrates  

NASA Astrophysics Data System (ADS)

SnO2 gas sensors were fabricated on polyurethane (PU) polymer surfaces with nanospike structures. These nanospikes are replicated with a low-cost soft nanolithography method from silicon nanospike surfaces formed by femtosecond pulsed laser irradiation. The hydrophobicity of the sensing surface was enhanced by a monolayer coating of silane (1H,1H,2H,2H-perfluorooctyltrichlorosilane, PFOTS). The resulting self-cleaning behavior enabled sensing in environments with high moisture and heavy particulate content, while performing cleaning-in-place operations to prolong the lifetime of the sensors. Failure studies were performed to quantify the effects on the sensitivity of water washing. Contact angle measurements showed that the hydrophobicity was weakened after many cycles of droplet washing due to wear of the PFOTS film and/or damage of the nanoscale spike structure. It was also found that the baseline signal increased with droplet washing, while the sensitivity changed randomly within about 7.5%, so that the sensitivity of the gas sensor remained at a constant level after several thousand cycles of water washing.

Wang, Pengtao; Ren, Haizhou; Huo, Haibin; Shen, Mengyan; Sun, Hongwei; Ruths, Marina

2012-04-01

372

Laser Spectroscopic Trace-Gas Sensor Networks for Atmospheric Monitoring Applications  

E-print Network

as the final target. Our prototype sensor measures atmospheric oxygen concentration in the form of a batteryLaser Spectroscopic Trace-Gas Sensor Networks for Atmospheric Monitoring Applications Stephen So@princeton.edu ABSTRACT Laser-based atmospheric trace-gas sensors have great potential for long-term, real

Zhong, Lin

373

MEASUREMENT AND ANALYSIS OF ADSISTOR AND FIGARO GAS SENSORS USED FOR UNDERGROUND STORAGE TANK LEAK DETECTION  

EPA Science Inventory

Two different sensor technologies and their properties were analyzed. he nalysis simulated a leak which occurs from an underground storage tank. igaro gas sensors and the Adsistor gas sensor were tested in simulated underground storage tank nvironments using the Carnegie Mellon R...

374

Filters for tin dioxide CO gas sensors to pass the UL2034 standard  

Microsoft Academic Search

CO gas sensors have to fulfil the requirements of standards like the UL2034 or BS7860. Unfortunately, tin oxide gas sensors are also highly sensitive to volatile organic compounds (VOCs) like long chain hydrocarbons, alcohols or ethyl acetate. These standards require negligible interference in cross-sensitivity tests of CO sensors. To fulfil the standards, charcoal filters were used combined with a micromachined

M Schweizer-Berberich; S Strathmann; W Göpel; R Sharma; A Peyre-Lavigne

2000-01-01

375

The theory and design of piezoelectric/pyroelectric polymer film sensors for biomedical engineering applications.  

PubMed

The unique properties of piezoelectric/pyroelectric polymers offer many new opportunities for biomedical engineering sensor applications. Since their discovery nearly 20 years ago, the polymer films have been used for many novel switching and sensor applications. Despite the prodigious exposure from many recent publications describing piezo film applications, methods of sensor fabrication and circuit interfacing still elude most engineers. This paper is presented as a tutorial guide to applying piezo polymers to biomedical engineering applications. A review of the fundamentals of piezoelectricity/pyroelectricity in piezo polymers is first presented. Their material properties are contrasted with piezoelectric ceramic materials. Some advantages and disadvantages of the films for biomedical sensors are discussed. Specific details on the fabrication of piezo film sensors are presented. Methods are described for forming, cutting, and mounting film sensors, and making lead connections. A brief discussion of equivalent circuit models for the design and simulation of piezoelectric/pyroelectric sensors is included, as well as common circuit interface techniques. Finally, several sources are recommended for further information on a variety of biomedical sensor applications. PMID:2742957

Brown, L F

1989-01-01

376

Scanning electron microscopy to probe working nanowire gas sensors  

NASA Astrophysics Data System (ADS)

This study is dedicated to the implementing of Electron-Beam-Induced Current (EBIC) microscopy to study the behavior of metal oxide semiconducting (MOS) nanowire (NW) gas sensor in situ under exposure to different environment. First, we reported the development of a single nanowire gas sensor compatible with an environmental cell. The major component of the device we use in this study is a single SnO2 nanowire attached to an electron transparent SiN membrane (50-100 nm thick), which was used for mounting nanowire working electrodes and surface imaging of NW. First the NW's conductivity is investigated in different temperatures. Higher temperature is proved to cause higher conductivity of NW. We also found that often the Schottky barrier is formed at the nanowire's contacts with Au and Au/Cr electrodes. Then NW's responses to gas and electron beam (from SEM) are analyzed quantitatively by current measurement. Electron-Beam-Induced Current technique was introduced for the first time to characterize the conductivity behavior of the nanowire during the gas sensing process. Resistive contrast was observed in the EBIC image.

Liu, Yangmingyue

377

Foil level packaging of a chemical gas sensor  

NASA Astrophysics Data System (ADS)

A generic method for the packaging of transducers at the foil level is proposed and was demonstrated on chemical gas sensors made on a plastic foil. The processing was based on the lamination of pre-patterned polymeric structures on the fabricated devices and covered by a gas permeable membrane. This polymeric packaging can be either applied on plastic foils or on conventional substrates such as silicon or glass. It can be used when standard packaging techniques might not be applied or when they can represent a significant cost. Using the lamination of a foil, the dry process presented here is compatible with large-scale fabrication techniques, such as roll-to-roll processing, and aims at reducing the global fabrication cost of sensing devices made on a plastic foil. It can further lead to the fabrication of all polymeric devices. This generic processing can be used for a wide range of applications in the field of microsystems, especially for which the foil level is required and where standard techniques at the wafer level are not applicable. The foil level packaging (FLP) was implemented here for the encapsulation of gas sensors on a plastic foil and validated through gas measurements.

Courbat, J.; Briand, D.; de Rooij, N. F.

2010-05-01

378

Measurement Of Quasiparticle Transport In Aluminum Films Using Tungsten Transition-Edge Sensors  

E-print Network

We report new experimental studies to understand the physics of phonon sensors which utilize quasiparticle diffusion in thin aluminum films into tungsten transition-edge-sensors (TESs) operated at 35 mK. We show that basic TES physics and a simple physical model of the overlap region between the W and Al films in our devices enables us to accurately reproduce the experimentally observed pulse shapes from x-rays absorbed in the Al films. We further estimate quasiparticle loss in Al films using a simple diffusion equation approach.

