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Sample records for film gas sensor

  1. Sol-Gel Thin Films for Plasmonic Gas Sensors

    PubMed Central

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-01-01

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

  2. Sol-Gel Thin Films for Plasmonic Gas Sensors.

    PubMed

    Della Gaspera, Enrico; Martucci, Alessandro

    2015-01-01

    Plasmonic gas sensors are optical sensors that use localized surface plasmons or extended surface plasmons as transducing platform. Surface plasmons are very sensitive to dielectric variations of the environment or to electron exchange, and these effects have been exploited for the realization of sensitive gas sensors. In this paper, we review our research work of the last few years on the synthesis and the gas sensing properties of sol-gel based nanomaterials for plasmonic sensors. PMID:26184216

  3. Micromachined thin-film gas flow sensor for microchemical reactors

    E-print Network

    Besser, Ronald S.

    by the emergence of MEMS (Micro Electro Mechanical Systems). Miniaturization of sensors has enabled many new applications not practical before such as highly compact, non-invasive pressure sensors, accelerometers and gas sensors [5], micro heaters [5,8], micro pressure sensors [5], etc. As an early example of a MEMS

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  5. The Effects of Two Thick Film Deposition Methods on Tin Dioxide Gas Sensor Performance

    PubMed Central

    Bakrania, Smitesh D.; Wooldridge, Margaret S.

    2009-01-01

    This work demonstrates the variability in performance between SnO2 thick film gas sensors prepared using two types of film deposition methods. SnO2 powders were deposited on sensor platforms with and without the use of binders. Three commonly utilized binder recipes were investigated, and a new binder-less deposition procedure was developed and characterized. The binder recipes yielded sensors with poor film uniformity and poor structural integrity, compared to the binder-less deposition method. Sensor performance at a fixed operating temperature of 330 °C for the different film deposition methods was evaluated by exposure to 500 ppm of the target gas carbon monoxide. A consequence of the poor film structure, large variability and poor signal properties were observed with the sensors fabricated using binders. Specifically, the sensors created using the binder recipes yielded sensor responses that varied widely (e.g., S = 5 – 20), often with hysteresis in the sensor signal. Repeatable and high quality performance was observed for the sensors prepared using the binder-less dispersion-drop method with good sensor response upon exposure to 500 ppm CO (S = 4.0) at an operating temperature of 330 °C, low standard deviation to the sensor response (±0.35) and no signal hysteresis. PMID:22399977

  6. Gas sensor

    DOEpatents

    Schmid, Andreas K.; Mascaraque, Arantzazu; Santos, Benito; de la Figuera, Juan

    2014-09-09

    A gas sensor is described which incorporates a sensor stack comprising a first film layer of a ferromagnetic material, a spacer layer, and a second film layer of the ferromagnetic material. The first film layer is fabricated so that it exhibits a dependence of its magnetic anisotropy direction on the presence of a gas, That is, the orientation of the easy axis of magnetization will flip from out-of-plane to in-plane when the gas to be detected is present in sufficient concentration. By monitoring the change in resistance of the sensor stack when the orientation of the first layer's magnetization changes, and correlating that change with temperature one can determine both the identity and relative concentration of the detected gas. In one embodiment the stack sensor comprises a top ferromagnetic layer two mono layers thick of cobalt deposited upon a spacer layer of ruthenium, which in turn has a second layer of cobalt disposed on its other side, this second cobalt layer in contact with a programmable heater chip.

  7. Planar Zeolite Film-Based Potentiometric Gas Sensors Manufactured by a Combined Thick-Film and Electroplating Technique

    PubMed Central

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

    2011-01-01

    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

  8. Zinc oxide thin film/nanorods based lossy mode resonance hydrogen sulphide gas sensor

    NASA Astrophysics Data System (ADS)

    Usha, Sruthi P.; Mishra, Satyendra K.; Gupta, Banshi D.

    2015-09-01

    We report a fiber optic hydrogen sulfide gas sensor based on lossy mode resonance utilizing a coating of zinc oxide thin film along with nanorods over the unclad core of the fiber. The sensor is characterized in terms of peak absorbance wavelength determined from the recorded lossy mode resonance spectra for different concentrations of the hydrogen sulfide gas. To achieve the maximum sensitivity of the sensor, the growing period of the nanorods is optimized. It is found that the sensitivity of the sensor depends on the concentration of the gas. Further, the sensor is best suited for low concentrations (less than 60 ppm) of the gas. Experiments are also performed on the probe fabricated with zinc oxide nanorods grown over the unclad portion of the fiber. On comparison, it is found that the probe with layers of zinc oxide thin film and its nanorods is more sensitive than the probe that has layer of nanorods only. This is because of the large active surface area available in the probe fabricated with zinc oxide thin film and its nanorods. In addition, the probe with zinc oxide thin film and its nanorods is highly selective to hydrogen sulfide gas.

  9. Performance and Stress Analysis of Metal Oxide Films for CMOS-Integrated Gas Sensors

    PubMed Central

    Filipovic, Lado; Selberherr, Siegfried

    2015-01-01

    The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250 °C and 550 °C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed. PMID:25815445

  10. Performance and stress analysis of metal oxide films for CMOS-integrated gas sensors.

    PubMed

    Filipovic, Lado; Selberherr, Siegfried

    2015-01-01

    The integration of gas sensor components into smart phones, tablets and wrist watches will revolutionize the environmental health and safety industry by providing individuals the ability to detect harmful chemicals and pollutants in the environment using always-on hand-held or wearable devices. Metal oxide gas sensors rely on changes in their electrical conductance due to the interaction of the oxide with a surrounding gas. These sensors have been extensively studied in the hopes that they will provide full gas sensing functionality with CMOS integrability. The performance of several metal oxide materials, such as tin oxide (SnO2), zinc oxide (ZnO), indium oxide (In2O3) and indium-tin-oxide (ITO), are studied for the detection of various harmful or toxic cases. Due to the need for these films to be heated to temperatures between 250°C and 550°C during operation in order to increase their sensing functionality, a considerable degradation of the film can result. The stress generation during thin film deposition and the thermo-mechanical stress that arises during post-deposition cooling is analyzed through simulations. A tin oxide thin film is deposited using the efficient and economical spray pyrolysis technique, which involves three steps: the atomization of the precursor solution, the transport of the aerosol droplets towards the wafer and the decomposition of the precursor at or near the substrate resulting in film growth. The details of this technique and a simulation methodology are presented. The dependence of the deposition technique on the sensor performance is also discussed. PMID:25815445

  11. Transparent conducting films of hierarchically nanostructured polyaniline networks on flexible substrates for high-performance gas sensors.

    PubMed

    Bai, Shouli; Sun, Chaozheng; Wan, Pengbo; Wang, Cheng; Luo, Ruixian; Li, Yaping; Liu, Junfeng; Sun, Xiaoming

    2015-01-21

    Transparent chemical gas sensors are assembled from a transparent conducting film of hierarchically nanostructured polyaniline (PANI) networks fabricated on a flexible PET substrate, by coating silver nanowires (Ag NWs) followed by the in situ polymerization of aniline near the sacrificial Ag NW template. The sensor exhibits enhanced gas sensing performance at room temperature in both sensitivity and selectivity to NH3 compared to pure PANI film. PMID:25164185

  12. Low temperature deposition of silver sulfide thin films by AACVD for gas sensor application

    NASA Astrophysics Data System (ADS)

    Hussain, Syed Tajammul; Bakar, Shahzad Abu; Saima, BiBi; Muhammad, Bakhtiar

    2012-10-01

    Crack free Ag2S thin films were deposited on glass substrates by aerosol assisted chemical vapor deposition (AACVD) using [Ag(S2CN (C2H5)2)3]2 (1) as a precursor. Thin films were deposited from solution of methanol at 400 °C and characterized by X-ray diffraction (XRD), UV-vis spectroscopy, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. SEM image of thin film showed well-defined and porous surface morphology with an average particle size of 0.3-0.5 ?m. Optical band gaps energy of 1.33 eV was estimated for Ag2S thin film, by extrapolating the linear part of the Tauc plot recorded at room temperature. The gas sensing characteristics of the novel gas sensors based on Ag2S were investigated for the detection carbon monoxide. The effect of operating temperature and change in gas concentration on the performance of carbon monoxide were investigated. The sensing mechanism of sensor was discussed.

  13. Low-cost self-cleaning room temperature SnO2 thin film gas sensor on polymer nanostructures

    NASA Astrophysics Data System (ADS)

    Huo, Haibin; Yan, Fadong; Wang, Cong; Ren, Haizhou; Shen, Mengyan

    2010-04-01

    We have successfully fabricated SnO2 thin film CO gas sensors on nanospiked polyurethane (PU) polymer surfaces that are replicated with a low-cost soft nanolithography method from nanospiked silicon surfaces formed with femtosecond laser irradiations. The sensors show sensitive responses to the CO gas at room temperature because of the sharp structures of the nanospikes. This is much different from the sensors of SnO2 thin film coated on smooth surfaces that show no response to the CO gas at room temperature. To make the nanostructure sensor surface behave self-cleaning like lotus leaves, we deposited a silane monolayer on the surface of the sensors with the 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) which has low surface energy. The contact angle measurement conducted on the PFOTS monolayer-coated SnO2 gas sensors indicates that a super-hydrophobic surface formed on the nanospike sensor. The CO gas response sensitivity of the PFOTS-coated SnO2 sensors is almost the same to that of the as-fabricated SnO2 sensors without the PFOTS coating. Such a super-hydrophobic surface can protect the sensors exposed to moisture and heavy particulates, and can perform cleaning-in-place operations to prolong the lifetime of the sensors. These results show a great potential to fabricate thousands of identical gas sensors at low cost.

  14. Thin film temperature sensor

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    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.

  15. Thin film temperature sensor

    NASA Astrophysics Data System (ADS)

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

    1980-02-01

    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.

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

    E-print Network

    ZnO transparent thin films for gas sensor applications M. Suchea a,b,, S. Christoulakis a,b , K (ZnO) transparent thin films were deposited onto silicon and Corning glass substrates by dc magnetron sputtering using metallic and ceramic targets. Surface investigations carried out by Atomic Force Microscopy

  17. Visual gas sensors based on dye thin films and resonant waveguide gratings

    NASA Astrophysics Data System (ADS)

    Davoine, L.; Schnieper, M.; Barranco, A.; Aparicio, F. J.

    2011-05-01

    A colorimetric sensor that provides a direct visual indication of chemical contamination was developed. The detection is based on the color change of the reflected light after exposure to a gas or a liquid. The sensor is a combination of a chemically sensitive dye layer and a subwavelength grating structure. To enhance the perception of color change, a reference area sealed under a non-contaminated atmosphere is used and placed next to the sensor. The color change is clearly visible by human eyes. The device is based on photonic resonant effects; the visible color is a direct reflection of some incoming light, therefore no additional supplies are needed. This makes it usable as a standalone disposable sensor. The dye thin film is deposited by Plasma enhanced chemical vapor deposition (PECVD) on top of the subwavelength structure. The latter is made by combining a replication process of a Sol-Gel material and a thin film deposition. Lowcost fabrication and compatibility with environments where electricity cannot be used make this device very attractive for applications in hospitals, industries, with explosives and in traffic.

  18. Micro-machined thin film hydrogen gas sensor, and method of making and using the same

    NASA Technical Reports Server (NTRS)

    DiMeo, Jr., Frank (Inventor); Bhandari, Gautam (Inventor)

    2001-01-01

    A hydrogen sensor including a thin film sensor element formed, e.g., by metalorganic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD), on a microhotplate structure. The thin film sensor element includes a film of a hydrogen-interactive metal film that reversibly interacts with hydrogen to provide a correspondingly altered response characteristic, such as optical transmissivity, electrical conductance, electrical resistance, electrical capacitance, magnetoresistance, photoconductivity, etc., relative to the response characteristic of the film in the absence of hydrogen. The hydrogen-interactive metal film may be overcoated with a thin film hydrogen-permeable barrier layer to protect the hydrogen-interactive film from deleterious interaction with non-hydrogen species. The hydrogen sensor of the invention may be usefully employed for the detection of hydrogen in an environment susceptible to the incursion or generation of hydrogen and may be conveniently configured as a hand-held apparatus.

  19. Chemical gas sensor application of open-pore mesoporous thin films based on integrated optical polarimetric interferometry.

    PubMed

    Qi, Zhi-Mei; Honma, Itaru; Zhou, Haoshen

    2006-02-15

    Chemical gas sensors that employ integrated optical polarimetric interferometry were fabricated by the sol-gel synthesis of transparent mesoporous thin films of TiO2-P2O5 nanocomposite on tapered layers of TiO2 sputtered on tin-diffused glass waveguides. Atomic force microscopy images of the mesoporous thin film clearly show the open pore mouths on the film surface that favor rapid diffusion and adsorption of gas-phase analytes within the entire film. Adsorption of gas and vapor induces changes (Deltan) in the refractive index of the mesoporous thin film that lead to shifts in the phase difference between the fundamental transverse electric and magnetic modes simultaneously excited in the glass waveguide via single-beam incidence. Upon exposure to NH3 gas at concentrations as low as 100 ppb in dry air at room temperature, the sensor exhibits a reversible change in the phase difference with the response and recovery times of less than 60 and 90 s, respectively. It is unexpected that the sensor is unresponsive to either NO2 or C6H6 vapor, leading to a somewhat selective sensitivity to NH3. Determination of Deltan was carried out with a combination of the experimental results and the theoretical calculations. The sensor design represents a novel, effective, and easily accessible approach to mesoporous thin-film-based integrated optical chemical sensors. PMID:16478093

  20. Thin film hydrogen sensor

    DOEpatents

    Lauf, Robert J. (Oak Ridge, TN); Hoffheins, Barbara S. (Knoxville, TN); Fleming, Pamela H. (Oak Ridge, TN)

    1994-01-01

    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.

  1. Indium and tin oxide multilayered thin films as gas sensors based on reactive pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Marotta, Veronica; Orlando, Stefano; Parisi, Giovanni P.; Giardini-Guidoni, Anna

    2000-02-01

    Pulsed laser ablation is a very interesting method to deposit thin films of several materials and compounds as oxides, nitrides, insulators, semi- and super-conductors. Indium and In Oxide polycrystalline thin films have been gown on silicon substrates by reactive pulsed laser deposition from two metallic targets of indium and Tin by a multilayered deposition, both in presence of oxygen, using a frequency doubled Nd:YAG laser. These In2O3, SnO2 thin films find valid application as antistatic coatings, transparent resistive heaters, electrical electrodes for flat panel display and electrochromic device.s A comparison has been performed, among Indium Oxide, Tin Oxide, and multilayers of Indium and Tin Oxides, to evaluate their use as gas sensor devices. The influence of the physical parameters such as the substrate temperature, the laser energy, and the oxygen pressure in the deposition chamber has been investigated. The plume has been monitored by fast photography. The characterization of the films has been performed by X-Ray Diffraction, showing a preferential orientation. A four-contact probe shows that our films exhibit an increase in resistivity when exposed to NO.

  2. Gas Sensor Test Chip

    NASA Technical Reports Server (NTRS)

    Buehler, M.; Ryan, M.

    1995-01-01

    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.

  3. A new room temperature gas sensor based on pigment-sensitized TiO2 thin film for amines determination.

    PubMed

    Yanxiao, Li; Xiao-bo, Zou; Xiao-wei, Huang; Ji-yong, Shi; Jie-wen, Zhao; Holmes, Mel; Hao, Limin

    2015-05-15

    A new room temperature gas sensor was fabricated with pigment-sensitized TiO2 thin film as the sensing layer. Four natural pigments were extracted from spinach (Spinacia oleracea), red radish (Raphanus sativus L), winter jasmine (Jasminum nudiflorum), and black rice (Oryza sativa L. indica) by ethanol. Natural pigment-sensitized TiO2 sensor was prepared by immersing porous TiO2 films in an ethanol solution containing a natural pigment for 24h. The hybrid organic-inorganic formed films here were firstly exposed to atmospheres containing methylamine vapours with concentrations over the range 2-10 ppm at room temperature. The films sensitized by the pigments from black-rice showed an excellent gas-sensitivity to methylamine among the four natural pigments sensitized films due to the anthocyanins. The relative change resistance, S, of the films increased almost linearly with increasing concentrations of methylamine (r=0.931). At last, the black rice pigment sensitized TiO2 thin film was used to determine the biogenic amines generated by pork during storage. The developed films had good sensitivity to analogous gases such as putrscine, and cadaverine that will increase during storage. PMID:24934102

  4. Thin film hydrogen sensor

    DOEpatents

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

    1994-11-22

    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.

  5. SnO2/Pt thin film laser ablated gas sensor array.

    PubMed

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

    2011-01-01

    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

  6. SnO2/Pt Thin Film Laser Ablated Gas Sensor Array

    PubMed Central

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

    2011-01-01

    A gas sensor array was developed in a 10 × 10 mm2 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 SnO2 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 O2. 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

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

    SciTech Connect

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

    2014-10-20

    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 H{sub 2}S 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 H{sub 2}S gas concentration, and the sensing mechanism was discussed using the completely depletion model with a flat band diagram.

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

    SciTech Connect

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

    2014-07-21

    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.

  9. A highly sensitive and selective hydrogen gas sensor from thick oriented films of MoS2

    NASA Astrophysics Data System (ADS)

    Miremadi, Bijan K.; Singh, Ravi C.; Morrison, S. Roy; Colbow, Konrad

    1996-09-01

    A new process is developed to fabricate a highly sensitive and selective hydrogen sensor by depositing a partially crystalline and highly oriented film of MoS2 from its single layer suspension on an alumina substrate. When these films are promoted with some catalysts selected from Pt-group metals (Pt, Pd, Ru or any combination of these metals) they exhibit a high sensitivity and selectivity to hydrogen gas. Unlike other metal oxide sensors which are sensitive to many reducing and oxidizing gases and operate at a temperature of 350 °C or higher; this sensor is highly selective to hydrogen gas and its operating temperature is from 25 to 150°C. The lower operating temperature enhances safety when dealing with hydrogen gas. The sensor response to hydrogen at 120 °C is linear in concentration from 30 to 104 ppm with a 10 to 30 second response time and a 45 to 90 second recovery time. Above 104 ppm the sensor is still linear but the slope of conductance versus hydrogen concentration changes.

  10. Study on Ni-doped ZnO films as gas sensors

    NASA Astrophysics Data System (ADS)

    Rambu, A. P.; Ursu, L.; Iftimie, N.; Nica, V.; Dobromir, M.; Iacomi, F.

    2013-09-01

    Ni doped ZnO films were obtained by spin coating, using zinc acetate and nickel acetate as starting materials and N,N-dimethylformamide as solvent. The X-ray diffraction (XRD) analysis indicates that, spin coated films posses a polycrystalline structure. Ni doped ZnO films are single phase and no trace of nickel metal or binary zinc nickel phases are observed. The values of some structural parameters (crystallite size, surface roughness) are varying with the variation of Ni concentration. The sensitivity of Ni:ZnO films, at three different gasses (ammonia, liquefied petroleum gas and ethanol) was investigated. Obtained results indicate that our films are most sensitive to ammonia, the operating temperature was found to be 190 °C and the response time is 35 s. The gas sensitivity was found to depend on the Ni concentration in ZnO films.

  11. Room-temperature NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films with sub-ppm detection ability.

    PubMed

    Tang, Yongliang; Li, Zhijie; Zu, Xiaotao; Ma, Jinyi; Wang, Lu; Yang, Jing; Du, Bo; Yu, Qingkai

    2015-11-15

    In this report, NH3 gas sensors based on Ag-doped ?-Fe2O3/SiO2 composite films are investigated. The composite films were prepared with a sol-gel process, and the films' electrical resistance responded to the change of NH3 concentration in the environment. The SEM and AFM investigations showed that the films had a porous structure, and the XRD investigation indicated that the size of Ag particles changed with the modification of Ag loading content. Through a comparative gas sensing study among the Ag-doped composite films, undoped composite film, ?-Fe2O3 film, and SiO2 film, the Ag-doped composite films were found to be much more sensitive than the sensors based on the undoped composite film and ?-Fe2O3 film at room temperature, indicating the significant influences of the SiO2 and Ag on the sensing property. Moreover, the sensor based on Ag-doped (4%) ?-Fe2O3/SiO2 composite film was able to detect the NH3 gas at ppb level. Conversely, the responses of the sensor to other test gases (C2H5OH, CO, H2, CH4 and H2S) were all markedly low, suggesting excellent selectivity. PMID:26057440

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

    SciTech Connect

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

    2000-01-10

    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.

  13. Thick film hydrogen sensor

    DOEpatents

    Hoffheins, B.S.; Lauf, R.J.

    1995-09-19

    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.

  14. Room Temperature ppb Level Chlorine Gas Sensor Based on Copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine Films

    SciTech Connect

    Bedi, R. K.; Saini, Rajan; Mahajan, Aman

    2010-12-01

    Spin coating technique has been used to fabricate room temperature chlorine gas sensor based on copper (II) 1, 4, 8, 11, 15, 18, 22, 25-octabutoxy-29 H, 31 H-phthalocyanine (CuPc(OBu){sub 8}) films. Gas sensor shows a response of 185% to few parts per billion level of Cl{sub 2} gas with response time of 9.5 minutes at room temperature. The interactions between sensor and analytes followed first order kinetics with rate constant 0.01{<=}k{<=}0.02. The chemiresistive sensor showed very good stability at room temperature over a long period of time.

  15. Toxic gas sensors using thin film transistor platform at low temperature

    E-print Network

    Jin, Yoonsil

    2009-01-01

    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 ...

  16. Thin film hydrogen sensor

    DOEpatents

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

    1999-03-23

    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.

  17. Thin film hydrogen sensor

    DOEpatents

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

    1999-01-01

    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.

  18. Gas Sensor

    NASA Technical Reports Server (NTRS)

    1990-01-01

    High Technology Sensors, Inc.'s Model SS-250 carbon dioxide detector uses a patented semiconductor optical source that efficiently creates infrared radiation, which is focused through an airway on a detector. Carbon dioxide passing through the airway absorbs the radiation causing the detector to generate a signal. The small size and low power requirements of the SS-250 make it attractive for incorporation in a variety of medical instruments.

  19. 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)

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

    2014-08-01

    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.

  20. Gas sensor

    SciTech Connect

    Bunner, T.A.

    1982-03-16

    A detection unit for detecting hydrocarbon gases includes a cylindrical housing having a pair of opposed rectangular slots formed in the wall of the housing near the lower end. A support is mounted within the housing adjacent the upper end. A pair of baffle plates are mounted within the housing from the walls thereof. A semiconductor hydrocarbon gas detector is mounted to the support and is connected by electrical leads to an analyzer and recorder. The detection unit is mounted at the mouth of an oil or gas drilling rig and receives drilling mud into the housing at the rectangular slots such that gases released from the drilling mud are analyzed by the gas detector to determine the hydrocarbon gas content therein.

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

    PubMed

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

    2013-10-01

    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. PMID:23948985

  2. In situ synthesis of porous array films on a filament induced micro-gap electrode pair and their use as resistance-type gas sensors with enhanced performances

    NASA Astrophysics Data System (ADS)

    Xu, Zongke; Duan, Guotao; Zhang, Hongwen; Wang, Yingying; Xu, Lei; Cai, Weiping

    2015-08-01

    Resistance-type metal-oxide semiconductor gas sensors with high sensitivity and low detection limit have been explored for practical applications. They require both sensing films with high sensitivity to target gases and an appropriate structure of the electrode-equipped substrate to support the sensing films, which is still challenging. In this paper, a new gas sensor of metal-oxide porous array films on a micro-gap electrode pair is designed and implemented by taking ZnO as a model material. First, a micro-gap electrode pair was constructed by sputtering deposition on a filament template, which was used as the sensor's supporting substrate. Then, the sensing film, made up of ZnO porous periodic arrays, was in situ synthesized onto the supporting substrate by a solution-dipping colloidal lithography strategy. The results demonstrated the validity of the strategy, and the as-designed sensor shows a small device-resistance, an enhanced sensing performance with high resolution and an ultralow detection limit. This work provides an alternative method to promote the practical application of resistance-type gas sensors.Resistance-type metal-oxide semiconductor gas sensors with high sensitivity and low detection limit have been explored for practical applications. They require both sensing films with high sensitivity to target gases and an appropriate structure of the electrode-equipped substrate to support the sensing films, which is still challenging. In this paper, a new gas sensor of metal-oxide porous array films on a micro-gap electrode pair is designed and implemented by taking ZnO as a model material. First, a micro-gap electrode pair was constructed by sputtering deposition on a filament template, which was used as the sensor's supporting substrate. Then, the sensing film, made up of ZnO porous periodic arrays, was in situ synthesized onto the supporting substrate by a solution-dipping colloidal lithography strategy. The results demonstrated the validity of the strategy, and the as-designed sensor shows a small device-resistance, an enhanced sensing performance with high resolution and an ultralow detection limit. This work provides an alternative method to promote the practical application of resistance-type gas sensors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02099a

  3. Influence of humidity on CO2 gas sensors based on polyetherimide polymer film

    NASA Astrophysics Data System (ADS)

    Kang, Ting; Xie, Guangzhong; Zhou, Yong; Xie, Tao; Tai, Huiling

    2014-09-01

    Quartz Crystal Microbalance (QCM) coated with polyetherimide (PEI) by spin coating method was applied for carbon dioxide (CO2) gas detection at room temperature in this study. The experiments were performed in dry and humid air atmospheres, and the results revealed that the prepared CO2 sensor in moisture circumstance exhibited a larger sensing response than that at dry condition. An enhanced sensing response took place for CO2 detection with the existence of water molecules. The effect of different humidity on QCM sensor performances was investigated as well in this paper. A curve, which displayed a proportional relationship between sensing response and water vapor concentration, was obtained. Moreover, the relevant sensing mechanisms were investigated.

  4. Thin-film temperature sensors for gas turbine engines Problems and prospects

    NASA Technical Reports Server (NTRS)

    Budhani, R. C.; Prakash, S.; Bunshah, R. F.

    1986-01-01

    The erosion and corrosion of thermocouples used to measure the temperature in turbine engines are studied. Structural and metallurgical interactions and instabilities at thermocouple interfaces are analyzed. Consideration is given to the adhesion, dielectric quality, surface topography, and hardness of the thermal oxides; it is observed that the structural and thermoelectric stability of thin-film thermocouple elements depends on adhesion, surface topography, and dielectric strength. The electrical conductivity and impurity content of the oxide scale are evaluated. Methods for improving the adhesion of thermocouples on the alumina surfaces are described. Compositional inhomogeneities in the sensors and contamination of the thermocouple elements are examined. The fabrication of the thermocouples is discussed. It is noted that Al2O3 and Si3N4 are useful for developing stable thermocouple elements on the surface of the blades and vanes.

  5. Development of new metal-oxide thin film gas sensors by conductivity and workfunction correlations

    SciTech Connect

    Doll, T.; Mutschall, D.; Winter, R.; Boegner, M.

    1996-12-31

    Commercially available semiconducting gas sensors usually are based on tin dioxide, although there is a wide variety of metal oxides with capabilities for gas sensing. This derives from restrictions to predict the gas sensitivity under real conditions from clean surface measurements or sensitivity deviations due to different preparation techniques. Hence tedious sample variation and testing is required. It is known that beside pure conductivity studies, combined methods provide a better distinction between preparation-dependent and general chemical effects. For samples with a polycrystalline grain size smaller than the Debye length of the material the correlation of workfunction responses A{Delta}{Phi} to conductivity measurements with the relation {Delta}{Phi} {approximately} log G is one powerful combination. In the present paper, this comparison is shown for nickel oxide layers prepared in two different ways: Reactive sputtering, which leads to partly polycrystalline layers of grain sizes of about 5 to 15 nm according to, and amorphous nickel oxide prepared by ozone enhanced molecular beam epitaxy. The work function and conductivity responses to H{sub 2}, NH{sub 3}, NO{sub 2}, SO{sub 2}, CO and Cl{sub 2} in synthetic air show a very similar sensitivity for the amorphous and the polycrystalline nickeloxides which indicates that the above mentioned correlation range includes amorphous states, too.

  6. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    PubMed

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors. PMID:26381613

  7. Fiber optic gas sensor

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  8. Thin film porous membranes for catalytic sensors

    SciTech Connect

    Hughes, R.C.; Boyle, T.J.; Gardner, T.J.

    1997-06-01

    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.

  9. Sol-Gel derived Sb-doped SnO II/SiO II nano-composite thin films for gas sensors

    NASA Astrophysics Data System (ADS)

    Gu, Zhengtian; Liang, Peihui; Zhang, Weiqing

    2006-05-01

    Sb-doped SnO II/SiO II nano-composite thin films prepared by sol-gel dip-coating method have been studied. By using X-ray diffraction (XRD), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy, detailed investigation on the structure and morphology of the films has shown the crystalline grain size of Sb-doped SnO II/SiO II thin films is about 34nm, with larger specific surface area and duty porosity, which is fit for gas-sensing materials. The adulteration of SiO II particles leads to the condensation of Sn-OH and the strengthening of gel network, and improve the adhesion of the films. In addition, the optical properties of the thin films were studied by UV-Vis spectra and p-polarized light reflectance angular spectrum. The results showthat the optical transmissivity of Sb-doped SnO II/SiO II thin films is higher, near 95% in visible spectrum range, the measured optical gap is found equal to 3.67eV, also the films take on smaller refractive index and extinction coefficient compared with those of the SnO II and Sb:SnO II films, which is compatible with the semiconductor substrate in the solar cell. Further, the gas-sensing test was made to three kinds of gas C 3H 8, C IIH 5OH and NH 3 in our novel high sensitive scheme for optical film sensors. The results indicate that Sb doping to SnO II films greatly improves the gas sensitivity to C IIH 5OH, and the gas sensitivity of Sb:SnO II/SiO II nano-composite thin films are higher than that of Sb:SnO II thin films. The detection sensitivity of this optical film sensor is available to 10 -1ppm provided that the resolution of reflectance ratio is 10 -2.

  10. Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands.

    PubMed

    Van Toan, Nguyen; Viet Chien, Nguyen; Van Duy, Nguyen; Si Hong, Hoang; Nguyen, Hugo; Duc Hoa, Nguyen; Van Hieu, Nguyen

    2016-01-15

    Ultrasensitive and selective hydrogen gas sensor is vital component in safe use of hydrogen that requires a detection and alarm of leakage. Herein, we fabricated a H2 sensing devices by adopting a simple design of planar-type structure sensor in which the heater, electrode, and sensing layer were patterned on the front side of a silicon wafer. The SnO2 thin film-based sensors that were sensitized with microsized Pd islands were fabricated at a wafer-scale by using a sputtering system combined with micro-electronic techniques. The thicknesses of SnO2 thin film and microsized Pd islands were optimized to maximize the sensing performance of the devices. The optimized sensor could be used for monitoring hydrogen gas at low concentrations of 25-250ppm, with a linear dependence to H2 concentration and a fast response and recovery time. The sensor also showed excellent selectivity for monitoring H2 among other gases, such as CO, NH3, and LPG, and satisfactory characteristics for ensuring safety in handling hydrogen. The hydrogen sensing characteristics of the sensors sensitized with Pt and Au islands were also studied to clarify the sensing mechanisms. PMID:26410272

  11. Thin film oxygen partial pressure sensor

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  12. Hydrogen gas sensors based on electrostatically spray deposited nickel oxide thin film structures

    NASA Astrophysics Data System (ADS)

    Jamal, Raied K.; Aadim, Kadhim A.; Al-Zaidi, Qahtan G.; Taaban, Iman N.

    2015-09-01

    A simple, low-cost, and home-built electrostatic spray deposition (ESD) system with the stable cone-jet mode was used to deposit nickel oxide (NiO) thin films on glass substrates kept at temperature of 400 °C as the primary precursor solution of 0.1 M concentration hydrated nickel chloride was dissolved in isopropyl alcohol. Electrical measurements showed that these films were of n-type conductivity while their resistance response to hydrogen flow in air ambient was varied by 2.81% with the rise and recovery time of 48 s and 40 s, respectively.

  13. Gas Sensors Based on Electrospun Nanofibers

    PubMed Central

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

    2009-01-01

    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

  14. Microfabricated Formaldehyde Gas Sensors

    PubMed Central

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

    2009-01-01

    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

  15. Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation

    NASA Astrophysics Data System (ADS)

    Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

    2015-03-01

    A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties.

  16. Fabrication of SnO?-reduced graphite oxide monolayer-ordered porous film gas sensor with tunable sensitivity through ultra-violet light irradiation.

    PubMed

    Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

    2015-01-01

    A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

  17. Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation

    PubMed Central

    Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

    2015-01-01

    A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

  18. Calorimetric gas sensor

    DOEpatents

    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

    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.

  19. Calorimetric gas sensor

    DOEpatents

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

    1998-11-10

    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.

  20. Effects of Ti addiction in WO 3 thin film ammonia gas sensor prepared by dc reactive magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Hu, Ming; Yong, Cholyun; Feng, Youcai; Lv, Yuqiang; Han, Lei; Liang, Jiran; Wang, Haopeng

    2006-11-01

    WO 3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness (100-500 Å) onto WO 3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition on sensitive properties of WO 3 thin film to the NH 3 gas was then discussed. WO 3 thin films added Ti revealed excellent sensitivity and response characteristics in the presence of low concentration of NH 3 (5-400 ppm) gas in air at 200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO 3 thin films have a promotional effect on the response speed to NH 3 and selectivity enhanced with respect to other gases (CO, C IIH 5OH, CH 4). The influence of different substrates, including alumina, silicon and glass, on sensitivity to NH 3 gas has also been investigated.

  1. Thin-film sensors for space propulsion technology

    NASA Astrophysics Data System (ADS)

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

    1985-05-01

    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.

  2. Sensing Properties of Pd-Loaded Co3O4 Film for a ppb-Level NO Gas Sensor

    PubMed Central

    Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck; Sato, Kazuo

    2015-01-01

    We prepared 0.1 wt%–30 wt% Pd-loaded Co3O4 by a colloidal mixing method and investigated the sensing properties of a Pd-loaded Co3O4 sensor element, such as the sensor response, 90% response time, 90% recovery time, and signal-to-noise (S/N) ratio, toward low nitric oxide (NO) gas levels in the range from 50 to 200 parts per billion. The structural properties of the Pd-loaded Co3O4 powder were investigated using X-ray diffraction analysis and transmission electron microscopy. Pd in the powder existed as PdO. The sensor elements with 0.1 wt%–10 wt% Pd content have higher sensor properties than those without any Pd content. The response of the sensor element with a 30 wt% Pd content decreased markedly because of the aggregation and poor dispersibility of the PdO particles. High sensor response and S/N ratio toward the NO gas were achieved when a sensor element with 10 wt% Pd content was used. PMID:25853408

  3. Preparation of Mesoporous and/or Macroporous SnO2-Based Powders and Their Gas-Sensing Properties as Thick Film Sensors

    PubMed Central

    Yuan, Luyang; Hyodo, Takeo; Shimizu, Yasuhiro; Egashira, Makoto

    2011-01-01

    Mesoporous and/or macroporous SnO2-based powders have been prepared and their gas-sensing properties as thick film sensors towards H2 and NO2 have been investigated. The mesopores and macropores of various SnO2-based powders were controlled by self-assembly of sodium bis(2-ethylhexyl)sulfosuccinate and polymethyl-methacrylate (PMMA) microspheres (ca. 800 nm in diameter), respectively. The introduction of mesopores and macropores into SnO2-based sensors increased their sensor resistance in air significantly. The additions of SiO2 and Sb2O5 into mesoporous and/or macroporous SnO2 were found to improve the sensing properties of the sensors. The addition of SiO2 into mesoporous and/or macroporous SnO2 was found to increase the sensor resistance in air, whereas doping of Sb2O5 into mesoporous and/or macroporous SnO2 was found to markedly reduce the sensor resistance in air, and to increase the response to 1,000 ppm H2 as well as 1 ppm NO2 in air. Among all the sensors tested, meso-macroporous SnO2 added with 1 wt% SiO2 and 5 wt% Sb2O5, which were prepared with the above two templates simultaneously, exhibited the largest H2 and NO2 responses. PMID:22319350

  4. Enhanced Sensitivity of Gas Sensor Based on Poly(3-hexylthiophene) Thin-Film Transistors for Disease Diagnosis and Environment Monitoring

    PubMed Central

    Cavallari, Marco R.; Izquierdo, José E. E.; Braga, Guilherme S.; Dirani, Ely A. T.; Pereira-da-Silva, Marcelo A.; Rodríguez, Estrella F. G.; Fonseca, Fernando J.

    2015-01-01

    Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the demand for portable and low-cost gadgets, mainly as sensors for in situ disease diagnosis and environment monitoring. For that reason, poly(3-hexylthiophene) (P3HT) as the active layer in the widely-used bottom-gate/bottom-contact OTFT structure was deposited over highly-doped silicon substrates covered with thermally-grown oxide to detect vapor-phase compounds. A ten-fold organochloride and ammonia sensitivity compared to bare sensors corroborated the application of this semiconducting polymer in sensors. Furthermore, P3HT TFTs presented approximately three-order higher normalized sensitivity than any chemical sensor addressed herein. The results demonstrate that while TFTs respond linearly at the lowest concentration values herein, chemical sensors present such an operating regime mostly above 2000 ppm. Simultaneous alteration of charge carrier mobility and threshold voltage is responsible for pushing the detection limit down to units of ppm of ammonia, as well as tens of ppm of alcohol or ketones. Nevertheless, P3HT transistors and chemical sensors could compose an electronic nose operated at room temperature for a wide range concentration evaluation (1–10,000 ppm) of gaseous analytes. Targeted analytes include not only biomarkers for diseases, such as uremia, cirrhosis, lung cancer and diabetes, but also gases for environment monitoring in food, cosmetic and microelectronics industries. PMID:25912354

  5. SiC-Based Gas Sensor Development

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Gray, M.; Androjna, D.; Chen, L.-Y.; Hoffman, R. W., Jr.; Liu, C. C.; Wu, Q. H.

    2000-01-01

    Silicon carbide based Schottky diode gas sensors are being developed for applications such as emission measurements and leak detection. The effects of the geometry of the tin oxide film in a Pd/SnO2/SiC structure will be discussed as well as improvements in packaging SiC-based sensors. It is concluded that there is considerable versatility in the formation of SiC-based Schottky diode gas sensing structures which will potentially allow the fabrication of a SiC-based gas sensor array for a variety of gases and temperatures.

  6. Metal oxide gas sensors on the nanoscale

    NASA Astrophysics Data System (ADS)

    Plecenik, A.; Haidry, A. A.; Plecenik, T.; Durina, P.; Truchly, M.; Mosko, M.; Grancic, B.; Gregor, M.; Roch, T.; Satrapinskyy, L.; Moskova, A.; Mikula, M.; Kus, P.

    2014-06-01

    Low cost, low power and highly sensitive gas sensors operating at room temperature are very important devices for controlled hydrogen gas production and storage. One of the disadvantages of chemosensors is their high operating temperature (usually 200 - 400 °C), which excludes such type of sensors from usage in explosive environment. In this report, a new concept of gas chemosensors operating at room temperature based on TiO2 thin films is discussed. Integration of such sensor is fully compatible with sub-100 nm semiconductor technology and could be transferred directly from labor to commercial sphere.

  7. Properties and sensor performance of zinc oxide thin films

    E-print Network

    Min, Yongki, 1965-

    2003-01-01

    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 ...

  8. Thin Film Sensors for Surface Measurements

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  9. Porous Nickel Oxide Film Sensor for Formaldehyde

    NASA Astrophysics Data System (ADS)

    Cindemir, U.; Topalian, Z.; Österlund, L.; Granqvist, C. G.; Niklasson, G. A.

    2014-11-01

    Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 °C.

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

    PubMed Central

    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

    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

  11. Bimodular high temperature planar oxygen gas sensor

    NASA Astrophysics Data System (ADS)

    Sun, Xiangcheng; Liu, Yixin; Gao, Haiyong; Gao, Puxian; Lei, Yu

    2014-08-01

    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 nanoparticles film was characterized by atomic force microscopy (AFM) and scanning electron microscopy (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 °C, 600 °C 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.

  12. Chemoresistive gas sensor

    DOEpatents

    Hirschfeld, T.B.

    1987-06-23

    A chemoresistive gas sensor is provided which has improved sensitivity. A layer of organic semiconductor is disposed between two electrodes which, in turn, are connected to a voltage source. High conductivity material is dispersed within the layer of organic semiconductor in the form of very small particles, or islands. The average interisland spacing is selected so that the predominant mode of current flow is by way of electron funneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner. 2 figs.

  13. Chemoresistive gas sensor

    DOEpatents

    Hirschfeld, Tomas B. (Livermore, CA)

    1987-01-01

    A chemoresistive gas sensor is provided which has improved sensitivity. A layer of organic semiconductor is disposed between two electrodes which, in turn, are connected to a voltage source. High conductivity material is dispersed within the layer of organic semiconductor in the form of very small particles, or islands. The average interisland spacing is selected so that the predominant mode of current flow is by way of electron funneling. Adsorption of gaseous contaminant onto the layer of organic semiconductor modulates the tunneling current in a quantitative manner.

  14. Process for manufacture of thick film hydrogen sensors

    DOEpatents

    Perdieu, Louisa H. (Overland Park, KS)

    2000-09-09

    A thick film process for producing hydrogen sensors capable of sensing down to a one percent concentration of hydrogen in carrier gasses such as argon, nitrogen, and air. The sensor is also suitable to detect hydrogen gas while immersed in transformer oil. The sensor includes a palladium resistance network thick film printed on a substrate, a portion of which network is coated with a protective hydrogen barrier. The process utilizes a sequence of printing of the requisite materials on a non-conductive substrate with firing temperatures at each step which are less than or equal to the temperature at the previous step.

  15. A Rapid Process for Fabricating Gas Sensors

    PubMed Central

    Hsiao, Chun-Ching; Luo, Li-Siang

    2014-01-01

    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

  16. Thin Hot-Film Sensors On Polyimide Film

    NASA Technical Reports Server (NTRS)

    Hopson, Purnell

    1993-01-01

    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.

  17. Multi-Gas Sensor

    NASA Technical Reports Server (NTRS)

    Sachse, Glenn W. (Inventor); Wang, Liang-Guo (Inventor); LeBel, Peter J. (Inventor); Steele, Tommy C. (Inventor); Rana, Mauro (Inventor)

    1999-01-01

    A multi-gas sensor is provided which modulates a polarized light beam over a broadband of wavelengths between two alternating orthogonal polarization components. The two orthogonal polarization components of the polarization modulated beam are directed along two distinct optical paths. At least one optical path contains one or more spectral discrimination element, with each spectral discrimination element having spectral absorption features of one or more gases of interest being measured. The two optical paths then intersect, and one orthogonal component of the intersected components is transmitted and the other orthogonal component is reflected. The combined polarization modulated beam is partitioned into one or more smaller spectral regions of interest where one or more gases of interest has an absorption band. The difference in intensity between the two orthogonal polarization components is then determined in each partitioned spectral region of interest as an indication of the spectral emission/absorption of the light beam by the gases of interest in the measurement path. The spectral emission/absorption is indicative of the concentration of the one or more gases of interest in the measurement path. More specifically, one embodiment of the present invention is a gas filter correlation radiometer which comprises a polarizer, a polarization modulator, a polarization beam splitter, a beam combiner, wavelength partitioning element, and detection element. The gases of interest are measured simultaneously and, further, can be measured independently or non-independently. Furthermore, optical or electronic element are provided to balance optical intensities between the two optical paths.

  18. New Gas Polarographic Hydrogen Sensor

    NASA Technical Reports Server (NTRS)

    Dominguez, Jesus A.; Barile, Ron

    2004-01-01

    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.

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

    SciTech Connect

    Gao, Pu-Xian; Lei, Yu

    2013-06-01

    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.

  20. Solid State Gas Sensor Research in Germany – a Status Report

    PubMed Central

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

    2009-01-01

    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

  1. Vibration welding system with thin film sensor

    DOEpatents

    Cai, Wayne W; Abell, Jeffrey A; Li, Xiaochun; Choi, Hongseok; Zhao, Jingzhou

    2014-03-18

    A vibration welding system includes an anvil, a welding horn, a thin film sensor, and a process controller. The anvil and horn include working surfaces that contact a work piece during the welding process. The sensor measures a control value at the working surface. The measured control value is transmitted to the controller, which controls the system in part using the measured control value. The thin film sensor may include a plurality of thermopiles and thermocouples which collectively measure temperature and heat flux at the working surface. A method includes providing a welder device with a slot adjacent to a working surface of the welder device, inserting the thin film sensor into the slot, and using the sensor to measure a control value at the working surface. A process controller then controls the vibration welding system in part using the measured control value.

  2. CO2 Selective Potentiometric Sensor in Thick-film Technology

    PubMed Central

    Sahner, Kathy; Schulz, Anne; Kita, Jaroslaw; Merkle, Rotraut; Maier, Joachim; Moos, Ralf

    2008-01-01

    A potentiometric sensor device based on screen-printed Nasicon films was investigated. In order to transfer the promising sensor concept of an open sodium titanate reference to thick film technology, “sodium-rich” and “sodium-poor” formulations were compared. While the “sodium-rich” composition was found to react with the ion conducting Nasicon during thermal treatment, the “sodium-poor” reference mixture was identified as an appropriate reference composition. Screen-printed sensor devices were prepared and tested with respect to CO2 response, reproducibility, and cross-interference of oxygen. Excellent agreement with the theory was observed. With the integration of a screen-printed heater, sensor elements were operated actively heated in a cold gas stream.

  3. Electrostatic thin film chemical and biological sensor

    DOEpatents

    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

    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.

  4. Micro-sensor thin-film anemometer

    NASA Technical Reports Server (NTRS)

    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

    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.

  5. Integrated Mirco-Machined Hydrogen Gas Sensors

    SciTech Connect

    Frank DiMeoJr. Ing--shin Chen

    2005-12-15

    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.

  6. Exhaust gas sensors

    SciTech Connect

    Hiller, J.; Miree, T.J.

    1997-02-09

    The automotive industry needed a fast, reliable, under-the-hood method of determining nitrogen oxides in automobile exhaust. Several technologies were pursued concurrently. These sensing technologies were based on light absorption, electrochemical methods, and surface mass loading. The Y-12 plant was selected to study the methods based on light absorption. The first phase was defining the detailed technical objectives of the sensors--this was the role of the automobile companies. The second phase was to develop prototype sensors in the laboratories--the national laboratories. The final phase was testing of the prototype sensors by the automobile industries. This program was canceled a few months into what was to be a three-year effort.

  7. WO3 thin film based multiple sensor array for electronic nose application

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Multiple sensor array comprising 16 x 2 sensing elements were realized using RF sputtered WO3 thin films. The sensor films were modified with a thin layer of sensitizers namely Au, Ni, Cu, Al, Pd, Ti, Pt. The resulting sensor array were tested for their response towards different gases namely H2S, NH3, NO and C2H5OH. The sensor response values measured from the response curves indicates that the sensor array generates a unique signature pattern (bar chart) for the gases. The sensor response values can be used to get both qualitative and quantitative information about the gas.

  8. Zinc oxide thin film acoustic sensor

    SciTech Connect

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

    2013-12-16

    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.

  9. Thin-film fiber optic hydrogen and temperature sensor system

    DOEpatents

    Nave, S.E.

    1998-07-21

    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 fiber optic 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. 3 figs.

  10. Thin-film fiber optic hydrogen and temperature sensor system

    DOEpatents

    Nave, Stanley E. (Evans, GA)

    1998-01-01

    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.

  11. Gas Sensor Test Chip

    NASA Technical Reports Server (NTRS)

    Buehler, M. G.; Ryan, M. A.

    1996-01-01

    The use of organic polymers to detect gasses has been known for several years to be an effective means for gas detection via conductivity changes. These chemoresistors offer significant advantages over other gas detectors in that they operate near room temperature and thus can be used in compact, low-power applications.

  12. Advances in Thin Film Sensor Technologies for Engine Applications

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  13. Hydrogen Gas Sensors Based on Semiconductor Oxide Nanostructures

    PubMed Central

    Gu, Haoshuang; Wang, Zhao; Hu, Yongming

    2012-01-01

    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

  14. Black phosphorus gas sensors.

    PubMed

    Abbas, Ahmad N; Liu, Bilu; Chen, Liang; Ma, Yuqiang; Cong, Sen; Aroonyadet, Noppadol; Köpf, Marianne; Nilges, Tom; Zhou, Chongwu

    2015-05-26

    The utilization of black phosphorus and its monolayer (phosphorene) and few-layers in field-effect transistors has attracted a lot of attention to this elemental two-dimensional material. Various studies on optimization of black phosphorus field-effect transistors, PN junctions, photodetectors, and other applications have been demonstrated. Although chemical sensing based on black phosphorus devices was theoretically predicted, there is still no experimental verification of such an important study of this material. In this article, we report on chemical sensing of nitrogen dioxide (NO2) using field-effect transistors based on multilayer black phosphorus. Black phosphorus sensors exhibited increased conduction upon NO2 exposure and excellent sensitivity for detection of NO2 down to 5 ppb. Moreover, when the multilayer black phosphorus field-effect transistor was exposed to NO2 concentrations of 5, 10, 20, and 40 ppb, its relative conduction change followed the Langmuir isotherm for molecules adsorbed on a surface. Additionally, on the basis of an exponential conductance change, the rate constants for adsorption and desorption of NO2 on black phosphorus were extracted for different NO2 concentrations, and they were in the range of 130-840 s. These results shed light on important electronic and sensing characteristics of black phosphorus, which can be utilized in future studies and applications. PMID:25945545

  15. Augmenting Film and Video Footage with Sensor Data

    E-print Network

    Su, Norman Makoto

    Augmenting Film and Video Footage with Sensor Data Norman Makoto Su, Heemin Park , Eric Bostrom of Electrical Engineering, School of Theater, Film and Television University of California, Los Angeles normsu application of sensor networks to the film industry. In particular, we are interested in augmenting film

  16. Development of a hydrogen gas sensor using microfabrication technology

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  17. Combustion Sensors: Gas Turbine Applications

    NASA Technical Reports Server (NTRS)

    Human, Mel

    2002-01-01

    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.

  18. Zeolite-based Impedimetric Gas Sensor Device in Low-cost Technology for Hydrocarbon Gas Detection

    PubMed Central

    Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

    2008-01-01

    Due to increasing environmental concerns the need for inexpensive selective gas sensors is increasing. This work deals with transferring a novel zeolite-based impedimetric hydrocarbon gas sensor principle, which has been originally manufactured in a costly combination of photolithography, thin-film processes, and thick-film processes to a low-cost technology comprising only thick-film processes and one electroplating step. The sensing effect is based on a thin chromium oxide layer between the interdigital electrodes and a Pt-loaded ZSM-5 zeolite film. When hydrocarbons are present in the sensor ambient, the electrical sensor impedance increases strongly and selectively. In the present work, the chromium oxide film is electroplated on Au screen-printed interdigital electrodes and then oxidized to Cr2O3. The electrode area is covered with the screen-printed zeolite. The sensor device is self-heated utilizing a planar platinum heater on the backside. The best sensor performance is obtained at a frequency of 3 Hz at around 350 °C. The good selectivity of the original sensor setup could be confirmed, but a strong cross-sensitivity to ammonia occurs, which might prohibit its original intention for use in automotive exhausts.

  19. Enhanced Sensing Characteristics in MEMS-based Formaldehyde Gas Sensor

    E-print Network

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

    2008-01-01

    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.

  20. Developing Multilayer Thin Film Strain Sensors With High Thermal Stability

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

  1. Thin film mixed potential sensors

    DOEpatents

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

    2007-09-04

    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.

  2. Thin-film spectroscopic sensor

    DOEpatents

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

    1992-01-01

    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.

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

    PubMed Central

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

    2009-01-01

    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

  4. Gas sensor with attenuated drift characteristic

    DOEpatents

    Chen, Ing-Shin (Danbury, CT) [Danbury, CT; Chen, Philip S. H. (Bethel, CT) [Bethel, CT; Neuner, Jeffrey W. (Bethel, CT) [Bethel, CT; Welch, James (Fairfield, CT) [Fairfield, CT; Hendrix, Bryan (Danbury, CT) [Danbury, CT; Dimeo, Jr., Frank [Danbury, CT

    2008-05-13

    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 layer and the micro-hotplate, and with a tantalum barrier layer between the yttrium layer and an overlying palladium protective layer. The gas sensor is useful for detection of a target gas in environments susceptible to generation or incursion of such gas, and achieves substantial (e.g., >90%) reduction of signal drift from the gas sensor in extended operation, relative to a corresponding gas sensor lacking the diffusional barrier structure of the invention

  5. Development of a fluidic gas concentration sensor

    NASA Astrophysics Data System (ADS)

    Stevens, G. E.; Funke, M. F.

    1980-06-01

    This document is the final report of a program to design, test, and evaluate the performance of fluidic gas concentration sensing systems and their component parts for monitoring CxHy and H2S on offshore platforms. This program consisted of investigating three major portions of a systems: Gas Sensors, Chemical Processors and Sensor System. Three candidate fluidic sensors (Resistor Bridge Sensor, Vortex Sensor, Jet Edge Resonator Oscillator Sensor) were evaluated for use in the sensor system. The resistor bridge sensor was chosen as the most appropriate. Several chemical processors were evaluated for each gas sensing system. Palladium coated alumina was chosen for the CxHy system and lead acetate was chosen for the H2S systems.

  6. Electrospray-printed nanostructured graphene oxide gas sensors.

    PubMed

    Taylor, Anthony P; Velásquez-García, Luis F

    2015-12-18

    We report low-cost conductometric gas sensors that use an ultrathin film made of graphene oxide (GO) nanoflakes as transducing element. The devices were fabricated by lift-off metallization and near-room temperature, atmospheric pressure electrospray printing using a shadow mask. The sensors are sensitive to reactive gases at room temperature without requiring any post heat treatment, harsh chemical reduction, or doping with metal nanoparticles. The sensors' response to humidity at atmospheric pressure tracks that of a commercial sensor, and is linear with changes in humidity in the 10%-60% relative humidity range while consuming <6 ?W. Devices with GO layers printed by different deposition recipes yielded nearly identical response characteristics, suggesting that intrinsic properties of the film control the sensing mechanism. The gas sensors successfully detected ammonia at concentrations down to 500 ppm (absolute partial pressure of ?5 × 10(-4) T) at ?1 T pressure, room temperature conditions. The sensor technology can be used in a great variety of applications including air conditioning and sensing of reactive gas species in vacuum lines and abatement systems. PMID:26579701

  7. Electrospray-printed nanostructured graphene oxide gas sensors

    NASA Astrophysics Data System (ADS)

    Taylor, Anthony P.; Velásquez-García, Luis F.

    2015-12-01

    We report low-cost conductometric gas sensors that use an ultrathin film made of graphene oxide (GO) nanoflakes as transducing element. The devices were fabricated by lift-off metallization and near-room temperature, atmospheric pressure electrospray printing using a shadow mask. The sensors are sensitive to reactive gases at room temperature without requiring any post heat treatment, harsh chemical reduction, or doping with metal nanoparticles. The sensors’ response to humidity at atmospheric pressure tracks that of a commercial sensor, and is linear with changes in humidity in the 10%–60% relative humidity range while consuming <6 ?W. Devices with GO layers printed by different deposition recipes yielded nearly identical response characteristics, suggesting that intrinsic properties of the film control the sensing mechanism. The gas sensors successfully detected ammonia at concentrations down to 500 ppm (absolute partial pressure of ?5 × 10?4 T) at ?1 T pressure, room temperature conditions. The sensor technology can be used in a great variety of applications including air conditioning and sensing of reactive gas species in vacuum lines and abatement systems.

  8. Nanocrystalline films for gas-reactive applications

    DOEpatents

    Eastman, Jeffrey A.; Thompson, Loren J.

    2004-02-17

    A gas sensor for detection of oxidizing and reducing gases, including O.sub.2, CO.sub.2, CO, and H.sub.2, monitors the partial pressure of a gas to be detected by measuring the temperature rise of an oxide-thin-film-coated metallic line in response to an applied electrical current. For a fixed input power, the temperature rise of the metallic line is inversely proportional to the thermal conductivity of the oxide coating. The oxide coating contains multi-valent cation species that change their valence, and hence the oxygen stoichiometry of the coating, in response to changes in the partial pressure of the detected gas. Since the thermal conductivity of the coating is dependent on its oxygen stoichiometry, the temperature rise of the metallic line depends on the partial pressure of the detected gas. Nanocrystalline (<100 nm grain size) oxide coatings yield faster sensor response times than conventional larger-grained coatings due to faster oxygen diffusion along grain boundaries rather than through grain interiors.

  9. Gas sensitivity measurements on NO{sub 2} sensors based on copper(II) tetrakis(n-butylaminocarbonyl)phthalocyanine LB films

    SciTech Connect

    Capone, S.; Rella, R.; Siciliano, P.; Mongelli, S.; Valli, L.

    1999-03-02

    The NO{sub 2} gas-sensing characteristics of chemiresistors in the form of multilayered Langmuir-Blodgett films of a symmetrically substituted phthalocyanine, containing on the periphery four amidic groups -CONH-, have been studied. Floating layers were spread onto the water surface from a chloroform solution and were transferred onto both hydrophilic and hydrophobic quartz substrates using the vertical lifting method. Response and recovery times have been measured for different working temperatures at a fixed NO{sub 2} concentration. Dynamic response characteristics of the electrical conductance of the LB films to different NO{sub 2} concentrations, carried out in dry air, have shown a high sensitivity to concentrations of nitrogen dioxide smaller than 20 ppm at room temperature. All measurements have been carried out using coplanar configurations of the devices.

  10. Silicon Carbide Gas Sensors for Propulsion Emissions and Safety Applications

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Xu, J.; Neudeck, P. G.; Lukco, D.; Trunek, A.; Spry, D.; Lampard, P.; Androjna, D.; Makel, D.; Ward, B.

    2007-01-01

    Silicon carbide (SiC) based gas sensors have the ability to meet the needs of a range of aerospace propulsion applications including emissions monitoring, leak detection, and hydrazine monitoring. These applications often require sensitive gas detection in a range of environments. An effective sensing approach to meet the needs of these applications is a Schottky diode based on a SiC semiconductor. The primary advantage of using SiC as a semiconductor is its inherent stability and capability to operate at a wide range of temperatures. The complete SiC Schottky diode gas sensing structure includes both the SiC semiconductor and gas sensitive thin film metal layers; reliable operation of the SiC-based gas sensing structure requires good control of the interface between these gas sensitive layers and the SiC. This paper reports on the development of SiC gas sensors. The focus is on two efforts to better control the SiC gas sensitive Schottky diode interface. First, the use of palladium oxide (PdOx) as a barrier layer between the metal and SiC is discussed. Second, the use of atomically flat SiC to provide an improved SiC semiconductor surface for gas sensor element deposition is explored. The use of SiC gas sensors in a multi-parameter detection system is briefly discussed. It is concluded that SiC gas sensors have potential in a range of propulsion system applications, but tailoring of the sensor for each application is necessary.

  11. Thin Film Heat Flux Sensors: Design and Methodology

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Wrbanek, John D.

    2013-01-01

    Thin Film Heat Flux Sensors: Design and Methodology: (1) Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc. of interest to engine designers and fluid dynamists, (2) The measurement of heat flux is of interest in directly determining the cooling requirements of hot section blades and vanes, and (3)In addition, if the surface and gas temperatures are known, the measurement of heat flux provides a value for the convective heat transfer coefficient that can be compared with the value provided by CFD codes.

  12. Optical Temperature Sensor For Gas Turbines

    NASA Technical Reports Server (NTRS)

    Mossey, P. W.

    1987-01-01

    New design promises accuracy even in presence of contamination. Improved sensor developed to measure gas temperatures up to 1,700 degree C in gas-turbine engines. Sensor has conical shape for mechanical strengths and optical configuration insensitive to deposits of foreign matter on sides of cone.

  13. Nanoparticle thin films deposited by MAPLE for sensor applications

    NASA Astrophysics Data System (ADS)

    Caricato, A. P.; Capone, S.; Epifani, M.; Lomascolo, M.; Luches, A.; Martino, M.; Romano, F.; Rella, R.; Siciliano, P.; Spadavecchia, J.; Taurino, A.; Tunno, T.; Valerini, D.

    2008-01-01

    We report on the potentiality of the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique for the deposition of thin films of colloidal nanoparticles to be used for gas sensors based on electrical transduction mechanisms. The MAPLE technique seems very promising, since it permits a good thickness control even on rough substrates, generally used to enhance the active surface for gas adsorption. TiO II (with a capping layer of benzyl alcohol) and SnO II (with a capping layer of trioctylphosphine) colloidal nanoparticles were diluted in suitable solvents (0.2% concentration), frozen at liquid nitrogen temperature and ablated with a ArF (?=193 nm) or KrF (248 nm) excimer laser. The nanoparticle thin films were deposited on silica, interdigitated alumina and <100> Si substrates and submitted to morphological (SEM-FEG), structural (XRD, FTIR), optical (UV-Vis transmission) and electrical (sensing tests) characterizations. A uniform distribution of TiO II nanoparticles, with an average size of ~10 nm, was obtained on flat and rough substrates. The deposited TiO II nanoparticles preserved the anatase crystalline structure, as evidenced by the XRD spectra. FTIR analysis showed that the SnO II nanoparticles maintained the capping layer after the laser-assisted transfer process. This protective layer was removed after annealing at 400 °C. The starting nanoparticle dimensions were preserved also in this case. Electrical tests, performed on TiO II nanoparticle films, in controlled atmosphere in presence of ethanol and acetone vapors, evidenced a high value of the sensor response even at very low concentrations (20-200 ppm in dry air). In contrast, in the case of SnO II nanoparticle films, electrical tests to ethanol vapor presence showed poor gas sensing properties probably due to the small nanoparticle sizes and interconnections.

  14. Formaldehyde Gas Sensors: A Review

    PubMed Central

    Chung, Po-Ren; Tzeng, Chun-Ta; Ke, Ming-Tsun; Lee, Chia-Yen

    2013-01-01

    Many methods based on spectrophotometric, fluorometric, piezoresistive, amperometric or conductive measurements have been proposed for detecting the concentration of formaldehyde in air. However, conventional formaldehyde measurement systems are bulky and expensive and require the services of highly-trained operators. Accordingly, the emergence of sophisticated technologies in recent years has prompted the development of many microscale gaseous formaldehyde detection systems. Besides their compact size, such devices have many other advantages over their macroscale counterparts, including a real-time response, a more straightforward operation, lower power consumption, and the potential for low-cost batch production. This paper commences by providing a high level overview of the formaldehyde gas sensing field and then describes some of the more significant real-time sensors presented in the literature over the past 10 years or so. PMID:23549368

  15. Temperature modulation of a catalytic gas sensor.

    PubMed

    Brauns, Eike; Morsbach, Eva; Kunz, Sebastian; Baeumer, Marcus; Lang, Walter

    2014-01-01

    The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms) was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal. PMID:25356643

  16. Temperature Modulation of a Catalytic Gas Sensor

    PubMed Central

    Brauns, Eike; Morsbach, Eva; Kunz, Sebastian; Baeumer, Marcus; Lang, Walter

    2014-01-01

    The use of catalytic gas sensors usually offers low selectivity, only based on their different sensitivities for various gases due to their different heats of reaction. Furthermore, the identification of the gas present is not possible, which leads to possible misinterpretation of the sensor signals. The use of micro-machined catalytic gas sensors offers great advantages regarding the response time, which allows advanced analysis of the sensor response. By using temperature modulation, additional information about the gas characteristics can be measured and drift effects caused by material shifting or environmental temperature changes can be avoided. In this work a miniaturized catalytic gas sensor which offers a very short response time (<150 ms) was developed. Operation with modulated temperature allows analysis of the signal spectrum with advanced information content, based on the Arrhenius approach. Therefore, a high-precise electronic device was developed, since theory shows that harmonics induced by the electronics must be avoided to generate a comprehensible signal. PMID:25356643

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

    PubMed Central

    Liewhiran, Chaikarn; Phanichphant, Sukon

    2007-01-01

    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).

  18. A miniature interferometry sensor for monitoring the changes of film thickness and refractive index

    E-print Network

    Wu, Chi

    . The swelling of thin gelatin gel film has been used to demonstrate the use of this novel sensor. The sensor gelatin FIG. 4. Film thickness change (As) vs time (t) in a thin gelatin film film swelling process

  19. Development of Sic Gas Sensor Systems

    NASA Technical Reports Server (NTRS)

    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

    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.

  20. Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  1. Gas Sensors Based on Semiconducting Nanowire Field-Effect Transistors

    PubMed Central

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

    2014-01-01

    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

  2. High Sensitive Formaldehyde Gas Sensor Prepared by R.F. Induction Plasma Deposition Method

    NASA Astrophysics Data System (ADS)

    Shi, Liqin; Gao, Wei; Hasegawa, Yuki; Katsube, Teruaki; Nakano, Mamoru; Nakamura, Kiyozumi

    The present work is concerned on developing high sensitive and high performance SnO2-based gas sensors for detecting indoor air pollutant formaldehyde gas. The film was deposited on an alumina substrate using R.F. Induction Plasma Deposition technique. Physical properties of sensing films were examined by SEM, XRD method. The sensors showed high sensitivity to typical HCHO gas at an extremely low gas concentration of 20 parts-per-billion (ppb) with quick response and recovery time at several minutes. The effect of the doping of various metallic additives on the gas-sensing properties and operating temperature dependency were also investigated in the work.

  3. SiC-Based Gas Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak; Liu, C. C.; Wu, Q. H.

    1997-01-01

    Electronic grade Silicon Carbide (SiC) is a ceramic material which can operate as a semiconductor at temperatures above 600 C. Recently, SiC semiconductors have been used in Schottky diode gas sensor structures. These sensors have been shown to be functional at temperatures significantly above the normal operating range of Si-based devices. SiC sensor operation at these higher temperatures allows detection of gases such as hydrocarbons which are not detectable at lower temperatures. This paper discusses the development of SiC-based Schottky diode gas sensors for the detection of hydrogen, hydrocarbons, and nitrogen oxides (NO(x)). Sensor designs for these applications are discussed. High sensitivity is observed for the hydrogen and hydrocarbon sensors using Pd on SiC Schottky diodes while the NO(x) sensors are still under development. A prototype sensor package has been fabricated which allows high temperature operation in a room temperature ambient by minimizing heat loss to that ambient. It is concluded that SiC-based gas sensors have considerable potential in a variety of gas sensing applications.

  4. Porous Silicon Structures as Optical Gas Sensors

    PubMed Central

    Levitsky, Igor A.

    2015-01-01

    We present a short review of recent progress in the field of optical gas sensors based on porous silicon (PSi) and PSi composites, which are separate from PSi optochemical and biological sensors for a liquid medium. Different periodical and nonperiodical PSi photonic structures (bares, modified by functional groups or infiltrated with sensory polymers) are described for gas sensing with an emphasis on the device specificity, sensitivity and stability to the environment. Special attention is paid to multiparametric sensing and sensor array platforms as effective trends for the improvement of analyte classification and quantification. Mechanisms of gas physical and chemical sorption inside PSi mesopores and pores of PSi functional composites are discussed. PMID:26287199

  5. Integrated Micro-Machined Hydrogen Gas Sensor. Final Report

    SciTech Connect

    Frank DiMeo, Jr.

    2000-10-02

    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.

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

    NASA Astrophysics Data System (ADS)

    Bansal, Lalitkumar; El-Sherif, Mahmoud

    2004-09-01

    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.

  7. Resistive oxygen gas sensors for harsh environments.

    PubMed

    Moos, Ralf; Izu, Noriya; Rettig, Frank; Reiss, Sebastian; Shin, Woosuck; Matsubara, Ichiro

    2011-01-01

    Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations. PMID:22163805

  8. Resistive Oxygen Gas Sensors for Harsh Environments

    PubMed Central

    Moos, Ralf; Izu, Noriya; Rettig, Frank; Reiß, Sebastian; Shin, Woosuck; Matsubara, Ichiro

    2011-01-01

    Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations. PMID:22163805

  9. Mechanical Drawing of Gas Sensors on Paper

    E-print Network

    Esser, Birgit

    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 ...

  10. Integrated Microfluidic Gas Sensors for Water Monitoring

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  11. Hydrogen gas sensor and method of manufacture

    DOEpatents

    McKee, John M. (Hinsdale, IL)

    1991-01-01

    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.

  12. Self-assembled thin film chemical sensors

    SciTech Connect

    Swanson, B.; Li, DeQuan

    1996-11-01

    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.

  13. Sensor array for toxic gas detection

    DOEpatents

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

    1987-01-01

    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.

  14. Spin coated unsubstituted copper phthalocyanine thin films for nitrogen dioxide sensors

    NASA Astrophysics Data System (ADS)

    Chakane, Sanjay; Datir, Ashok; Koinkar, Pankaj

    2015-03-01

    Copper phthalocyanine (CuPc) is synthesized chemically and used for making CuPc thin films using spin coating technique. Films were prepared from trifluroacetic acid (TFA) and chlorobenzene mixed solution on the glass substrate. Spin coated films of unsubstituted CuPc films were heat annealed at 150°C for 2 h duration and were used to study NO2 gas sensing characteristics. ?-phase of CuPc is noted by UV-visible absorption spectra. IR spectra of undoped CuPc films and doped CuPc films with NO2 revealed that, doping of nitrogen dioxide modifies and deletes some of the bands. The effect of NO2 at various concentrations from 50 ppm to 500 ppm in atmospheric air at room temperature on the electrical conductivity of CuPc films was studied. Sensitivity, response time and repeatability of the CuPc sensor were discussed in this paper.

  15. Acoustic composition sensor for cryogenic gas mixtures

    NASA Technical Reports Server (NTRS)

    Shakkottai, P.; Kwack, E. Y.; Luchik, T. S.; Back, L. H.

    1991-01-01

    An acoustic sensor useful for the determination of the composition of a gaseous binary mixture in cryogenic liquid spills has been characterized. One version of the instrument traps a known mixture of helium and nitrogen at ambient temperature in a tube which is interrogated by sonic pulses to determine the speed of sound and hence the composition. Experimental data shows that this sensor is quite accurate. The second version uses two unconfined microphones which sense sound pulses. Experimental data acquired during mixing when liquid nitrogen is poured into a vessel of gaseous helium is presented. Data during transient cooling of the tubular sensor containing nitrogen when the sensor is dipped into liquid nitrogen and during transient warm-up when the sensor is withdrawn are also presented. This sensor is being developed for use in the mixing of liquid cryogens with gas evolution in the simulation of liquid hydrogen/liquid oxygen explosion hazards.

  16. Platinum thin film resistors as accurate and stable temperature sensors

    NASA Technical Reports Server (NTRS)

    Diehl, W.

    1984-01-01

    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.

  17. CSA doped polypyrrole-zinc oxide thin film sensor

    NASA Astrophysics Data System (ADS)

    Chougule, M. A.; Jundale, D. M.; Raut, B. T.; Sen, Shashwati; Patil, V. B.

    2013-02-01

    The polypyrrole-zinc oxide (PPy-ZnO) hybrid sensor doped with different weight ratios of camphor sulphonic acid (CSA) were prepared by spin coating technique. These CSA doped PPy-ZnO hybrids were characterized by field emission scanning electron microscope (FESEM) and fourier transform infrared (FTIR) which proved the formation of polypyrrole, PPy-ZnO and the interaction between polypyrrole - ZnO (PPy-ZnO) hybrid with CSA doping. The gas sensing properties of the PPy-ZnO hybrid films doped with CSA have been studied for oxidizing (NO2) as well as reducing (H2S, NH3, CH4OH and CH3OH) gases at room temperature. We demonstrate that CSA doped PPy-ZnO hybrid films are highly selective to NO2 along with high-sensitivity at low concentration (80% to 100 ppm) and better stability, which suggested that the CSA doped PPy-ZnO hybrid films are potential candidate for NO2 detection at room temperature.

  18. Biomaterial based sulphur di oxide gas sensor

    NASA Astrophysics Data System (ADS)

    Ghosh, P. K.; Sarkar, A.

    2013-06-01

    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.

  19. Graphene Based Flexible Gas Sensors

    NASA Astrophysics Data System (ADS)

    Yi, Congwen

    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.

  20. Miniaturized gas ionization sensors using carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Modi, Ashish; Koratkar, Nikhil; Lass, Eric; Wei, Bingqing; Ajayan, Pulickel M.

    2003-07-01

    Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.

  1. Tunable fiber ring laser absorption spectroscopic sensors for gas detection

    NASA Astrophysics Data System (ADS)

    Zheng, Shijie; Zhu, Yinian; Krishnaswamy, Sridhar

    2013-04-01

    Fiber-optic gas sensing techniques are commonly based on the recognition of a wide range of chemical species from characteristic absorption, fluorescence or Raman-scattering spectra signatures. By tuning over the vibrational lines of species in the path of laser beam, tunable diode laser gas sensors measure signal spectroscopic intensity, gas concentration, and other properties. However, they have limitations of bulk architecture, small change of signal on top of large background, and low sensitivity of direct absorption. Here we report the fabrication and optical measurements of tunable Er-doped fiber ring laser absorption spectroscopic sensor featuring a gas cell that is a segment of photonic crystal fiber (PCF) with a long-period grating (LPG) inscribed. The tunable laser beam is coupled into the cladding of the PCF by the LPG where the gas in air holes absorbs light. The light travels along the PCF cladding and reflects at the end of the fiber where a silver film is coated as a mirror at one end facet. The light propagates back within cladding and passes through the gas one more time thus increasing the interaction length. This light is finally recoupled into the fiber core for intensity measurement. The proposed fiber gas sensors have been experimentally used for ammonia (NH3) concentration detection. They show excellent sensitivity and selectivity, and are minimally affected by temperature and/or humidity changes. The sensors using PCF-LPG gas cell are simple to fabricate, cost-effective, and are deployed for a variety of applications not possible using conventional optical fibers.

  2. Ultra-Low-Power MEMS Selective Gas Sensors

    NASA Technical Reports Server (NTRS)

    Stetter, Joseph

    2012-01-01

    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.

  3. A magnonic gas sensor based on magnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Matatagui, D.; Kolokoltsev, O. V.; Qureshi, N.; Mejía-Uriarte, E. V.; Saniger, J. M.