Yen, J J; Young, B A; Cabrera, B; Brink, P L; Cherry, M; Kreikebaum, J M; Moffatt, R; Redl, P; Tomada, A; Tortorici, E C

2014-01-01

379

Thick-film amperometric zirconia oxygen sensors: influence of cobalt oxide as a sintering aid  

NASA Astrophysics Data System (ADS)

Amperometric thick-film zirconia oxygen sensors are electrochemical devices in which the zirconia thick-film acts as both electrolyte and diffusion barrier. Their preparation involves temperatures of 1300-1400 °C to sinter the thick-film and reduce the through-porosity to a sufficiently low value to restrict oxygen diffusion rates and hence sensor limiting currents. The resulting sensors normally require an operating temperature of 800 °C to enable operation in the percentage oxygen concentration range. In this work sensors were prepared with and without doping with cobalt oxide. Thick-films were characterized using scanning electron microscopy to view a fracture edge and by plotting current-voltage curves of the prepared sensors operated at 600-800 °C in oxygen concentrations up to 21% at atmospheric pressure. It was found that doping with cobalt oxide markedly increased the sintering rate and enabled a reduction of 100-110 °C in sintering temperature for a given final through-porosity. As a result it was possible to operate doped sensors at a temperature around 200 °C lower than otherwise identically-prepared undoped sensors. This is expected to have a beneficial effect on sensor life and reduce operating power. This paper was an invited article at the Sensors and Applications XVII conference.

Maskell, William C.; Brett, Daniel J. L.; Brandon, Nigel P.

2014-06-01

380

Nickel-oxide film as an AR coating of Si window for IR sensor packaging  

NASA Astrophysics Data System (ADS)

An infrared (IR) transparent window is necessary for the IR sensor package. The most commonly used materials for IR transparent window are germanium (Ge) and silicon (Si). Ge has excellent optical properties but also the disadvantage of expensive price. Si has merits such as inexpensive cost and CMOS process compatibility but it has lower transmittance in the range of LWIR region than Ge. Therefore, an alternative anti-reflection (AR) coating is necessary to increase the transmittance of Si as an IR transparent window in the LWIR region. A simple single layer antireflection coating was newly designed on the silicon window for the infrared sensor package. Among the various materials, nickel oxide (NiO) was selected as an AR coating material due to its suitable optical properties and simple process. NiO film was deposited onto the double sided polished Si wafer by reactive rf sputtering with Ni target in an environment of Ar and O2 mixed gas. The thickness of the NiO film was determined by Essential Macleod simulation. FT-IR was used to measure the transmittance of the samples in the LWIR region. After the nickel oxide film was sputtered onto the double sides of the silicon wafer, the measured transmittance of the Si wafer was increased over 20% in the LWIR region compared with that of uncoated Si wafer. Additionally, annealing effect on the transmittance of NiO coated Si wafer was studied. By increasing the annealing temperature from 300° to 700°, an additional increase of transmittance was achieved.

Shim, Hyunbin; Kim, Dongsoo; Kang, Ingu; Kim, Jinkwan; Lee, Hee Chul

2013-06-01

381

Gas turbine blade film cooling and blade tip heat transfer  

Microsoft Academic Search

The detailed heat transfer coefficient and film cooling effectiveness distributions as well as the detailed coolant jet temperature profiles on the suction side of a gas turbine blade were measured using a transient liquid crystal image method and a traversing cold wire and thermocouple probe, respectively. The blade has only one row of film holes near the gill hole portion

Shuye Teng

2000-01-01

382

Prototype thin-film thermocouple/heat-flux sensor for a ceramic-insulated diesel engine  

NASA Technical Reports Server (NTRS)

A platinum versus platinum-13 percent rhodium thin-film thermocouple/heat-flux sensor was devised and tested in the harsh, high-temperature environment of a ceramic-insulated, low-heat-rejection diesel engine. The sensor probe assembly was developed to provide experimental validation of heat transfer and thermal analysis methodologies applicable to the insulated diesel engine concept. The thin-film thermocouple configuration was chosen to approximate an uninterrupted chamber surface and provide a 1-D heat-flux path through the probe body. The engine test was conducted by Purdue University for Integral Technologies, Inc., under a DOE-funded contract managed by NASA Lewis Research Center. The thin-film sensor performed reliably during 6 to 10 hr of repeated engine runs at indicated mean surface temperatures up to 950 K. However, the sensor suffered partial loss of adhesion in the thin-film thermocouple junction area following maximum cyclic temperature excursions to greater than 1150 K.

Kim, Walter S.; Barrows, Richard F.

1988-01-01

383

Novel Thin Film Sensor Technology for Turbine Engine Hot Section Components  

NASA Technical Reports Server (NTRS)

Degradation and damage that develops over time in hot section components can lead to catastrophic failure of the turbine section of aircraft engines. A range of thin film sensor technology has been demonstrated enabling on-component measurement of multiple parameters either individually or in sensor arrays including temperature, strain, heat flux, and flow. Conductive ceramics are beginning to be investigated as new materials for use as thin film sensors in the hot section, leveraging expertise in thin films and high temperature materials. The current challenges are to develop new sensor and insulation materials capable of withstanding the extreme hot section environment, and to develop techniques for applying sensors onto complex high temperature structures for aging studies of hot propulsion materials. The technology research and development ongoing at NASA Glenn Research Center for applications to future aircraft, launch vehicles, space vehicles, and ground systems is outlined.

Wrbanek, John D.; Fralick, Gustave C.

2007-01-01

384

Semiconductor TiO 2 Gas Sensor for Controlling Nitrocarburizing Processes  

Microsoft Academic Search

TiO2 films can serve as oxygen sensors for controlling the nitrogen potential in the process of nitrocarburizing. In contrast to conventional semiconductor-base oxygen sensors that lose stability under extreme thermal and chemical conditions in nitriding and carburizing atmospheres, TiO2 films obtained by the sol-gel method offer a promising alternative. In the present work TiO2 films with a density of about

H. Klümper-Westkamp; S. Beling; A. Mehner; F. Hoffmann; P. Mayr

2004-01-01

385

Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures  

PubMed Central

This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. PMID:22303154

Huang, Jin; Wan, Qing

2009-01-01

386

Laser deposition of sulfonated phthalocyanines for gas sensors  

NASA Astrophysics Data System (ADS)

Thin layers of nickel and copper tetrasulfonated phthalocyanines (NiPcTS and CuPcTS) were prepared by Matrix Assisted Pulsed Laser Evaporation method. The depositions were carried out with KrF excimer laser (energy density of laser radiation EL = 0.1-0.5 J cm-2) from dimethylsulfoxide matrix. For both materials the ablation threshold EL-th was determined. The following properties of deposited layers were characterized: (a) chemical composition (FTIR spectra); (b) morphology (SEM and AFM portraits); and (c) impedance of gas sensors based on NiPcTS and CuPcTS layers in the presence of two analytes - hydrogen and ozone. The prepared sensors exhibit response to 1000 ppm of hydrogen and 100 ppb of ozone even at laboratory temperature.

Fitl, Premysl; Vrnata, Martin; Kopecky, Dusan; Vlcek, Jan; Skodova, Jitka; Bulir, Jiri; Novotny, Michal; Pokorny, Petr

2014-05-01

387

Evaluation of Some Thick Film Materials for Temperature, Force, and Humidity Sensors  

Microsoft Academic Search

\\u000a Thick film technology is a well known, mature and versatile technology for producing hybrid circuits. Also, for some applications\\u000a it provides a relatively inexpensive and convenient way to produce sensors which can be integrated in to hybrid circuits.\\u000a The aim of this paper is to present some results obtained with commercial thick film pastes for temperature and strain sensors\\u000a (thick

M. Hrovat; D. Belavi?; J. Holc

388

Fabrication and testing of a PZT thin film high-pressure sensor  

Microsoft Academic Search

A thin film pressure sensor was fabricated and tested to a high pressure of 40,000 psi. The MEMS fabrication process utilized a 0.5 ?m film of sol-gel deposited PZT (PbZr0.52Ti0.48O3) and platinum metallization for the top and bottom electrodes. The sensor was mounted on a customized stainless steel housing and placed into a high-pressure vessel for both calibration and testing.