    2015-05-01

    In this paper, we propose an innovative, simple and inexpensive gas sensor based on the variation in the magnetic properties of nanoparticles due to their interaction with gases. To measure the nanoparticle response a magnetostatic spin wave (MSW) tunable oscillator has been developed using an yttrium iron garnet (YIG) epitaxial thin film as a delay line (DL). The sensor has been prepared by coating a uniform layer of CuFe2O4 nanoparticles on the YIG film. The unperturbed frequency of the oscillator is determined by a bias magnetic field, which is applied parallel to the YIG film and perpendicularly to the wave propagation direction. In this device, the total bias magnetic field is the superposition of the field of a permanent magnet and the field associated with the layer of magnetic nanoparticles. The perturbation produced in the magnetic properties of the nanoparticle layer due to its interaction with gases induces a frequency shift in the oscillator, allowing the detection of low concentrations of gases. In order to demonstrate the ability of the sensor to detect gases, it has been tested with organic volatile compounds (VOCs) which have harmful effects on human health, such as dimethylformamide, isopropanol and ethanol, or the aromatic hydrocarbons like benzene, toluene and xylene more commonly known by its abbreviation (BTX). All of these were detected with high sensitivity, short response time, and good reproducibility.

  4. Engineered nanostructured thin films for enhanced surface acoustic wave sensors

    NASA Astrophysics Data System (ADS)

    Kwan, Jonathan Kwok Wah

    Sensor technologies profoundly impact all aspects of our everyday lives. Advances have led to smaller devices, faster response times, reduced costs, higher specificity and sensitivity, and even new sensing technologies. Surface acoustic wave (SAW) technology, which has been around for many decades already, is an example of a newer sensing technology that has begun to be studied for sensing applications. Many advantages of SAW sensors have been identified, in particular the high sensitivity, low cost and wireless capability. However, as the technology is still in its infancy for sensing applications, many improvements and refinements on the platform have yet to be explored. With the arrival of nanotechnology, many existing technologies have benefited from integrating with the new findings that nanotechnology has brought forth. This thesis investigates the enhancement of existing SAW sensors using nanostructured films fabricated by a thin film deposition process known as glancing angle deposition (GLAD). The GLAD technique is a highly flexible and precise thin film fabrication method that is able to create high-surface-area thin films. This high-surface-area characteristic of these films is the driving motivation in their utilization to enhance the performance of SAW sensors. This thesis first demonstrates that dense, extremely high surface area films can be deposited on SAW sensors without adversely affecting device performance. These modified sensors were then studied as humidity sensors to demonstrate improved sensitivity with the addition of the GLAD films. Before the sensors with GLAD films could be tested in a liquid environment, ion-milling was investigated as a method of eliminating the clustering of the individual structures typically seen after exposure to liquids. These modified films were extended for use on the SAW sensors to investigate liquid sensing performance. The performance of SAW devices with clustered films was also studied for comparison. Both types of films were shown to increase sensitivity greatly over the reference SAW device. The success of these results validates the ability of GLAD films to enhance the sensitivity of not only SAW devices, but potentially other sensing technologies as well.

  5. Surface acoustic wave ammonia sensor based on ZnO/SiO2 composite film.

    PubMed

    Wang, Shuang-Yue; Ma, Jin-Yi; Li, Zhi-Jie; Su, H Q; Alkurd, N R; Zhou, Wei-Lie; Wang, Lu; Du, Bo; Tang, Yong-Liang; Ao, Dong-Yi; Zhang, Shou-Chao; Yu, Q K; Zu, Xiao-Tao

    2015-03-21

    A surface acoustic wave (SAW) resonator with ZnO/SiO2 (ZS) composite film was used as an ammonia sensor in this study. ZS composite films were deposited on the surface of SAW devices using the sol-gel method, and were characterized using SEM, AFM, and XRD. The performance of the sensors under ammonia gas was optimized by adjusting the molar ratio of ZnO:SiO2 to 1:1, 1:2 and 1:3, and the sensor with the ratio of ZnO to SiO2 equaling to 1:2 was found to have the best performance. The response of sensor was 1.132 kHz under 10 ppm NH3, which was much higher than that of the sensor based on a pristine ZnO film. Moreover, the sensor has good selectivity, reversibility and stability at room temperature. These can be attributed to the enhanced absorption of ammonia and unique surface reaction on composite films due to the existence of silica. PMID:25528236

  6. A Novel "Green" Fully-integrated Ultrasensitive RFID-enabled Gas Sensor Utilizing Inkjet-printed Antennas and Carbon Nanotubes

    E-print Network

    Tentzeris, Manos

    A Novel "Green" Fully-integrated Ultrasensitive RFID-enabled Gas Sensor Utilizing Inkjet RFID tag with an inkjet-printed Single Walled Carbon Nanotube (SWCNT) film in a chipless sensor node oxide. The RFID tag is designed for the 868 MHz UHF band. When NOx gas is present, the resistance

  7. Method of Forming Micro-Sensor Thin-Film Anemometer

    NASA Technical Reports Server (NTRS)

    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

    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.

  8. Mechanical Drawing of Gas Sensors on Paper

    PubMed Central

    Mirica, Katherine A.; Weis, Jonathan G.; Schnorr, Jan M.; Esser, Birgit

    2012-01-01

    This communication describes a simple solvent-free method for fabricating chemoresistive gas sensors on the surface of paper. The method involves mechanical abrasion of compressed powders of sensing materials on the fibers of cellulose. We illustrate this approach by depositing conductive layers of several forms of carbon (e.g., single-walled carbon nanotubes [SWCNTs], multi-walled carbon nanotubes, and graphite) on the surface of different papers (Figure 1, Figure S1). The resulting sensors based on SWCNTs are capable of detecting NH3 gas at concentrations as low as 0.5 part-per-million. PMID:23037938

  9. Ink-jet printed colorimetric gas sensors on plastic foil

    NASA Astrophysics Data System (ADS)

    Courbat, Jerome; Briand, Danick; de Rooij, Nico F.

    2010-08-01

    An all polymeric colorimetric gas sensor with its associated electronics for ammonia (NH3) detection targeting low-cost and low-power applications is presented. The gas sensitive layer was inkjet printed on a plastic foil. The use of the foil directly as optical waveguide simplified the fabrication, made the device more cost effective and compatible with large scale fabrication techniques, such as roll to roll processes. Concentrations of 500 ppb of NH3 in nitrogen with 50% of RH were measured with a power consumption of about 868 ?W in an optical pulsed mode of operation. Such sensors foresee applications in the field of wireless systems, for environmental and safety monitoring. The fabrication of the planar sensor was based on low temperature processing. The waveguide was made of PEN or PET foil and covered with an ammonia sensitive layer deposited by inkjet printing, which offered a proper and localized deposition of the film. The influence of the substrate temperature and its surface pretreatment were investigated to achieve the optimum deposition parameters for the printed fluid. To improve the light coupling from the light source (LED) to the detectors (photodiodes), polymeric micro-mirrors were patterned in an epoxy resin. With the printing of the colorimetric film and additive patterning of polymeric micro-mirrors on plastic foil, a major step was achieved towards the implementation of full plastic selective gas sensors. The combination with printed OLED and PPD would further lead to an integrated all polymeric optical transducer on plastic foil fully compatible with printed electronics processes.

  10. Selective, pulsed CVD of platinum on microfilament gas sensors

    SciTech Connect

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

    1996-05-01

    A post-processing, selective micro-chemical vapor deposition (``micro-CVD``) technology for the deposition of catalytic films on surface-micromachined, nitride-passivated polysilicon filaments has been investigated. Atmospheric pressure deposition of Pt on microfilaments was accomplished by thermal decomposition of Pt acetylacetonate; deposition occurs selectively only on those filaments which are electrically heated. Catalyst morphology, characterized by SEM, can be controlled by altering deposition time, filament temperature, and through the use of pulsed heating of the filament during deposition. Morphology plays an important role in determining the sensitivity of these devices when used as combustible gas sensors.

  11. Development of High Temperature Gas Sensor Technology

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

    1997-01-01

    The measurement of engine emissions is important for their monitoring and control. However, the ability to measure these emissions in-situ is limited. We are developing a family of high temperature gas sensors which are intended to operate in harsh environments such as those in an engine. The development of these sensors is based on progress in two types of technology: (1) The development of SiC-based semiconductor technology; and (2) Improvements in micromachining and microfabrication technology. These technologies are being used to develop point-contact sensors to measure gases which are important in emission control especially hydrogen, hydrocarbons, nitrogen oxides, and oxygen. The purpose of this paper is to discuss the development of this point-contact sensor technology. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. Of particular importance is sensor sensitivity, selectivity, and stability in long-term, high temperature operation. An overview is presented of each sensor type with an evaluation of its stage of development. It is concluded that this technology has significant potential for use in engine applications but further development is necessary.

  12. Test Structures for Rapid Prototyping of Gas and Pressure Sensors

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  13. Optical Sensor Of High Gas Temperatures

    NASA Technical Reports Server (NTRS)

    Hill, Arthur J.

    1988-01-01

    Contact pyrometer resists effects of heat, vibration, and moisture. New sensor consists of shielded sapphire rod with sputtered layer of precious metal on end. Metal layer acts as blackbody. Emits radiation having known dependence of spectral distribution with temperature of metal and temperature of hot gas flowing over metal. Fiber-optic cable carries radiation from sapphire rod to remote photodetector.

  14. Black Phosphorus Gas Sensors Ahmad N. Abbas ,

    E-print Network

    Zhou, Chongwu

    1 Black Phosphorus Gas Sensors Ahmad N. Abbas ,¶ , Bilu Liu , Liang Chen , Yuqiang Ma , Sen Cong comprised of a bottom monolayer CVD graphene electrode/BP/top (Ti/Au) electrode with a P++ Si/ 300 nm SiO2 back gated structure. Dashed line is a guide to the eye of the monolayer CVD graphene border. b, d) Id

  15. Construction of a Polyaniline Nanofiber Gas Sensor

    ERIC Educational Resources Information Center

    Virji, Shabnam; Weiller, Bruce H.; Huang, Jiaxing; Blair, Richard; Shepherd, Heather; Faltens, Tanya; Haussmann, Philip C.; Kaner, Richard B.; Tolbert, Sarah H.

    2008-01-01

    The electrical properties of polyaniline changes by orders of magnitude upon exposure to analytes such as acids or bases, making it a useful material for detection of these analytes in the gas phase. The objectives of this lab are to synthesize different diameter polyaniline nanofibers and compare them as sensor materials. In this experiment…

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

    NASA Astrophysics Data System (ADS)

    Andio, Mark A.

    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.

  17. A Micro-Fabricated Force Sensor Using an All Thin Film Piezoelectric Active Sensor

    PubMed Central

    Lee, Junwoo; Choi, Wook; Yoo, Yong Kyoung; Hwang, Kyo Seon; Lee, Sang-Myung; Kang, Sungchul; Kim, Jinseok; Lee, Jeong Hoon

    2014-01-01

    The ability to measure pressure and force is essential in biomedical applications such as minimally invasive surgery (MIS) and palpation for detecting cancer cysts. Here, we report a force sensor for measuring a shear and normal force by combining an arrayed piezoelectric sensors layer with a precut glass top plate connected by four stress concentrating legs. We designed and fabricated a thin film piezoelectric force sensor and proposed an enhanced sensing tool to be used for analyzing gentle touches without the external voltage source used in FET sensors. Both the linear sensor response from 3 kPa to 30 kPa and the exact signal responses from the moving direction illustrate the strong feasibility of the described thin film miniaturized piezoelectric force sensor. PMID:25429407

  18. Thin Film Ceramic Strain Sensor Development for High Temperature Environments

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  19. Metal oxide semi-conductor gas sensors in environmental monitoring.

    PubMed

    Fine, George F; Cavanagh, Leon M; Afonja, Ayo; Binions, Russell

    2010-01-01

    Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases--CO, NO(x), NH(3) and the particularly challenging case of CO(2). Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

  20. Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

    PubMed Central

    Fine, George F.; Cavanagh, Leon M.; Afonja, Ayo; Binions, Russell

    2010-01-01

    Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition. PMID:22219672

  1. Model of Transient Response of Semiconductor Gas Sensors

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Kuwahara, Takashi

    The model of transient response of semiconductor gas sensor under modulation heating has been constructed successfully. The model consists of the heat conduction process from heater to the sensor surface, the reaction process on the sensor surface and diffusion process near the sensor surface to supply the inflammable gas. The calculated sensor response agreed well with experimental result under step power supplying to the heater. We can predict the sensor transient response so that the model will be useful to distinguish gases and smells by using transient response of semiconductor gas sensors.

  2. Temperature dependence of gas sensing behaviour of TiO{sub 2} doped PANI composite thin films

    SciTech Connect

    Srivastava, Subodh Sharma, Preetam; Singh, M.; Vijay, Y. K.; Sharma, S. S.; Sharma, Vinay; Rajura, Rajveer Singh

    2014-04-24

    In the present work we have reported the effect of temperature on the gas sensing properties of TiO{sub 2} doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO{sub 2} doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO{sub 2} doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

  3. Properties of a lithium solid electrolyte gas sensor based on reaction kinetics

    NASA Astrophysics Data System (ADS)

    Jasinski, Grzegorz; Jasinski, Piotr; Nowakowski, Antoni; Chachulski, Bogdan

    2006-01-01

    Principle of operation, construction and properties of a gas sensor based on lithium ion-conductor solid electrolyte (Lisicon) are presented. The sensor has been prepared using thick film technology. Its working principle is based on electric current acquisition, while a voltage ramp is applied to the sensor. The current-voltage plot has a unique shape, which depends on the surrounding gas type and its concentration. Results of measurements conducted in mixtures of high purity gases—nitrogen dioxide, sulfur dioxide, carbon dioxide and synthetic air of controlled concentration—over a wide range of temperatures are presented and discussed.

  4. Spectroelectrochemical sensors: new polymer films for improved sensitivity

    NASA Astrophysics Data System (ADS)

    Morris, Laura K.; Seliskar, Carl J.; Bryan, Samuel A.; Heineman, William R.

    2014-10-01

    The selectivity of an optical sensor can be improved by combining optical detection with electrochemical oxidation or reduction of the target analyte to change its spectral properties. The changing signal can distinguish the analyte from interferences with similar spectral properties that would otherwise interfere. The analyte is detected by measuring the intensity of the electrochemically modulated signal. In one form this spectroelectrochemical sensor consists of an optically transparent electrode (OTE) coated with a film that preconcentrates the target analyte. The OTE functions as an optical waveguide for attenuated total reflectance (ATR) spectroscopy, which detects the analyte by absorption. Sensitivity relies in part on a large change in molar absorptivity between the two oxidation states used for electrochemical modulation of the optical signal. A critical part of the sensor is the ion selective film. It should preconcentrate the analyte and exclude some interferences. At the same time the film must not interfere with the electrochemistry or the optical detection. Therefore, since the debut of the sensor's concept one major focus of our group has been developing appropriate films for different analytes. Here we report the development of a series of quaternized poly(vinylpyridine)-co-styrene (QPVP-co-S) anion exchange films for use in spectroelectrochemical sensors to enable sensitive detection of target anionic analytes in complex samples. The films were either 10% or 20% styrene and were prepared with varying degrees of quaternized pyridine groups, up to 70%. Films were characterized with respect to thickness with spectroscopic ellipsometry, degree of quaternization with FTIR, and electrochemically and spectroelectrochemically using the anions ferrocyanide and pertechnetate.

  5. Enhanced electrodes for solid state gas sensors

    DOEpatents

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

    2001-01-01

    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.

  6. Magnetoelastic sensor for characterizing properties of thin-film/coatings

    NASA Technical Reports Server (NTRS)

    Bachas, Leonidas G. (Inventor); Barrett, Gary (Inventor); Grimes, Craig A. (Inventor); Kouzoudis, Dimitris (Inventor); Schmidt, Stefan (Inventor)

    2004-01-01

    An apparatus for determining elasticity characteristics of a thin-film layer. The apparatus comprises a sensor element having a base magnetostrictive element at least one surface of which is at least partially coated with the thin-film layer. The thin-film layer may be of a variety of materials (having a synthetic and/or bio-component) in a state or form capable of being deposited, manually or otherwise, on the base element surface, such as by way of eye-dropper, melting, dripping, brushing, sputtering, spraying, etching, evaporation, dip-coating, laminating, etc. Among suitable thin-film layers for the sensor element of the invention are fluent bio-substances, thin-film deposits used in manufacturing processes, polymeric coatings, paint, an adhesive, and so on. A receiver, preferably remotely located, is used to measure a plurality of values for magneto-elastic emission intensity of the sensor element in either characterization: (a) the measure of the plurality of values is used to identify a magneto-elastic resonant frequency value for the sensor element; and (b) the measure of the plurality of successive values is done at a preselected magneto-elastic frequency.

  7. Characterization of the polypyrrole film-piezoelectric sensor combination.

    PubMed

    Vigmond, S J; Kallury, K M; Ghaemmaghami, V; Thompson, M

    1992-04-01

    Polymerization of pyrrole onto the electrode surfaces of thickness-shear-mode acoustic wave sensors at various levels of oxidation has been performed with electrochemical methods. The resulting films of polypyrrole have been characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. Frequency decreases for the polypyrrole-coated sensors exposed to methanol, toluene and ammonia have been evaluated in terms of the various interactions occurring at the polymer surface. PMID:18965400

  8. Photonic crystals enable infrared gas sensors

    NASA Astrophysics Data System (ADS)

    Puscasu, Irina; Johnson, Edward A.; Pralle, Martin U.; McNeal, Mark P.; Daly, James T.; Greenwald, Anton C.

    2004-10-01

    Sensors of trace gases are of enormous importance to diverse fields such as environmental protection, household safety, homeland security, bio-hazardous material identification, meteorology and industrial environments. The gases of interest include CO for home environments, CO2 for industrial and environment applications and toxic effluents such as SO2, CH4, NO for various manufacturing environments. We propose a new class of IR gas sensors, where the enabling technology is a spectrally tuned metallo-dielectric photonic crystal. Building both the emitting and sensing capabilities on to a single discrete element, Ion Optics" infrared sensorchip brings together a new sensor paradigm to vital commercial applications. Our design exploits Si-based suspended micro-bridge structures fabricated using conventional photolithographic processes. Spectral tuning, control of bandwidth and direction of emission were accomplished by specially designed metallo-dielectric photonic crystal surfaces.

  9. A pressurized gas squeeze film journal damper

    NASA Technical Reports Server (NTRS)

    Stiffler, A. K.

    1977-01-01

    A lumped parameter model is developed to determine the stiffness and damping characteristics of inherently compensated gas film bearings. The model relies on the average static pressure over a one dimensional strip bearing. Results of the model are compared with known computer solutions for the distributed strip and a two dimensional square bearing. The results for the stiffness agree well with the computer solutions although the model proved to be inadequate for predicting the film damping.

  10. Nanostructure Engineered Chemical Sensors for Hazardous Gas and Vapor Detection

    NASA Technical Reports Server (NTRS)

    Li, Jing; Lu, Yijiang

    2005-01-01

    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.

  11. Method of forming multi-element thin hot film sensors on polyimide film

    NASA Technical Reports Server (NTRS)

    Hopson, Jr., Purnell (Inventor)

    1996-01-01

    The invention comprises a method of forming a multi-element, thin hot film sensor on a polyimide film. The sensor is formed by first cleaning one surface of the polyimide. Then, under a continuous vacuum, the surface is simultaneously cleaned by ion bombardment while nickel is deposited by evaporation. The ion beam cleaning is discontinued and copper is then deposited to an initial thickness by evaporation without a break in the vacuum. The vacuum is then removed and a final thickness of copper is deposited by plating. Sensor patterns are then defined in the nickel and copper layers using conventional photolithography and etching techniques.

  12. Gas Sensors Based on Ceramic p-n Heterocontacts

    SciTech Connect

    Seymen Murat Aygun

    2004-12-19

    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.

  13. Flexible Carbon Nanotube Films for High Performance Strain Sensors

    PubMed Central

    Kanoun, Olfa; Müller, Christian; Benchirouf, Abderahmane; Sanli, Abdulkadir; Dinh, Trong Nghia; Al-Hamry, Ammar; Bu, Lei; Gerlach, Carina; Bouhamed, Ayda

    2014-01-01

    Compared with traditional conductive fillers, carbon nanotubes (CNTs) have unique advantages, i.e., excellent mechanical properties, high electrical conductivity and thermal stability. Nanocomposites as piezoresistive films provide an interesting approach for the realization of large area strain sensors with high sensitivity and low manufacturing costs. A polymer-based nanocomposite with carbon nanomaterials as conductive filler can be deposited on a flexible substrate of choice and this leads to mechanically flexible layers. Such sensors allow the strain measurement for both integral measurement on a certain surface and local measurement at a certain position depending on the sensor geometry. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors, e.g., sensitivity, adjustable measurement range and integral measurement on big surfaces. The novel technology allows realizing strain sensors which can be easily integrated even as buried layers in material systems. In this review paper, we discuss the dependence of strain sensitivity on different experimental parameters such as composition of the carbon nanomaterial/polymer layer, type of polymer, fabrication process and processing parameters. The insights about the relationship between film parameters and electromechanical properties can be used to improve the design and fabrication of CNT strain sensors. PMID:24915183

  14. Parametric Study of Gas Turbine Film-Cooling 

    E-print Network

    Liu, Kevin

    2012-10-19

    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. The study consisted of three parts: 1) turbine blade span film...

  15. Temperature and Humidity Dependence of a Polymer-Based Gas Sensor

    NASA Technical Reports Server (NTRS)

    Ryan, M. A.; Buehler, M. G.

    1997-01-01

    This paper quantifies the temperature and humidity dependence of a polymer-based gas sensor. The measurement and analysis of three polymers indicates that resistance changes in the polymer films, due to temperature and humidity, can be positive or negative. The temperature sensitivity ranged from +1600 to -320 ppm/nd the relative sensitivity ranged from +1100 to -260 ppm/%.

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

    E-print Network

    Kummel, Andrew C.

    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

  17. Fiber-Optic Sensor Would Monitor Growth of Polymer Film

    NASA Technical Reports Server (NTRS)

    Beamesderfer, Michael

    2005-01-01

    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.

  18. Flush mounting of thin film sensors

    NASA Technical Reports Server (NTRS)

    Moore, Thomas C., Sr. (inventor)

    1992-01-01

    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.

  19. Thin film devices used as oxygen partial pressure sensors

    NASA Technical Reports Server (NTRS)

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

    1970-01-01

    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.

  20. Waveguide Zeeman interferometry for thin-film chemical sensors

    SciTech Connect

    Grace, K.M.; Shrouf, K.; Johnston, R.G.; Yang, X.; Swanson, B.; Honkanen, S.; Ayras, P.; Peyghambarian, N.; Katila, P.; Leppihalme, M.

    1997-10-01

    A chemical sensor is demonstrated which is based on Si{sub 3}N{sub 4} optical waveguides coated with species-selective thin films and using Zeeman interferometry as the detection technique. Relative phase change between TE and TM modes is measured. Real time and reversible response to toluene is shown with ppm level sensitivity.

  1. Fast Solid State Gas Sensor Characterization Ruby N. Ghosh1

    E-print Network

    Ghosh, Ruby N.

    Fast Solid State Gas Sensor Characterization Technique Ruby N. Ghosh1 , Peter Tobias1# , Hui Hu2@egr.msu.edu Abstract---- We describe a new technique for character- izing fast solid state planar gas sensors. Using can capture the fast com- ponent of the sensor response as well as the steady state value in a single

  2. Gas Main Sensor and Communications Network System

    SciTech Connect

    Hagen Schempf

    2006-05-31

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the Northeast Gas Association (NGA), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. This projected was completed in April 2006, and culminated in the installation of more than 2 dozen GasNet nodes in both low- and high-pressure cast-iron and steel mains owned by multiple utilities in the northeastern US. Utilities are currently logging data (off-line) and monitoring data in real time from single and multiple networked sensors over cellular networks and collecting data using wireless bluetooth PDA systems. The system was designed to be modular, using in-pipe sensor-wands capable of measuring, flow, pressure, temperature, water-content and vibration. Internal antennae allowed for the use of the pipe-internals as a waveguide for setting up a sensor network to collect data from multiple nodes simultaneously. Sensor nodes were designed to be installed with low- and no-blow techniques and tools. Using a multi-drop bus technique with a custom protocol, all electronics were designed to be buriable and allow for on-board data-collection (SD-card), wireless relaying and cellular network forwarding. Installation options afforded by the design included direct-burial and external polemounted variants. Power was provided by one or more batteries, direct AC-power (Class I Div.2) and solar-array. The utilities are currently in a data-collection phase and intend to use the collected (and processed) data to make capital improvement decisions, compare it to Stoner model predictions and evaluate the use of such a system for future expansion, technology-improvement and commercialization starting later in 2006.

  3. Thin Film Ceramic Strain Sensor Development for Harsh Environments

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Wrbanek, John D.

    2007-01-01

    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.

  4. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    SciTech Connect

    Mene, Ravindra U.; Mahabole, Megha P.; Mohite, K.C.; Khairnar, Rajendra S.

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  5. Transient hot-film sensor response in a shock tube

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

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

    SciTech Connect

    Garzon, F. H.; Mukundan, R.; Brosha, E. L.

    2002-01-01

    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.

  7. Study of quartz crystal microbalance NO2 sensor coated with sputtered indium tin oxide film

    NASA Astrophysics Data System (ADS)

    Georgieva, V.; Aleksandrova, M.; Stefanov, P.; Grechnikov, A.; Gadjanova, V.; Dilova, T.; Angelov, Ts

    2014-12-01

    A study of NO2 gas sorption ability of thin indium tin oxide (ITO) deposited on 16 MHz quartz crystal microbalance (QCM) is presented. ITO films are grown by RF sputtering of indium/tin target with weight proportion 95:5 in oxygen environment. The ITO films have been characterized by X-ray photoelectron spectroscopy measurements. The ITO surface composition in atomic % is defined to be: In-40.6%, Sn-4.3% and O-55%. The thickness and refractive index of the films are determined by ellipsometric method. The frequency shift of QCM-ITO is measured at different NO2 concentrations. The QCM-ITO system becomes sensitive at NO2 concentration >= 500 ppm. The sorbed mass for each concentration is calculated according the Sauerbrey equation. The results indicated that the 1.09 ng of the gas is sorbed into 150 nm thick ITO film at 500 ppm NO2 concentration. When the NO2 concentration increases 10 times the calculated loaded mass is 5.46 ng. The sorption process of the gas molecules is defined as reversible. The velocity of sorbtion /desorption processes are studied, too. The QCM coated with thin ITO films can be successfully used as gas sensors for detecting NO2 in the air at room temperature.

  8. Optical gas sensing of hematin Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Salleh, M. M.; Belal, A. S.; Yahaya, Muhammad

    1998-02-01

    This paper reports the use of hematin Langmuir-Blodgett (LB) films to detect carbon monoxide gas at the room temperature, based on changes in the optical absorption of the films. Hematin LB films were deposited on quartz and glass substrates. For the film deposited on quartz substrate, an increase in the absorption spectra of the film was achieved by exposing the film to carbon monoxide gas. The absorption spectra of the film recover back when the exposing gas was cut off. While for the film deposited on glass substrate, there is no significant change in the spectra due to this gas. Atomic force microscope images were taken for the hematin LB films both on glass and quartz substrates. Both images show different features indicating that the optical respond of the films to the gas depends on the arrangement of molecules on the substrate.

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

    SciTech Connect

    Khalid, Faridzatul Shahira; Awang, Rozidawati

    2014-09-03

    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.

  10. Pulse-driven micro gas sensor fitted with clustered Pd/SnO2 nanoparticles.

    PubMed

    Suematsu, Koichi; Shin, Yuka; Ma, Nan; Oyama, Tokiharu; Sasaki, Miyuki; Yuasa, Masayoshi; Kida, Tetsuya; Shimanoe, Kengo

    2015-08-18

    Real-time monitoring of specific gas concentrations with a compact and portable gas sensing device is required to sense potential health risk and danger from toxic gases. For such purposes, we developed an ultrasmall gas sensor device, where a micro sensing film was deposited on a micro heater integrated with electrodes fabricated by the microelectromechanical system (MEMS) technology. The developed device was operated in a pulse-heating mode to significantly reduce the heater power consumption and make the device battery-driven and portable. Using clustered Pd/SnO2 nanoparticles, we succeeded in introducing mesopores ranging from 10 to 30 nm in the micro gas sensing film (area: ? 150 ?m) to detect large volatile organic compounds (VOCs). The micro sensor showed quick, stable, and high sensor responses to toluene at ppm (parts per million) concentrations at 300 °C even by operating the micro heater in a pulse-heating mode where switch-on and -off cycles were repeated at one-second intervals. The high performance of the micro sensor should result from the creation of efficient diffusion paths decorated with Pd sensitizers by using the clustered Pd/SnO2 nanoparticles. Hence we demonstrate that our pulse-driven micro sensor using nanostructured oxide materials holds promise as a battery-operable, portable gas sensing device. PMID:26196499

  11. Turbine Blade Temperature Measurements Using Thin Film Temperature Sensors

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  12. "Metal-oxide gas sensors have been around for

    E-print Network

    Diebold, Ulrike

    Publishing "Metal-oxide gas sensors have been around for over 40 years, but only now we have: Surface Studies of Gas Sensing Metal Oxides 21 February 2007 1. Could you explain the significance of your article to the non-specialist? Metal oxide-gas sensors are practical devices used in a variety of every

  13. Liquid Crystalline Compositions as Gas Sensors

    NASA Astrophysics Data System (ADS)

    Shibaev, Petr; Murray, John; Tantillo, Anthony; Wenzlick, Madison; Howard-Jennings, Jordan

    2015-03-01

    Droplets and films of nematic and cholesteric liquid crystalline mixtures were studied as promising detectors of volatile organic compounds (VOCs) in the air. Under increasing concentration of VOC in the air the detection may rely on each of the following effects sequentially observed one after the other due to the diffusion of VOC inside liquid crystalline matrix: i. slight changes in orientation and order parameter of liquid crystal, ii. formation of bubbles on the top of the liquid crystalline droplet due to the mass transfer between the areas with different order parameter, iii. complete isotropisation of the liquid crystal. All three stages can be easily monitored by optical microscopy and photo camera. Detection limits corresponding to the first stage are typically lower by a factor of 3-6 than detection limits corresponding to the beginning of mass transfer and isotropisation. The prototype of a compact sensor sensitive to the presence of organic solvents in the air is described in detail. The detection limits of the sensor is significantly lower than VOC exposure standards. The qualitative model is presented to account for the observed changes related to the diffusion, changes of order parameter and isotropisation.

  14. A Thin Film Multifunction Sensor for Harsh Environments

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  15. Detecting insect infestation with poly3-hexylthiophenethin thin film sensor

    NASA Astrophysics Data System (ADS)

    Weerakoon, Kanchana; Li, Suiquing; Shu, Hungjen J.; Chin, Bryan A.

    2009-05-01

    The financial losses and destruction of crops due to insect infestation in the United States are estimated by the USDA to exceed 20 billion dollars annually. Much of these losses could be avoided by having a sensor that could effectively identify the early stages of insect infestation. However, traditional detection methods are time consuming, require trained personnel, and are not sufficient for early detection. Several previous research studies showed that emitting organic volatile compounds is a defensive mechanism activated by some plant species after being attacked by herbivores and parasites. Corn, cotton, pine, Brussels sprouts when attacked by Beet army worm, spider mites, bark beetles and caterpillars respectively, emits different blends of plant volatiles including ?-terpinene, ?-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate, with a concentration of about 50 ppm. Therefore, monitoring for these volatile compounds may enable on-site early detection of insect infestations. In this study, a chemical resistor sensor to detect plant volatiles was designed and fabricated. The sensor platform consists of micro electronically fabricated interdigitated electrodes. On to this platform, a poly3-hexylthiophene (P3HT) thin film was deposited, using a spin coater at 8000 rpm for 30 seconds. The sensor was tested and found to be sensitive to a variety of plant volatiles, including ?-terpinene, ?-pinene, p-cymene, farnesene, limonene and cis-hexenyl acetate at room temperature. These vapors interacted with the P3HT film causing an increase in the resistance of the sensor by more than one order of magnitude

  16. Fabrication of a SnO2-Based Acetone Gas Sensor Enhanced by Molecular Imprinting

    PubMed Central

    Tan, Wenhu; Ruan, Xiaofan; Yu, Qiuxiang; Yu, Zetai; Huang, Xintang

    2015-01-01

    This work presents a new route to design a highly sensitive SnO2–based sensor for acetone gas enhanced by the molecular imprinting technique. Unassisted and acetone-assisted thermal synthesis methods are used to synthesis SnO2 nanomaterials. The prepared SnO2 nanomaterials have been characterized by X-ray powder diffraction, scanning electron microscopy and N2 adsorption?desorption. Four types of SnO2 films were obtained by mixing pure deionized water and liquid acetone with the two types of as-prepared powders, respectively. The acetone gas sensing properties of sensors coated by these films were evaluated. Testing results reveal that the sensor coated by the film fabricated by mixing liquid acetone with the SnO2 nanomaterial synthesized by the acetone-assisted thermal method exhibits the best acetone gas sensing performance. The sensor is optimized for the smooth adsorption and desorption of acetone gas thanks to the participation of acetone both in the procedure of synthesis of the SnO2 nanomaterial and the device fabrication, which results in a distinct response–recovery behavior. PMID:25549174

  17. In2O3 Nanoparticles for Gas Sensors

    NASA Astrophysics Data System (ADS)

    Zhang, Zengxing; Caruntu, Daniela; O'Connor, Charles J.; Zhou, Weilie

    2008-03-01

    In the last decades, sensors based on nanostructured materials have attracted much attention. Generally, nanosensors often demonstrate excellent sensitivities because of their high specific surface area and comparable size to the detected targets (chemicals or biomolecules). So far, lots of efforts have been put on the fabrication of nanowires based nanosensors. In this talk, we reported our recent work on employing wet-chemically synthesized indium oxide (In2O3) nanoparticles for gas sensing. The nanoparticles were self-assembled between the gold electrodes patterned on silicon substrates covered with thermal oxide film using e-beam nanolithography. Several gases, such as ammonia (NH3), hydrogen sulfide (H2S), etc., were used for the testing. The results exhibit that the sensitivity can be reached down to PPM order. In addition, the sensitivity in terms of nanoparticle size, temperature, etc, were also investigated.

  18. Chemoresistive Gas Sensors for the Detection of Colorectal Cancer Biomarkers

    PubMed Central

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

    2014-01-01

    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

  19. CCD imaging sensor with flashed backside metal film

    NASA Technical Reports Server (NTRS)

    Janesick, James R. (Inventor)

    1991-01-01

    A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

  20. Producing CCD imaging sensor with flashed backside metal film

    NASA Technical Reports Server (NTRS)

    Janesick, James R. (Inventor)

    1988-01-01

    A backside illuminated CCD imaging sensor for reading out image charges from wells of the array of pixels is significantly improved for blue, UV, far UV and low energy x-ray wavelengths (1-5000.ANG.) by so overthinning the backside as to place the depletion edge at the surface and depositing a thin transparent metal film of about 10.ANG. on a native-quality oxide film of less than about 30.ANG. grown on the thinned backside. The metal is selected to have a higher work function than that of the semiconductor to so bend the energy bands (at the interface of the semiconductor material and the oxide film) as to eliminate wells that would otherwise trap minority carriers. A bias voltage may be applied to extend the frontside depletion edge to the interface of the semiconductor material with the oxide film in the event there is not sufficient thinning. This metal film (flash gate), which improves and stabilizes the quantum efficiency of a CCD imaging sensor, will also improve the QE of any p-n junction photodetector.

  1. Properties of thin films for high temperature flow sensors

    NASA Technical Reports Server (NTRS)

    Albin, Sacharia

    1991-01-01

    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.

  2. Carbon-Nanotube-Based Chemical Gas Sensor

    NASA Technical Reports Server (NTRS)

    Kaul, Arunpama B.

    2010-01-01

    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.

  3. 1708 IEEE SENSORS JOURNAL, VOL. 13, NO. 5, MAY 2013 Integration of Thin Film Strain Sensors Into Hard

    E-print Network

    Horowitz, Roberto

    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 ZnO. The associate editor coordinating the review of this paper and approving it for publication was Prof. Kiseon Kim

  4. Nanoporous thin film platform for biophotonic sensors

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    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.

  5. Co-polymer films for sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2010-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  6. Co-polymer Films for Sensors

    NASA Technical Reports Server (NTRS)

    Ryan, Margaret A. (Inventor); Homer, Margie L. (Inventor); Yen, Shiao-Pin S. (Inventor); Kisor, Adam (Inventor); Jewell, April D. (Inventor); Shevade, Abhijit V. (Inventor); Manatt, Kenneth S. (Inventor); Taylor, Charles (Inventor); Blanco, Mario (Inventor); Goddard, William A. (Inventor)

    2012-01-01

    Embodiments include a sensor comprising a co-polymer, the co-polymer comprising a first monomer and a second monomer. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is polystyrene and the second monomer is poly-2-vinyl pyridinium propylamine chloride. For some embodiments, the first monomer is poly-4-vinyl pyridine, and the second monomer is poly-4-vinyl pyridinium benzylamine chloride. Other embodiments are described and claimed.

  7. Gas-film coefficients for streams

    USGS Publications Warehouse

    Rathbun, R.E.; Tai, D.Y.