Eugene Zakar; Ronald Polcawich; Madan Dubey; Brett Piekarski; G. Mclane; John Conrad; Richard Piekarz; Dennis Wickenden; John Champion; William DAmico; Michael S. L. Hollis; Kenneth Mcmullen; David Porter

2001-01-01

389

Electrochromic Phosphate-Ion Sensor Based on Nickel-Oxide Thin-Film Electrode  

Microsoft Academic Search

An electrochromic phosphate-ion sensor was developed with a nickel-oxide thin-film electrode. The nickel-oxide (NiO) thin-film electrode exhibited a remarkable change of the transmittance at 530 nm, under a positive potential at {+}0.55 V vs saturated calomel electrode (SCE), which was dependent on the HPO42- concentration. The change of transmittance at 530 nm, the sensor signal, was almost linear to the

Youichi Shimizu; Tohru Yamashita; Satoko Takase

2000-01-01

390

Determination of partition coefficients from surface acoustic wave vapor sensor responses and correlation with gas-liquid chromatographic partition coefficients  

SciTech Connect

Surface acoustic wave (SAW) devices coated with a thin film of a stationary phase sense chemical vapors in the gas phase by detecting the mass of the vapor that distributes into the stationary phase. This distribution can be described by the partition coefficient. An equation is presented that allows partition coefficients to be calculated from SAW vapor sensor frequency shifts. The experimental responses of fluoropolyol-coated 158-MHz dual delay line SAW vapor sensors are converted to partition coefficients by this method, and these results are compared with partition coefficients determined by gas-liquid chromatography. These two methods rank the vapors in the same order of increasing sorption, but individual partition coefficient values are not always in precise agreement. The influence of temperature and gas-phase vapor concentration on vapor sorption is also examined.

Grate, J.W.; Snow, A.; Ballantine, D.S. Jr.; Wohltjen, H.; Abraham, M.H.; McGill, R.A.; Sasson, P.

1988-05-01

391

Semiconducting Thin-Film Sensors for Detection of Polluting Gases and Floating Particles  

NASA Astrophysics Data System (ADS)

A micro sensor for polluting gases and organic floating particles has been developed. The sensor is composed of two parts: a sensing element and a micro heater. Both parts are fabricated using thin-film technology, IC fabrication, and a micromachining technique. The sensing film has a double-layered structure; the first layer is a Fe2O3-based thin-film and the second layer is a SnO2-based thin-film. They are deposited by r.f. sputtering on a SiO2/Al2O3/SiO2 diaphragm formed on a Si substrate. A thin-film heater is also fabricated on a similar diaphragm on another Si substrate. The sensing element and the micro heater are placed in parallel at a distance of about 50?m. The sensor is sensitive to polluting gases such as NOX, exhaust gases, cigarette smoke, and organic floating particles such as pollen.

Yokoyama, Tatsuya; Hara, Kazuhiro

392

Development of Resistive Oxygen Sensors Based on Cerium Oxide Thick Film  

Microsoft Academic Search

It is important to shorten the response time of resistive oxygen sensor in order to reduce harmful emission of automobiles. The diffusion and surface reaction theory tells us that reducing particle size leads to shortening the response time. The fine ceria powder was prepared a by new precipitation method and the oxygen sensors having ceria thick film with the particle

Noriya Izu; Woosuck Shin; Ichiro Matsubara; Norimitsu Murayama

2004-01-01

393

Characterization of integrated thin film Pt heater and temperature sensors on Si platform  

Microsoft Academic Search

In this paper the design, fabrication methods and characterization of thin film meandered Pt resistive heater (size 20 ?? 20 mm2) with integrated Pt sensors on Si platform is presented. Pt heaters and temperature sensors were fabricated simultaneously by DC sputtering method. It was found that the fabrication process has significant influence on the electrical properties of the realized thin

Drago Resnik; D. Vrtacnik; U. Aljancic; M. Mozek; B. Pecar; S. Penic; S. Amon

2009-01-01

394

Development of new capacitive strain sensors based on thick film polymer and cermet technologies  

Microsoft Academic Search

In this work, the strain sensing characteristics of new thick film capacitive sensors are presented. New cermet and polymer dielectric pastes based on lead–zirconate–titanate (PZT) and polyvinylidene fluoride (PVDF) have been developed. The screen printing technique has been used to fabricate the sensors on 96% alumina substrates. Various strain gauge characteristics have been studied, including the electrical properties of both

K. I. Arshak; D. McDonagh; M. A. Durcan

2000-01-01

395

Thin film dissolved oxygen sensor based on platinum octaethylporphyrin encapsulated in an elastic fluorinated polymer  

Microsoft Academic Search

A robust thin film dissolved oxygen sensor was fabricated by encapsulating platinum octaethylporphyrin (PtOEP) in an oxygen permeable elastic fluorinated co-polymer matrix. Phosphorescence, which was partially quenched by dissolved oxygen, was observed when the sensor was immersed in water. Aggregation of the dye was observed at elevated temperatures. Dye aggregate phosphorescence was not or only partially quenched by dissolved oxygen.

R. N. Gillanders; M. C. Tedford; P. J. Crilly; R. T. Bailey

2004-01-01

396

Sensors and Actuators A 135 (2007) 262272 Alternative dielectric films for rf MEMS capacitive switches deposited  

E-print Network

Sensors and Actuators A 135 (2007) 262­272 Alternative dielectric films for rf MEMS capacitive University of Colorado, Department of Chemical and Biological Engineering, Boulder, CO 80309, USA d Sensors in radio frequency microelectromechanical systems (rf MEMS). The layer is an alloy mixture of Al2O3 and Zn

George, Steven M.

397

Optical Breath Gas Sensor for Extravehicular Activity Application  

NASA Technical Reports Server (NTRS)

The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation Portable Life Support System (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) spectrometer based on wavelength modulation spectroscopy (WMS) is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen (O2) channel using a vertical cavity surface emitting laser (VCSEL). Both prototypes are controlled digitally with a field-programmable gate array (FPGA)/microcontroller architecture. Based on the results of the initial instrument development, further prototype development and testing of instruments leveraging the lessons learned were desired. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU. .

Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S> ; Chullen, Cinda; Falconi, Eric A.