    1983-01-01

    Equations for predicting the gas-film coefficient for the volatilization of organic solutes from streams are developed. The film coefficient is a function of windspeed and water temperature. The dependence of the coefficient on windspeed is determined from published information on the evaporation of water from a canal. The dependence of the coefficient on temperature is determined from laboratory studies on the evaporation of water. Procedures for adjusting the coefficients for different organic solutes are based on the molecular diffusion coefficient and the molecular weight. The molecular weight procedure is easiest to use because of the availability of molecular weights. However, the theoretical basis of the procedure is questionable. The diffusion coefficient procedure is supported by considerable data. Questions, however, remain regarding the exact dependence of the film coefficint on the diffusion coefficient. It is suggested that the diffusion coefficient procedure with a 0.68-power dependence be used when precise estimate of the gas-film coefficient are needed and that the molecular weight procedure be used when only approximate estimates are needed.

  8. Ballistocardiogaphic studies with acceleration and electromechanical film sensors.

    PubMed

    Alametsä, J; Värri, A; Viik, J; Hyttinen, J; Palomäki, A

    2009-11-01

    The purpose of this research is to demonstrate and compare the utilization of electromechanical film (EMFi) and two acceleration sensors, ADXL202 and MXA2500U, for ballistocardiographic (BCG) and pulse transit time (PTT) studies. We have constructed a mobile physiological measurement station including amplifiers and a data collection system to record the previously mentioned signals and an electrocardiogram signal. Various versions of the measuring systems used in BCG studies in the past are also presented and evaluated. We have showed the ability of the EMFi sensor to define the elastic properties of the cardiovascular system and to ensure the functionality of the proposed instrumentation in different physiological loading conditions, before and after exercise and sauna bath. The EMFi sensor provided a BCG signal of good quality in the study of the human heart and function of the cardiovascular system with different measurement configurations. EMFi BCG measurements provided accurate and repeatable results for the different components of the heart cycle. In multiple-channel EMFi measurements, the carotid and limb pulse signals acquired were detailed and distinctive, allowing accurate PTT measurements. Changes in blood pressure were clearly observed and easily determined with EMFi sensor strips in pulse wave velocity (PWV) measurements. In conclusion, the configuration of the constructed device provided reliable measurements of the electrocardiogram, BCG, heart sound, and carotid and ankle pulse wave signals. Attached EMFi sensor strips on the neck and limbs yield completely new applications of the EMFi sensors aside from the conventional seat and supine recordings. Higher sensitivity, ease of utilization, and minimum discomfort of the EMFi sensor compared with acceleration sensors strengthen the status of the EMFi sensor for accurate and reliable BCG and PWV measurements, providing novel evaluation of the elastic properties of the cardiovascular system. PMID:19713144

  9. Optical sensors and multisensor arrays containing thin film electroluminescent devices

    DOEpatents

    Aylott, Jonathan W. (Ann Arbor, MI); Chen-Esterlit, Zoe (Ann Arbor, MI); Friedl, Jon H. (Ames, IA); Kopelman, Raoul (Ann Arbor, MI); Savvateev, Vadim N. (Ames, IA); Shinar, Joseph (Ames, IA)

    2001-12-18

    Optical sensor, probe and array devices for detecting chemical biological, and physical analytes. The devices include an analyte-sensitive layer optically coupled to a thin film electroluminescent layer which activates the analyte-sensitive layer to provide an optical response. The optical response varies depending upon the presence of an analyte and is detected by a photodetector and analyzed to determine the properties of the analyte.

  10. The simulation for optimal design of metal film on surface plasmon resonance sensor

    NASA Astrophysics Data System (ADS)

    Chen, HuiBin

    2014-11-01

    Based on the principle of surface plasmon resonance (SPR) sensor, the influence of mental film was illuminated. According to the MATLAB simulation, the performance of SPR sensor using Au and Ag film was compared. The optimal thickness was 52nm and 38nm, respectively. In view of the features of Au and Ag film, Ag+Au hybrid metal film was proposed. On the basis of simulated result, it could be concluded that the performance of SPR sensor with 50nm composite film (Ag film 20nm ) was excellent.

  11. Self-powered thin-film motion vector sensor.

    PubMed

    Jing, Qingshen; Xie, Yannan; Zhu, Guang; Han, Ray P S; Wang, Zhong Lin

    2015-01-01

    Harnessing random micromeso-scale ambient energy is not only clean and sustainable, but it also enables self-powered sensors and devices to be realized. Here we report a robust and self-powered kinematic vector sensor fabricated using highly pliable organic films that can be bent to spread over curved and uneven surfaces. The device derives its operational energy from a close-proximity triboelectrification of two surfaces: a polytetrafluoroethylene film coated with a two-column array of copper electrodes that constitutes the mover and a polyimide film with the top and bottom surfaces coated with a two-column aligned array of copper electrodes that comprises the stator. During relative reciprocations, the electrodes in the mover generate electric signals of ±5?V to attain a peak power density of ?65?mW?m(-2) at a speed of 0.3?ms(-1). From our 86,000 sliding motion tests of kinematic measurements, the sensor exhibits excellent stability, repeatability and strong signal durability. PMID:26271603

  12. Self-powered thin-film motion vector sensor

    PubMed Central

    Jing, Qingshen; Xie, Yannan; Zhu, Guang; Han, Ray P. S.; Wang, Zhong Lin

    2015-01-01

    Harnessing random micromeso-scale ambient energy is not only clean and sustainable, but it also enables self-powered sensors and devices to be realized. Here we report a robust and self-powered kinematic vector sensor fabricated using highly pliable organic films that can be bent to spread over curved and uneven surfaces. The device derives its operational energy from a close-proximity triboelectrification of two surfaces: a polytetrafluoroethylene film coated with a two-column array of copper electrodes that constitutes the mover and a polyimide film with the top and bottom surfaces coated with a two-column aligned array of copper electrodes that comprises the stator. During relative reciprocations, the electrodes in the mover generate electric signals of ±5?V to attain a peak power density of ?65?mW?m?2 at a speed of 0.3?ms?1. From our 86,000 sliding motion tests of kinematic measurements, the sensor exhibits excellent stability, repeatability and strong signal durability. PMID:26271603

  13. Self-powered thin-film motion vector sensor

    NASA Astrophysics Data System (ADS)

    Jing, Qingshen; Xie, Yannan; Zhu, Guang; Han, Ray P. S.; Wang, Zhong Lin

    2015-08-01

    Harnessing random micromeso-scale ambient energy is not only clean and sustainable, but it also enables self-powered sensors and devices to be realized. Here we report a robust and self-powered kinematic vector sensor fabricated using highly pliable organic films that can be bent to spread over curved and uneven surfaces. The device derives its operational energy from a close-proximity triboelectrification of two surfaces: a polytetrafluoroethylene film coated with a two-column array of copper electrodes that constitutes the mover and a polyimide film with the top and bottom surfaces coated with a two-column aligned array of copper electrodes that comprises the stator. During relative reciprocations, the electrodes in the mover generate electric signals of +/-5 V to attain a peak power density of >=65 mW m-2 at a speed of 0.3 ms-1. From our 86,000 sliding motion tests of kinematic measurements, the sensor exhibits excellent stability, repeatability and strong signal durability.

  14. Elaboration and characterization of doped barium titanate films for gas sensing

    SciTech Connect

    Romh, M. A. El Fasquelle, D. Mascot, M.; Députier, S.

    2014-11-05

    Barium titanate (BaTiO{sub 3}) thick films were prepared from commercial powder to develop and optimize the film elaboration. Then, BaTiO{sub 3} was doped by strontium and iron to increase the conductivity by a double substitution on site A and B of the perovskite structure in view to develop semiconductor gas sensors. Film inks were prepared by mixing BT and BSTF powder with an organic vehicle, using a ratio of 50:50; 60:40, respectively and deposited on alumina substrates. The BT and BSTF films were sintered at 1100°C for 2h. The structural and physical properties of the films have been studied by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The dielectric measurements showed a huge increase in the a.c. conductivity for the BSTF films, by a factor of 10000 at low frequency, when the temperature ranges from 25°C to 500°C.

  15. Wet Chemical Synthesis and Screening of Thick Porous Oxide Films for Resistive Gas Sensing Applications

    PubMed Central

    Frenzer, Gerald; Frantzen, Andreas; Sanders, Daniel; Simon, Ulrich; Maier, Wilhelm F.

    2006-01-01

    A method of wet chemical synthesis suitable for high throughput and combinatorial applications has been developed for the synthesis of porous resistive thick-film gas sensors. This method is based on the robot-controlled application of unstable metal oxide suspensions on an array of 64 inter-digital electrodes positioned on an Al2O3 substrate. SnO2, WO3, ZrO2, TiO2, CeO2, In2O3 and Bi2O3 were chosen as base oxides, and were optimised by doping or mixed oxide formation. The parallel synthesis of mixed oxide sensors is illustrated by representative examples. The electrical characteristics and the sensor performance of the films were measured by high-throughput impedance spectroscopy while supplying various test gases (H2, CO, NO, NO2, propene). Data collection, data mining techniques applied and the best potential sensor materials discovered are presented.

  16. Isolating Gas Sensor From Pressure And Temperature Effects

    NASA Technical Reports Server (NTRS)

    Sprinkle, Danny R.; Chen, Tony T. D.; Chaturvedi, Sushi K.

    1994-01-01

    Two-stage flow system enables oxygen sensor in system to measure oxygen content of low-pressure, possibly-high-temperature atmosphere in test environment while protecting sensor against possibly high temperature and fluctuations in pressure of atmosphere. Sensor for which flow system designed is zirconium oxide oxygen sensor sampling atmospheres in high-temperature wind tunnels. Also adapted to other gas-analysis instruments that must be isolated from pressure and temperature effects of test environments.

  17. Oxygen sensor for monitoring gas mixtures containing hydrocarbons

    DOEpatents

    Ruka, Roswell J. (Pittsburgh, PA); Basel, Richard A. (Pittsburgh, PA)

    1996-01-01

    A gas sensor measures O.sub.2 content of a reformable monitored gas containing hydrocarbons H.sub.2 O and/or CO.sub.2, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system.

  18. Oxygen sensor for monitoring gas mixtures containing hydrocarbons

    DOEpatents

    Ruka, R.J.; Basel, R.A.

    1996-03-12

    A gas sensor measures O{sub 2} content of a reformable monitored gas containing hydrocarbons, H{sub 2}O and/or CO{sub 2}, preferably in association with an electrochemical power generation system. The gas sensor has a housing communicating with the monitored gas environment and carries the monitored gas through an integral catalytic hydrocarbon reforming chamber containing a reforming catalyst, and over a solid electrolyte electrochemical cell used for sensing purposes. The electrochemical cell includes a solid electrolyte between a sensor electrode that is exposed to the monitored gas, and a reference electrode that is isolated in the housing from the monitored gas and is exposed to a reference gas environment. A heating element is also provided in heat transfer communication with the gas sensor. A circuit that can include controls operable to adjust operations via valves or the like is connected between the sensor electrode and the reference electrode to process the electrical signal developed by the electrochemical cell. The electrical signal varies as a measure of the equilibrium oxygen partial pressure of the monitored gas. Signal noise is effectively reduced by maintaining a constant temperature in the area of the electrochemical cell and providing a monitored gas at chemical equilibria when contacting the electrochemical cell. The output gas from the electrochemical cell of the sensor is fed back into the conduits of the power generating system. 4 figs.

  19. Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.

    2005-01-01

    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.

  20. AZO thin film-based UV sensors: effects of RF power on the films

    NASA Astrophysics Data System (ADS)

    Akin, Nihan; Ceren Baskose, U.; Kinaci, Baris; Cakmak, Mehmet; Ozcelik, Suleyman

    2015-06-01

    Al-doped zinc oxide (AZO) thin films of thickness 150 nm were deposited on polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering method under various RF powers in the range of 25-100 W. Structural, morphological, optical and electrical properties of the films were investigated by X-ray diffractometer, atomic force microscope, UV-Vis spectrometer and Hall effect measurement system. All the obtained films had a highly preferred orientation along [002] direction of the c-axis perpendicular to the flexible PET substrate and had a high-quality surface. The energy band gap ( E g) values of the films varied in the range of 3.30-3.43 eV. The minimum resistivity of 1.84 × 10-4 ? cm was obtained at a 50 W RF power. The small changes in the RF power had a critical important role on the structural, optical and electrical properties of the sputtered AZO thin films on flexible PET substrate. In addition, UV sensing of the fabricated AZO thin film-based sensors was explored by using current-voltage (I-V) characteristics. The sensors were sensitive in the UV region of the electromagnetic spectrum.

  1. Design and Deployment of Low-Cost Plastic Optical Fiber Sensors for Gas Monitoring

    PubMed Central

    Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

    2015-01-01

    This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva. PMID:25558990

  2. Design and deployment of low-cost plastic optical fiber sensors for gas monitoring.

    PubMed

    Grassini, Sabrina; Ishtaiwi, Maen; Parvis, Marco; Vallan, Alberto

    2015-01-01

    This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva. PMID:25558990

  3. The Enhanced Formaldehyde-Sensing Properties of P3HT-ZnO Hybrid Thin Film OTFT Sensor and Further Insight into Its Stability

    PubMed Central

    Tai, Huiling; Li, Xian; Jiang, Yadong; Xie, Guangzhong; Du, Xiaosong

    2015-01-01

    A thin-film transistor (TFT) having an organic–inorganic hybrid thin film combines the advantage of TFT sensors and the enhanced sensing performance of hybrid materials. In this work, poly(3-hexylthiophene) (P3HT)-zinc oxide (ZnO) nanoparticles' hybrid thin film was fabricated by a spraying process as the active layer of TFT for the employment of a room temperature operated formaldehyde (HCHO) gas sensor. The effects of ZnO nanoparticles on morphological and compositional features, electronic and HCHO-sensing properties of P3HT-ZnO thin film were systematically investigated. The results showed that P3HT-ZnO hybrid thin film sensor exhibited considerable improvement of sensing response (more than two times) and reversibility compared to the pristine P3HT film sensor. An accumulation p-n heterojunction mechanism model was developed to understand the mechanism of enhanced sensing properties by incorporation of ZnO nanoparticles. X-ray photoelectron spectroscope (XPS) and atomic force microscopy (AFM) characterizations were used to investigate the stability of the sensor in-depth, which reveals the performance deterioration was due to the changes of element composition and the chemical state of hybrid thin film surface induced by light and oxygen. Our study demonstrated that P3HT-ZnO hybrid thin film TFT sensor is beneficial in the advancement of novel room temperature HCHO sensing technology. PMID:25608214

  4. Experimental investigation of film cooling effectiveness on gas turbine blades 

    E-print Network

    Gao, Zhihong

    2009-05-15

    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...

  5. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section 870.4410...Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the...

  6. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section 870.4410...Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the...

  7. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section 870.4410...Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the...

  8. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section 870.4410...Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the...

  9. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section 870.4410...Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures...

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  11. Gas Sensing Properties of Epitaxial LaBaCo2O5.5+? Thin Films

    PubMed Central

    Liu, M.; Ren, S. P.; Zhang, R. Y.; Xue, Z. Y.; Ma, C. R.; Yin, M. L.; Xu, X.; Bao, S. Y.; Chen, C. L.

    2015-01-01

    Chemical reactivity and stability of highly epitaxial mixed-conductive LaBaCo2O5.5+? (LBCO) thin films on (001) LaAlO3 (LAO) single-crystalline substrates, fabricated by using pulsed laser deposition system, were systematically investigated. Microstructure studies from x-ray diffraction indicate that the films are c-axis oriented with the interface relationship of [100]LBCO//[100]LAO and (001)LBCO//(001)LAO. LBCO thin films can detect the ethanol vapor concentration as low as 10ppm and the response of LBCO thin film to various ethanol vapor concentrations is very reliable and reproducible with the switch between air and ethanol vapor. Moreover, the fast response of the LBCO thin film, as the p-type gas sensor, is better than some n-type oxide semiconductor thin films and comparable with some nanorods and nanowires. These findings indicate that the LBCO thin films have great potential for the development of gas sensors in reducing/oxidizing environments. PMID:26146369

  12. Gas Sensing Properties of Epitaxial LaBaCo2O5.5+? Thin Films.

    PubMed

    Liu, M; Ren, S P; Zhang, R Y; Xue, Z Y; Ma, C R; Yin, M L; Xu, X; Bao, S Y; Chen, C L

    2015-01-01

    Chemical reactivity and stability of highly epitaxial mixed-conductive LaBaCo2O5.5+? (LBCO) thin films on (001) LaAlO3 (LAO) single-crystalline substrates, fabricated by using pulsed laser deposition system, were systematically investigated. Microstructure studies from x-ray diffraction indicate that the films are c-axis oriented with the interface relationship of [100]LBCO//[100]LAO and (001)LBCO//(001)LAO. LBCO thin films can detect the ethanol vapor concentration as low as 10 ppm and the response of LBCO thin film to various ethanol vapor concentrations is very reliable and reproducible with the switch between air and ethanol vapor. Moreover, the fast response of the LBCO thin film, as the p-type gas sensor, is better than some n-type oxide semiconductor thin films and comparable with some nanorods and nanowires. These findings indicate that the LBCO thin films have great potential for the development of gas sensors in reducing/oxidizing environments. PMID:26146369

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

  14. Chemical Gas Sensors for Aeronautic and Space Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liang-Yu; Neudeck, Philip G.; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai; Zhou, Huan-Jun

    1997-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Two areas of particular interest are safety monitoring and emission monitoring. In safety monitoring, detection of low concentrations of hydrogen at potentially low temperatures is important while for emission monitoring the detection of nitrogen oxides, hydrogen, hydrocarbons and oxygen is of interest. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: (1) Micromachining and microfabrication technology to fabricate miniaturized sensors. (2) The development of high temperature semiconductors, especially silicon carbide. The detection of each type of gas involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this general area of sensor development a field of significant interest.

  15. GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM

    SciTech Connect

    Hagen Schempf, Ph.D.

    2003-02-27

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. A prototype system was built for low-pressure cast-iron mains and tested in a spider- and serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The prototype unit combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-slave architecture to collect data from a distributed spider-arrangement, and in a master-repeater-slave configuration in serial or ladder-network arrangements. It was found that the system was capable of performing all data-sampling and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and valuable data was collected in order to determine how to improve on range and data-quality in the future.

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

    NASA Astrophysics Data System (ADS)

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

    1998-07-01

    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.

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

    PubMed

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

    2014-01-01

    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

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

    PubMed Central

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

    2014-01-01

    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

  19. Electronic characterization of thin diamondlike carbon films for pH sensor applications

    NASA Astrophysics Data System (ADS)

    Schitthelm, Frank; Roever, Kai-Sven; Ferretti, Ruediger

    1998-12-01

    Amorphous Diamond like carbon (DLC) thin films were deposited on to 4'-silicon wafers by an electron cyclotron resonance microwave excited methan (CH4) or ethin (C2H2) plasma at low pressure. Electronic characterization of DLC films were performed by I/V and C/V measurements using MIS-structures. Whereas the electrochemical pH-characteristics were measured using ion- sensitive field-effect transistors. It is shown, that the type of carrier transport mechanism in DLC films depends on the process conditions and that the electrical conductivity varies over a wide range. This can be adjusted mainly by the kinetic energy of the CxHx+ ions and the C to H ratio, which depends on the type of process gas. The dominant charge transport mechanism in DLC films based on a methan plasma is the Poole-Frenkel emission whereas the charge flow for ethin based DLC films is space-charged limited. The electronic conductivity of DLC films deposited with ethin as process gas is typically about five orders of magnitude higher than methan based films. The electrochemical characterization shows a pH-sensitivity in the range of 50 - 57 mV/pH and a long-term pH signal stability in the range of 0.3 - 25 (mu) V/h. Based on the different pH-sensitivities int will be possible to produce a pH-sensor in differential mode using DLC/DLC or DLC/Ta2O5 combinations for the sensitive layers.

  20. Chemical Gas Sensors for Aeronautics and Space Applications III

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Chen, L. Y.; Liu, C. C.; Wu, Q. H.; Sawayda, M. S.; Jin, Z.; Hammond, J.; Makel, D.; Liu, M.; Rauch, W. A.; Hall, G.

    1999-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of interest include launch vehicle safety monitoring, emission monitoring, and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this area of sensor development a field of significant interest.

  1. Chemical Gas Sensors for Aeronautic and Space Applications 2

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Chen, L. Y.; Neudeck, P. G.; Knight, D.; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, D.; Liu, M.; Rauch, W. A.

    1998-01-01

    Aeronautic and Space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of most interest include launch vehicle safety monitoring emission monitoring and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensor is based on progress two types of technology: 1) Micro-machining and micro-fabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this micro-fabricated gas sensor technology make this area of sensor development a field of significant interest.

  2. Chemical Gas Sensors for Aeronautic and Space Applications 2

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Chen, Liong-Yu; Neudeck, Phil G.; Knight, Dale; Liu, C. C.; Wu, Q. H.; Zhou, H. J.; Makel, Darby; Liu, M.; Rauch, W. A.

    1998-01-01

    Aeronautic and space applications require the development of chemical sensors with capabilities beyond those of commercially available sensors. Areas of interest include launch vehicle safety monitoring, emission monitoring, and fire detection. This paper discusses the needs of aeronautic and space applications and the point-contact sensor technology being developed to address these needs. The development of these sensors is based on progress in two types of technology: 1) Micromachining and microfabrication technology to fabricate miniaturized sensors. 2) The development of high temperature semiconductors, especially silicon carbide. Sensor development for each application involves its own challenges in the fields of materials science and fabrication technology. The number of dual-use commercial applications of this microfabricated gas sensor technology make this area of sensor development a field of significant interest.

  3. Investigation of the Carbon Monoxide Gas Sensing Characteristics of Tin Oxide Mixed Cerium Oxide Thin Films

    PubMed Central

    Durrani, Sardar M. A.; Al-Kuhaili, Mohammad F.; Bakhtiari, Imran A.; Haider, Muhammad B.

    2012-01-01

    Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 °C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6–21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 °C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively. PMID:22736967

  4. ?-Amylase sensor based on the degradation of oligosaccharide hydrogel films monitored with a quartz crystal sensor.

    PubMed

    Gibbs, Martin John; Biela, Anna; Krause, Steffi

    2015-05-15

    ?-Amylase hydrolyses starch molecules to produce smaller oligosaccharides and sugars. Amylases are of great importance in biotechnology and find application in fermentation, detergents, food and the paper industry. The measurement of ?-amylase activity in serum and urine has been used in the diagnosis of acute pancreatitis. Salivary amylase has also been shown to be a stress indicator. Sensor coatings suitable for the detection of ?-amylase activity have been developed. Oligosaccharides such as glycogen and amylopectin were spin-coated onto gold coated quartz crystals with a base frequency of 10 MHz. The films were subsequently cross-linked with hexamethylene diisocyanate. Film degradation was monitored with a quartz crystal microbalance (QCM) and electrochemical impedance measurements. The films were shown to be stable in phosphate buffered saline (PBS). Addition of ?-amylase to the solution resulted in the rapid degradation of the films. The maximum rate of degradation was found to be strongly dependent on the amylase activity in the range typically found in serum when diagnosing pancreatitis (0.08-8 U/ml). Sensor responses in serum were found to be very similar to those obtained in buffer indicating the absence of non-specific binding. PMID:25266253

  5. Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Basu, Palash Kr.; Kallatt, Sangeeth; Anumol, Erumpukuthickal A.; Bhat, Navakanta

    2015-06-01

    High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with built-in electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (<5 ?W), room temperature operation.

  6. Examining graphene field effect sensors for ferroelectric thin film studies.

    PubMed

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

    2013-09-11

    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

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

    PubMed

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

    2008-10-01

    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

  8. Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S.

    1997-01-01

    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.

  9. SiC-Based Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai

    1997-01-01

    Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.

  10. Selective Gas Sensing With h -BN Capped MoS2 Heterostructure Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Liu, G.; Rumyantsev, S. L.; Jiang, C.; Shur, M. S.; Balandin, A. A.

    2015-11-01

    We have demonstrated selective gas sensing with molybdenum disulfide (MoS2) thin films transistors capped with a thin layer of hexagonal boron nitride (h-BN). The resistance change was used as a sensing parameter to detect chemical vapors such as ethanol, acetonitrile, toluene, chloroform and methanol. It was found that h-BN dielectric passivation layer does not prevent gas detection via changes in the source-drain current in the active MoS2 thin film channel. The use of h-BN cap layers (thickness H=10 nm) in the design of MoS2 thin film gas sensors improves device stability and prevents device degradation due to environmental and chemical exposure. The obtained results are important for applications of van der Waals materials in chemical and biological sensing.

  11. GAS MAIN SENSOR AND COMMUNICATIONS NETWORK SYSTEM

    SciTech Connect

    Hagen Schempf

    2004-09-30

    Automatika, Inc. was contracted by the Department of Energy (DOE) and with co-funding from the New York Gas Group (NYGAS), to develop an in-pipe natural gas prototype measurement and wireless communications system for assessing and monitoring distribution networks. In Phase II of this three-phase program, an improved prototype system was built for low-pressure cast-iron and high-pressure steel (including a no-blow installation system) mains and tested in a serial-network configuration in a live network in Long Island with the support of Keyspan Energy, Inc. The experiment was carried out in several open-hole excavations over a multi-day period. The prototype units (3 total) combined sensors capable of monitoring pressure, flow, humidity, temperature and vibration, which were sampled and combined in data-packages in an in-pipe master-repeater-slave configuration in serial or ladder-network arrangements. It was verified that the system was capable of performing all data-sampling, data-storage and collection as expected, yielding interesting results as to flow-dynamics and vibration-detection. Wireless in-pipe communications were shown to be feasible and the system was demonstrated to run off in-ground battery- and above-ground solar power. The remote datalogger access and storage-card features were demonstrated and used to log and post-process system data. Real-time data-display on an updated Phase-I GUI was used for in-field demonstration and troubleshooting.

  12. Dry Process Based Infrared Sensors with CNT Film Absorber

    NASA Astrophysics Data System (ADS)

    Yoo, Kum-Pyo; Hong, Hyun Pyo; Lim, Lee-Taek; Choi, Chang-Seon; Lee, Dong Il; Lee, Cheol Jin; Park, Chan-Won; Min, Nam Ki

    In this paper, we describe the fabrication and characterization of a front-side micromachined thermopiles consisting of a suspended membrane and a carbon nanotube (CNT) film absorber. Thermocouples of 52 pairs which are composed of phosphorous-doped silicon and aluminum were formed and connected in series. A CNT film collected by filter was transferred on hot junction. A CNT absorber has an absorptance of about 50% in the midinfrared region. The suspended membrane was fabricated by an isotropic silicon dry etching process with XeF2 gas at the front side of the substrates. The output voltage with the CNT film is found to be 250.2 mV at 7 mW of incident power, approximately 1.8 times higher than that of one without an absorber.

  13. Metal oxide gas sensors upon various temperature-induced profiles

    NASA Astrophysics Data System (ADS)

    Gwi?d?, Patryk; Brudnik, Andrzej; Zakrzewska, Katarzyna

    2014-08-01

    This paper presents how an array of sensors with different sensitivities to gases can be applied for detection of hydrogen in the presence of humidity when operated upon various temperature - induced profiles. The sensors in the array are subject to temperature modulation over the range of 350 - 500°C. Temperature profiles are based on a cardinal sine as well as Meyer wavelet phi and psi functions. Changes in the sensor operating temperature lead to distinct resistance patterns of the sensors depending on gas concentration. The sensors responses are studied as a function of target gas concentration (0 - 3000 ppm) and relative humidity level (0 - 75%Rh). Feedforward back-propagation neural networks are used in order to facilitate gas concentration and humidity level prediction. The results show reliable hydrogen detection upon temperature modulation and a reduction of the total power consumption.

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

    PubMed Central

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

    2012-01-01

    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.

  15. Polymer flip-chip bonding of pressure sensors on a flexible Kapton film for neonatal catheters

    NASA Astrophysics Data System (ADS)

    Li, Chunyan; Sauser, Frank E.; Azizkhan, Richard G.; Ahn, Chong H.; Papautsky, Ian

    2005-09-01

    In this paper, we describe the development of a new approach to mounting silicon pressure microsensors inside a 5 French (1.67 mm outer diameter) neonatal catheter tube for intravascular blood pressure measurements. Kapton film was used as a low-cost, flexible interface between the flip-chip bonded sensors at one end and wires to external electronics at the other end. Conductive polymer paste was used to flip-chip bond sensors to the flexible Kapton substrate at low temperature, while gold traces were used to form electrical interconnects on the film surface. Conductivity and bonding strength of the resulting polymer bumps were on the order of 100 m? and 4.43 mN mm-2, respectively. Piezoresistive pressure microsensors were successfully mounted on Kapton carriers, packaged inside catheter tubes, and characterized in both gas and liquid environments. The sensors exhibited sensitivity of approximately 60 µV mmHg-1 over the target pressure range of 0-350 mmHg. Two-week tests in water at 27 °C and 36 °C showed only slight variations in contact resistances, indicating that the developed approach to packaging microsensors was sufficiently robust for the target application.

  16. 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)

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

    2006-01-01

    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.

  17. Flexible thin-film PVDF-TrFE based pressure sensor for smart catheter applications.

    PubMed

    Sharma, Tushar; Aroom, Kevin; Naik, Sahil; Gill, Brijesh; Zhang, John X J

    2013-04-01

    We demonstrate the design of thin flexible pressure sensors based on piezoelectric PVDF-TrFE (polyvinyledenedifluoride-tetrafluoroethylene) co-polymer film, which can be integrated onto a catheter, where the compact inner lumen space limit the dimensions of the pressure sensors. Previously, we demonstrated that the thin-film sensors of one micrometer thickness were shown to have better performance compared to the thicker film with no additional electrical poling or mechanical stretching due to higher crystallinity. The pressure sensors can be mass producible using standard lithography process, with excellent control of film uniformity and thickness down to one micrometer. The fabricated pressure sensors were easily mountable on external surface of commercial catheters. Elaborate experiments were performed to demonstrate the applicability of PVDF sensors towards catheter based biomedical application. The resonant frequency of the PVDF sensor was found to be 6.34 MHz. The PVDF sensors can operate over a broad pressure range of 0-300 mmHg. The average sensitivity of the PVDF sensor was found to be four times higher (99 ?V/mmHg) than commercial pressure sensor while the PVDF sensor (0.26 s) had fivefold shorter response time than commercial pressure sensor (1.30 s), making the PVDF sensors highly suitable for real-time pressure measurements using catheters. PMID:23519532

  18. Reflectance Infrared Spectroscopy on Operating Surface Acoustic Wave Chemical Sensors During Exposure to Gas-Phase Analytes

    SciTech Connect

    Hierlemann, A.; Hill, M.; Ricco, A.J.; Staton, A.W.; Thomas, R.C.

    1999-01-11

    We have developed instrumentation to enable the combination of surface acoustic wave (SAW) sensor measurements with direct, in-situ molecular spectroscopic measurements to understand the response of the SAW sensors with respect to the interfacial chemistry of surface-confined sensing films interacting with gas-phase analytes. Specifically, the instrumentation and software was developed to perform in-situ Fourier-transform infrared external-reflectance spectroscopy (FTIR-ERS) on operating SAW devices during dosing of their chemically modified surfaces with analytes. By probing the surface with IR spectroscopy during gas exposure, it is possible to understand in unprecedented detail the interaction processes between the sorptive SAW coatings and the gaseous analyte molecules. In this report, we provide details of this measurement system, and also demonstrate the utility of these combined measurements by characterizing the SAW and FTIR-ERS responses of organic thin-film sensor coatings interacting with gas-phase analytes.

  19. Design of nanoscale responsive polymer film for sensor application

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Hsi

    The concept of fabricating sensing or responsive surfaces at the nanoscale has been the subject of extensive investigations since they can function as nanoscale device as well as next-generation miniaturized sensor. Polymers offer particular insights into the developments of novel responsive materials, which can be integrated with sensory systems to alter structure and properties in response to environmental stimuli. These responsive polymer nanolayers change surface composition and properties modulated by external triggers such as temperature, pH, solvent exposure, and light. This study explores possibilities of designing such polymer surfaces that possess versatile sensing mechanisms via controlled reorganization of chain and functional groups in multi-component and composite surface and then applying this into actual sensory systems of critical relevance. To achieve this, we designed novel nano-structured materials based on the employment of polymer methodologies, chemical functionality, and provide new capabilities by adding nanoparticles/nanowires to alter responsive polymer systems. We selected polymer with very different chemistry, switchable properties, and the surface composition which can be precisely controlled and divided into four groups: (1) switchable adaptive polymer nanolayer on planar silicon substrates, (2) compliant polymer or nanocomposite nanolayer enhancing/improving the sensitivity of current cantilever based sensors, (3) polymer nanolayer on ZnO nanobelt with enhanced photosensitivity (4) assembled ultra thin film with optical grating 3D structures. Furthermore, we designed and fabricated compliant polymer or nanocomposite films for thermal, chemical and light sensitive systems which can greatly enhance the sensitivity of corresponding micro/nanodevices.

  20. Measurement of quasiparticle transport in aluminum films using tungsten transition-edge sensors

    SciTech Connect

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

    2014-10-20

    We report on experimental studies of phonon sensors which utilize quasiparticle diffusion in thin aluminum films connected to 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. These studies allow the design of phonon sensors with improved performance.

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

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.

    2006-01-01

    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.

  2. Amorphous silicon thin-films for uncooled infrared microbolometer sensors

    NASA Astrophysics Data System (ADS)

    Ajmera, Sameer K.; Syllaios, A. J.; Tyber, Greg S.; Taylor, Michael F.; Hollingsworth, Russell E.

    2010-04-01

    An important application of thin-film hydrogenated amorphous silicon (?-Si:H) is infrared detection and imaging with microbolometer focal plane arrays. Key ?-Si:H electrical transport properties that influence detector design and performance are resistivity and temperature coefficient of resistance (TCR). These properties have been measured over a wide temperature range for p- and n-type doped ?-Si:H thin-films deposited by plasma enhanced chemical vapor deposition using silane as a precursor gas. Resistivity near and above room temperature follows an Arrhenius thermally activated dependence. At low temperatures, resistivity transitions from Arrhenius behavior to a variable range hopping mechanism described by the Mott relation and TCR changes at a slower rate than predicted by thermally activated transport alone. Resistivity and TCR are affected by doping and film growth parameters such as dilution of the silane precursor with hydrogen. Resistivity decreases with dopant concentration for both p-type and n-type dopants. Resistivity and TCR increase with hydrogen dilution of silane. TCR and resistivity are interrelated and optimization of thin-film preparation and processing is necessary to obtain high TCR with resistivity values compatible with readout integrated circuit designs. Such optimization of transport properties of ?-Si:H films has been applied to the development of high performance ambient operating temperature (uncooled) microbolometer arrays.

  3. IEEE SENSORS JOURNAL, VOL. 2, NO. 5, OCTOBER 2003 543 Interface States in High-Temperature Gas Sensors

    E-print Network

    Ghosh, Ruby N.

    IEEE SENSORS JOURNAL, VOL. 2, NO. 5, OCTOBER 2003 543 Interface States in High-Temperature Gas Sensors Based on Silicon Carbide Peter Tobias, Brage Golding, and Ruby N. Ghosh, Member, IEEE Abstract of these results on sensor design and the choice of operating point. Index Terms--Gas sensor, hydrogen, interface

  4. Responsive ionic liquidpolymer 2D photonic crystal gas sensors

    E-print Network

    Asher, Sanford A.

    Responsive ionic liquid­polymer 2D photonic crystal gas sensors Natasha L. Smith, Zhenmin Hong and Sanford A. Asher* We developed novel air-stable 2D polymerized photonic crystal (2DPC) sensing materials

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

    E-print Network

    Dutta, Prabir K.

    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

  6. Nanoporous metal oxides thin-films as "chemical reactive layers" for magnetoelastic sensors

    NASA Astrophysics Data System (ADS)

    Zhang, Rong

    Freestanding magnetoelastic sensors are good candidates for in situ analysis of gases. After coating magnetoelastic ribbons with suitable nanoporous thin films, chemical reactive layers (CRL), sensitivity and specificity of the sensor for targeted gas increases. This thesis addresses two major aspects concerning magnetoelastic sensing of gases. The first aspect relates to developing methodology to measure mass of gas adsorbed from frequency shifts. Effective Young's modulus of the sensor coated with porous thin-films suffers large changes upon mass loading. This study demonstrates that changes in Young's modulus produced upon mass loading can be eliminated from the relationship between the magnitude of mass loaded and shifts in resonant frequency using the Two Different Length Sensors method. Sensitivity of the sensor not only depends on its properties but also depends on the nature of material being loaded and on its mass. Results show that sensitivity for the same sensor can range between 214 Hz/mg for mass loads of Au to 438,809 Hz/mg for acetone. The second aspect of this research deals with the development of CRL for ethylene sensing. Nanoporous metal oxides (TiO2 and SiO 2) surface modified with metals Pt(0) and metal ions Pt(II), Pd(II), Ag(I) were synthesized and evaluated as potential candidates. These materials were evaluated as ethylene adsorbents. We also studied the gain in weight upon ethylene adsorption and the nature of their chemical interaction with ethylene. Results from these studies showed that ethylene is completely mineralized (CO2+H2O) upon exposure to Pt(0)-modified TiO2 cermets. TiO2 modified with Pd(II) and Pt(II) oxidizes a fraction of ethylene to carboxylic and carboxylate species, causing adsorption of ethylene to be partially irreversible at room temperature. Ag(I)-doped materials react with ethylene to form surface complexes with sigma bonding character. Adsorption of ethylene is reversible process in this case. While the adsorption of ethylene by TiO2 is very small (0.02 mmols/g) at equilibrium with 40 ppmv in gas phase, the Pd(II), Pt(II) and Ag(I)-doped TiO2 adsorb, 0.50, 015 and 0.20 mmols/g respectively. The change in weight of materials upon exposure to ethylene is always less than 20% of that predicted by ethylene adsorption. This is due to desorption of water that takes place upon ethylene adsorption.

  7. Fiber-Optic Temperature Sensor Using a Thin-Film Fabry-Perot Interferometer

    NASA Technical Reports Server (NTRS)

    Beheim, Glenn

    1997-01-01

    A fiber-optic temperature sensor was developed that is rugged, compact, stable, and can be inexpensively fabricated. This thin-film interferometric temperature sensor was shown to be capable of providing a +/- 2 C accuracy over the range of -55 to 275 C, throughout a 5000 hr operating life. A temperature-sensitive thin-film Fabry-Perot interferometer can be deposited directly onto the end of a multimode optical fiber. This batch-fabricatable sensor can be manufactured at a much lower cost than can a presently available sensor, which requires the mechanical attachment of a Fabry-Perot interferometer to a fiber. The principal disadvantage of the thin-film sensor is its inherent instability, due to the low processing temperatures that must be used to prevent degradation of the optical fiber's buffer coating. The design of the stable thin-film temperature sensor considered the potential sources of both short and long term drifts. The temperature- sensitive Fabry-Perot interferometer was a silicon film with a thickness of approx. 2 microns. A laser-annealing process was developed which crystallized the silicon film without damaging the optical fiber. The silicon film was encapsulated with a thin layer of Si3N4 over coated with aluminum. Crystallization of the silicon and its encapsulation with a highly stable, impermeable thin-film structure were essential steps in producing a sensor with the required long-term stability.

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

    SciTech Connect

    Srivastava, Subodh; Kumar, Sumit; Agrawal, Shweta; Saxena, Arpita; Choudhary, B. L.; Mathur, Shubhra; Singh, M.; Vijay, Y. K.

    2010-12-01

    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.

  9. NOVEL GAS SENSORS FOR HIGH-TEMPERATURE FOSSIL FUEL APPLICATIONS

    SciTech Connect

    Palitha Jayaweera

    2004-05-01

    SRI is developing ceramic-based microsensors for detection of exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes and are designed to operate at high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. Under this research project we are developing sensors for multiple gas detection in a single package along with data acquisition and control software and hardware. The sensor package can be easily integrated into online monitoring systems for active emission control. This report details the research activities performed from October 2003 to April 2004.

  10. Optical Sensors Based on Single on Arm Thin Film Waveguide Interferometer

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  11. 40 Å Platinum-porous SiC gas sensor: Investigation sensing properties of H2 gas

    NASA Astrophysics Data System (ADS)

    Keffous, A.; Cheriet, A.; Hadjersi, T.; Boukennous, Y.; Gabouze, N.; Boukezzata, A.; Belkacem, Y.; Kechouane, M.; Kerdja, T.; Menari, H.; Berouaken, M.; Talbi, L.; Ouadah, Y.

    2013-01-01

    The present paper reports on a new structure for H2 gas sensing based on thin porous silicon carbide (PSiC) films. The PSiC layer has been formed by electrochemical etching of SiC films previously deposited onto p-type silicon substrate by pulsed laser deposition (PLD) using 6H-SiC target. Current-voltage (I-V) and current-time (I-t) characteristics have been measured. A thin platinum (Pt) film (40 Å thickness) deposited onto PSiC layer has been used as a catalytic metal. The Schottky diode parameters such as ideality factor (n), barrier height (?Bp) and series resistance (RS) have been evaluated under different concentrations of H2 gas. The experimental results show that upon exposure to H2 gas the barrier height, the ideality factor and the series resistance change significantly. The different changes in the electrical parameters of the structure (increase and decrease as a function of the H2 concentration) have been explained by the formation of two inversion layers. The first one forms as soon as the gas is in contact with the sensor and the second when the concentration reaches 90 ppm. Subsequently, the effect of gas concentration on the maximum sensitivity value of the sensor has been investigated. A high sensitivity (?I/I) value around 86% is found at about 1 V bias voltage. In addition, the response and recovery times were determined to be around 55 s and 160 s, respectively. Finally, the structure shows a reversible response for low gas concentration at room temperature.

  12. Portable mid-infrared gas sensors: Development and applications

    NASA Astrophysics Data System (ADS)

    Richter, Dirk

    Several novel compact architectures of diode laser based absorption gas sensors have been developed, characterized and applied to real world applications. The motivation for this research has been the need to develop highly sensitive, selective and rapid response gas sensors that operate reliably in a non-laboratory environment. The gas sensors utilize rare earth doped fiber amplified near infrared diode lasers and are difference frequency mixed in periodically poled LiNbO3 to generate narrow linewidth ?W to mW-level mid infrared light in the molecular fingerprint region from 3 to 5 ?m. In particular, the spectroscopic performance of an automated widely tunable (3.3-4.4 ?m) multi-species and a high-power single species (3.5 ?m) gas detection sensor are discussed. Sensitive, selective and real-time detection of over 10 gas species including CH4, H2CO, CO2, CH 3OH, NO2, N2O; SO2, HCl, C6H 6, and H2O using extractive gas sampling in a multi- pass cell was demonstrated. The gas sensors were used for an evaluation of a trace contaminant catalyst system at TDA Research, Wheat Ridge, Colorado, and successfully applied to the detection of volcanic gases at Masaya volcano, Nicaragua.

  13. Electrochemical amperometric gas sensors for environmental monitoring and control

    NASA Technical Reports Server (NTRS)

    Venkatasetty, H. V.

    1990-01-01

    Theoretical considerations and experimental results regarding a unique class of vapor sensors are presented, and the sensors are compared to semiconductor-based sensors. The electrochemical sensors are based on nonaquaeous electrolytes, and gas-detection selectivity achieved by applying a known potential to the sensing electrode using a reference electrode and a counter electrode. Results are given regarding the detection of oxygen and carbon dioxide using one cell, the detection of 3-percent carbon dioxide in nitrogen, and the detection of carbon dioxide in air at percentages ranging from 3 to 6. The sensors are found to be effective in the detection of toxic chemical species including CO, NO2, and formaldehyde; the sensors are further found to require minimal power, operate over long periods of time, and function over a wide temperature range.

  14. High-Temperature Gas Sensor Array (Electronic Nose) Demonstrated

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.

    2002-01-01

    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.

  15. Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior

    PubMed Central

    Cui, Ling; Murray, Erica P.

    2015-01-01

    The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sensors was collected via impedance spectroscopy under various operating conditions where gas concentrations ranged from 0 to 100 ppm NO and 1%–18% O2 at temperatures varying from 600 to 700 °C. Gas diffusion appeared to be a rate-limiting mechanism in sensors where the electrode configuration resulted in longer diffusion pathways. The temperature dependence of the NO sensors studied was independent of the electrode configuration. Analysis of the impedance data, along with equivalent circuit modeling indicated the electrode configuration of the sensor effected gas and ionic transport pathways, capacitance behavior, and NO sensitivity. PMID:26404312

  16. Effect of Electrode Configuration on Nitric Oxide Gas Sensor Behavior.

    PubMed

    Cui, Ling; Murray, Erica P

    2015-01-01

    The influence of electrode configuration on the impedancemetric response of nitric oxide (NO) gas sensors was investigated for solid electrochemical cells [Au/yttria-stabilized zirconia (YSZ)/Au)]. Fabrication of the sensors was carried out at 1050 °C in order to establish a porous YSZ electrolyte that enabled gas diffusion. Two electrode configurations were studied where Au wire electrodes were either embedded within or wrapped around the YSZ electrolyte. The electrical response of the sensors was collected via impedance spectroscopy under various operating conditions where gas concentrations ranged from 0 to 100 ppm NO and 1%-18% O? at temperatures varying from 600 to 700 °C. Gas diffusion appeared to be a rate-limiting mechanism in sensors where the electrode configuration resulted in longer diffusion pathways. The temperature dependence of the NO sensors studied was independent of the electrode configuration. Analysis of the impedance data, along with equivalent circuit modeling indicated the electrode configuration of the sensor effected gas and ionic transport pathways, capacitance behavior, and NO sensitivity. PMID:26404312

  17. Application of ZnO single-crystal wire grown by the thermal evaporation method as a chemical gas sensor for hydrogen sulfide.

    PubMed

    Park, N K; Lee, S Y; Lee, T J

    2011-01-01

    A zinc oxide single-crystal wire was synthesized for application as a gas-sensing material for hydrogen sulfide, and its gas-sensing properties were investigated in this study. The gas sensor consisted of a ZnO thin film as the buffer layer and a ZnO single-crystal wire. The ZnO thin film was deposited over a patterning silicon substrate with a gold electrode by the CFR method. The ZnO single-crystal wire was synthesized over the ZnO thin film using zinc and activated carbon as the precursor for the thermal evaporation method at 800 degrees C. The electrical properties of the gas sensors that were prepared for the growth of ZnO single-crystal wire varied with the amount of zinc contained in the precursor. The charged current on the gas sensors increased with the increasing amount of zinc in the precursor. It was concluded that the charged current on the gas sensors was related to ZnO single-crystal wire growth on the silicon substrate area between the two electrodes. The charged current on the gas sensor was enhanced when the ZnO single-crystal wire was exposed to a H2S stream. The experimental results obtained in this study confirmed that a ZnO single-crystal wire can be used as a gas sensor for H2S. PMID:21446509

  18. A Room Temperature Nitric Oxide Gas Sensor Based on a Copper-Ion-Doped Polyaniline/Tungsten Oxide Nanocomposite

    PubMed Central

    Wang, Shih-Han; Shen, Chi-Yen; Su, Jian-Ming; Chang, Shiang-Wen

    2015-01-01

    The parts-per-billion-level nitric oxide (NO) gas sensing capability of a copper-ion-doped polyaniline/tungsten oxide nanocomposite (Cu2+/PANI/WO3) film coated on a Rayleigh surface acoustic wave device was investigated. The sensor developed in this study was sensitive to NO gas at room temperature in dry nitrogen. The surface morphology, dopant distribution, and electric properties were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy mapping, and Hall effect measurements, respectively. The Cu2+/PANI/WO3 film exhibited high NO gas sensitivity and selectivity as well as long-term stability. At 1 ppb of NO, a signal with a frequency shift of 4.3 ppm and a signal-to-noise ratio of 17 was observed. The sensor exhibited distinct selectivity toward NO gas with no substantial response to O2, NH3 and CO2 gases. PMID:25811223

  19. Theory for a gas composition sensor based on acoustic properties

    NASA Astrophysics Data System (ADS)

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

    2003-01-01

    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.

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

    PubMed Central

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

    2014-01-01

    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

  1. Highly sensitive and fast response gas sensor based on a light reflection at the glass-photonic crystal interface

    NASA Astrophysics Data System (ADS)

    Kuchyanov, A. S.; Chubakov, P. A.; Plekhanov, A. I.

    2015-09-01

    We develop a versatile gas sensor based on the condition for total internal reflection at the glass-photonic crystal interface and corresponding detection scheme for rapid and precise measurement of vapors. The sensor consists of a vapor sensitive photonic crystal film as a Fabry-Perot etalon coated on a solid substrate (e.g., large face of a glass prism or glass slide). Such scheme and specific physicochemical properties of submicron silica particles provide photonic crystal sensor selectivity due to the capillary condensation of ammonia vapor with a sensitivity of 1 ppm with a response time of 100 ms.

  2. Compact Laser Multi-gas Spectral Sensors for Spacecraft Systems

    NASA Technical Reports Server (NTRS)

    Tittel, Frank K.

    1997-01-01

    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.

  3. Gas Sensor for Volatile Anesthetic Agents Based on Raman Scattering

    NASA Astrophysics Data System (ADS)

    Schlüter, Sebastian; Popovska-Leipertz, Nadejda; Seeger, Thomas; Leipertz, Alfred

    Continuous monitoring of respiratory and anesthetic gases during a surgery is of vital importance for the patient safety. Commonly the gas composition is determined by gas chromatography or a combination of IR-spectroscopy and electrochemical sensors. This study presents a concept for an optical sensor based on spontaneous Raman scattering which offers several advantages compared to established systems. All essential components can be detected simultaneously, no sample preparation is necessary and it provides fast response times. To reach the performance of a commonly used gas monitor signal gain has to be increased e.g. by using a multi pass setup.

  4. Thin-film chemical sensors based on electron tunneling

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  5. Alpha-Particle Gas-Pressure Sensor

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  6. Photoacoustic photonic crystal fiber gas sensor

    E-print Network

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

    2007-01-01

    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, ...

  7. Improved 02/H2 Gas Mixture Sensor

    NASA Technical Reports Server (NTRS)

    Moulthrop, L. C.

    1983-01-01

    Monitor of mixture concentrations uses catalyzed and uncatalyzed temperature probe. Sensor includes Pt-catalyzed temperature probe mounted in line with similar uncatalyzed temperature probe. Use of common temperature probes and standard, flareless, high-pressure tubefittings resulted in design conductive to installation in almost any system. Suitable for use in regenerative fuel cells, life-support systems, and other closed systems.

  8. MEMS device for mass market gas and chemical sensors

    NASA Astrophysics Data System (ADS)

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

    2000-08-01

    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.

  9. Thermal stability of piezoelectric properties and infrared sensor performance of spin-coated polyurea thin films

    NASA Astrophysics Data System (ADS)

    Morimoto, Masahiro; Koshiba, Yasuko; Misaki, Masahiro; Ishida, Kenji

    2015-10-01

    We have investigated the temperature dependence of the piezoelectric coefficients and infrared sensor performance of spin-coated thin films of polyundecylurea (PUA11). The piezoelectric coefficients of the PUA11 films remained constant at temperatures above 180 °C and these films demonstrated thermal resistance superior to those of poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)] films. The infrared sensor performance of the PUA11 films was measured after annealing at 125 °C for 500 h and was found to have retained 84% of its preannealing level. The thermal stability of the PUA11 films was higher than that of the P(VDF/TrFE) films; moreover, PUA11 is also expected to have superior electrothermal stability.

  10. Illicit material detector based on gas sensors and neural networks

    NASA Astrophysics Data System (ADS)

    Grimaldi, Vincent; Politano, Jean-Luc

    1997-02-01

    In accordance with its missions, le Centre de Recherches et d'Etudes de la Logistique de la Police Nationale francaise (CREL) has been conducting research for the past few years targeted at detecting drugs and explosives. We have focused our approach of the underlying physical and chemical detection principles on solid state gas sensors, in the hope of developing a hand-held drugs and explosives detector. The CREL and Laboratory and Scientific Services Directorate are research partners for this project. Using generic hydrocarbon, industrially available, metal oxide sensors as illicit material detectors, requires usage precautions. Indeed, neither the product's concentrations, nor even the products themselves, belong to the intended usage specifications. Therefore, the CREL is currently investigating two major research topics: controlling the sensor's environment: with environmental control we improve the detection of small product concentration; determining detection thresholds: both drugs and explosives disseminate low gas concentration. We are attempting to quantify the minimal concentration which triggers detection. In the long run, we foresee a computer-based tool likely to detect a target gas in a noisy atmosphere. A neural network is the suitable tool for interpreting the response of heterogeneous sensor matrix. This information processing structure, alongside with proper sensor environment control, will lessen the repercussions of common MOS sensor sensitivity characteristic dispersion.

  11. Gas sensing properties of very thin TiO2 films prepared by atomic layer deposition (ALD)

    NASA Astrophysics Data System (ADS)

    Boyadjiev, S.; Georgieva, V.; Vergov, L.; Baji, Zs; Gáber, F.; Szilágyi, I. M.

    2014-11-01

    Very thin titanium dioxide (TiO2) films of less than 10 nm were deposited by atomic layer deposition (ALD) in order to study their gas sensing properties. Applying the quartz crystal microbalance (QCM) method, prototype structures with the TiO2 ALD deposited thin films were tested for sensitivity to NO2. Although being very thin, the films were sensitive at room temperature and could register low concentrations as 50-100 ppm. The sorption is fully reversible and the films seem to be capable to detect for long term. These initial results for very thin ALD deposited TiO2 films give a promising approach for producing gas sensors working at room temperature on a fast, simple and cost-effective technology.

  12. Investigation of thiol derivatized gold nanoparticle sensors for gas analysis

    NASA Astrophysics Data System (ADS)

    Stephens, Jared S.

    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.

  13. Gas sensors characterization and multilayer perceptron (MLP) hardware implementation for gas identification using a Field Programmable Gate Array (FPGA).

    PubMed

    Benrekia, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

    2013-01-01

    This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

  14. Gas Sensors Characterization and Multilayer Perceptron (MLP) Hardware Implementation for Gas Identification Using a Field Programmable Gate Array (FPGA)

    PubMed Central

    Benrekia, Fayçal; Attari, Mokhtar; Bouhedda, Mounir

    2013-01-01

    This paper develops a primitive gas recognition system for discriminating between industrial gas species. The system under investigation consists of an array of eight micro-hotplate-based SnO2 thin film gas sensors with different selectivity patterns. The output signals are processed through a signal conditioning and analyzing system. These signals feed a decision-making classifier, which is obtained via a Field Programmable Gate Array (FPGA) with Very High-Speed Integrated Circuit Hardware Description Language. The classifier relies on a multilayer neural network based on a back propagation algorithm with one hidden layer of four neurons and eight neurons at the input and five neurons at the output. The neural network designed after implementation consists of twenty thousand gates. The achieved experimental results seem to show the effectiveness of the proposed classifier, which can discriminate between five industrial gases. PMID:23529119

  15. Three-gas detection system with IR optical sensor based on NDIR technology

    NASA Astrophysics Data System (ADS)

    Tan, Qiulin; Tang, Licheng; Yang, Mingliang; Xue, Chenyang; Zhang, Wendong; Liu, Jun; Xiong, Jijun

    2015-11-01

    In this paper, a three-gas detection system with a environmental parameter compensation method is proposed based on Non-dispersive infra-red (NDIR) technique, which can be applied to detect multi-gas (methane, carbon dioxide and carbon monoxide). In this system, an IR source and four single-channel pyroelectric sensors are integrated in the miniature optical gas chamber successfully. Inner wall of the chamber coated with Au film is designed as paraboloids. The infrared light is reflected twice before reaching to detectors, thus increasing optical path. Besides, a compensation method is presented to overcome the influence in variation of environment (ambient temperature, humidity and pressure), thus leading to improve the accuracy in gas detection. Experimental results demonstrated that detection ranges are 0-50,000 ppm for CH4, 0-44,500 ppm for CO, 0-48,000 ppm for CO2 and the accuracy is ±0.05%.

  16. Prototype thin-film thermocouple/heat-flux sensor for a ceramic-insulated diesel engine

    NASA Technical Reports Server (NTRS)

    Kim, Walter S.; Barrows, Richard F.

    1988-01-01

    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.

  17. Hydrogen Sensor Based on RF-Sputtered Thermoelectric SiGe Film

    NASA Astrophysics Data System (ADS)

    Qiu, Fabin; Shin, Woosuck; Matsumiya, Masahiko; Izu, Noriya; Murayama, Norimitsu

    2003-04-01

    Si0.8Ge0.2 thin film was sputtered on an alumina substrate by the RF-sputtering method. After annealing in flowing Ar atmosphere, platinum film, which acts as a catalyst of the combustible sample gas, was further sputtered on half the surface area of SiGe film. The hydrogen-sensing properties were investigated for the development of potential applications of the device structure as a hydrogen sensor that makes use of the thermoelectric (TE) effect. The measurement results indicate that a reliable output voltage signal was successfully realized when the element was exposed to an environment with a certain hydrogen concentration. The operating temperature for the device was around 100°C, and the response and recovery time corresponding to 90% voltage change were both shorter than 50 s on switching the atmosphere from synthetic air to 3% H2. The detectable concentration of the device ranged from 0.01% to 3%. Furthermore, a good selectivity to hydrogen was also exhibited.

  18. Detection of Smoldering Fire Using Tin Oxide Gas Sensors

    NASA Astrophysics Data System (ADS)

    Higashino, Tsubasa; Sawada, Ayako; Oyabu, Takashi; Takei, Yoshinori; Nanto, Hidehito; Toko, Kiyoshi

    Detecting technique of smoldering fire was examined using tin oxide gas sensors. Eight sensors were installed in a room. They were same type. Four kinds of materials were adopted as a fire-source material. The materials were cotton cloth, wallpaper, curtain cloth and woodchip, which were main smoldering fire-source materials in an indoor environment. The sensor outputs to gases evolved upon the smoldering fire of the materials were measured. The differential characteristic of the output was derived to analyze. As for the results, it became obvious that the sensor locating at higher position had a higher sensitivity and it could sense the fire instantaneously. It is thought that the generated gases rise up directly toward the ceiling and reflect downward. A small type of electric cooking stove was used as a fire-source. The surface temperature of the stove plate arrived at 340 °C. A bar was adopted to set the sensors freely. In this experiment, three bars were adopted and the heights of the sensor position were 50, 100, 150 and 200 cm from the floor. It is effective to locate the sensor at higher position in detecting a smoldering fire. The sensor characteristics were analyzed using principal component analysis (PCA). The system could discriminate source materials among wallpaper, woodchip and curtain for smoldering fire by utilizing the result of PCA. But, the smoldering fire of cotton cloth could not be distinguished from that of curtain by this system. Each fire could be identified in four minutes.

  19. Gas-Sensing Performance of M-Doped CuO-Based Thin Films Working at Different Temperatures upon Exposure to Propane.

    PubMed

    Rydosz, Artur; Szkudlarek, Aleksandra

    2015-01-01

    Cupric oxide (CuO) thin films are promising materials in gas sensor applications. The CuO-based gas sensors behaved as p-type semiconductors and can be used as part of an e-nose or smart sensor array for breath analysis. The authors present the investigation results on M-doped CuO-based (M = Ag, Au, Cr, Pd, Pt, Sb, Si) sensors working at various temperatures upon exposure to a low concentration of C3H8, which can be found in exhaled human breath, and it can be considered as a one of the biomarkers of several diseases. The films have been deposited in magnetron sputtering technology on low temperature cofired ceramics substrates. The results of the gas sensors' response are also presented and discussed. The Cr:CuO-based structure, annealed at 400 °C for 4 h in air, showed the highest sensor response, of the order of 2.7 at an operation temperature of 250 °C. The response and recovery time(s) were 10 s and 24 s, respectively. The results show that the addition of M-dopants in the cupric oxide films effectively act as catalysts in propane sensors and improve the gas sensing properties. The films' phase composition, microstructure and surface topography have been assessed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) methods. PMID:26287204

  20. Gas-Sensing Performance of M-Doped CuO-Based Thin Films Working at Different Temperatures upon Exposure to Propane

    PubMed Central

    Rydosz, Artur; Szkudlarek, Aleksandra

    2015-01-01

    Cupric oxide (CuO) thin films are promising materials in gas sensor applications. The CuO-based gas sensors behaved as p-type semiconductors and can be used as part of an e-nose or smart sensor array for breath analysis. The authors present the investigation results on M-doped CuO-based (M = Ag, Au, Cr, Pd, Pt, Sb, Si) sensors working at various temperatures upon exposure to a low concentration of C3H8, which can be found in exhaled human breath, and it can be considered as a one of the biomarkers of several diseases. The films have been deposited in magnetron sputtering technology on low temperature cofired ceramics substrates. The results of the gas sensors’ response are also presented and discussed. The Cr:CuO-based structure, annealed at 400 °C for 4 h in air, showed the highest sensor response, of the order of 2.7 at an operation temperature of 250 °C. The response and recovery time(s) were 10 s and 24 s, respectively. The results show that the addition of M-dopants in the cupric oxide films effectively act as catalysts in propane sensors and improve the gas sensing properties. The films’ phase composition, microstructure and surface topography have been assessed by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) methods. PMID:26287204

  1. Increasing the selectivity and sensitivity of gas sensors for the detection of explosives

    NASA Astrophysics Data System (ADS)

    Mallin, Daniel

    Over the past decade, the use of improvised explosive devices (IEDs) has increased, domestically and internationally, highlighting a growing need for a method to quickly and reliably detect explosive devices in both military and civilian environments before the explosive can cause damage. Conventional techniques have been successful in explosive detection, however they typically suffer from enormous costs in capital equipment and maintenance, costs in energy consumption, sampling, operational related expenses, and lack of continuous and real-time monitoring. The goal was thus to produce an inexpensive, portable sensor that continuously monitors the environment, quickly detects the presence of explosive compounds and alerts the user. In 2012, here at URI, a sensor design was proposed for the detection of triacetone triperoxide (TATP). The design entailed a thermodynamic gas sensor that measures the heat of decomposition between trace TATP vapor and a metal oxide catalyst film. The sensor was able to detect TATP vapor at the part per million level (ppm) and showed great promise for eventual commercial use, however, the sensor lacked selectivity. Thus, the specific objective of this work was to take the original sensor design proposed in 2012 and to make several key improvements to advance the sensor towards commercialization. It was demonstrated that a sensor can be engineered to detect TATP and ignore the effects of interferent H2O2 molecules by doping SnO2 films with varying amounts of Pd. Compared with a pure SnO2 catalyst, a SnO2, film doped with 8 wt. % Pd had the highest selectivity between TATP and H2O2. Also, at 12 wt. % Pd, the response to TATP and H2O2 was enhanced, indicating that sensitivity, not only selectivity, can be increased by modifying the composition of the catalyst. An orthogonal detection system was demonstrated. The platform consists of two independent sensing mechanisms, one thermodynamic and one conductometric, which take measurements from the same catalyst simultaneously and provide a redundancy in response for positive explosive identification. TATP, 2,6-DNT and ammonium nitrate were reliably detected. Each analyte displayed a unique conductometric signature and the results indicated a detection limit at the ppb level. A preconcentrator was designed to enhance the sensitivity of the sensor and was successfully demonstrated. The magnitude of the sensor response increased from by 50% and the preconcentrator could be operated semi-continuously, maintaining one of the most attractive features of this sensor platform: the capability to operate in real time. A method to filter out extraneous heat signals from sensor response using a dynamic control was also successfully demonstrated and will likely be a fixture in all sensor experimentation and design moving forward. Finally, two MEMS based sensor platforms were designed and fabricated. It was theoretically demonstrated that the newest iteration of the MEMS sensor consumes considerably less power due to thinner membranes, a smaller active surface area and an overall smaller thermal mass, allowing for the possibility of creating networks of sensor arrays, even in a portable device.

  2. Novel Thin Film Sensor Technology for Turbine Engine Hot Section Components

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.

    2007-01-01

    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.

  3. Structure of Palladium Nanoclusters for Hydrogen Gas Sensors

    SciTech Connect

    Stevens, K.J.; Ingham, B.; Toney, M.F.; Brown, S.A.; Lassesson, A.; /SLAC, SSRL /Canterbury U.

    2009-05-11

    Palladium nanoclusters produced by inert gas aggregation/magnetron sputtering are used as building blocks for the construction of nano electronic devices with large surface to volume ratios that can be used as sensitive hydrogen gas sensors in fuel cells and in petrochemical plants. X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), and high resolution transmission electron microscopy (HRTEM) have been used to characterize the structure, lattice constant, particle diameter and oxide thickness of the palladium nanoclusters in order to understand the operation of these sensors. Grazing incidence XRD (GIXRD) of heat treated Pd clusters has shown that the palladanite structure forms at elevated temperatures.

  4. Novel SH-SAW gas sensor based on graphene

    NASA Astrophysics Data System (ADS)

    Nikolaou, I.; Hallil, H.; Deligeorgis, G.; Conedera, V.; Garcia, H.; Dejous, C.; Rebière, D.

    2015-05-01

    In this article, a novel gas sensor platform has been studied. Several layers of graphene have been deposited on a SH-SAW, as a sensitive layer. Innovative methods of graphene solutions have been prepared in order to explore gas sensing applications. The real time detection measurement of the coated sensor under ethanol and humidity is presented. The adsorption of vapors leads to a frequency shift of 10.5 kHz and 22.7 kHz, at exposure of 100 ppm of ethanol and 6.22% of Relative Humidity, respectively. The experiments have been realized at room temperature; rapid response and recovery time were observed.

  5. Semiconducting Thin-Film Sensors for Detection of Polluting Gases and Floating Particles

    NASA Astrophysics Data System (ADS)

    Yokoyama, Tatsuya; Hara, Kazuhiro

    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.

  6. Electrodes for solid state gas sensor

    DOEpatents

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

    2007-05-08

    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.

  7. Electrodes for solid state gas sensor

    DOEpatents

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

    2003-08-12

    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.

  8. An automatic data acquisition system for optical characterization of PEDOT:PSS-based gas sensor

    NASA Astrophysics Data System (ADS)

    Junaidi, Aba, La; Triyana, Kuwat

    2015-04-01

    A measurement system that consists of a pair of laser diode and photodiode coupled with an automatic data acquisition system based on microcontroller of AVR ATMega16 (hereafter to be called DAQ MA-16) has been developed for measuring optical response of polymer-based gas sensor. In this case, the optical response was represented by the voltage output of the photodiode. The polymer-based gas sensor was a thin film of polymer of Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) or PEDOT:PSS deposited on a glass substrate. For measurement, the sensor was placed in the chamber, and then the gas ammonia with a fix flow rate was flowed into the chamber. The opposite part of the chamber was installed a pump to throw the gas. The National Instrument Data Acquisition (NI DAQ) BNC-2110 has been used to calibrate the DAQ MA-16 system. From the calibration, it can be estimated that the accuracy of DAQ MA-16 is about 99.4%.

  9. Chemical Gas Sensors for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Liu, C. C.

    1998-01-01

    Chemical sensors often need to be specifically designed (or tailored) to operate in a given environment. It is often the case that a chemical sensor that meets the needs of one application will not function adequately in another application. The more demanding the environment and specialized the requirement, the greater the need to adapt exiting sensor technologies to meet these requirements or, as necessary, develop new sensor technologies. Aerospace (aeronautic and space) applications are particularly challenging since often these applications have specifications which have not previously been the emphasis of commercial suppliers. Further, the chemical sensing needs of aerospace applications have changed over the years to reflect the changing emphasis of society. Three chemical sensing applications of particular interest to the National Aeronautics and Space Administration (NASA) which illustrate these trends are launch vehicle leak detection, emission monitoring, and fire detection. Each of these applications reflects efforts ongoing throughout NASA. As described in NASA's "Three Pillars for Success", a document which outlines NASA's long term response to achieve the nation's priorities in aerospace transportation, agency wide objectives include: improving safety and decreasing the cost of space travel, significantly decreasing the amount of emissions produced by aeronautic engines, and improving the safety of commercial airline travel. As will be discussed below, chemical sensing in leak detection, emission monitoring, and fire detection will help enable the agency to meet these objectives. Each application has vastly different problems associated with the measurement of chemical species. Nonetheless, the development of a common base technology can address the measurement needs of a number of applications.

  10. Latest developments for low-power infrared laser-based trace gas sensors for sensor networks

    NASA Astrophysics Data System (ADS)

    So, Stephen; Thomazy, David; Wang, Wen; Marchat, Oscar; Wysocki, Gerard

    2011-09-01

    Academic and industrial researchers require ultra-low power, compact laser based trace-gas sensor systems for the most demanding environmental and space-borne applications. Here the latest results from research projects addressing these applications will be discussed: 1) an ultra-compact CO2 sensor based on a continuous wave quantum cascade laser, 2) an ultra-sensitive Faraday rotation spectrometer for O2 detection, 3) a fully ruggedized compact and low-power laser spectrometer, and 4) a novel non-paraxial nonthin multipass cell. Preliminary tests and projection for performance of future sensors based on this technology is presented.

  11. Development of Taste Sensor with LB Films for Measurement of High-intensity Sweetener

    NASA Astrophysics Data System (ADS)

    Asami, Tetsuya; Hasegawa, Yuki; Ando, Ki; Uchida, Hidekazu; Yaji, Tamaki

    Recently, development of taste sensor is furthered for quality control of foods. In this study, we developed taste sensor with stearic acid LB films for measurement of high-intensity sweetener taste. We measured several high-intensity sweeteners with the number of layers of stearic acid LB films as 10 and 20 layers. And we also measured mixed high-intensity sweeteners. The result showed that the stearic acid LB films taste sensor was used to detect glucose and high-intensity sweeteners at a threshold level of taste. Stearic acid LB films sensor detects different response by mixed ratio of high-intensity sweeteners. In addition, we compared difference of sensor responses by three kind of storing conditions (vacuum vessel, KCl solution and the air storing). The result showed that the structure of stearic acid LB films is easily affected by moisture in storage environment. This study indicated that the modification of stearic acid LB film layers and materials makes it possible to develop high sensitivity and selectivity taste sensor for sweeteners.

  12. Flexible Transparent Films Based on Nanocomposite Networks of Polyaniline and Carbon Nanotubes for High-Performance Gas Sensing.

    PubMed

    Wan, Pengbo; Wen, Xuemei; Sun, Chaozheng; Chandran, Bevita K; Zhang, Han; Sun, Xiaoming; Chen, Xiaodong

    2015-10-01

    A flexible, transparent, chemical gas sensor is assembled from a transparent conducting film of carbon nanotube (CNT) networks that are coated with hierarchically nanostructured polyaniline (PANI) nanorods. The nanocomposite film is synthesized by in-situ, chemical oxidative polymerization of aniline in a functional multiwalled CNT (FMWCNT) suspension and is simultaneously deposited onto a flexible polyethylene terephthalate (PET) substrate. An as-prepared flexible transparent chemical gas sensor exhibits excellent transparency of 85.0% at 550 nm using the PANI/FMWCNT nanocomposite film prepared over a reaction time of 8 h. The sensor also shows good flexibility, without any obvious decrease in performance after 500 bending/extending cycles, demonstrating high-performance, portable gas sensing at room temperature. This superior performance could be attributed to the improved electron transport and collection due to the CNTs, resulting in reliable and efficient sensing, as well as the high surface-to-volume ratio of the hierarchically nanostructured composites. The excellent transparency, improved sensing performance, and superior flexibility of the device, may enable the integration of this simple, low-cost, gas sensor into handheld flexible transparent electronic circuitry and optoelectronic devices. PMID:26294393

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

    SciTech Connect

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

    2012-09-30

    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.

  14. 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

  15. Deposition Of Thin-Film Sensors On Glass-Fiber/Epoxy Models

    NASA Technical Reports Server (NTRS)

    Tran, Sang Q.

    1995-01-01

    Direct-deposition process devised for fabrication of thin-film sensors on three-dimensional, curved surfaces of models made of stainless steel covered with glass-fiber/epoxy-matrix composite material. Models used under cryogenic conditions, and sensors used to detect on-line transitions between laminar and turbulent flows in wind tunnel environments. Sensors fabricated by process used at temperatures from minus 300 degrees F to 175 degrees F.

  16. Microfabricated Thin Film Impedance Sensor & AC Impedance Measurements

    PubMed Central

    Yu, Jinsong; Liu, Chung-Chiun

    2010-01-01

    Thin film microfabrication technique was employed to fabricate a platinum based parallel-electrode structured impedance sensor. Electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis of the small amplitude (±5 mV) AC impedance measurements (frequency range: 1 MHz to 0.1 Hz) at ambient temperature were carried out. Testing media include 0.001 M, 0.01 M, 0.1 M NaCl and KCl solutions, and alumina (?3 ?m) and sand (?300 ?m) particulate layers saturated with NaCl solutions with the thicknesses ranging from 0.6 mm to 8 mm in a testing cell, and the results were used to assess the effect of the thickness of the particulate layer on the conductivity of the testing solution. The calculated resistances were approximately around 20 M?, 4 M?, and 0.5 M? for 0.001 M, 0.01 M, and 0.1 M NaCl solutions, respectively. The presence of the sand particulates increased the impedance dramatically (6 times and 3 times for 0.001 M and 0.1 M NaCl solutions, respectively). A cell constant methodology was also developed to assess the measurement of the bulk conductivity of the electrolyte solution. The cell constant ranged from 1.2 to 0.8 and it decreased with the increase of the solution thickness. PMID:22219690

  17. Adsorption semiconductor gas sensors and heterogeneous catalytic reaction mechanisms

    SciTech Connect

    Vorotyntsev, V.; Maksimovich, N.; Yeremina, L.; Kaskevich, O.; Nikitina, N.

    1996-12-31

    The sufficiently general kinetic characterization of semiconductor gas sensors may be obtained by the analysis of the real mechanisms of chemical reactions which take place on the surface. The authors have considered the reaction model of surface redox processes which was proved to be true for heterogeneous catalytic oxidation by oxygen of a large variety of organic and inorganic substances.