2012-01-01

398

SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION  

E-print Network

1 SELECTIVE FILTER FOR SnO2 BASED GAS SENSOR : APPLICATION TO HYDROGEN TRACE DETECTION G dioxide, silicon oxide, filter, hydrogen, selectivity. #12;2 I INTRODUCTION Today hydrogen gas sensors safety problems due to the extremely explosive hydrogen gas. In other cases, hydrogen trace detection

Paris-Sud XI, Université de

399

A low cost fiber-optic humidity sensor based on silica sol–gel film  

Microsoft Academic Search

A highly sensitive low cost fiber-optic humidity sensor based on evanescent wave scattering and evanescent wave absorption has been developed. The sensor is fabricated using a U-bend optical fiber which is coated with silica film using sol–gel process and doped with Methylene Blue. We investigated the sensing property of the sensor in different aspects and found that the normalized absorbance

Zhongjun Zhao; Yixiang Duan

400

A Thermal Sensor for Water Using Self-Heated NTC Thick-Film Segmented Thermistors  

Microsoft Academic Search

A simple thermal (heat loss) sensor system was de- signed in a small plastic tube housing using a negative thermal co- efficient (NTC) thick-film thermistor as a self-heating sensor. The voltage power supply (range constant voltage (RCV)-range con- stant voltage) uses the measured input water temperature to select theappliedvoltageinsteps(upanddown)inordertoenableopera- tion of the sensor at optimal sensitivity for different water temper-

Maria V. Nikolic; Branka M. Radojcic; Obrad S. Aleksic; Miloljub D. Lukovic; Pantelija M. Nikolic

2011-01-01

401

Intelligent optical fiber sensor system for measurement of gas concentration  

NASA Astrophysics Data System (ADS)

A measuring, controlling, and alarming system for the concentration of a gas or transparent liquid is described. In this system, a Fabry-Perot etalon with an optical fiber is used as the sensor, a charge-coupled device (CCD) is used as the photoelectric converter, and a single- chip microcomputer 8031 along with an interface circuit is used to measure the interference ring signal. The system has such features as real-time and on-line operation, continuous dynamic handling, and intelligent control.

Pan, Jingming; Yin, Zongmin

1991-08-01

402

Development of nanostructured protective "sight glasses" for IR gas sensors  

NASA Astrophysics Data System (ADS)

In this work protective "sight glasses" for infrared gas sensors showing a sub-wavelength nanostructure with random patterns have been fabricated by reactive ion etching (RIE) in an easy and comparable cheap single step mask-less process. By an organic coating, the intrinsic water repellent property of the surface could be enhanced, shown by contact angle and roll-off angle measurements. The "self-cleaning" surface property and chemical robustness towards aggressive environments are demonstrated. FT-IR spectroscopy concerning the optical properties of these nanostructured silicon windows revealed a stable anti-reflective "moth-eye" effect in certain wavelength ranges owing to the nanostructures.

Bergmann, René; Davis, Zachary James; Schmidt, Michael Stenbæk; Clausen, Sønnik; Boisen, Anja; Jensen, Jens Møller; Buchner, Rainer; Stolberg-Rohr, Thomine; Jakobsen, Mogens Havsteen

2011-06-01

403

Effects of Activation Energy to Transient Response of Semiconductor Gas Sensor  

NASA Astrophysics Data System (ADS)

The smell classifiable gas sensor will be desired for many applications such as gas detection alarms, process controls for food production and so on. We have tried to realize the sensor using transient responses of semiconductor gas sensor consisting of tin dioxide and pointed out that the sensor gave us different transient responses for kinds of gas. Results of model calculation showed the activation energy of chemical reaction on the sensor surface strongly depended on the transient response. We tried to estimate the activation energies by molecular orbital calculation with SnO2 Cluster. The results show that there is a liner relationship between the gradient of the transient responses and activation energies for carboxylic and alcoholic gases. Transient response will be predicted from activation energy in the same kind of gas and the smell discrimination by single semiconductor gas sensor will be realized by this relationship.

Fujimoto, Akira; Ohtani, Tatsuki

404

Gas sensor technology at Sandia National Laboratories: Catalytic gate, Surface Acoustic Wave and Fiber Optic Devices  

SciTech Connect

Sandia`s gas sensor program encompasses three separate electronic platforms: Acoustic Wave Devices, Fiber Optic Sensors and sensors based on silicon microelectronic devices. A review of most of these activities was presented recently in a article in Science under the title ``Chemical Microsensors.`` The focus of the program has been on understanding and developing the chemical sensor coatings that are necessary for using these electronic platforms as effective chemical sensors.

Hughes, R.C.; Moreno, D.J.; Jenkins, M.W.; Rodriguez, J.L.

1993-10-01

405

Field testing the Raman gas composition sensor for gas turbine operation  

SciTech Connect

A gas composition sensor based on Raman spectroscopy using reflective metal lined capillary waveguides is tested under field conditions for feed-forward applications in gas turbine control. The capillary waveguide enables effective use of low powered lasers and rapid composition determination, for computation of required parameters to pre-adjust burner control based on incoming fuel. Tests on high pressure fuel streams show sub-second time response and better than one percent accuracy on natural gas fuel mixtures. Fuel composition and Wobbe constant values are provided at one second intervals or faster. The sensor, designed and constructed at NETL, is packaged for Class I Division 2 operations typical of gas turbine environments, and samples gas at up to 800 psig. Simultaneous determination of the hydrocarbons methane, ethane, and propane plus CO, CO2, H2O, H2, N2, and O2 are realized. The capillary waveguide permits use of miniature spectrometers and laser power of less than 100 mW. The capillary dimensions of 1 m length and 300 μm ID also enable a full sample exchange in 0.4 s or less at 5 psig pressure differential, which allows a fast response to changes in sample composition. Sensor operation under field operation conditions will be reported.

Buric, M.; Chorpening, B.; Mullem, J.; Ranalli, J.; Woodruff, S.

2012-01-01

406

Low-Temperature Thick-Film Systems for Electronic and Sensor Applications  

Microsoft Academic Search

This paper presents recent work on complete thick-film systems, including dielectrics, conductors and resistors, with a lowered firing temperature range of 450…750°C. These materials allow the extension of proven, reliable and inexpensive thick-film technology to novel applications in electronics and sensors.

Thomas Maeder; Claudio Grimaldi; Sonia Vionnet; Caroline Jacq; Hansu Birol; Sigi Strässler; Peter Ryser

407

Miniaturized implantable pressure and oxygen sensors based on polydimethylsiloxane thin films  

Microsoft Academic Search

We demonstrate the application of polydimethylsiloxane (PDMS) thin films in highly sensitive pressure and oxygen sensors, designed for pressure and oxygen content measurements within the heart and blood vessels. PDMS thin film displacement as a result of pressure changes was transduced by a capacitive detection technique to produce quantitative measurement of absolute pressures. Oxygen measurements were obtained by transducing the

Goutam Koley; Jie Liu; Moonbin Yim; Xuejun Wen; Tain-Yen Hsia

2009-01-01

408

Multilayer silver / dielectric thin-film coated hollow waveguides for sensor and laser power delivery applications  

E-print Network

Multilayer silver / dielectric thin-film coated hollow waveguides for sensor and laser power thin film designs deposited on silver coated silica hollow waveguides have been used for low-loss transmission of infrared radiation in the 2 ­ 14 micrometer region. Silver iodide has traditionally been

409

A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film  

PubMed Central

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10?4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

410

A Micro Oxygen Sensor Based on a Nano Sol-Gel TiO2 Thin Film.  