  18. Multichannel Monolithic Quartz Crystal Microbalance Gas Sensor Array

    E-print Network

    Mason, Andrew

    Multichannel Monolithic Quartz Crystal Microbalance Gas Sensor Array Xiaoxia Jin, Yue Huang, Andrew Multichannel Monolithic Quartz Crystal Microbalance (MQCM), in which an array of electrodes is fabricated on a monolithic quartz wafer, is a very attractive approach for miniaturization using Micro-Electro-Mechanical Sys

  19. Dataset from chemical gas sensor array in turbulent wind tunnel

    PubMed Central

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

    2015-01-01

    The dataset includes the acquired time series of a chemical detection platform exposed to different gas conditions in a turbulent wind tunnel. The chemo-sensory elements were sampling directly the environment. In contrast to traditional approaches that include measurement chambers, open sampling systems are sensitive to dispersion mechanisms of gaseous chemical analytes, namely diffusion, turbulence, and advection, making the identification and monitoring of chemical substances more challenging. The sensing platform included 72 metal-oxide gas sensors that were positioned at 6 different locations of the wind tunnel. At each location, 10 distinct chemical gases were released in the wind tunnel, the sensors were evaluated at 5 different operating temperatures, and 3 different wind speeds were generated in the wind tunnel to induce different levels of turbulence. Moreover, each configuration was repeated 20 times, yielding a dataset of 18,000 measurements. The dataset was collected over a period of 16 months. The data is related to “On the performance of gas sensor arrays in open sampling systems using Inhibitory Support Vector Machines”, by Vergara et al.[1]. The dataset can be accessed publicly at the UCI repository upon citation of [1]: http://archive.ics.uci.edu/ml/datasets/Gas+sensor+arrays+in+open+sampling+settings PMID:26217739

  20. Towards a transparent, flexible, scalable and disposable image sensor using thin-film luminescent concentrators.

    PubMed

    Koppelhuber, Alexander; Bimber, Oliver

    2013-02-25

    Most image sensors are planar, opaque, and inflexible. We present a novel image sensor that is based on a luminescent concentrator (LC) film which absorbs light from a specific portion of the spectrum. The absorbed light is re-emitted at a lower frequency and transported to the edges of the LC by total internal reflection. The light transport is measured at the border of the film by line scan cameras. With these measurements, images that are focused onto the LC surface can be reconstructed. Thus, our image sensor is fully transparent, flexible, scalable and, due to its low cost, potentially disposable. PMID:23482014

  1. Electrocatalytic cermet gas detector/sensor

    DOEpatents

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

    1995-01-01

    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.

  2. Polyvinylidene fluoride film sensors in collocated feedback structural control: application for suppressing impact-induced disturbances.

    PubMed

    Ma, Chien-Ching; Chuang, Kuo-Chih; Pan, Shan-Ying

    2011-12-01

    Polyvinylidene fluoride (PVDF) films are light, flexible, and have high piezoelectricity. Because of these advantages, they have been widely used as sensors in applications such as underwater investigation, nondestructive damage detection, robotics, and active vibration suppression. PVDF sensors are especially preferred over conventional strain gauges in active vibration control because the PVDF sensors are easy to cut into different sizes or shapes as piezoelectric actuators and they can then be placed as collocated pairs. In this work, to focus on demonstrating the dynamic sensing performance of the PVDF film sensor, we revisit the active vibration control problem of a cantilever beam using a collocated lead zirconate titanate (PZT) actuator/PVDF film sensor pair. Before applying active vibration control, the measurement characteristics of the PVDF film sensor are studied by simultaneous comparison with a strain gauge. The loading effect of the piezoelectric actuator on the cantilever beam is also investigated in this paper. Finally, four simple, robust active vibration controllers are employed with the collocated PZT/PVDF pair to suppress vibration of the cantilever beam subjected to impact loadings. The four controllers are the velocity feedback controller, the integral resonant controller (IRC), the resonant controller, and the positive position feedback (PPF) controller. Suppression of impact disturbances is especially suitable for the purpose of demonstrating the dynamic sensing performance of the PVDF sensor. The experimental results also provide suggestions for choosing between the previously mentioned controllers, which have been proven to be effective in suppressing impact-induced vibrations. PMID:23443690

  3. Zinc oxide nanowires on carbon microfiber as flexible gas sensor

    NASA Astrophysics Data System (ADS)

    Tonezzer, M.; Lacerda, R. G.

    2012-03-01

    In the past years, zinc oxide nanowires (ZnO NWs) have been proven to be an excellent material for gas sensors. In this work, we used ZnO nanowires in a novel architecture integrated on a carbon microfiber (?C) textile. This innovative design permits us to obtain mechanical flexibility, while the absence of any lithographic technique allows a large-area and low-cost fabrication of gas sensors. The performances of the devices are investigated for both oxidizing and reducing gases. The nano-on-micro structure of the sensor provides a high surface-to-volume ratio, leading to a fast and intense response for both oxygen (O2) and hydrogen (H2) gases. The sensor response has an optimum temperature condition at 280 °C with a response value of 10 for oxygen and 11 for hydrogen. The limit of detection (LoD) has been found to be 2 and 4 ppm for oxygen and hydrogen, respectively. Additionally, the sensor response and recovery time is small being less than 10 s for both O2 and H2.

  4. Performance of a CVD grown graphene-based planar device for a hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Dutta, D.; Hazra, A.; Hazra, S. K.; Das, J.; Bhattacharyya, S.; Sarkar, C. K.; Basu, S.

    2015-11-01

    A multilayer graphene (MLG) film was grown on thermally oxidized silicon (SiO2/Si) substrate by atmospheric pressure chemical vapor deposition (APCVD). The formation of the MLG and the presence of the oxide on the graphene surface were confirmed by Raman spectroscopy and electron dispersive spectroscopy (EDS), respectively. An energy gap of 0.234?eV was determined by the optical transmission method. The surface morphology of the graphene film was studied by field emission scanning electron microscopy (FESEM) and by atomic force microscopy (AFM). A planar device with lateral Pd metal contacts was used for the hydrogen sensor studies. The sensor performance in the temperature range (110 °C–150 °C) revealed a relatively fast response (~12 s) and recovery (~24 s) for hydrogen sensing. The reproducibility, the selectivity, and the stability of the device were also studied. The sensor was found to be selective for hydrogen relative to methane in the temperature range studied. The gas sensing mechanism has been suggested on the basis of the interaction of palladium with hydrogen, the change in the interface barrier, and the adsorption–desorption processes related to the change in the hydrogen partial pressure and temperature. The AFM study indicates the reorientation of the graphene surface after the sensing operation, most probably due to hydrogen passivation.

  5. Optical waveguide lightmode spectroscopy (OWLS) as a sensor for thin film and quantum dot corrosion.

    PubMed

    Yu, Hao; Eggleston, Carrick M; Chen, Jiajun; Wang, Wenyong; Dai, Qilin; Tang, Jinke

    2012-01-01

    Optical waveguide lightmode spectroscopy (OWLS) is usually applied as a biosensor system to the sorption-desorption of proteins to waveguide surfaces. Here, we show that OWLS can be used to monitor the quality of oxide thin film materials and of coatings of pulsed laser deposition synthesized CdSe quantum dots (QDs) intended for solar energy applications. In addition to changes in data treatment and experimental procedure, oxide- or QD-coated waveguide sensors must be synthesized. We synthesized zinc stannate (Zn(2)SnO(4)) coated (Si,Ti)O(2) waveguide sensors, and used OWLS to monitor the relative mass of the film over time. Films lost mass over time, though at different rates due to variation in fluid flow and its physical effect on removal of film material. The Pulsed Laser Deposition (PLD) technique was used to deposit CdSe QD coatings on waveguides. Sensors exposed to pH 2 solution lost mass over time in an expected, roughly exponential manner. Sensors at pH 10, in contrast, were stable over time. Results were confirmed with atomic force microscopy imaging. Limiting factors in the use of OWLS in this manner include limitations on the annealing temperature that maybe used to synthesize the oxide film, and limitations on the thickness of the film to be studied. Nevertheless, the technique overcomes a number of difficulties in monitoring the quality of thin films in-situ in liquid environments. PMID:23443400

  6. 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)

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

    2006-01-01

    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.

  7. Methods for gas detection using stationary hyperspectral imaging sensors

    DOEpatents

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

    2012-04-24

    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.

  8. Nanostructured Gas Sensors for Health Care: An Overview

    PubMed Central

    Kaushik, Ajeet; Kumar, Rajesh; Jayant, Rahul Dev; Nair, Madhavan

    2015-01-01

    Nanostructured platforms have been utilized for fabrication of small, sensitive and reliable gas sensing devices owing to high functionality, enhanced charge transport and electro-catalytic property. As a result of globalization, rapid, sensitive and selective detection of gases in environment is essential for health care and security. Nonmaterial such as metal, metal oxides, organic polymers, and organic-inorganic hybrid nanocomposites exhibit interesting optical, electrical, magnetic and molecular properties, and hence are found potential gas sensing materials. Morphological, electrical, and optical properties of such nanostructures can be tailored via controlling the precursor concentration and synthesis conditions resulting to achieve desired sensing. This review presents applications of nano-enabling gas sensors to detect gases for environment monitoring. The recent update, challenges, and future vision for commercial applications of such sensor are also described here. PMID:26491544

  9. Gas Sensor Evaluations in Polymer Combustion Product Atmospheres

    NASA Technical Reports Server (NTRS)

    Delgado, Rafael H.; Davis, Dennis D.; Beeson, Harold D.

    1999-01-01

    Toxic gases produced by the combustion or thermo-oxidative degradation of materials such as wire insulation, foam, plastics, or electronic circuit boards in space shuttle or space station crew cabins may pose a significant hazard to the flight crew. Toxic gas sensors are routinely evaluated in pure gas standard mixtures, but the possible interferences from polymer combustion products are not routinely evaluated. The NASA White Sands Test Facility (WSTF) has developed a test system that provides atmospheres containing predetermined quantities of target gases combined with the coincidental combustion products of common spacecraft materials. The target gases are quantitated in real time by infrared (IR) spectroscopy and verified by grab samples. The sensor responses are recorded in real time and are compared to the IR and validation analyses. Target gases such as carbon monoxide, hydrogen cyanide, hydrogen chloride, and hydrogen fluoride can be generated by the combustion of poly(vinyl chloride), polyimide-fluoropolymer wire insulation, polyurethane foam, or electronic circuit board materials. The kinetics and product identifications for the combustion of the various materials were determined by thermogravimetric-IR spectroscopic studies. These data were then scaled to provide the required levels of target gases in the sensor evaluation system. Multisensor toxic gas monitors from two manufacturers were evaluated using this system. In general, the sensor responses satisfactorily tracked the real-time concentrations of toxic gases in a dynamic mixture. Interferences from a number of organic combustion products including acetaldehyde and bisphenol-A were minimal. Hydrogen bromide in the products of circuit board combustion registered as hydrogen chloride. The use of actual polymer combustion atmospheres for the evaluation of sensors can provide additional confidence in the reliability of the sensor response.

  10. Gas sensing studies of pulsed laser deposition deposited WO3 nanorod based thin films.

    PubMed

    Ahmad, Muhammad Z; Kang, Joonhee; Zoolfakar, Ahmad S; Sadek, Abu Z; Wlodarski, Wojtek

    2013-12-01

    WO3 nanorod based thin films were deposited via pulsed laser deposition onto quartz conductometric transducers with pre-patterned gold interdigitated transducers (IDT) employing the shortest wavelength (193 nm) ArF excimer laser. Micro-characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to study surface morphology and crystal structure. It was observed that the fabricated films showed nanocolumnar features perpendicular to the surface. The measured sizes of the nanorods were found to be approximately -50 nm in diameter. The high resolution TEM (HRTEM) image of the nanorods based WO3 showed the WO3 lattice spacing of 3.79 angstroms corresponding to the (020) plane of monoclinic WO3. Gas sensing characterizations of the developed sensors were tested towards hydrogen and ethanol at temperatures between room and 400 degrees C. The sensor exhibited high response towards H2 and ethanol at operating temperatures of 170 and 400 degrees C, respectively. The excellent sensing characteristics of WO3 films towards ethanol and H2 at low concentrations offer great potential for low cost and stable gas sensing. PMID:24266229

  11. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  12. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cardiopulmonary bypass in-line blood gas sensor... Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that measures the level of gases in the blood. (b) Classification. Class...

  13. 08ICES-0031 Advanced quartz-enhanced photoacoustic trace gas sensor for

    E-print Network

    08ICES-0031 Advanced quartz-enhanced photoacoustic trace gas sensor for early fire detection A. A A spectroscopic trace gas sensor using a distributed feedback diode laser at =1.53 m and based on quartz enhanced]. In this paper we desribe a multi-species trace gas sensor based on quartz enhanced photoacoustic spectroscopy

  14. Novel diode laser-based sensors for gas sensing applications

    NASA Technical Reports Server (NTRS)

    Tittel, F. K.; Lancaster, D. G.; Richter, D.

    2000-01-01

    The development of compact spectroscopic gas sensors and their applications to environmental sensing will be described. These sensors employ mid-infrared difference-frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystals pumped by two single-frequency solid state lasers such as diode lasers, diode-pumped solid state, and fiber lasers. Ultrasensitive, highly selective, and real-time measurements of several important atmospheric trace gases, including carbon monoxide, nitrous oxide, carbon dioxide, formaldehyde [correction of formaldehye], and methane, have been demonstrated.

  15. Electrocatalytic cermet gas detector/sensor

    DOEpatents

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

    1995-07-04

    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.

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

    PubMed Central

    Kulkarni, Atul; Kim, Byeonghoon; Dugasani, Sreekantha Reddy; Joshirao, Pranav; Kim, Jang Ah; Vyas, Chirag; Manchanda, Vijay; Kim, Taesung; Park, Sung Ha

    2013-01-01

    The unexpected nuclear accidents have provided a challenge for scientists and engineers to develop sensitive detectors, especially for alpha radiation. Due to the high linear energy transfer value, sensors designed to detect such radiation require placement in close proximity to the radiation source. Here we report the morphological changes and optical responses of artificially designed DNA thin films in response to exposure to alpha radiation as observed by an atomic force microscope, a Raman and a reflectance spectroscopes. In addition, we discuss the feasibility of a DNA thin film as a radiation sensing material. The effect of alpha radiation exposure on the DNA thin film was evaluated as a function of distance from an 241Am source and exposure time. Significant reflected intensity changes of the exposed DNA thin film suggest that a thin film made of biomolecules can be one of promising candidates for the development of online radiation sensors. PMID:23792924

  17. Reliability consideration of thin-film temperature sensors in future Space Shuttle propulsion systems

    NASA Astrophysics Data System (ADS)

    Huang, Hsien-Lu

    1994-01-01

    The paper investigates the failure modes of the thin-film thermocouple, high-temperature sensors being newly developed, and it analyzes theoretically the probabilistic risks of flying the Space Shuttle equipped with such new sensors with and without fuel turbine discharge temperature 'redline' protection. Newly observed facts include a new failure mode not associated with the existing thermistor-type sensors and a probability risk math model with three sensors per turbopump. The probability of erroneous engine shutdown is significantly reduced from the existing 37.94(exp -5) to 1.85(exp -5); thus, a better Shuttle engine reliability may be achieved.

  18. Bolometric properties of reactively sputtered TiO2-x films for thermal infrared image sensors

    NASA Astrophysics Data System (ADS)

    Reddy, Y. Ashok Kumar; Kang, In-Ku; Shin, Young Bong; Lee, Hee Chul

    2015-09-01

    A heat-sensitive layer (TiO2-x ) was successfully deposited by RF reactive magnetron sputtering for infrared (IR) image sensors at different relative mass flow of oxygen gas (R O2) levels. The deposition rate was decreased with an increase in the percentage of R O2 from 3.4% to 3.7%. TiO2-x samples deposited at room temperature exhibited amorphous characteristics. Oxygen deficiency causes a change in the oxidation state and is assumed to decrease the Ti4+ component on the surfaces of TiO2-x films. The oxygen stoichiometry (x) in TiO2-x films decreased from 0.35 to 0.05 with increasing the R O2 level from 3.4% to 3.7%, respectively. In TiO2-x -test-patterned samples, the resistivity decreased with the temperature, confirming the typical semiconducting property. The bolometric properties of the resistivity, temperature coefficient of resistance (TCR), and the flicker (1/?f) noise parameter were determined at different x values in TiO2-x samples. The rate of TCR dependency with regard to the 1/?f noise parameter is a universal bolometric parameter (?), acting as the dynamic element in a bolometer. It is high when a sample has a relatively low resistivity (0.82 ?·cm) and a lower 1/?f noise parameter (3.16???×???10-12). The results of this study indicate that reactively sputtered TiO2-x is a viable bolometric material for uncooled IR image sensor devices.

  19. Investigation of substrate-mounted thin-film meteoroid sensors for use in large area impact experiments

    NASA Technical Reports Server (NTRS)

    Carollo, S. F.; Davis, J. M.; Dance, W. E.

    1973-01-01

    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.

  20. Varying potential silicon carbide gas sensor

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

  1. On the dependence of structural and sensing properties of sputtered MoO3 thin films on argon gas flow

    NASA Astrophysics Data System (ADS)

    Khojier, K.; Savaloni, H.; Zolghadr, S.

    2014-11-01

    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.

  2. Novel Gas Sensors for High-Temperature Fossil Fuel Applications

    SciTech Connect

    Palitha Jayaweera; Francis Tanzella

    2005-03-01

    SRI International (SRI) is developing ceramic-based microsensors to detect exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems under this DOE NETL-sponsored research project. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes attached to a solid state electrolyte and are designed to operate at the high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. The sensors can be easily integrated into online monitoring systems for active emission control. The ultimate objective is to develop sensors for multiple gas detection in a single package, along with data acquisition and control software and hardware, so that the information can be used for closed-loop control in novel advanced power generation systems. This report details the Phase I Proof-of-Concept, research activities performed from October 2003 to March 2005. SRI's research work includes synthesis of catalytic materials, sensor design and fabrication, software development, and demonstration of pulse voltammetric analysis of NO, NO{sub 2}, and CO gases on catalytic electrodes.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  4. Ultrasonic performance of the PVDF thin film sensors under thermal fatigue

    NASA Astrophysics Data System (ADS)

    Rathod, Vivek T.; Roy Mahapatra, D.; Jain, Anjana; Gayathri, A.

    2012-04-01

    In the present work, the ultrasonic strain sensing performance of the large area PVDF thin film subjected to the thermal fatigue is studied. The PVDF thin film is prepared using hot press and the piezoelectric phase ( ?-phase) has been achieved by thermo-mechanical treatment and poling under DC field. The sensors used in aircrafts for structural health monitoring applications are likely to be subjected to a wide range of temperature fluctuations which may create thermal fatigue in both aircraft structures and in the sensors. Thus, the sensitivity of the PVDF sensors for thermal fatigue needs to be studied for its effective implementation in the structural health monitoring applications. In present work, the fabricated films have been subjected to certain number of thermal cycles which serve as thermal fatigue and are further tested for ultrasonic strain sensitivity at various different frequencies. The PVDF sensor is bonded on the beam specimen at one end and the ultrasonic guided waves are launched with a piezoelectric wafer bonded on another end of the beam. Sensitivity of PVDF sensor in terms of voltage is obtained for increasing number of thermal cycles. Sensitivity variation is studied at various different extent of thermal fatigue. The variation of the sensor sensitivity with frequency due to thermal fatigue at different temperatures is also investigated. The present investigation shows an appropriate temperature range for the application of the PVDF sensors in structural health monitoring.

  5. Fiber Optic Speed Sensor For Gas Turbine Engine Control

    NASA Astrophysics Data System (ADS)

    Overstreet, Mark A.; Bird, Victor J.; Varshneya, Deepak; Maida, John L.

    1990-02-01

    Allison Gas Turbine Division of General Motors Corporation, with Teledyne Ryan Electronics, has developed and demonstrated a fiber optic speed sensor (FOSS) for application to advanced fiber optic based control systems for gas turbine engines. The subject FOSS is capable of measuring turbine engine rotational speed throughout a speed range of 0-22,000+ rpm, which is equivalent to a sensor bandwidth of approximately 25 KHz. The principle of operation is based on directly sensing the pressure pulses generated by passing turbine blades via a pressure tube, a diaphragm at the top of the pressure tube, and a fiber optic microbend transducer affixed to the diaphragm. Transceiver electronics/optoelectronics are remotely located.

  6. Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors.

    PubMed

    Chen, Siyuan Feng; Aldalbahi, Ali; Feng, Peter Xianping

    2015-01-01

    We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

  7. Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

    PubMed Central

    Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

    2015-01-01

    We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

  8. Sensor and Actuator Needs for More Intelligent Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    Garg, Sanjay; Schadow, Klaus; Horn, Wolfgang; Pfoertner, Hugo; Stiharu, Ion

    2010-01-01

    This paper provides an overview of the controls and diagnostics technologies, that are seen as critical for more intelligent gas turbine engines (GTE), with an emphasis on the sensor and actuator technologies that need to be developed for the controls and diagnostics implementation. The objective of the paper is to help the "Customers" of advanced technologies, defense acquisition and aerospace research agencies, understand the state-of-the-art of intelligent GTE technologies, and help the "Researchers" and "Technology Developers" for GTE sensors and actuators identify what technologies need to be developed to enable the "Intelligent GTE" concepts and focus their research efforts on closing the technology gap. To keep the effort manageable, the focus of the paper is on "On-Board Intelligence" to enable safe and efficient operation of the engine over its life time, with an emphasis on gas path performance

  9. Thin film heat flux sensors for accurate transient and unidirectional heat transfer analysis

    NASA Astrophysics Data System (ADS)

    Azerou, B.; Garnier, B.; Lahmar, J.

    2012-11-01

    Heat flux measurement is needed in many heat transfer studies. For the best unbiased heat flux sensors (HFS), the heat flux is obtained using temperature measurements at different locations and also an inverse heat conduction method (function specification...) in order to calculate the heat flux. Systematic errors can come from the uncertainty in the wire thermocouples locations and from errors in the knowledge of distances between two consecutive wire thermocouples. The main idea in this work is to use thin film thermoresistances deposited on a flexible thin polymer substrate instead of wire thermocouples welded on metallic sample. The interest of using thin film thermoresistances instead of wire thermocouples is a lower disturbance due to the smaller thickness of the thin film sensors (typically less than 1?m) and a much better knowledge of the distances between the different thin film thermoresistances which are precisely defined in the mask used for the metallic thin film pattern fabrication. In this paper, we present the fabrication of the new heat flux sensor with thin film thermoresistances, the study of the effect of the self heating (due to Joule effect in thermoresistances) and the performances of this new HFS with the comparison with classical HFS using wire thermocouples. For this study, a symmetric experimental setup is used with metallic samples equipped with an etched foil heater and both classical and new HFS. For several heating conditions, it appears that a better accuracy is always obtained with the new HFS using thin film thermoresistances.

  10. Preparation and Analysis of Platinum Thin Films for High Temperature Sensor Applications

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Laster, Kimala L. H.

    2005-01-01

    A study has been made of platinum thin films for application as high temperature resistive sensors. To support NASA Glenn Research Center s high temperature thin film sensor effort, a magnetron sputtering system was installed recently in the GRC Microsystems Fabrication Clean Room Facility. Several samples of platinum films were prepared using various system parameters to establish run conditions. These films were characterized with the intended application of being used as resistive sensing elements, either for temperature or strain measurement. The resistances of several patterned sensors were monitored to document the effect of changes in parameters of deposition and annealing. The parameters were optimized for uniformity and intrinsic strain. The evaporation of platinum via oxidation during annealing over 900 C was documented, and a model for the process developed. The film adhesion was explored on films annealed to 1000 C with various bondcoats on fused quartz and alumina. From this compiled data, a list of optimal parameters and characteristics determined for patterned platinum thin films is given.

  11. Characterization of mixed xWO3(1-x)Y2O3 nanoparticle thick film for gas sensing application.

    PubMed

    Abadi, M H Shahrokh; Hamidon, M N; Shaari, Abdul Halim; Abdullah, Norhafizah; Misron, Norhisam; Wagiran, Rahman

    2010-01-01

    Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO(3)(1-x)Y(2)O(3) 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 (CH(4)) and butane (C(4)H(10)) 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

  12. Laser Raman sensor for measurement of trace-hydrogen gas

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  13. Optical Breath Gas Sensor for Extravehicular Activity Application

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

    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.

  14. Fabrication of a miniaturized ionization gas sensor with polyimide spacer

    NASA Astrophysics Data System (ADS)

    Walewyns, T.; Scheen, G.; Tooten, E.; El Fissi, L.; Dupuis, P.; Francis, L. A.

    2011-06-01

    Gas sensing can be achieved by fingerprinting the ionization characteristics of distinct species. In this study, the fabrication of a miniaturized gas ionization sensor using polyimide as sacrificial layer is reported. The sensor consists of two planar metallic electrodes with a gap spacing obtained by the polyimide under-etching. This known sacrificial layer has the advantage besides a high planarization factor, to be CMOS compatible. Furthermore, its chemical resistance up to high temperatures, high resistance to radiation from both electrons and neutrons, and low outgassing are of primary importance to avoid interferences with the ionization gas sensing. A suspended micro-bridge with dimensions 20 ?m width and 220 ?m length has been developed and released by using etching holes in the membrane. The ionization characteristics of air at controlled temperature, humidity and pressure (21°C, 40% humidity and 1 atm) have been obtained during non-destructive electrical characterizations, with a breakdown voltage of 350 V for a 6 ?m gap. The growth of metallic nanowires templated in ion track-etched polyimide on the electrode is envisioned in order to enhance the ionization field and to reduce the required measurement power of the sensor.

  15. On optimization of sensor selection for aircraft gas turbine engines Ramgopal Mushini

    E-print Network

    Simon, Dan

    On optimization of sensor selection for aircraft gas turbine engines Ramgopal Mushini Cleveland sets for the problem of aircraft gas turbine engine health parameter estimation. The performance metric for generating an optimal sensor set [3]. 3. Aircraft gas turbine engines An aircraft gas turbine engine

  16. Determination of partition coefficients from surface acoustic wave vapor sensor responses and correlation with gas-liquid chromatographic partition coefficients

    SciTech Connect

    Grate, J.W.; Snow, A.; Ballantine, D.S. Jr.; Wohltjen, H.; Abraham, M.H.; McGill, R.A.; Sasson, P.

    1988-05-01

    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.

  17. Thin film molybdenum silicide as potential temperature sensors for turbine engines

    NASA Technical Reports Server (NTRS)

    Ho, C. H.; Prakash, S.; Deshpandey, C. V.; Doerr, H. J.; Bunshah, R. F.

    1989-01-01

    Temperature measurements of Mo-Si-based thin-film resistance thermometers were studied. Annealing in an argon ambient at a temperature above 1000 C for at least 1 h is required to form the stable tetragonal MoSi2 phase. With a crack-free 2-micron-thick AlN barrier layer on top, a sensor was tested up to 1200 C. The resistivity vs temperature characteristic shows the room temperature resistivity and temperature coefficient of resistivity (TCR) of the sensor to be approximately 350 microohm and 0.01195 K, respectively. No film adhesion problems were observed for at least four testing cycles.

  18. Ceramic thick film humidity sensor based on MgTiO{sub 3} + LiF

    SciTech Connect

    Kassas, Ahmad; Bernard, Jérôme; Lelièvre, Céline; Besq, Anthony; Guhel, Yannick; Houivet, David; Boudart, Bertrand; Lakiss, Hassan; Hamieh, Tayssir

    2013-10-15

    Graphical abstract: - Highlights: • The fabricated sensor based on MgTiO{sub 3} + LiF materials used the spin coating technology. • The response time is 70 s to detect variation between 5 and 95% relative humidity. • The addition of Scleroglucan controls the viscosity and decreases the roughness of thick film surface. • This humidity sensor is a promising, low-cost, high-quality, reliable ceramic films, that is highly sensitive to humidity. - Abstract: The feasibility of humidity sensor, consisting of a thick layer of MgTiO{sub 3}/LiF materials on alumina substrate, was studied. The thermal analysis TGA-DTGA and dilatometric analysis worked out to confirm the sintering temperature. An experimental plan was applied to describe the effects of different parameters in the development of the thick film sensor. Structural and microstructural characterizations of the developed thick film were made. Rheological study with different amounts of a thickener (scleroglucan “sclg”), showing the behavior variation, as a function of sclg weight % was illustrated and rapprochement with the results of thickness variation as a function of angular velocity applied in the spin coater. The electrical and dielectric measurements confirmed the sensitivity of the elaborated thick film against moisture, along with low response time.

  19. Vapor pressures and gas-film coefficients for ketones

    USGS Publications Warehouse

    Rathbun, R.E.; Tai, D.Y.

    1987-01-01

    Comparison of handbook vapor pressures for seven ketones with more recent literature data showed large differences for four of the ketones. Gas-film coefficients for the volatilization of these ketones from water determined by two different methods were in reasonable agreement. ?? 1987.

  20. 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...

  1. Laser Spectroscopic Trace-Gas Sensor Networks for Atmospheric Monitoring Applications

    E-print Network

    Zhong, Lin

    Laser 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 a laser based chemical sensing technology with wide-area autonomous wireless sensor networking

  2. Highly Sensitive and Selective NiO Film / K+ -Exchanged Glass Composite Optical Waveguide Sensor for Chlorobenzene Vapor Detection

    NASA Astrophysics Data System (ADS)

    Abulaiti, Hairisha; Yimiti, Abulizi; Talifu, Dilinuer; Abudureheman, Adalaiti

    2011-08-01

    In this paper, we propose a new and simple NiO-based Chlorobenzene vapor optical waveguide (OWG) sensor. The highly sensitive element of this sensor was made by coating the nickel oxide film over a single-mode potassium ion (K+) exchanged glass OWG. Sensitivity of the NiO film composite OWG sensor was estimated by the change of absorption properties of the film. The sensor has a linear response to Chlorobenzene concentration, and sensitivity up to 1.8ppm. Moreover, it shows a satisfactory repeatability and a low sensitivity to common interfering gases such as benzene, toluene, xylene and ethanol vapors.

  3. Nanocomposite thin films for optical gas sensing

    SciTech Connect

    Ohodnicki, Paul R; Brown, Thomas D

    2014-06-03

    The disclosure relates to a plasmon resonance-based method for gas sensing in a gas stream utilizing a gas sensing material. In an embodiment the gas stream has a temperature greater than about 500.degree. C. The gas sensing material is comprised of gold nanoparticles having an average nanoparticle diameter of less than about 100 nanometers dispersed in an inert matrix having a bandgap greater than or equal to 5 eV, and an oxygen ion conductivity less than approximately 10.sup.-7 S/cm at a temperature of 700.degree. C. Exemplary inert matrix materials include SiO.sub.2, Al.sub.2O.sub.3, and Si.sub.3N.sub.4 as well as modifications to modify the effective refractive indices through combinations and/or doping of such materials. Changes in the chemical composition of the gas stream are detected by changes in the plasmon resonance peak. The method disclosed offers significant advantage over active and reducible matrix materials typically utilized, such as yttria-stabilized zirconia (YSZ) or TiO.sub.2.

  4. Gas permeability measurements for film envelope materials

    DOEpatents

    Ludtka, Gerard M. (Oak Ridge, TN); Kollie, Thomas G. (Oak Ridge, TN); Watkin, David C. (Clinton, TN); Walton, David G. (Knoxville, TN)

    1998-01-01

    Method and apparatus for measuring the permeability of polymer film materials such as used in super-insulation powder-filled evacuated panels (PEPs) reduce the time required for testing from several years to weeks or months. The method involves substitution of a solid non-outgassing body having a free volume of between 0% and 25% of its total volume for the usual powder in the PEP to control the free volume of the "body-filled panel". Pressure versus time data for the test piece permit extrapolation to obtain long term performance of the candidate materials.

  5. Gas permeability measurements for film envelope materials

    DOEpatents

    Ludtka, G.M.; Kollie, T.G.; Watkin, D.C.; Walton, D.G.

    1998-05-12

    Method and apparatus for measuring the permeability of polymer film materials such as used in super-insulation powder-filled evacuated panels (PEPs) reduce the time required for testing from several years to weeks or months. The method involves substitution of a solid non-outgassing body having a free volume of between 0% and 25% of its total volume for the usual powder in the PEP to control the free volume of the ``body-filled panel.`` Pressure versus time data for the test piece permit extrapolation to obtain long term performance of the candidate materials. 4 figs.

  6. Sensitivity of Micro Cantilever Mass Sensor Transduced by PZT Film

    NASA Astrophysics Data System (ADS)

    Lu, Jian; Ikehara, Tsuyoshi; Konno, Mitsuo; Maeda, Ryutaro; Mihara, Takashi

    Piezoelectric thin film transduced micro resonator offers competitive potential applications in mass sensing technology because of its low driving-voltage, self-actuation self-sensation capability and better impedance-matching with electronics. In this paper, the authors fabricated PZT cantilevers with different geometries and PZT thicknesses. Then the authors investigated the essential aspects of the PZT cantilever for mass-detection sensitivity from the viewpoint of mechanical quality factor of the cantilever and piezoelectric induced output of the PZT film. It was found that the mass-detection sensitivity of the cantilever was improved at thicker PZT film under atmospheric conditions by taking advantage of quality factor. The sensitivity can be further improved several times when pressure was reduced into the molecular flow region and the intrinsic region. For a given material properties and structural layer thickness, the cantilever with thicker PZT film was expected to exhibit high open circuit voltage output, while the cantilever with thinner PZT film was expected to show high piezoelectric charge output. In addition, the residual stress of PZT film was found decreased at thicker film. The effects of residual stress in PZT film on cantilever's sensitivity were therefore discussed in this paper.

  7. Design and fabrication of a CMOS-compatible MHP gas sensor

    SciTech Connect

    Li, Ying; Yu, Jun Wu, Hao; Tang, Zhenan

    2014-03-15

    A novel micro-hotplate (MHP) gas sensor is designed and fabricated with a standard CMOS technology followed by post-CMOS processes. The tungsten plugging between the first and the second metal layer in the CMOS processes is designed as zigzag resistor heaters embedded in the membrane. In the post-CMOS processes, the membrane is released by front-side bulk silicon etching, and excellent adiabatic performance of the sensor is obtained. Pt/Ti electrode films are prepared on the MHP before the coating of the SnO{sub 2} film, which are promising to present better contact stability compared with Al electrodes. Measurements show that at room temperature in atmosphere, the device has a low power consumption of ?19 mW and a rapid thermal response of 8 ms for heating up to 300 °C. The tungsten heater exhibits good high temperature stability with a slight fluctuation (<0.3%) in the resistance at an operation temperature of 300 °C under constant heating mode for 336 h, and a satisfactory temperature coefficient of resistance of about 1.9‰/°C.

  8. Sub-ppm multi-gas photoacoustic sensor.

    PubMed

    Besson, Jean-Philippe; Schilt, Stéphane; Thévenaz, Luc

    2006-04-01

    A photoacoustic multi-gas sensor using tuneable laser diodes in the near-infrared region is reported. An optimized resonant configuration based on an acoustic longitudinal mode is described. Automatic tracking of the acoustic resonance frequency using a piezo-electric transducer and a servo electronics is demonstrated. Water vapour, methane and hydrogen chloride have been measured at sub-ppm level in different buffer gas mixtures. The importance of the system calibration in presence of several diluting gases is discussed. Finally, trace gas measurements have been assessed and detection limits (signal-to-noise ratio=3) of 80 ppb at 1651.0 nm for CH(4), 24 ppb at 1368.6 nm for H(2)O and 30 ppb at 1737.9 for HCl have been demonstrated. PMID:16495131

  9. [A mobile sensor for remote detection of natural gas leakage].

    PubMed

    Zhang, Shuai; Liu, Wen-qing; Zhang, Yu-jun; Kan, Rui-feng; Ruan, Jun; Wang, Li-ming; Yu, Dian-qiang; Dong, Jin-ting; Han, Xiao-lei; Cui, Yi-ben; Liu, Jian-guo

    2012-02-01

    The detection of natural gas pipeline leak becomes a significant issue for body security, environmental protection and security of state property. However, the leak detection is difficult, because of the pipeline's covering many areas, operating conditions and complicated environment. A mobile sensor for remote detection of natural gas leakage based on scanning wavelength differential absorption spectroscopy (SWDAS) is introduced. The improved soft threshold wavelet denoising was proposed by analyzing the characteristics of reflection spectrum. And the results showed that the signal to noise ratio (SNR) was increased three times. When light intensity is 530 nA, the minimum remote sensitivity will be 80 ppm x m. A widely used SWDAS can make quantitative remote sensing of natural gas leak and locate the leak source precisely in a faster, safer and more intelligent way. PMID:22512213

  10. Miniature Hall sensor based ac susceptometer for measurements of vortex and superfluid dynamics in superconducting films

    NASA Astrophysics Data System (ADS)

    Senapati, K.; Chakrabarty, S.; Sahoo, Leena K.; Budhani, R. C.

    2004-01-01

    A highly sensitive ac susceptometer has been fabricated using a commercially available thin film Hall sensor of effective area 25×25 ?m2. This instrument allows measurements of superfluid density and dynamical behavior of vortices in thin film superconductors over a broad range of frequency (10 Hz-100 kHz), temperature (4.2-300 K), and ac-field amplitude (2-150 Oe), and in static magnetic field as high as 5 T collinear with the ac field. The applicability of the susceptometer has been tested on Y1Ba2Cu3O7 films of thickness as small as ˜7 nm.