PubMed

An oxygen gas microsensor based on nanostructured sol-gel TiO2 thin films with a buried Pd layer was developed on a silicon substrate. The nanostructured titania thin films for O2 sensors were prepared by the sol-gel process and became anatase after heat treatment. A sandwich TiO2 square board with an area of 350 ?m × 350 ?m was defined by both wet etching and dry etching processes and the wet one was applied in the final process due to its advantages of easy control for the final structure. A pair of 150 nm Pt micro interdigitated electrodes with 50 nm Ti buffer layer was fabricated on the board by a lift-off process. The sensor chip was tested in a furnace with changing the O2 concentration from 1.0% to 20% by monitoring its electrical resistance. Results showed that after several testing cycles the sensor's output becomes stable, and its sensitivity is 0.054 with deviation 2.65 × 10-4 and hysteresis is 8.5%. Due to its simple fabrication process, the sensor has potential for application in environmental monitoring, where lower power consumption and small size are required. PMID:25192312

Wang, Hairong; Chen, Lei; Wang, Jiaxin; Sun, Quantao; Zhao, Yulong

2014-01-01

411

High-performance gas sensors with temperature measurement  

PubMed Central

There are a number of gas ionization sensors using carbon nanotubes as cathode or anode. Unfortunately, their applications are greatly limited by their multi-valued sensitivity, one output value corresponding to several measured concentration values. Here we describe a triple-electrode structure featuring two electric fields with opposite directions, which enable us to overcome the multi-valued sensitivity problem at 1 atm in a wide range of gas concentrations. We used a carbon nanotube array as the first electrode, and the two electric fields between the upper and the lower interelectrode gaps were designed to extract positive ions generated in the upper gap, hence significantly reduced positive ion bombardment on the nanotube electrode, which allowed us to maintain a high electric field near the nanotube tips, leading to a single-valued sensitivity and a long nanotube life. We have demonstrated detection of various gases and simultaneously monitoring temperature, and a potential for applications. PMID:23405281

Zhang, Yong; Li, Shengtao; Zhang, Jingyuan; Pan, Zhigang; Min, Daomin; Li, Xin; Song, Xiaoping; Liu, Junhua

2013-01-01

412

Gas-leak localization using distributed ultrasonic sensors  

NASA Astrophysics Data System (ADS)

We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators are used for approximating the source location when closed-form solutions fail in the presence of ambient background nuisance and inherent electronic noise. The proposed localization algorithms were implemented and tested using a Java-based simulation platform connected to four or more distributed MEMS microphones observing a broadband nitrogen leak from an orifice. The performance of centralized and decentralized algorithms under ED and TDOA schemes is analyzed and compared in terms of communication overhead and accuracy in presence of additive white Gaussian noise (AWGN).

Huseynov, Javid; Baliga, Shankar; Dillencourt, Michael; Bic, Lubomir; Bagherzadeh, Nader

2009-03-01

413

Squeeze-film gas bearing technology  

NASA Technical Reports Server (NTRS)

Squeeze-film bearing is studied to develop a low-friction suspension for the output-axis gimbal of a single-degree-of-freedom gyroscope. Included are a review of pertinent literature, the theory of squeeze-film lubrication, and design elements.

Pan, C. H. T.

1968-01-01

414

Ga 2O 3 thin film for oxygen sensor at high temperature  

Microsoft Academic Search

Gallium oxide thin film has properties of n-type semiconductor and it is stable at high temperature. The resistivity of Ga2O3 changes with the concentration of oxygen in the thin film. An oxygen sensor was made on the basis of this principle. Gallium oxide thin film was deposited on the Si substrate from a sintered powder target by a rf magnetron

M. Ogita; K Higo; Y Nakanishi; Y Hatanaka

2001-01-01

415

Bismuth titanate thin film for pressure sensor prepared by sol gel method  

Microsoft Academic Search

Bismuth titanate, Bi4Ti3O12 thin film pressure sensor was fabricated by sol gel method. The Bi4Ti3O12 thin film was synthesized on substrate Si\\/ SiO2 \\/ RuO2 at low temperature to avoid short-circuit problem. The film was obtained by depositing multiple Bi-Ti-O spin coat layers on substrate, followed by heating of each layer at 300 C in air for 15 mins. Ag

Chong Cheong Wei; M. Yahaya; M. M. Salleh

2004-01-01

416

Breath acetone monitoring by portable Si:WO3 gas sensors  

PubMed Central

Breath analysis has the potential for early stage detection and monitoring of illnesses to drastically reduce the corresponding medical diagnostic costs and improve the quality of life of patients suffering from chronic illnesses. In particular, the detection of acetone in the human breath is promising for non-invasive diagnosis and painless monitoring of diabetes (no finger pricking). Here, a portable acetone sensor consisting of flame-deposited and in situ annealed, Si-doped epsilon-WO3 nanostructured films was developed. The chamber volume was miniaturized while reaction-limited and transport-limited gas flow rates were identified and sensing temperatures were optimized resulting in a low detection limit of acetone (~20 ppb) with short response (10–15 s) and recovery times (35–70 s). Furthermore, the sensor signal (response) was robust against variations of the exhaled breath flow rate facilitating application of these sensors at realistic relative humidities (80–90%) as in the human breath. The acetone content in the breath of test persons was monitored continuously and compared to that of state-of-the-art proton transfer reaction mass spectrometry (PTR-MS). Such portable devices can accurately track breath acetone concentration to become an alternative to more elaborate breath analysis techniques. PMID:22790702

Righettoni, Marco; Tricoli, Antonio; Gass, Samuel; Schmid, Alex; Amann, Anton; Pratsinis, Sotiris E.

2013-01-01

417

Breath acetone monitoring by portable Si:WO3 gas sensors.  

PubMed

Breath analysis has the potential for early stage detection and monitoring of illnesses to drastically reduce the corresponding medical diagnostic costs and improve the quality of life of patients suffering from chronic illnesses. In particular, the detection of acetone in the human breath is promising for non-invasive diagnosis and painless monitoring of diabetes (no finger pricking). Here, a portable acetone sensor consisting of flame-deposited and in situ annealed, Si-doped epsilon-WO(3) nanostructured films was developed. The chamber volume was miniaturized while reaction-limited and transport-limited gas flow rates were identified and sensing temperatures were optimized resulting in a low detection limit of acetone (?20ppb) with short response (10-15s) and recovery times (35-70s). Furthermore, the sensor signal (response) was robust against variations of the exhaled breath flow rate facilitating application of these sensors at realistic relative humidities (80-90%) as in the human breath. The acetone content in the breath of test persons was monitored continuously and compared to that of state-of-the-art proton transfer reaction mass spectrometry (PTR-MS). Such portable devices can accurately track breath acetone concentration to become an alternative to more elaborate breath analysis techniques. PMID:22790702

Righettoni, Marco; Tricoli, Antonio; Gass, Samuel; Schmid, Alex; Amann, Anton; Pratsinis, Sotiris E

2012-08-13

418

Development of an optically modulated piezoelectric sensor/actuator based on titanium oxide phthalocyanine thin film  

NASA Astrophysics Data System (ADS)

A photosensitive electrode made of titanium oxide phthalocyanine (TiOPc) was modulated optically and integrated with a piezoelectric sensor/actuator which allowed us to obtain in situ tailoring of real-time spatial performance. The TiOPc thin film was formed using a spin-coating process. The experimental results showed that the impedance of the TiOPc thin film irradiated by visible light was 0.053 times that of the film not irradiated by visible light. With the successful tailoring of the impedance of the photosensitive electrode, we designed an optically modulated lead zirconate titanate (PZT) sensor/actuator and tested it for different applications. The influence of the impedance match between the TiOPc thin film and PZT of our various optically modulated PZT sensor/actuator designs is discussed in detail. The optically modulated PZT sensor was designed for one-dimensional mode 1 sensor applications. In addition, the successful implementation of the DC effect allowed us to control the mode shape using our optically modulated PZT actuator which was tailored in real time in situ with different optical images. Potential applications of this newly developed TiOPc thin film sensor/actuator include deformable mirrors, microfluidic control applications, and vibration sensing/actuating.

Chen, Kuan-Ting; Huang, Shiu-Duo; Chien, Ying-Heng; Chang, Wen-Chi; Lee, Chih-Kung

2012-11-01

419

Data Processing from Micro-Plasma Gas Analytical Sensor  

NASA Astrophysics Data System (ADS)

Theoretical consideration of signal formation at micro-plasma gas analyzer based on Collisional Electron Spectroscopy (CES) and experimental results on CES sensor are presented. It is demonstrated that a diffusion path confinement for characteristic electrons provides a possibility to measure electrons energy distribution function (EEDF) and to find characteristic spectra of species at high (up to atmospheric) gas pressure. Simple micro-plasma CES sensor of two plane parallel electrode configuration with current-voltage measurement in afterglow discharge may be operated in two possible modes. The first mode presumes application of classic 2-nd derivative of current-voltage curve to select characteristic peaks in electron energy spectra of the species to be detected. In the case of a deeper collisional dissipation of characteristic peaks, a 3-rd derivative may be used. Said derivatives were obtained by differentiating of a spline providing least-squares approximation of current-voltage curve. Model and experimental electron energy spectra of pair He metastables collisions in dependence of inter-electrode gap are discussed.

Mustafaev, Alexander; Tsyganov, Alexander

2011-11-01

420

Optical sensor for carbon dioxide gas determination, characterization and improvements.  

PubMed

A study of different alternatives to improve the stability and lifetime of sensors for the determination of gaseous CO2 has been performed. It includes the characterization of different sensing membranes, a discussion of the results obtained and possibilities for the future. The solid sensor membrane for gaseous CO2 based on changes in the luminiscence of a luminophore immobilized on O2-insensitive film, concurrent with the displacement of a pH indicator, has some drawbacks, such as the loss of efficiency over time and the need to maintain the sensor in special atmospheric conditions. As a solution to these drawbacks, two alternatives were tested, the first alternative was replacing the newly proposed tetraoctyl ammonium hydroxide (TOAOH ) phase transfer agent with other basic agents that did not undergo a Hoffman degradation reaction, and the second alternative was the use of hydrophilic polymers that could retain water needed for CO2 sensing more efficiently. The different membranes tested indicated that the use of tetramethyl ammonium (TMAOH) instead of TOAOH as the phase transfer agent produced better results regarding stability and sensitivity. In addition, replacing the membrane polymer with hydrophilic polymers improved the sensing characteristics in terms of response time and stability over hydrophobic polymers. With a detection limit of 0.006%, the response time is 19s and the recovery time is 100s. The lifetime of the sensing membranes, which do not need to be held in any special atmosphere other than darkness, is longer than at least 300 days for membranes with TMAOH in hydrophilic polymer and 515 days for membranes with TMAOH in ethyl cellulose. PMID:24881553

Aguayo-López, M L; Capitán-Vallvey, L F; Fernández-Ramos, M D

2014-08-01

421

Optical fiber gas sensor for remote detection of methane gas in coal mines  

NASA Astrophysics Data System (ADS)

Characteristic molecular and atomic absorption spectra in the middle infrared and near infrared regions are extensively used for chemical analysis and spectroscopic detection of gases. The absorption of electromagnetic radiation in this spectral region is due to the vibration-rotational bands of molecular structure. Various techniques have been developed for high resolution and high sensitivity absorption spectroscopic detection. Optical gas sensors based on absorption of light by the vibrational-rotational energy levels of gas molecules at near-IR (1-1.8mum) wavelength have attracted considerable attention recently [1]-[4]. The advantages of fiber sensors are remote detection capability, safety in hazardous environments, immunity to electromagnetic fields, etc. The possible gases that can be detected are methane, acetylene, hydrogen sulphide, carbon dioxide, carbon monoxide, etc. In this Dissertation, a particular one-channel optical-fiber-based CH 4 gas real-time monitoring system which can be deployed in mining complexes has been developed. A long-distance silica fiber link with double-pass gas sensor head has been employed in conjunction with a wavelength-tunable InGaAsP DFB laser diode at 1.64 mum (at R(6)line of the 2nu3 absorption band of methane) to realize highly sensitive remote interrogation of CH 4. By wavelength modulation with the DFB laser diode together with a self-designed processing circuit and data processing software, sensitivities of less than 0.1% (volume) and response time of less than 6 sec. have been achieved. Extensive tests have been carried out, and comparisons made with existing conventional CH4 gas detection systems, it is shown, that the performance of the optical fiber sensor system is generally better and is completely qualified for application in the coal mine safety monitoring.

Li, Sanguo

422

Thin Film Ceramic Strain Sensor Development for Harsh Environments: Interim Report on Identification of Candidate Thin Film Ceramics to Test for Viability for Static Strain Sensor Development  

NASA Technical Reports Server (NTRS)

The need to consider ceramic sensing elements is brought about by the temperature limits of metal thin film sensors in propulsion system applications. In order to have a more passive method of negating changes of resistance due to temperature, an effort is underway at NASA Glenn to develop high temperature thin film ceramic static strain gauges for application in turbine engines, specifically in the fan and compressor modules on blades. Other applications can be on aircraft hot section structures and on thermal protection systems. The near-term interim goal of the research effort was to identify candidate thin film ceramic sensor materials to test for viability and provide a list of possible thin film ceramic sensor materials and corresponding properties to test for viability. This goal was achieved by a thorough literature search for ceramics that have the potential for application as high temperature thin film strain gauges, reviewing potential candidate materials for chemical and physical compatibility with our microfabrication procedures and substrates.

Wrbanek, John D.; Fralick, Gustave C.; Hunter, Gary W.