  11. Potassium polytitanate gas-sensor study by impedance spectroscopy.

    PubMed

    Fedorov, F S; Varezhnikov, A S; Kiselev, I; Kolesnichenko, V V; Burmistrov, I N; Sommer, M; Fuchs, D; Kübel, C; Gorokhovsky, A V; Sysoev, V V

    2015-10-15

    Nanocrystalline potassium polytitanates K2O·nTiO2·mH2O represent a new type of semiconducting compounds which are characterized by a high specific surface that makes them promising for use in gas sensors. In this work, we have studied potassium polytitanate mesoporous nanoparticle agglomerates placed over a SiO2/Si substrate equipped with multiple coplanar electrodes to measure the electrical response to various organic vapors, 1000 ppm of concentration, mixed with air by impedance spectrometry in range of the 10(-2)-10(6) Hz. The recorded impedance data for each sensor segment are associated with RC components of an equivalent circuit which are applied to selectively recognize the test vapors exploiting a "multisensor array" approach. PMID:26515008

  12. A stretchable strain sensor based on a metal nanoparticle thin film for human motion detection.

    PubMed

    Lee, Jaehwan; Kim, Sanghyeok; Lee, Jinjae; Yang, Daejong; Park, Byong Chon; Ryu, Seunghwa; Park, Inkyu

    2014-10-21

    Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness. PMID:25175360

  13. Mesoporous Thin-Film on Highly-Sensitive Resonant Chemical Sensor for Relative Humidity and CO2 Detection

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    Mesoporous Thin-Film on Highly-Sensitive Resonant Chemical Sensor for Relative Humidity and CO2 for relative humidity and CO2 detection. Using mesoporous silica thin-film, we report one of the lowest volume for relative humidity and CO2 detection. The applied thin-films were first characterized through high

  14. Effect of Additives on LiMo3Se3 Nanowire Film Chemical Sensors Xiubin Qi, Frank E. Osterloh,*, J. A. Giacomo, and S. Chiang*,

    E-print Network

    Chiang, Shirley

    Effect of Additives on LiMo3Se3 Nanowire Film Chemical Sensors Xiubin Qi, Frank E. Osterloh,*, J. A nanowire film sensors to bind and detect organic solvents electrically. Both additives decrease are involved in analyte binding in native LiMo3Se3 films and that a programming of LiMo3Se3 nanowire film

  15. Optical Sensors based on single arm thin film Waveguide Interferometer

    NASA Technical Reports Server (NTRS)

    Sarkisov, Sergey S.

    1998-01-01

    The second achievement meets the second objective for the second year. We choose adjustable prism couplers for connecting the sensor to optical fiber lines in our design of a breadboard prototype of the sensor. These couplers have good coupling efficiency at relatively low cost comparing to any other alternatives such as grating couplers. The third accomplishment meets the third objective for the second year. We performed testing the breadboard prototype of the sensor using heating as a technique of changing its refractive index. The only difference is that we ruled out the channel waveguides as irrelevant to the final goals of the project. The feasibility of the sensor can be shown for the slab waveguide configuration without usage of relatively expensive technologies of channel waveguide delineation.

  16. Gas sensor technology at Sandia National Laboratories: Catalytic gate, Surface Acoustic Wave and Fiber Optic Devices

    SciTech Connect

    Hughes, R.C.; Moreno, D.J.; Jenkins, M.W.; Rodriguez, J.L.

    1993-10-01

    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.

  17. A stretchable strain sensor based on a metal nanoparticle thin film for human motion detection

    NASA Astrophysics Data System (ADS)

    Lee, Jaehwan; Kim, Sanghyeok; Lee, Jinjae; Yang, Daejong; Park, Byong Chon; Ryu, Seunghwa; Park, Inkyu

    2014-09-01

    Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness.Wearable strain sensors for human motion detection are being highlighted in various fields such as medical, entertainment and sports industry. In this paper, we propose a new type of stretchable strain sensor that can detect both tensile and compressive strains and can be fabricated by a very simple process. A silver nanoparticle (Ag NP) thin film patterned on the polydimethylsiloxane (PDMS) stamp by a single-step direct transfer process is used as the strain sensing material. The working principle is the change in the electrical resistance caused by the opening/closure of micro-cracks under mechanical deformation. The fabricated stretchable strain sensor shows highly sensitive and durable sensing performances in various tensile/compressive strains, long-term cyclic loading and relaxation tests. We demonstrate the applications of our stretchable strain sensors such as flexible pressure sensors and wearable human motion detection devices with high sensitivity, response speed and mechanical robustness. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03295k

  18. Homogenization studies for optical sensors based on sculptured thin films 

    E-print Network

    Jamaian, Siti Suhana

    2013-07-01

    In this thesis we investigate theoretically various types of sculptured thin film (STF) envisioned as platforms for optical sensing. A STF consists of an array of parallel nanowires which can be grown on a substrate using ...

  19. Surface Plasmon Sensor Based on the Enhanced Light Transmission through Arrays of Nanoholes in Gold Films

    E-print Network

    Brolo, Alexandre G.

    Surface Plasmon Sensor Based on the Enhanced Light Transmission through Arrays of Nanoholes in Gold of nanoholes in a gold film were used to monitor the binding of organic and biological molecules upon the resonant surface plasmon enhanced transmission through the array of nanoholes. The sensitivity

  20. TiO2 nanoparticle thin film-coated optical fiber Fabry-Perot sensor.

    PubMed

    Jiang, Mingshun; Li, Qiu-Shun; Wang, Jun-Nan; Jin, Zhongwei; Sui, Qingmei; Ma, Yaohong; Shi, Jianguo; Zhang, Faye; Jia, Lei; Yao, Wei-Guo; Dong, Wen-Fei

    2013-02-11

    In this paper, a novel TiO(2) nanoparticle thin film coated optical fiber Fabry-Perot (F-P) sensor had been developed for refractive index (RI) sensing by monitoring the shifts of the fringe contrast in the reflectance spectra. Using in situ liquid phase deposition approach, the TiO(2) nanoparticle thin film could be formed on the fiber surface in a controlled fashion. The optical properties of as-prepared F-P sensors were investigated both theoretically and experimentally. The results indicated that the RI sensitivity of F-P sensors could be effectively improved after the deposition of nanoparticle thin-films. It was about 69.38 dB/RIU, which was 2.6 times higher than that of uncoated one. The linear RI measurement range was also extended from 1.333~1.457 to 1.333~1.8423. More importantly, its optical properties exhibited the unique temperature-independent performance. Therefore, owing to these special optical properties, the TiO(2) nanoparticle thin film coated F-P sensors have great potentials in medical diagnostics, food quality testing, environmental monitoring, biohazard detection and homeland security, even at elevated temperature. PMID:23481766

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

    E-print Network

    Raghavan, Srinivasa

    demonstrated how low oxygen levels lead to vasoocclusion in sickle cell anemia.7 Cancer cells that existA Noninvasive Thin Film Sensor for Monitoring Oxygen Tension during in Vitro Cell Culture Peter C of Maryland, College Park, Maryland 20742, and SAIC, Arlington, VA 22203 Oxygen tension in mammalian cell

  2. A wafer-level liquid cavity integrated amperometric gas sensor with ppb-level nitric oxide gas sensitivity

    NASA Astrophysics Data System (ADS)

    Gatty, Hithesh K.; Stemme, Göran; Roxhed, Niclas

    2015-10-01

    A miniaturized amperometric nitric oxide (NO) gas sensor based on wafer-level fabrication of electrodes and a liquid electrolyte chamber is reported in this paper. The sensor is able to detect NO gas concentrations of the order of parts per billion (ppb) levels and has a measured sensitivity of 0.04 nA ppb-1 with a response time of approximately 12 s. A sufficiently high selectivity of the sensor to interfering gases such as carbon monoxide (CO) and to ammonia (NH3) makes it potentially relevant for monitoring of asthma. In addition, the sensor was characterized for electrolyte evaporation which indicated a sensor operation lifetime allowing approximately 200 measurements.

  3. An interferometric humidity sensor based on a thin gelatin film

    NASA Astrophysics Data System (ADS)

    Calixto, Sergio; Montes-Perez, Areli

    2014-07-01

    Gelatin thin films inserted in a Mach - Zehnder interferometer were used to monitor Relative Humidity (RH). When RH varied, gelatin film thickness and refractive index also changed. As a result interference pattern moved horizontally. A fixed detector, with a pinhole in front of it, was placed at the interference pattern. It sampled the pattern when it moved. These intensity values were used to find a calibration plot relating intensity as a function of RH.

  4. Thin-Film Air-Mass-Flow Sensor of Improved Design Developed

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Wrbanek, John D.; Hwang, Danny P.

    2003-01-01

    Researchers at the NASA Glenn Research Center have developed a new air-mass-flow sensor to solve the problems of existing mass flow sensor designs. NASA's design consists of thin-film resistors in a Wheatstone bridge arrangement. The resistors are fabricated on a thin, constant-thickness airfoil to minimize disturbance to the airflow being measured. The following photograph shows one of NASA s prototype sensors. In comparison to other air-mass-flow sensor designs, NASA s thin-film sensor is much more robust than hot wires, causes less airflow disturbance than pitot tubes, is more accurate than vane anemometers, and is much simpler to operate than thermocouple rakes. NASA s thin-film air-mass-flow sensor works by converting the temperature difference seen at each leg of the thin-film Wheatstone bridge into a mass-flow rate. The following figure shows a schematic of this sensor with air flowing around it. The sensor operates as follows: current is applied to the bridge, which increases its temperature. If there is no flow, all the arms are heated equally, the bridge remains in balance, and there is no signal. If there is flow, the air passing over the upstream legs of the bridge reduces the temperature of the upstream legs and that leads to reduced electrical resistance for those legs. After the air has picked up heat from the upstream legs, it continues and passes over the downstream legs of the bridge. The heated air raises the temperature of these legs, increasing their electrical resistance. The resistance difference between the upstream and downstream legs unbalances the bridge, causing a voltage difference that can be amplified and calibrated to the airflow rate. Separate sensors mounted on the airfoil measure the temperature of the airflow, which is used to complete the calculation for the mass of air passing by the sensor. A current application for air-mass-flow sensors is as part of the intake system for an internal combustion engine. A mass-flow sensor is used to provide accurate information about the amount of air entering the engine so that the amount of fuel can be adjusted to give the most efficient combustion. The ideal mass-flow sensor would be a rugged design that minimizes the disturbance to the flow stream and provides an accurate reading of both smooth and turbulent flows; NASA's design satisfies these requirements better than any existing design. Most of the mass-flow sensors used today are the hot wire variety. Hot wires can be fragile and cannot accurately measure a turbulent or reversing flow, which is often encountered in an intake manifold. Other types of mass-flow sensors include pitot tubes, vane anemometers, and thermocouple rakes-all of which suffer from some type of performance problem. Because it solves these performance problems while maintaining a simple design that lends itself to low-cost manufacturing techniques, NASA s thin-film resistance temperature detector air-mass-flow sensor should lead to more widespread use of mass-flow sensors.

  5. Development of a Prototype Optical Hydrogen Gas Sensor Using a Getter-Doped Polymer Transducer for Monitoring Cumulative Exposure: Preliminary Results

    SciTech Connect

    Small IV, W; Maitland, D J; Wilson, T S; Bearinger, J P; Letts, S A; Trebes, J E

    2008-06-05

    A novel prototype optical sensor for monitoring cumulative hydrogen gas exposure was fabricated and evaluated. Chemical-to-optical transduction was accomplished by detecting the intensity of 670 nm laser light transmitted through a hydrogen getter-doped polymer film mounted at the end of an optical fiber; the transmittance of the composite film increased with uptake of hydrogen by the embedded getter. The composite film consisted of the hydrogen getter 1,4-bis(phenylethynyl)benzene, also known as DEB, with carbon-supported palladium catalyst embedded in silicone elastomer. Because the change in transmittance was irreversible and occurred continuously as the getter captured hydrogen, the sensor behaved like a dosimeter, providing a unique indication of the cumulative gas exposure.

  6. Optical Breath Gas Sensor for Extravehicular Activity Application

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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. .

  7. Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion

    SciTech Connect

    Thornton, J.D.; Chorpening, B.T.; Sidwell, T.; Strakey, P.A.; Huckaby, E.D.; Benson, K.J.

    2007-05-01

    The use of hydrogen augmented fuel is being investigated by various researchers as a method to extend the lean operating limit, and potentially reduce thermal NOx formation in natural gas fired lean premixed (LPM) combustion systems. The resulting increase in flame speed during hydrogen augmentation, however, increases the propensity for flashback in LPM systems. Real-time in-situ monitoring of flashback is important for the development of control strategies for use of hydrogen augmented fuel in state-of-the-art combustion systems, and for the development of advanced hydrogen combustion systems. The National Energy Technology Laboratory (NETL) and Woodward Industrial Controls are developing a combustion control and diagnostics sensor (CCADS), which has already been demonstrated as a useful sensor for in-situ monitoring of natural gas combustion, including detection of important combustion events such as flashback and lean blowoff. Since CCADS is a flame ionization sensor technique, the low ion concentration produced in pure hydrogen combustion raises concerns of whether CCADS can be used to monitor flashback in hydrogen augmented combustion. This paper discusses CCADS tests conducted at 0.2-0.6 MPa (2-6 atm), demonstrating flashback detection with fuel compositions up to 80% hydrogen (by volume) mixed with natural gas. NETL’s Simulation Validation (SimVal) combustor offers full optical access to pressurized combustion during these tests. The CCADS data and high-speed video show the reaction zone moves upstream into the nozzle as the hydrogen fuel concentration increases, as is expected with the increased flame speed of the mixture. The CCADS data and video also demonstrate the opportunity for using CCADS to provide the necessary in-situ monitor to control flashback and lean blowoff in hydrogen augmented combustion applications.

  8. Absolute and differential measurement of water vapor supersaturation using a commercial thin-film sensor

    NASA Astrophysics Data System (ADS)

    Chng, C. K.; Yu, H.; Libbrecht, K. G.

    2000-01-01

    We describe a technique for measuring the water vapor supersaturation of normal air over a temperature range of -40?T?0 °C. The measurements use an inexpensive commercial hygrometer which is based on a thin-film capacitive sensor. The time required for the sensor to reach equilibrium was found to increase exponentially with decreasing sensor temperature, exceeding 2 min for T=-30 °C; however, the water vapor sensitivity of the device remained high down to this temperature. After calibrating our measurement procedure, we found residual scatter in the data corresponding to an uncertainty in the absolute water vapor pressure of about ±15%. This scatter was due mainly to long-term drift, which appeared to be intrinsic to the capacitive thin-film sensor. The origin of this drift is not clear, but it effectively limits the applicability of this instrument for absolute measurements. We also found, however, that the high sensitivity of the thin-film sensor makes it rather well suited for differential measurements. By comparing supersaturated and saturated air at the same temperature we obtained a relative measurement uncertainty of about ±1.5%, an order of magnitude better than the absolute measurements.

  9. Photometer for monitoring the thickness of inkjet printed films for organic electronic and sensor applications.

    PubMed

    Im, Jisun; Sengupta, Sandip K; Whitten, James E

    2010-03-01

    Inkjet printed organic thin films are being used for a variety of electronic and sensor applications with advantages that include ease of fabrication and reproducibility. Construction and use of a low-cost photometer based on a light-emitting diode (LED) light source and a photodiode detector are described. The photometer attaches to the exit of the printer with the transparent substrate onto which the film is printed passing between the LED and photodiode. By measuring the output voltage of the detector, the transmittance and absorbance of the inkjet printed film can be calculated in real-time. Since absorbance is linearly proportional to thickness in the Beer-Lambert regime, the thickness of the film may be monitored and controlled by varying the number of passes through the printer. Use of the photometer is demonstrated for inkjet printed films of monolayer-protected colloidal gold nanoparticles that function as chemical vapor sensors. The photometer may find applications in both research and quality control related to the manufacture of organic electronic devices and sensors and enables "feedback-controlled" inkjet printing. PMID:20370198

  10. Photometer for monitoring the thickness of inkjet printed films for organic electronic and sensor applications

    NASA Astrophysics Data System (ADS)

    Im, Jisun; Sengupta, Sandip K.; Whitten, James E.

    2010-03-01

    Inkjet printed organic thin films are being used for a variety of electronic and sensor applications with advantages that include ease of fabrication and reproducibility. Construction and use of a low-cost photometer based on a light-emitting diode (LED) light source and a photodiode detector are described. The photometer attaches to the exit of the printer with the transparent substrate onto which the film is printed passing between the LED and photodiode. By measuring the output voltage of the detector, the transmittance and absorbance of the inkjet printed film can be calculated in real-time. Since absorbance is linearly proportional to thickness in the Beer-Lambert regime, the thickness of the film may be monitored and controlled by varying the number of passes through the printer. Use of the photometer is demonstrated for inkjet printed films of monolayer-protected colloidal gold nanoparticles that function as chemical vapor sensors. The photometer may find applications in both research and quality control related to the manufacture of organic electronic devices and sensors and enables "feedback-controlled" inkjet printing.

  11. Effects of Activation Energy to Transient Response of Semiconductor Gas Sensor

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Ohtani, Tatsuki

    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.

  12. Gas sensor characterization at low concentrations of natural oils

    NASA Astrophysics Data System (ADS)

    Sambemana, H.; Siadat, M.; Lumbreras, M.

    2009-05-01

    Inhalation of essential oils can be used in aromatherapy due to their activating or relaxing effects. The study of these effects requires behavioral measurements on living subjects, by varying the nature and also the quantity of the volatile substances to be present in the atmosphere. So, to permit the evaluation of therapeutic effects of a variety of natural oils, we propose to develop an automatic diffusion/detection system capable to create an ambient air with low stabilized concentration of chosen oil. In this work, we discuss the performance of an array of eight gas sensors to discriminate low and constant concentrations of a chosen natural oil.

  13. Intelligent optical fiber sensor system for measurement of gas concentration

    NASA Astrophysics Data System (ADS)

    Pan, Jingming; Yin, Zongmin

    1991-08-01

    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.

  14. Honeycomb-like periodic porous LaFeO? thin film chemiresistors with enhanced gas-sensing performances.

    PubMed

    Dai, Zhengfei; Lee, Chul-Soon; Kim, Bo-Young; Kwak, Chang-Hoon; Yoon, Ji-Wook; Jeong, Hyun-Mook; Lee, Jong-Heun

    2014-09-24

    The use of composite materials and polynary compounds is a promising strategy to promote conductometric sensor performances. The perovskite oxides provide various compositional combinations between different oxides for tuning gas-sensing reaction and endowing rich oxygen deficiencies for preferable gas adsorption. Herein, a sacrificial colloidal template approach is exploited to fabricate crystalline ternary LaFeO3 perovskite porous thin films, by transferring a La(3+)-Fe(3+) hybrid solution-dipped template onto a substrate and sequent heat treatment. The honeycomb-like LaFeO3 film consisted of monolayer periodic pore (size: ? 500 nm) array can be successfully in situ synthesized in a homogeneous layout with a single phase of perovskite. This periodic porous LaFeO3 film with p-type semiconductivity exhibits a high gas response, fast response (?4 s), trace detection capacity (50 ppb), and favorable ethanol selectivity from similar acetone. It exhibits enhanced sensing performances compared to those of a binary n-type Fe2O3 film and a nontemplated dense LaFeO3 film. In addition, a five-axe spiderweb diagram is introduced to make a feasible evaluation of the optimal practical work condition, comprehensively regarding the response/recovery rate, gas response, selectivity and operating temperature. The enhanced ethanol sensing mechanism of honeycomb-like LaFeO3 periodic porous film is also addressed. This novel and facile route to fabricate well-ordered porous LaFeO3 thin film can also be applied to many fields to obtain special performances, such as solar cells, ion conductors, gas separation, piezoelectricity, and self-powered sensing device system. PMID:25166756

  15. Convective response of a wall-mounted hot-film sensor in a shock tube

    NASA Technical Reports Server (NTRS)

    Roberts, A. Sidney, Jr.; Ortgies, Kelly R.; Gartenberg, Ehud; Carraway, Debra L.

    1991-01-01

    Shock tube experiments were performed in order to determine the response of a single hot-film element of a sensor array to transiently induced flow behind weak normal shock waves. The experiments attempt to isolate the response due only to the change in convective heat transfer at the hot-film surface mounted on the wall of the shock tube. The experiments are described, the results being correlated with transient boundary layer theory and compared with an independent set of experimental results. One of the findings indicates that the change in the air properties (temperature and pressure) precedes the air mass transport, causing an ambiguity in the sensor response to the development of the velocity boundary layer. Also, a transient, local heat transfer coefficient is formulated to be used as a forcing function in an hot-film instrument model and simulation which remains under investigation.

  16. Field testing the Raman gas composition sensor for gas turbine operation

    SciTech Connect

    Buric, M.; Chorpening, B.; Mullem, J.; Ranalli, J.; Woodruff, S.

    2012-01-01

    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.

  17. Two-dimensional ZnO nanowalls for gas sensor and photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Chang, Sheng-Po; Wen, Chen-Hua; Chang, Shoou-Jinn

    2014-07-01

    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.

  18. Molecularly imprinted polymer films for reflectometric interference spectroscopic sensors.

    PubMed

    Belmont, Anne-Sophie; Jaeger, Stefanie; Knopp, Dietmar; Niessner, Reinhard; Gauglitz, Guenter; Haupt, Karsten

    2007-06-15

    Reflectometric interference spectroscopic measurements were performed on molecularly imprinted polymer (MIP) films with the herbicide atrazine as the template molecule. A conventional imprinting protocol was used relying on non-covalent interactions between the functional monomers and the template. The MIPs were deposited on glass transducers by two different methods: spin-coating followed by in situ polymerization of thin films of monomers containing a sacrificial polymeric porogen, and autoassembly of MIP nanoparticles with the aid of an associative linear polymer. Reproducible results were obtained upon measurements of atrazine solutions in toluene with both films. Atrazine concentrations as low as 1.7 ppm could be detected with the autoassembled particle film. No or very little analyte adsorption was observed onto non-imprinted control films made by spin-coating and by particle assembly, respectively. We believe that these MIP layers in combination with the general reflectrometric transduction scheme could be a versatile sensing tool for the detection of environmentally important and other analytes. PMID:17368014

  19. Temperature sensor based on composite film of vanadium complex (VO2(3-fl)) and CNT

    NASA Astrophysics Data System (ADS)

    Karimov, Kh. S.; Mahroof-Tahir, M.; Saleem, M.; Tariq Saeed Chani, M.; Niaz, A. Khan

    2015-07-01

    A vanadium complex (VO2(3-fl)) and CNT composite film based temperature sensor is reported in this study. Surface-type silver electrodes were deposited on the glass substrates. A thin film of VO2(3-fl) and CNT composite was coated as a temperature-sensing material on the top of the pre-patterned Ag electrodes. The temperature-sensing principle of the sensor was based on the conductivity change of the coated sensing element upon heating or cooling processes. DC and AC (100 Hz) resistances of the temperature sensor decreased quasilinearly with increasing the temperature in the range of 25-80 °C. The overall resistance of the sensor decreases by 1.8-2.1 and 1.9-2.0 times at DC and AC voltage, respectively. The resistance temperature coefficients of the sensor were in the range of -(0.9-1.3)% and -(1.1-1.3)% at DC and AC voltage, respectively. The properties of the sensor studied in this work, make it beneficial to be used in the instruments for environmental monitoring of temperature.

  20. Effect of RF power and annealing on chemical bonding and morphology of a-CN{sub x} thin films as humidity sensor

    SciTech Connect

    Aziz, N. F. H; Hussain, N. S. Mohamed; Awang, R.; Ritikos, R.; Kamal, S. A. A.

    2013-11-27

    Amorphous carbon nitride (a-CN{sub x}) thin films were deposited using radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) technique. A set of a-CN{sub x} thin films were prepared using pure methane (CH{sub 4}) gas diluted with nitrogen (N{sub 2}) gas. The rf power was varied at 50, 60, 70, 80, 90 and 100 W. These films were then annealed at 400 °C in a quartz tube furnace in argon (Ar) gas. The effects of rf power and thermal annealing on the chemical bonding and morphology of these samples were studied. Surface profilometer was used to measure film thickness. Fourier transform infra-red spectroscopy (FTIR) and Field emission scanning electron microscopy (FESEM) measurements were used to determine their chemical bonding and morphology respectively. The deposition rate of the films increased constantly with increasing rf power up to 80W, before decreasing with further increase in rf power. Fourier transform infra-red spectroscopy (FTIR) studies showed a systematic change in the spectra and revealed three main peaks included C-N, C=N, C=C and C?N triple bond. C=N and C?N bonds decreased with increased C-N bonds after thermal annealing process. The FESEM images showed that the structure is porous for as-deposited and covered by granule-like grain structure after thermal annealing process was done. The resistance of the a-CN{sub x} thin film changed from 23.765 k? to 5.845 k? in the relative humidity range of 5 to 92 % and the film shows a good response and repeatability as a humidity sensing materials. This work showed that rf power and thermal annealing has significant effects on the chemical bonding and surface morphology of the a-CN{sub x} films and but yield films which are potential candidate as humidity sensor device.

  1. SAW chemical sensor arrays using new thin-film materials

    SciTech Connect

    Ricco, A.J.; Xu, Chuanjing; Crooks, R.M.; Allred, R.E.

    1994-05-01

    We have used two classes of materials, self-assembled monolayers (SAMs) and plasma-grafted films (PGFs), as new chemically sensitive layers for an array of 97-MHz surface acoustic wave (SAW) delay-line-based devices. Responses of these materials to each of 14 different analytes, representing the classes of saturated alkane, aromatic hydrocarbon, chlorinated hydrocarbon, alcohol, ketone, organophosphonate, and water, have been evaluated using our six-SAW device array. Results reveal a qualitative ``chemical orthogonality`` of the films that is very promising for pattern recognition analysis.

  2. Electro-thermal modeling of a microbridge gas sensor

    SciTech Connect

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

    1997-08-01

    Fully CMOS-compatible, surface-micromachined polysilicon microbridges have been designed, fabricated, and tested for use in catalytic, calorimetric gas sensing. To improve sensor behavior, extensive electro-thermal modeling efforts were undertaken using SPICE. The validity of the SPICE model was verified comparing its simulated behavior with experiment. Temperature distribution of an electrically heated microbridges was measured using an infrared microscope. Comparisons among the measured distribution, the SPICE simulation, and distributions obtained by analytical methods show that heating at the ends of a microbridges has important implications for device response. Additional comparisons between measured and simulated current-voltage characteristics, as well as transient response, further support the accuracy of the model. A major benefit of electro- thermal modeling with SPICE is the ability to simultaneously simulate the behavior of a device and its control/sensing electronics. Results for the combination of a unique constant-resistance control circuit and microbridges gas sensor are given. Models of in situ techniques for monitoring catalyst deposition are shown to be in agreement with experiment. Finally, simulated chemical response of the detector is compared with the data, and methods of improving response through modifications in bridge geometry are predicted.

  3. Self-Activated Transparent All-Graphene Gas Sensor with Endurance to Humidity and Mechanical Bending.

    PubMed

    Kim, Yeon Hoo; Kim, Sang Jin; Kim, Yong-Jin; Shim, Yeong-Seok; Kim, Soo Young; Hong, Byung Hee; Jang, Ho Won

    2015-10-27

    Graphene is considered as one of leading candidates for gas sensor applications in the Internet of Things owing to its unique properties such as high sensitivity to gas adsorption, transparency, and flexibility. We present self-activated operation of all graphene gas sensors with high transparency and flexibility. The all-graphene gas sensors which consist of graphene for both sensor electrodes and active sensing area exhibit highly sensitive, selective, and reversible responses to NO2 without external heating. The sensors show reliable operation under high humidity conditions and bending strain. In addition to these remarkable device performances, the significantly facile fabrication process enlarges the potential of the all-graphene gas sensors for use in the Internet of Things and wearable electronics. PMID:26321290

  4. Acetone Sensing Properties of a Gas Sensor Composed of Carbon Nanotubes Doped With Iron Oxide Nanopowder.

    PubMed

    Tan, Qiulin; Fang, Jiahua; Liu, Wenyi; Xiong, Jijun; Zhang, Wendong

    2015-01-01

    Iron oxide (Fe?O?) nanopowder was prepared by a precipitation method and then mixed with different proportions of carbon nanotubes. The composite materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. A fabricated heater-type gas sensor was compared with a pure Fe?O? gas sensor under the influence of acetone. The effects of the amount of doping, the sintering temperature, and the operating temperature on the response of the sensor and the response recovery time were analyzed. Experiments show that doping of carbon nanotubes with iron oxide effectively improves the response of the resulting gas sensors to acetone gas. It also reduces the operating temperature and shortens the response recovery time of the sensor. The response of the sensor in an acetone gas concentration of 80 ppm was enhanced, with good repeatability. PMID:26569253

  5. Inorganic Thin-film Sensor Membranes with PLD-prepared Chalcogenide Glasses: Challenges and Implementation

    PubMed Central

    Kloock, Joachim P.; Mourzina, Youlia G.; Ermolenko, Yuri; Doll, Theodor; Schubert, Jürgen; Schöning, Michael J.

    2004-01-01

    Chalcogenide glasses offer an excellent “challenge” for their use and implementation in sensor arrays due to their good sensor-specific advantages in comparison to their crystalline counterparts. This paper will give an introduction on the preparation of chalcogenide glasses in the thin-film state. First, single microsensors have been prepared with the methods of semiconductor technology. In a next step, three microsensors are implemented onto one single silicon substrate to an “one chip” sensor array. Different ionselective chalcogenide glass membranes (PbSAgIAs2S3, CdSAgIAs2S3, CuAgAsSeTe and TlAgAsIS) were prepared by means of the pulsed laser deposition (PLD) process. The different sensor membranes and structures have been physically characterized by means of Rutherford backscattering spectrometry, scanning electron microscopy and video microscopy. The electrochemical behavior has been investigated by potentiometric measurements.

  6. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, III, Jerome J. (New Haven, CT); Halpern, Bret L. (Bethany, CT)

    1993-01-01

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures.

  7. Characteristics and Mechanisms in Ion-Conducting Polymer Films as Chemical Sensors

    SciTech Connect

    HUGHES,ROBERT C.; YELTON,WILLIAM G.; PFEIFER,KENT B.; PATEL,SANJAY V.

    2000-07-12

    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 published work on SPE films used as chemical sensors. The authors have found that thin films of polymers like polyethylene oxide (PEO) are very sensitive to low concentrations of volatile organic compounds (VOCs) such as common solvents. Evidence of a new sensing mechanism involving the percolation of ions through narrow channels of amorphous polymer is presented. They present impedance spectroscopy of PEO films in the frequency range 0.0001 Hz to 1 MHz for different concentrations of VOCs and relative humidity. They find that the measurement frequency is important for distinguishing ionic conductivity from the double layer capacitance and the parasitic capacitance.

  8. Quasiparticle Diffusion in Al Films Coupled to Tungsten Transition Edge Sensors

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We report recent results obtained from several W/Al test devices on Si wafers fabricated specifically to better understand energy collection in phonon sensors used for the Cryogenic Dark Matter Search (CDMS) experiment. The devices under study consist of three different lengths of 250 m-wide by 300 nm-thick Al absorber films, coupled to 250 m x 250 m (40 nm thick) W-TESs at each end of the Al film. An Fe source was used to excite a NaCl reflector producing 2.6 keV Cl X-rays that were absorbed in our test device after passing through a collimator. The impinging X-rays broke Cooper pairs in the Al film, producing quasiparticles that we detected after they propagated into the W-TESs. We studied the diffusion of these quasiparticles in the Al, trapping effects in the Al film, and energy transmission at the Al/W interfaces.

  9. Miniaturized acceleration sensors with in-plane polarized piezoelectric thin films produced by micromachining.

    PubMed

    Shanmugavel, Saravanan; Yao, Kui; Luong, Trung Dung; Oh, Sharon Roslyn; Chen, Yifan; Tan, Chin Yaw; Gaunekar, Ajit; Ng, Peter Hon Yu; Li, Marchy Hing Leung

    2011-11-01

    Miniaturized acceleration sensors employing piezoelectric thin films were fabricated through batch micromachining with silicon and silicon-on-insulator (SOI) wafers. The acceleration sensors comprised multiple suspension beams supporting a central seismic mass. Ferroelectric (Pb,La)(Zr,Ti) O(3) (PLZT) thin films were coated and in-plane polarized on the surfaces of the suspension beams for realizing electromechanical conversion through the piezoelectric effect. Interdigital electrodes were formed on the PLZT films and connected in parallel. Finite element analyses were conducted for the stress and strain distributions, providing guidance to the structural design, including optimizing electrode positioning for collecting the electrical output constructively. Uniformity of the beam thickness and sample consistency were significantly improved by using SOI wafers instead of silicon wafers. The measurement results showed that all the sensor samples had fundamental resonances of symmetric out-of-plane vibration mode at frequencies in the range of 8 to 35 kHz, depending on the sample dimensions. These sensors exhibited stable electrical outputs in response to acceleration input, achieving a high signal-to-noise ratio without any external amplifier or signal conditioning. PMID:22083762

  10. Polyvinylidene fluoride film based nasal sensor to monitor human respiration pattern: an initial clinical study.

    PubMed

    Roopa Manjunatha, G; Rajanna, K; Mahapatra, D Roy; Nayak, M M; Krishnaswamy, Uma Maheswari; Srinivasa, R

    2013-12-01

    Design and development of a piezoelectric polyvinylidene fluoride (PVDF) thin film based nasal sensor to monitor human respiration pattern (RP) from each nostril simultaneously is presented in this paper. Thin film based PVDF nasal sensor is designed in a cantilever beam configuration. Two cantilevers are mounted on a spectacle frame in such a way that the air flow from each nostril impinges on this sensor causing bending of the cantilever beams. Voltage signal produced due to air flow induced dynamic piezoelectric effect produce a respective RP. A group of 23 healthy awake human subjects are studied. The RP in terms of respiratory rate (RR) and Respiratory air-flow changes/alterations obtained from the developed PVDF nasal sensor are compared with RP obtained from respiratory inductance plethysmograph (RIP) device. The mean RR of the developed nasal sensor (19.65 ± 4.1) and the RIP (19.57 ± 4.1) are found to be almost same (difference not significant, p > 0.05) with the correlation coefficient 0.96, p < 0.0001. It was observed that any change/alterations in the pattern of RIP is followed by same amount of change/alterations in the pattern of PVDF nasal sensor with k = 0.815 indicating strong agreement between the PVDF nasal sensor and RIP respiratory air-flow pattern. The developed sensor is simple in design, non-invasive, patient friendly and hence shows promising routine clinical usage. The preliminary result shows that this new method can have various applications in respiratory monitoring and diagnosis. PMID:23771706

  11. Fabrication of an aluminum-porous alumina sensor by in situ monitoring anodization of thin aluminum films

    NASA Astrophysics Data System (ADS)

    Tassis, George; Christoulaki, Anastasia; Spiliopoulos, Nikolaos; Anastassopoulos, Dimitrios L.; Vradis, Alexandros A.; Mytilineou, Eugenia

    2015-09-01

    The aim of the present work is to optimize a well-known plasmon-based aluminum/porous anodic alumina sensor. This kind of sensors is produced by partial electrochemical anodization of an aluminum film, while the remaining, non-anodized metallic film is used for supporting the propagation of surface plasmons. The anodized porous alumina is preferable against a flat solid surface as it presents much larger sensing area and thus enhanced detecting efficiency. In this work, a novel method for controlling the remaining aluminum film thickness is reported, based on a simple optical reflectance measurement during the electrochemical anodization of the initial metallic film.

  12. Stable and very sensitive gas sensor based on novel mixed-metal oxides

    NASA Astrophysics Data System (ADS)

    Comini, Elisabetta; Faglia, Guido; Sberveglieri, Giorgio

    2004-03-01

    The material properties of the nano-structured materials show remarkable improvement or deviation from the properties exhibited by the coarser grained material. These unique properties are attributed to the significant increase in grain boundary area due to the small grain size. The possibility to manipulate the properties of a nanosized thin film simply through annealing appears to be of widespread interest for material science. In the gas sensing field of application there is a great effort in reducing the grain dimension and increasing the surface area exposed to the interaction with gaseous species. One of the strategies used is the addition of a second element, which can inhibit the grain growth. Furthermore, there may be a coexistence of two phases and one phase can act as a receptor while the other can act as transducers and an effect on film porosity is also expected, depending on the extent of oxide segregation from the nanosized film. Thin films made of Mo-Ti, Mo-W, Ti-W, Ti-Nb mixed oxides were achieved by reactive sputtering, assisted by thermal treatments. These layers were characterized by means of the electrical measurements in presence of different pollutants and alcohols and with the Kelvin probe at different working temperatures; the good sensing capabilities registered with these mixed oxide compared to their single oxides have to be ascribed to the nanosized structure of these layers. In particular different p-type sensing materials were produced, the opposite behavior of these layer is attractive to ease data processing in sensors arrays.

  13. Laboratory Connections: Gas Monitoring Transducers: Relative Humidity Sensors.

    ERIC Educational Resources Information Center

    Powers, Michael H.; Hull, Stacey E.

    1988-01-01

    Explains the operation of five relative humidity sensors: psychrometer, hair hygrometer, resistance hygrometer, capacitance hygrometer, and resistance-capacitance hygrometer. Outlines the theory behind the electronic sensors and gives computer interfacing information. Lists sensor responses for calibration. (MVL)

  14. Sensor Data Qualification Technique Applied to Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Simon, Donald L.

    2013-01-01

    This paper applies a previously developed sensor data qualification technique to a commercial aircraft engine simulation known as the Commercial Modular Aero-Propulsion System Simulation 40,000 (C-MAPSS40k). The sensor data qualification technique is designed to detect, isolate, and accommodate faulty sensor measurements. It features sensor networks, which group various sensors together and relies on an empirically derived analytical model to relate the sensor measurements. Relationships between all member sensors of the network are analyzed to detect and isolate any faulty sensor within the network.