2006-01-01

423

Self-activated ultrahigh chemosensitivity of oxide thin film nanostructures for transparent sensors  

PubMed Central

One of the top design priorities for semiconductor chemical sensors is developing simple, low-cost, sensitive and reliable sensors to be built in handheld devices. However, the need to implement heating elements in sensor devices, and the resulting high power consumption, remains a major obstacle for the realization of miniaturized and integrated chemoresistive thin film sensors based on metal oxides. Here we demonstrate structurally simple but extremely efficient all oxide chemoresistive sensors with ~90% transmittance at visible wavelengths. Highly effective self-activation in anisotropically self-assembled nanocolumnar tungsten oxide thin films on glass substrate with indium-tin oxide electrodes enables ultrahigh response to nitrogen dioxide and volatile organic compounds with detection limits down to parts per trillion levels and power consumption less than 0.2 microwatts. Beyond the sensing performance, high transparency at visible wavelengths creates opportunities for their use in transparent electronic circuitry and optoelectronic devices with avenues for further functional convergence. PMID:22905319

Moon, Hi Gyu; Shim, Young-Soek; Kim, Do Hong; Jeong, Hu Young; Jeong, Myoungho; Jung, Joo Young; Han, Seung Min; Kim, Jong Kyu; Kim, Jin-Sang; Park, Hyung-Ho; Lee, Jong-Heun; Tuller, Harry L.; Yoon, Seok-Jin; Jang, Ho Won

2012-01-01

424

Thick-Film Carbon Dioxide Sensor via Anodic Adsorbate Stripping Technique and Its Structural Dependence  

PubMed Central

A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the platinum nanoparticles. The sensing output was linearly related to the CO2 presented. Stability measurements demonstrated that the decline of the active surface area and the sensitivity of the sensor were 8% and 13%, respectively, over a two week period of time. The sensor response appeared to be a structural dependence of the crystallographic orientation of platinum electrode. PMID:22399993

Photinon, Kanokorn; Wang, Shih-Han; Liu, Chung-Chiun

2009-01-01

425

Two-dimensional ZnO nanowalls for gas sensor and photoelectrochemical applications  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanowalls were vertically grown on a glass substrate through a fast, low-temperature, catalyst-free process in a tube furnace. The morphology and microstructure of ZnO nanowalls were characterized by field-emission scanning electron microscopy, x-ray diffraction analysis, transmission electron microscopy, and photoluminescence measurements. The ZnO nanowall films showed strong UV emission and preferential c-axis orientation, with a hexagonal structure. Potential applications of the ZnO nanowalls were further investigated through experiments. The sensitivity of ZnO-based carbon monoxide gas sensors increased with increasing temperature and reached a maximum value at 300°C. In photoelectrochemical experiments, direct photoelectrolysis of water to generate hydrogen was performed using the ZnO nanowalls as the working photoelectrode. For an external bias of 1.2 V, the photocurrent densities reached 0.037 A/cm2 under Xe lamp illumination.

Chang, Sheng-Po; Wen, Chen-Hua; Chang, Shoou-Jinn

2014-07-01

426

Fibre optical sensor for C 2H 2 gas using gas-filled photonic bandgap fibre reference cell  

Microsoft Academic Search

We present results from the first optical fibre correlation spectroscopy gas sensor which uses no lenses other than in the measurement gas cell. The sensor measures acetylene (C2H2) gas concentration. A 1-m length of photonic bandgap fibre (PBGF) was filled with acetylene at atmospheric pressure, then fusion spliced to standard, solid-core, single-mode SMF-28 fibre to form a compact, coilable, reference

Ed Austin; Adriaan van Brakel; Marco N. Petrovich; David J. Richardson

2009-01-01

427

Deodorant Characteristics of Breath Odor Occurred from Favorite Foods Using Metal Oxide Gas Sensors  

Microsoft Academic Search

Three types of metal oxide gas sensors were adopted to detect the degree of breath odor. Various sorts of information are included in the odor. Each sensor has different sensitivities to gaseous chemical substances and the sensitivities also differ according to human behaviors, for example taking a meal, teeth-brushing and drinking something. There is also a possibility that the sensor

Shuichi Seto; Takashi Oyabu; Kuiqian Cai; Teruaki Katsube

2003-01-01

428

A Bio-Inspired Pattern Recognition System for Tin-Oxide Gas Sensor Applications  

Microsoft Academic Search

In this paper, a bio-inspired pattern recognition system for tin-oxide gas sensor applications is proposed. To mimic the biological olfactory system, temperature modulation is first used to virtually increase the number of sensors by periodically sampling the sensors' response at different temperatures. A convex microhotplate is used in order to improve the thermal properties of the structure enabling efficient temperature

Aicha Beya Far; Farid Flitti; Bin Guo; Amine Bermak

2009-01-01

429

Fiber optic gas sensors with vanadium oxide and tungsten oxide nanoparticle coated claddings  

NASA Astrophysics Data System (ADS)

Fiber optic gas sensors with nanoparticles of V2O5 and WO3 as the cladding of a PMMA fiber have been proposed in this work. The spectral response of these sensors for detection of ammonia, methanol and ethanol under various concentrations has been studied at room temperature. The time response characteristics of the sensors are also presented.

Renganathan, B.; Sastikumar, D.; Raj, S. Gokul; Ganesan, A. R.

2014-03-01

430

Bipolar strain sensor based on an ultra-thin film of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

A bipolar strain sensor based on an ultra-thin film of single-walled carbon nanotubes (SWNTs) has been fabricated. First, a random network of SWNTs was grown on a Si substrate with thermal oxide by using chemical vapor deposition and then transferred to a transparent poly(dimethyl)siloxane (PDMS) film. A mechanical load was applied by pressing the PDMS-SWNT film with a blunt micrometer tip, and its electrical conductance was found to decrease linearly with increasing pressure. Upward bending of the flexible PDMS-SWNT film was found to yield increases in conductance whereas downward bending of the film was found to result in decreases in the conductance. We modeled the SWNT network on the PDMS film with a two-dimensional percolation system, and found that the increases (decreases) in the conductance of the film upon bending could be explained in terms of stick-density changes in the 2-D percolation system. Finally, because PDMS swells with certain organic vapors, a PDMS-SWNT film can be used as a chemical sensor for volatile organic compounds. Unlike for three-dimensional composites of SWNTs and polymers, the bipolar response upon bending and simple fabrication process for the system introduced here mean that it is an attractive candidate for tactile and motion sensor applications.

Park, Dong-Won; Kim, Beom Soo; Park, Serin; Choi, Won-Jin; Yang, Cheol-Soo; Lee, Jeong-O.

2014-02-01

431

PENGARUH KONDISI POLIMERISASI TERHADAP SIFAT-SIFAT OPTIS FILM POLI o-TOLUIDIN SEBAGAI SENSOR pH  

Microsoft Academic Search

The Influence of Polymerization Condition to Optical Properties of Poly-o-toludine Films for PH Sensor Application. Properties of poly-o-toludine film strongly bonded to non polar substrate was studied for application as optical pH sensor. Characterization of film in various pH value is carried out by recording absorbance curve using uv-visible spectrophotometer. All poly-o-toluidine film was then found to be applicable as

Dieky Susanto; Yanti Sabarinah

432

Sensors  

NSDL National Science Digital Library

Electronic sensors exist in many facets of our lives, from measuring operating conditions of our vehicles to adjusting the temperature of our homes. They can even mean the difference between life and death when used to monitor patients in emergency rooms. Even though sensors work transparently in their multitude of functions, their importance cannot be understated.Sensorland (1) has basic descriptions of a wide variety of sensors and related concepts. Out of the 50 items in the list, some have full technical reports that explain physical processes, while others consist of succinct explanations of a device's operation. The site covers sensors that measure everything from atmospheric pressure to the pH value of liquid solutions. In September 2002, the US Army conducted exercises using the zNose, a sensor that can quickly and quantitatively analyze any smell or vapor. This paper (2) provides a complete technical description of the zNose. Several more documents, including the press release of the Army's use of the device, can be found on the Electronic Sensor Technology homepage. In a related story from Sandia National Laboratories, the SnifferSTAR (3) could be especially useful in case of a terrorist gas attack. The short article briefly discusses how the invention works, with an emphasis on its characteristics of low power consumption and rapid analysis. Environmental Research Aircraft and Sensor Technology (4) is a NASA program to develop unmanned aerial vehicles capable of conducting advanced scientific studies. A number of aircraft are highlighted on the program's Web site, many of which are designed for long-term flights or potentially dangerous missions. The February 2003 cover story of Sensors magazine (5) is inertial sensing technology made from microelectromechanical systems (MEMS). The article discusses the applications of MEMS in accelerometers and gyroscopes, as well as explaining some of the theory behind these devices. A streaming video presentation, given in May 2002, can be viewed from this site (6). The hour-long talk introduces Sensor Webs, a network of tiny sensors connected by wireless technology that can be scattered over a large area to gather scientific data. Sensors can even be used in performing arts, as is shown in this paper from the Massachusetts Institute of Technology Media Lab (7). The authors propose using motion sensors to monitor hundreds of performers simultaneously, thereby allowing for much improved lighting and music responses. In the wake of the Space Shuttle Columbia tragedy, a great deal of attention was given to the intermittent and failing sensors on the shuttle minutes before it broke apart. This document from NASA shows the status of several sensors at various intervals in the shuttle's decent (8).

Leske, Cavin.

2003-01-01

433

Air Monitoring System in Elders' Apartment with QCM Type Gas Sensors  

NASA Astrophysics Data System (ADS)

The gas monitoring system for elders' apartment using QCM sensors was newly developed. The QCM sensors for sulfide gas and ammonia gas were used for this system. The system for bodily wastes was fabricated and applied to nursing care system in elders' apartment. This system is composed by the sensor unit, communication unit and data server. Care person can see whether the linen should be changed or not without seeing over each room. The QCM sensors have some problems such as the interference of humidity and temperature, therefore these influences were dissolved using humidity sensor and temperature sensor as feedback source. The sensors were placed in several points of elders' apartment for 2 weeks. This system can be used in elders' apartment successfully.

Kikuchi, Masashi; Ito, Tsukasa; Shiratori, Seimei

434

On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow  

NASA Astrophysics Data System (ADS)

Nitrogen and carbon oxides (CO, NO and NO2), released from combustion facilities and automobiles, are known to be extremely harmful to the human body and also are the main cause of air pollution. Therefore, effective methods to monitor and suppress the carbon and nitrogen oxides have been highly demanded for atmospheric environmental measurements and controls. It is known that molybdenum oxide (MoO3) can be a good semiconductor material for use as a gas sensor in monitoring CO, NO and NO2. In this paper we report the structural characteristics and sensing properties of the sputtered MoO3 thin films as a function of argon gas flow. MoO3 thin films were deposited by DC reactive magnetron sputtering technique on glass substrates at different argon gas flows in the range of 5-20 sccm. X-ray diffraction (XRD) analysis was used for studying crystallographic structure. XRD results showed that all of our films were of polycrystalline structure and of ?-MoO3 stable orthorhombic phase. Results also showed that crystallite size increases while compressive nano-strain in the structure of the films decreases with increasing the argon gas flow. Atomic force microscope and the field emission scanning electron microscope studies showed granular structures for all samples, which increased in size consistent with the XRD results, with argon gas flow, while the surface roughness of the films also increased with argon gas flow. Chemical composition study showed optimum reaction between oxygen and molybdenum atoms for films produced at 15 sccm flow of argon gas. The electrical response of samples was measured in the vacuum and the CO environments in the temperature range of 150-350 K. All samples showed Ohmic behavior and the electrical resistances of the films measured in the CO environment were lower than those measured in vacuum. This study showed that the sensing ability of MoO3 for CO improves with increasing the argon gas flow.

Khojier, K.; Savaloni, H.; Zolghadr, S.

2014-11-01

435

Characterization of Mixed xWO3(1-x)Y2O3 Nanoparticle Thick Film for Gas Sensing Application  

PubMed Central

Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-x)Y2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH4) and butane (C4H10) at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder. PMID:22399925

Shahrokh Abadi, M. H.; Hamidon, M. N.; Shaari, Abdul Halim; Abdullah, Norhafizah; Misron, Norhisam; Wagiran, Rahman

2010-01-01

436

Investigation of substrate-mounted thin-film meteoroid sensors for use in large area impact experiments  

NASA Technical Reports Server (NTRS)

Two types of sensor designs were investigated: (1)a polysulfone dielectric film with vapor-deposited aluminum and gold sensor plates, bonded to a relatively thick aluminum substrate, and (2) an aluminum oxide (A1203) dielectric layer prepared on an aluminum substrate by anodization, with a layer of vapor-deposited aluminum providing one sensor plate and the substrate serving as the other plate. In the first design, specimens were prepared which indicate the state of the art for application of this type of sensor for elements of a meteoroid detection system having an area as large as 10 sq M. Techniques were investigated for casting large-area polysulfone films on the surface of water and for transferring the films from the water. Methods of preparing sensors by layering of films, the deposition of capacitor plates, and sensor film-to-substrate bonding, as well as techniques for making electrical connections to the capacitor plates, were studied.

Carollo, S. F.; Davis, J. M.; Dance, W. E.

1973-01-01

437

Mechanical response of noble gas films to an oscillating substrate  

NASA Astrophysics Data System (ADS)

We carried out quartz-crystal microbalance (QCM) experiments for Xe films adsorbed on an exfoliated single-crystalline graphite substrate (Xe/Gr) and Kr 1ms adsorbed on a synthetic mica substrate (Kr/mica) around LN2 temperature. For Xe/Gr, it was found that the resonance frequency decreases greatly around the first layer completion, while it does not decrease at low coverages. The observed behavior is similar to that of Kr films on a graphite substrate (Kr/Gr). This demonstrates that the layer completion strongly affects the sliding motion of noble gas films on graphite.

Kobayashi, Hajime; Taniguchi, Junko; Suzuki, Masaru; Miura, Kouji; Arakawa, Ichiro

2012-12-01

438

Functionalized single wall carbon nanotube sensor in a perturbed microwave resonant cavity based toxin\\/pollutant gas pressure sensor  

Microsoft Academic Search

The Vlasov and Maxwell's equations are established and solved numerically to describe the effects of toxin\\/pollutant gas pressure and functionalized single wall carbon nanotube (SWCNT) sensor in a perturbed microwave resonant cavity. The dependence of the absorption coefficient on incident frequency, toxin\\/pollutant gas pressure, electron density, and collision frequency is presented. The numerical results illustrate that the resonant frequency shifts

S. B. Tooski

2010-01-01

439

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications  

Microsoft Academic Search

Nanocrystalline metal\\/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low

Christina Hartsell Drake

2007-01-01

440

Optimization of the Temperature Sensor Position for MEMS Gas Flow Meters  

Microsoft Academic Search

A bulk micromachined structure for a thermal type gas flow meter is proposed. It is considered as the thermal type device and consists of a micro heater and two temperature sensors situated at both sides of the heating element. The sensor works on the bases of displacement of temperature profile around the heating element with the gas flow. The heater

E. AbbaspourSani; D. Javan

2006-01-01

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