  15. Multifunctional potentiometric gas sensor array with an integrated temperature control and temperature sensors

    DOEpatents

    Blackburn, Bryan M; Wachsman, Eric D

    2015-05-12

    Embodiments of the subject invention relate to a gas sensor and method for sensing one or more gases. An embodiment incorporates an array of sensing electrodes maintained at similar or different temperatures, such that the sensitivity and species selectivity of the device can be fine tuned between different pairs of sensing electrodes. A specific embodiment pertains to a gas sensor array for monitoring combustion exhausts and/or chemical reaction byproducts. An embodiment of the subject device related to this invention operates at high temperatures and can withstand harsh chemical environments. Embodiments of the device are made on a single substrate. The devices can also be made on individual substrates and monitored individually as if they were part of an array on a single substrate. The device can incorporate sensing electrodes in the same environment, which allows the electrodes to be coplanar and, thus, keep manufacturing costs low. Embodiments of the device can provide improvements to sensitivity, selectivity, and signal interference via surface temperature control.

  16. Polythiophene Transistors as Gas Sensors for Electronic Nose Applications

    E-print Network

    Liao, Frank

    2009-01-01

    stress effect in pentacene thin-film transistors,” Applied Physicsstress reversal in polyfluorene thin-film transistors,” Journal of Applied Physics ,stress in organic thin- film transistors and logic gates,” Applied Physics

  17. In situ measurement of gas composition changes in radio frequency plasmas using a quartz sensor

    SciTech Connect

    Suzuki, Atsushi; Nonaka, Hidehiko

    2009-09-15

    A simple method using a quartz sensor (Q-sensor) was developed to observe gas composition changes in radio frequency (rf) plasmas. The output depends on the gases' absolute pressure, molecular weight, and viscosity. The pressure-normalized quartz sensor output depends only on the molecular weight and viscosity of the gas. Consequently, gas composition changes can be detected in the plasmas if a sensor can be used in the plasmas. Influences imparted by the plasmas on the sensor, such as those by reactive particles (e.g., radicals and ions), excited species, electrons, temperature, and electric potentials during measurements were investigated to test the applicability of this quartz sensor measurement to plasma. The Q-sensor measurement results for rf plasmas with argon, hydrogen, and their mixtures are reproducible, demonstrating that the Q-sensor measurement is applicable for plasmas. In this work, pressure- and temperature-normalized Q-sensor output (NQO) were used to obtain the gas composition information of plasma. Temperature-normalization of the Q-sensor output enabled quartz sensor measurements near plasma electrodes, where the quartz sensor temperature increases. The changes in NQO agreed with results obtained by gas analysis using a quadrupole mass spectrometer. Results confirmed that the change in NQO is mainly attributable to changes in the densities and kinds of gas molecules in the plasma gas phase, not by other extrinsic influences of plasma. For argon, hydrogen, and argon-hydrogen plasmas, these changes correspond to reduction in nitrogen, production of carbon monoxide, and dissociation of hydrogen molecules, respectively. These changes in NQO qualitatively and somewhat quantitatively agreed with results obtained using gas analysis, indicting that the measurement has a potential application to obtain the gas composition in plasmas without disturbing industrial plasma processes.

  18. Air Monitoring System in Elders' Apartment with QCM Type Gas Sensors

    NASA Astrophysics Data System (ADS)

    Kikuchi, Masashi; Ito, Tsukasa; Shiratori, Seimei

    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.

  19. Preparation of a Porous Composite Film for the Fabrication of a Hydrogen Peroxide Sensor

    PubMed Central

    Hua, Mu-Yi; Chen, Chun-Jen; Chen, Hsiao-Chien; Tsai, Rung-Ywan; Cheng, Wen; Cheng, Chun-Lin; Liu, Yin-Chih

    2011-01-01

    A series of dopant-type polyaniline-polyacrylic acid composite (PAn-PAA) films with porous structures were prepared and developed for an enzyme-free hydrogen peroxide (H2O2) sensor. The composite films were highly electroactive in a neutral environment as compared to polyaniline (PAn). In addition, the carboxyl group of the PAA was found to react with H2O2 to form peroxy acid groups, and the peroxy acid could further oxidize the imine structure of PAn to form N-oxides. The N-oxides reverted to their original form via electrochemical reduction and increased the reduction current. Based on this result, PAn-PAA was used to modify a gold electrode (PAn-PAA/Au) as a working electrode for the non-enzymatic detection of H2O2. The characteristics of the proposed sensors could be tuned by the PAA/PAn molar ratio. Blending PAA with PAn enhanced the surface area, electrocatalytic activity, and conductivity of these sensors. Under optimal conditions, the linear concentration range of the H2O2 sensor was 0.04 to 12 mM with a sensitivity of 417.5 ?A/mM-cm2. This enzyme-free H2O2 sensor also exhibited a rapid response time, excellent stability, and high selectivity. PMID:22163932

  20. Metallic and Ceramic Thin Film Thermocouples for Gas Turbine Engines

    PubMed Central

    Tougas, Ian M.; Amani, Matin; Gregory, Otto J.

    2013-01-01

    Temperatures of hot section components in today's gas turbine engines reach as high as 1,500 °C, making in situ monitoring of the severe temperature gradients within the engine rather difficult. Therefore, there is a need to develop instrumentation (i.e., thermocouples and strain gauges) for these turbine engines that can survive these harsh environments. Refractory metal and ceramic thin film thermocouples are well suited for this task since they have excellent chemical and electrical stability at high temperatures in oxidizing atmospheres, they are compatible with thermal barrier coatings commonly employed in today's engines, they have greater sensitivity than conventional wire thermocouples, and they are non-invasive to combustion aerodynamics in the engine. Thin film thermocouples based on platinum:palladium and indium oxynitride:indium tin oxynitride as well as their oxide counterparts have been developed for this purpose and have proven to be more stable than conventional type-S and type-K thin film thermocouples. The metallic and ceramic thin film thermocouples described within this paper exhibited remarkable stability and drift rates similar to bulk (wire) thermocouples. PMID:24217356

  1. Metallic and ceramic thin film thermocouples for gas turbine engines.

    PubMed

    Tougas, Ian M; Amani, Matin; Gregory, Otto J

    2013-01-01

    Temperatures of hot section components in today's gas turbine engines reach as high as 1,500 °C, making in situ monitoring of the severe temperature gradients within the engine rather difficult. Therefore, there is a need to develop instrumentation (i.e., thermocouples and strain gauges) for these turbine engines that can survive these harsh environments. Refractory metal and ceramic thin film thermocouples are well suited for this task since they have excellent chemical and electrical stability at high temperatures in oxidizing atmospheres, they are compatible with thermal barrier coatings commonly employed in today's engines, they have greater sensitivity than conventional wire thermocouples, and they are non-invasive to combustion aerodynamics in the engine. Thin film thermocouples based on platinum:palladium and indium oxynitride:indium tin oxynitride as well as their oxide counterparts have been developed for this purpose and have proven to be more stable than conventional type-S and type-K thin film thermocouples. The metallic and ceramic thin film thermocouples described within this paper exhibited remarkable stability and drift rates similar to bulk (wire) thermocouples. PMID:24217356

  2. Transferable self-supporting ZnO porous films for low-cost piezoresistive sensors

    NASA Astrophysics Data System (ADS)

    Zeng, Qiongfang; Lei, Dingyou; Zhang, Yinggui; Huang, Huihui

    2014-04-01

    Transferable self-supporting ZnO porous films were synthesized via a hydrothermal approach without the presence of any substrates. Piezoresistive sensors were fabricated by directly transferring the ZnO porous films onto FTO, which show a pressure sensitivity of 0.005/KPa and a fast sensitive time with both response time and recovery time less than 1s. The results were discussed in terms of the current-voltage characteristics of the device. It is anticipated that this low-cost and large-area-compatible technology would have potential for applications in industrial, civil and transportation fields.

  3. Gas and aerosol wall losses in Teflon film smog chambers

    SciTech Connect

    McMurry, P.H.; Grosjean, D.

    1985-12-01

    Large smog chambers (approx.60 m/sup 3/) constructed of FEP Teflon film are frequently used to study photochemistry and aerosol formation in model chemical systems. In a previous paper a theory for aerosol wall loss rates in Teflon film smog chambers was developed; predicted particle loss rates were in good agreement with measured rates. In the present paper, measurements of wall deposition rates and the effects of wall losses on measurements of gas-to-particle conversion in smog chambers are discussed. Calculations indicate that a large fraction of the aerosol formed in several smog chamber experiments was on the chamber walls at the end of the experiment. Estimated values for particulate organic carbon yield for several precursor hydrocarbons increased by factors of 1.3-6.0 when wall deposition was taken into account. The theory is also extended to loss rates of gaseous species. Such loss rates are either limited by diffusion through a concentration boundary layer near the surface or by uptake at the surface. It is shown that for a typical 60-m/sup 3/ Teflon film smog chamber, gas loss rates are limited by surface reaction rates if mass accommodation coefficients are less than 6 x 10/sup -6/. It follows that previously reported loss rates of several gases in a chamber of this type were limited by surface reactions.

  4. Digital Architecture for a Trace Gas Sensor Platform

    NASA Technical Reports Server (NTRS)

    Gonzales, Paula; Casias, Miguel; Vakhtin, Andrei; Pilgrim, Jeffrey

    2012-01-01

    A digital architecture has been implemented for a trace gas sensor platform, as a companion to standard analog control electronics, which accommodates optical absorption whose fractional absorbance equivalent would result in excess error if assumed to be linear. In cases where the absorption (1-transmission) is not equivalent to the fractional absorbance within a few percent error, it is necessary to accommodate the actual measured absorption while reporting the measured concentration of a target analyte with reasonable accuracy. This requires incorporation of programmable intelligence into the sensor platform so that flexible interpretation of the acquired data may be accomplished. Several different digital component architectures were tested and implemented. Commercial off-the-shelf digital electronics including data acquisition cards (DAQs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), and microcontrollers have been used to achieve the desired outcome. The most completely integrated architecture achieved during the project used the CPLD along with a microcontroller. The CPLD provides the initial digital demodulation of the raw sensor signal, and then communicates over a parallel communications interface with a microcontroller. The microcontroller analyzes the digital signal from the CPLD, and applies a non-linear correction obtained through extensive data analysis at the various relevant EVA operating pressures. The microcontroller then presents the quantitatively accurate carbon dioxide partial pressure regardless of optical density. This technique could extend the linear dynamic range of typical absorption spectrometers, particularly those whose low end noise equivalent absorbance is below one-part-in-100,000. In the EVA application, it allows introduction of a path-length-enhancing architecture whose optical interference effects are well understood and quantified without sacrificing the dynamic range that allows quantitative detection at the higher carbon dioxide partial pressures. The digital components are compact and allow reasonably complete integration with separately developed analog control electronics without sacrificing size, mass, or power draw.

  5. GAS ANALYSIS SYSTEM COMPOSED OF A SOLID-STATE SENSOR ARRAY AND HYBRID NEURAL NETWORK

    E-print Network

    Osowski, Stanislaw

    1 GAS ANALYSIS SYSTEM COMPOSED OF A SOLID-STATE SENSOR ARRAY AND HYBRID NEURAL NETWORK STRUCTURE presents the application of the hybrid neural network to the solution of the calibration problem of the solid state sensor array used for the gas analysis. The applied neural network is composed of two parts

  6. Figure 1. Principle of wireless detection of gas centration with a chipless sensor.

    E-print Network

    Tentzeris, Manos

    been studied for their sensing properties are CNTs [3], graphene [5] and silicon nanowires [4Figure 1. Principle of wireless detection of gas centration with a chipless sensor. A Novel Inkjet Printed Carbon Nanotube-Based Chipless RFID Sensor for Gas Detection Arnaud Vena#1 , Lauri Sydänheimo#2

  7. A 3D scaffold for ultra-sensitive reduced graphene oxide gas sensors.

    PubMed

    Yun, Yong Ju; Hong, Won G; Choi, Nak-Jin; Park, Hyung Ju; Moon, Seung Eon; Kim, Byung Hoon; Song, Ki-Bong; Jun, Yongseok; Lee, Hyung-Kun

    2014-06-21

    An ultra-sensitive gas sensor based on a reduced graphene oxide nanofiber mat was successfully fabricated using a combination of an electrospinning method and graphene oxide wrapping through an electrostatic self-assembly, followed by a low-temperature chemical reduction. The sensor showed excellent sensitivity to NO2 gas. PMID:24839129

  8. TiO2-based gas sensor: a possible application to SO2.

    PubMed

    Nisar, Jawad; Topalian, Zareh; De Sarkar, Abir; Österlund, Lars; Ahuja, Rajeev

    2013-09-11

    Fixation of SO2 molecules on anatase TiO2 surfaces with defects have been investigated by first-principles density functional theory (DFT) calculations and in situ Fourier transform infrared (FTIR) surface spectroscopy on porous TiO2 films. Intrinsic oxygen-vacancy defects, which are formed on TiO2(001) and TiO2(101) surfaces by ultraviolet (UV) light irradiation and at elevated temperatures, are found to be most effective in anchoring the SO2 gas molecules to the TiO2 surfaces. Both TiO2(101) and TiO2(001) surfaces with oxygen vacancies are found to exhibit higher SO2 adsorption energies in the DFT calculations. The adsorption mechanism of SO2 is explained on the basis of electronic structure, charge transfer between the molecule and the surface, and the oxidation state of the adsorbed molecule. The theoretical findings are corroborated by FTIR experiments. Moreover, the (001) surface with oxygen vacancies is found to bind SO2 gas molecules more strongly, as compared to the (101) surface. Higher concentration of oxygen vacancies on the TiO2 surfaces is found to significantly increase the adsorption energy. The results shed new insight into the sensing properties of TiO2-based gas sensors. PMID:23915321

  9. Metallic LiMo3Se3 Nanowire Film Sensors for Electrical Detection of Metal Ions in Water

    E-print Network

    Osterloh, Frank

    Metallic LiMo3Se3 Nanowire Film Sensors for Electrical Detection of Metal Ions in Water Mark AllenVis, California 95616 ReceiVed February 5, 2008. ReVised Manuscript ReceiVed March 30, 2008 LiMo3Se3 nanowire film sensors were fabricated by drop-coating a 0.05% (mass) aqueous nanowire solution onto microfabricated

  10. Fiber optic speed sensor for advanced gas turbine engine control

    NASA Astrophysics Data System (ADS)

    Varshneya, Deepak; Maida, John L., Jr.; Overstreet, Mark A.

    1991-02-01

    A fiber optic speed sensor (FOSS) has been developed, bench tested and rig tested in a real turbine airflow environment. The FOSS employs an innovative design using a pressure tube and fiber optic microbend transducer in order to capture turbine blade pass wake frequency. The blade pass frequency can be converted by a signal processor into turbine rotational speed. The FOSS offers unique potential to meet future requirements for performance (0 to 25 KHz) and environmental tolerance (1200 F temperatures and EMI/EMP threats). Future efforts include development of the signal processor and environmental/durability testing focused on developing reliable, long life operation in the hostile environment of an advanced gas turbine engine.

  11. Langasite Surface Acoustic Wave Gas Sensors: Modeling and Verification

    SciTech Connect

    Zheng, Peng; Greve, David W.; Oppenheim, Irving J.

    2013-01-01

    We report finite element simulations of the effect of conductive sensing layers on the surface wave velocity of langasite substrates. The simulations include both the mechanical and electrical influences of the conducting sensing layer. We show that three-dimensional simulations are necessary because of the out-of-plane displacements of the commonly used (0, 138.5, 26.7) Euler angle. Measurements of the transducer input admittance in reflective delay-line devices yield a value for the electromechanical coupling coefficient that is in good agreement with the three-dimensional simulations on bare langasite substrate. The input admittance measurements also show evidence of excitation of an additional wave mode and excess loss due to the finger resistance. The results of these simulations and measurements will be useful in the design of surface acoustic wave gas sensors.

  12. Autonomous micro and nano sensors for upstream oil and gas

    NASA Astrophysics Data System (ADS)

    Chapman, David; Trybula, Walt

    2015-06-01

    This paper describes the development of autonomous electronic micro and nanoscale sensor systems for very harsh downhole oilfield conditions and provides an overview of the operational requirements necessary to survive and make direct measurements of subsurface conditions. One of several significant developmental challenges is selecting appropriate technologies that are simultaneously miniaturize-able, integrate-able, harsh environment capable, and economically viable. The Advanced Energy Consortium (AEC) is employing a platform approach to developing and testing multi-chip, millimeter and micron-scale systems in a package at elevated temperature and pressure in API brine and oil analogs, with the future goal of miniaturized systems that enable the collection of previously unattainable data. The ultimate goal is to develop subsurface nanosensor systems that can be injected into oil and gas well bores, to gather and record data, providing an unparalleled level of direct reservoir characterization. This paper provides a status update on the research efforts and developmental successes at the AEC.

  13. Carnegie Mellon Polythiophene-Based Gas Chemical Sensors for

    E-print Network

    Weiss, Lee E.

    BoardPrinted Circuit Board Humidity & Temperature Sensor Module -1v +1v Cartridge Simulator Test is mounted on a PCB containing sensor conditioning circuitry and a humidity & temperature sensor module and filtered, and the outputs of the temperature/humidity sensors are interfaced to PC through a NI AD card

  14. Analytical study of pressure balancing in gas film seals.

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1973-01-01

    Proper pressure balancing of gas film seals requires knowledge of the pressure profile load factor (load factor) values for a given set of design conditions. In this study, the load factor is investigated for subsonic and choked flow conditions, laminar and turbulent flows, and various seal entrance conditions. Both parallel sealing surfaces and surfaces with small linear deformation were investigated. The load factor for subsonic flow depends strongly on pressure ratio; under choked flow conditions, however, the load factor is found to depend more strongly on film thickness and flow entrance conditions rather than pressure ratio. The importance of generating hydrodynamic forces to keep the seal balanced under severe and multipoint operation is also discussed.

  15. Improved polarization contrast method for surface plasmon resonance imaging sensors by inert background gold film extinction

    NASA Astrophysics Data System (ADS)

    Dong, Wei; Pang, Kai; Luo, Qiaohui; Huang, Zihao; Wang, Xiaoping; Tong, Limin

    2015-07-01

    To improve the performance of high-throughput surface plasmon resonance (SPR) imaging sensors, the imperfections of the conventional gold film polarization contrast method and the bare prism polarization contrast method are discussed, and a background extinction method is proposed. Thick gold film is coated as the background area, surrounding gold sensing spots, to form a "gold microwell array". By blocking the light reflected from the background area with appropriate parameters, an opposite-oriented SPR curve is obtained, which can be exploited to achieve a high signal-to-noise ratio in trace amount detection. The contrast between the sensing spots and the background is effectively improved, and the background is inert to the change of solution. Influences of parameter errors on the SPR curve are also investigated, and results show that extinction adjustment in this method is easy to be realized. The practicability of the background extinction method is proved by an experiment using a home-built SPR imaging sensor.

  16. Freestanding polyelectrolyte films as sensors for osmotic pressure.

    PubMed

    Nolte, Marc; Dönch, Ingo; Fery, Andreas

    2006-09-11

    Freestanding ultrathin polyelectrolyte-multilayer membranes, transferred to topographically structured polydimethylsiloxane (PDMS), are used as mechanical sensors. Due to the membranes' semipermeability, high-molecular-weight molecules can be either entrapped inside them or excluded, thus generating an osmotic pressure. This leads to a deformation. We investigate the deformation as a function of the osmotic pressure and present an analytical theory that fully describes the data. Thus, osmotic pressures can be determined quantitatively. The individual osmotic-sensitive elements have only microscopic dimensions, and arrays can be easily produced. PMID:16929555

  17. Wet chemically grown composite thin film for room temperature LPG sensor

    NASA Astrophysics Data System (ADS)

    Birajadar, Ravikiran; Desale, Dipalee; Shaikh, Shaheed; Mahajan, Sandip; Upadhye, Deepak; Ghule, Anil; Sharma, Ramphal

    2014-04-01

    We have synthesized thin film of zinc oxide-polyaniline (ZnO/PANI) composite using a simple wet chemical approach. As-synthesized ZnO/PANI composite thin film studied using different characterization techniques. The optical study reveals the penetration and interaction of PANI molecules with ZnO thin film. Prominent blue shift in UV-vis due to interaction between ZnO and PANI indicate presence of zinc oxide in polyaniline matrix. It is observed that ZnO thin film is not sensitive to LPG (liquefied petroleum gas) at room temperature. On the other hand ZnO/PANI composite thin film shows good response and recovery behaviors at room temperature.

  18. A new monitor with a zinc-oxide thin film semiconductor sensor for the measurement of volatile sulfur compounds in mouth air.

    PubMed

    Shimura, M; Yasuno, Y; Iwakura, M; Shimada, Y; Sakai, S; Suzuki, K; Sakamoto, S

    1996-04-01

    Halitosis, defined as unpleasant oral odor, is a concern among the general public. Halitosis is generally diagnosed by organoleptic examination and by gas chromatographic analysis of the main source of halitosis, volatile sulfur compounds, such as hydrogen sulfide, methyl mercaptan, and dimethyl sulfide. Gas chromatography requires a large-scale system and a long running time. We investigated the use of a zinc-oxide thin film semiconductor sensor for measuring trace volatile sulfur compounds in mouth air. Mouth air samples collected in teflon bags from 21 volunteers were analyzed by 3 methods: the monitor analysis, gas chromatography, and organoleptic examination by 3 judges. The readings of the monitor were correlated with the values of the total volatile sulfur compounds measured by gas chromatography (r = 0.75, P < 0.01) and also with the organoleptic scores given by the judges (r = 0.76, P < 0.01). The organoleptic scores were correlated with the gas chromatographic values (r = 0.71, P < 0.01). These results suggest that this new monitor with a zinc-oxide thin film semiconductor sensor may be used for the diagnosis of halitosis. Its small size and simplicity of handling may enable its use for routine chair-side study and field surveys of halitosis. PMID:8708966

  19. Method of measuring cross-flow vortices by use of an array of hot-film sensors

    NASA Technical Reports Server (NTRS)

    Agarwal, Aval K. (inventor); Maddalon, Dal V. (inventor); Mangalam, Siva M. (inventor)

    1993-01-01

    The invention is a method for measuring the wavelength of cross-flow vortices of air flow having streamlines of flow traveling across a swept airfoil. The method comprises providing a plurality of hot-film sensors. Each hot-film sensor provides a signal which can be processed, and each hot-film sensor is spaced in a straight-line array such that the distance between successive hot-film sensors is less than the wavelength of the cross-flow vortices being measured. The method further comprises determining the direction of travel of the streamlines across the airfoil and positioning the straight-line array of hot film sensors perpendicular to the direction of travel of the streamlines, such that each sensor has a spanwise location. The method further comprises processing the signals provided by the sensors to provide root-mean-square values for each signal, plotting each root-mean-square value as a function of its spanwise location, and determining the wavelength of the cross-flow vortices by noting the distance between two maxima or two minima of root-mean-square values.

  20. Measurement of ammonia in human breath with a liquid-film conductivity sensor.

    PubMed

    Toda, Kei; Li, Jianzhong; Dasgupta, Purnendu K

    2006-10-15

    Measurement of breath NH3 is of interest in clinical applications as it can be used as a measure of kidney/liver functions as well as halitosis. We have developed a liquid-film conductivity sensor to measure NH3 in human breath. A film of dilute H2SO4 is formed on the top of two metal capillary tubes placed in a concentric annular arrangement. The tube exterior has been specially treated to render it hydrophilic. As breath passes over the sensor tip, the film collects NH3 and the solution conductivity (measured by the concentric capillaries functioning as electrodes) decreases accordingly. This initial rate of conductivity decrease was determined to be the best metric (most rapid and least dependent on breath pCO2) for ammonia, relative to time to attain complete neutralization (conductivity minimum) or the final rate of conductivity increase as more ammonia dissolves after neutralization. The absorbing solution composition was optimized so that CO2 does not interfere. Both dynamic measurement using mask sampling and offline balloon sampling were performed. Ammonia readily absorbs on surfaces when significant concentrations of water vapor are present. As such, memory effects are common when analyzing human breath for ammonia. This problem was successfully eliminated. The results from this sensor agreed well with data obtained by a solution-phase fluorometric technique using a porous membrane diffusion scrubber and o-phthalaldehyde derivatization chemistry. For breath CO2 measurement, the applicability of a similar sensor that relies on a NaOH film was also demonstrated. PMID:17037934

  1. New Hydrodynamic Electrochemical Arrangement for Cadmium Ions Detection Using Thick-Film Chemical Sensor Electrodes

    PubMed Central

    Prasek, Jan; Adamek, Martin; Hubalek, Jaromir; Adam, Vojtech; Trnkova, Libuse; Kizek, Rene

    2006-01-01

    Miniaturization and integration of chemical devices into modules that are dimensionally comparable with electronic chips (Lab on Chip) is nowadays developing worldwide. The aim of our work was to suggest and optimize the best conditions for fabrication of TFT sensor due to its sensitivity and low experimental deviations. New electrochemical analytical device was developed to ensure certain known mass transport to electrodes, which is the most limiting process that influencing the response quality of the sensor. The device consists from rotating conic vessel for measured sample and stick-in thick-film sensor. The sensors responses were tested under trace analysis of cadmium. Measurements were done also with the others electrochemical arrangements to compare with the new one. The sensor output current response dependence on the liquid velocity and geometrical arrangement within using standard electrochemical couple of potassium ferrocyanide-ferricyanide is presented. We found out that the new device with controlled flow of electrolyte to sensor worked properly and gave satisfactory results.

  2. Polyurea spin-coated thin films: Pyro- and piezoelectric properties and application to infrared sensors

    NASA Astrophysics Data System (ADS)

    Morimoto, Masahiro; Koshiba, Yasuko; Misaki, Masahiro; Ishida, Kenji

    2015-04-01

    We have investigated the pyro- and piezoelectric properties of polyurea spin-coated films with thermal and chemical stability and their performance as infrared sensors. The piezoelectric coefficient d33 was measured by a laser Doppler vibrometer to be 23.5 pC/N. This coefficient increased with the poling electric field up to around 75 MV/m, suggesting that the polyurea dipole is aligned by applying an electric field greater than 75 MV/m. When a triangular thermal wave was applied, a square-wave pyroelectric current was observed and the pyroelectric coefficient measured to be 5.11 µC/(m2·K). The infrared sensor performance of the polyurea thin film was examined by measuring the voltage sensitivity to infrared irradiation. The obtained result of 70.4 V/W at 1 Hz is consistent with the results calculated from the measured pyroelectric coefficient. Our findings suggest that the performance of the sensor may be improved by increasing the pyroelectric coefficient of the polyurea films.

  3. Application of principal component analysis to gas sensing characteristics of Cr0.8Fe0.2NbO4 thick film array.

    PubMed

    Sree Rama Murthy, A; Pathak, Dhruv; Sharma, Gautam; Gnanasekar, K I; Jayaraman, V; Umarji, A M; Gnanasekaran, T

    2015-09-10

    The transient changes in resistances of Cr0.8Fe0.2NbO4 thick film sensors towards specified concentrations of H2, NH3, acetonitrile, acetone, alcohol, cyclohexane and petroleum gas at different operating temperatures were recorded. The analyte-specific characteristics such as slopes of the response and retrace curves, area under the curve and sensitivity deduced from the transient curve of the respective analyte gas have been used to construct a data matrix. Principal component analysis (PCA) was applied to this data and the score plot was obtained. Distinguishing one reducing gas from the other is demonstrated based on this approach, which otherwise is not possible by measuring relative changes in conductivity. This methodology is extended for three Cr0.8Fe0.2NbO4 thick film sensor array operated at different temperatures. PMID:26388489

  4. Improving the H2 Gas Sensitivity of ZnO Thin Films by Modifying the Annealing Conditions

    NASA Astrophysics Data System (ADS)

    Khojier, K.; Savaloni, H.

    2015-10-01

    This paper explains the influence of annealing conditions on the sensing properties of ZnO thin films that can be used for the development of H2 gas sensors. Zn thin films were deposited by the e-beam deposition technique and subsequently annealed using different temperatures (400°C and 500°C), times (30 min and 60 min), and environments (air and oxygen flow). Detailed morphological, chemical, and structural investigations were carried out on all samples by field-emission scanning electron microscopy and x-ray diffraction analysis. The electrical response of the ZnO films was tested for H2 gas (40 ppm, 80 ppm, and 120 ppm concentrations) in the temperature range of 200°C to 450°C. Results showed that the maximum response for all samples was reached at operating temperature of 400°C and variation of the annealing conditions resulted in improvement of the H2 gas sensitivity of the ZnO thin films due to a change in the concentration of carriers.

  5. Gas-film coefficients for the volatilization of ethylene dibromide from water

    USGS Publications Warehouse

    Rathbun, R.E.; Tal, D.Y.

    1986-01-01

    Gas-film coefficients for the volatilization of ethylene dibromide (EDB) and water were determined in the laboratory as a function of wind speed and temperature. The ratio of the coefficients was independent of wind speed and increased slightly with temperature. Use of this ratio with an environmentally determined gas-film coefficient for the evaporation of water permits determination of the gas-film coefficient for the volatilization of EDB from environmental waters.

  6. Conformal Thin Film Packaging for SiC Sensor Circuits in Harsh Environments

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian C.; Karnick, David A.; Ponchak, George E.; Zorman, Christian A.

    2011-01-01

    In this investigation sputtered silicon carbide annealed at 300 C for one hour is used as a conformal thin film package. A RF magnetron sputterer was used to deposit 500 nm silicon carbide films on gold metal structures on alumina wafers. To determine the reliability and resistance to immersion in harsh environments, samples were submerged in gold etchant for 24 hours, in BOE for 24 hours, and in an O2 plasma etch for one hour. The adhesion strength of the thin film was measured by a pull test before and after the chemical immersion, which indicated that the film has an adhesion strength better than 10(exp 8) N/m2; this is similar to the adhesion of the gold layer to the alumina wafer. MIM capacitors are used to determine the dielectric constant, which is dependent on the SiC anneal temperature. Finally, to demonstrate that the SiC, conformal, thin film may be used to package RF circuits and sensors, an LC resonator circuit was fabricated and tested with and without the conformal SiC thin film packaging. The results indicate that the SiC coating adds no appreciable degradation to the circuits RF performance. Index Terms Sputter, silicon carbide, MIM capacitors, LC resonators, gold etchants, BOE, O2 plasma

  7. Modeling of tape tether vibration and vibration sensing using smart film sensors

    NASA Astrophysics Data System (ADS)

    Kunugi, Kouta; Kojima, Hirohisa; Trivailo, Pavel M.

    2015-02-01

    Tape-tethered satellite systems use long and flexible tape tethers, the bending and torsional vibrations of which affect the positions and attitude of attached satellites and climbers. Owing to the distribution characteristics of a tape tether, ordinary point sensors and actuators cannot be used easily to control the vibrations. Other types of sensors and actuators are required for this purpose. The flexibility and deformability of smart materials make them particularly suitable for integration into a tape-tethered system. Thus, in this paper, we propose a method for modeling the bending and torsional vibrations of a tape tether, and report our investigation into the feasibility of using smart film sensors to distinguish between the two vibration types. We formulate equations of motion for the tape tether using multibody dynamics techniques, and perform numerical simulations to study the behavior of the bending and torsional vibrations. The results of our experiments show that the bending and torsional vibrations of a tape tether can be measured using smart film sensors attached to the tether.

  8. Miniaturized implantable pressure and oxygen sensors based on polydimethylsiloxane thin films.

    PubMed

    Koley, Goutam; Liu, Jie; Nomani, Md W; Yim, Moonbin; Wen, Xuejun; Hsia, T-Y

    2009-04-30

    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 current change between a Pt and an Ag/AgCl electrode on a glass substrate, with KCl soaked filter paper as the electrolytic media that is separated from the oxygen carrying fluid by a thin PDMS membrane. The best sensitivity for the pressure sensor was ~0.1 nA/KPa, with a noise limited resolution of ~0.09 KPa. For the oxygen sensor, the best sensitivity was ~2.75 ?A for 1% change in oxygen content of the surrounding media, with a noise limited resolution of ~6.18 ppm oxygen. These experimental results agree with theoretical modeling predictions, and suggest that the semi-permeable and biocompatible PDMS can be successfully adopted as the contacting membrane in an integrated sensor design to quantify pressure and oxygen content in blood. PMID:20161216

  9. Underwater blast wave pressure sensor based on polymer film fiber Fabry-Perot cavity.

    PubMed

    Wang, Junjie; Wang, Meng; Xu, Jian; Peng, Li; Yang, Minghong; Xia, Minghe; Jiang, Desheng

    2014-10-01

    This paper describes the theoretical and experimental aspects of an optical underwater shock wave sensor based on a polymer film optical fiber Fabry-Perot cavity manufactured by vacuum deposition technology. The transduction mechanism of the sensor involves a normally incident acoustic stress wave that changes the thickness of the polymer film, thereby giving rise to a phase shift. This transient interferometric phase is interrogated by a three-phase-step algorithm. Theoretically, the sensor-acoustic-field interaction principle is analyzed, and the phase modulation sensitivity based on the theory of waves in the layered media is calculated. Experimentally, a static calibration test and a dynamic calibration test are conducted using a piston-type pressure calibration machine and a focusing-type electromagnetic shock wave. Results indicate that the repeatability, hysteresis, nonlinearity, and the overall measurement accuracy of the sensor within the full pressure range of 55 MPa are 1.82%, 0.86%, 1.81%, and 4.49%, respectively. The dynamic response time is less than 0.767 ?s. Finally, three aspects that need further study for practical use are pointed out. PMID:25322237

  10. Thin film electrodes and passivation coatings for harsh environment microwave acoustic sensors

    NASA Astrophysics Data System (ADS)

    Moulzolf, Scott C.; Frankel, David J.; Bernhardt, George P.; Nugent, Bryn; Lad, Robert J.

    2011-06-01

    °Stable nanostructured ultra-thin electrodes and protective passivation coatings have been developed for langasite (La3Ga5SiO14) based surface acoustic wave (SAW) sensors that can successfully operate in harsh high temperature environments up to 1000°C. Ultrathin (<100nm) nanocomposite Pt-Rh/ZrO2 electrode structures were fabricated by electron beam co-evaporation and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), 4-point resistivity, and scanning electron microscopy (SEM) studies. It was found that the incorporation of ZrO2 into the Pt-Rh electrode films retards recrystallization and de-wetting, thereby maintaining film continuity and low resistivity up to at least 1000°C. XPS results show that with heating at 800°C, the stoichiometry of the bare langasite SAW sensor surface becomes depleted of Ga in a reducing (vacuum) environment, but remains close to the bulk composition when heated in an oxidizing (air) environment. The incorporation of a thin oxynitride (SiAlON or SiZrON) coating over the entire sensor diminishes high temperature roughening and degradation of both the electrode and bare langasite surfaces. The viability and performance of these sensors was validated by experiments in which the SAW devices were tested in a controlled atmosphere laboratory furnace and also attached to rotating turbine blades within a small turbine engine operating with centripetal acceleration loads and temperatures in excess of 52,000g and 650°C, and under cyclical temperature shock conditions.

  11. Miniaturized implantable pressure and oxygen sensors based on polydimethylsiloxane thin films

    PubMed Central

    Liu, Jie; Nomani, Md. W; Yim, Moonbin; Wen, Xuejun; Hsia, T-Y

    2009-01-01

    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 current change between a Pt and an Ag/AgCl electrode on a glass substrate, with KCl soaked filter paper as the electrolytic media that is separated from the oxygen carrying fluid by a thin PDMS membrane. The best sensitivity for the pressure sensor was ~0.1 nA/KPa, with a noise limited resolution of ~0.09 KPa. For the oxygen sensor, the best sensitivity was ~2.75 ?A for 1% change in oxygen content of the surrounding media, with a noise limited resolution of ~6.18 ppm oxygen. These experimental results agree with theoretical modeling predictions, and suggest that the semi-permeable and biocompatible PDMS can be successfully adopted as the contacting membrane in an integrated sensor design to quantify pressure and oxygen content in blood. PMID:20161216

  12. Solid state gas sensors for detection of explosives and explosive precursors

    NASA Astrophysics Data System (ADS)

    Chu, Yun

    The increased number of terrorist attacks using improvised explosive devices (IEDs) over the past few years has made the trace detection of explosives a priority for the Department of Homeland Security. Considerable advances in early detection of trace explosives employing spectroscopic detection systems and other sensing devices have been made and have demonstrated outstanding performance. However, modern IEDs are not easily detectable by conventional methods and terrorists have adapted to avoid using metallic or nitro groups in the manufacturing of IEDs. Instead, more powerful but smaller compounds, such as TATP are being more frequently used. In addition, conventional detection techniques usually require large capital investment, labor costs and energy input and are incapable of real-time identification, limiting their application. Thus, a low cost detection system which is capable of continuous online monitoring in a passive mode is needed for explosive detection. In this dissertation, a thermodynamic based thin film gas sensor which can reliably detect various explosive compounds was developed and demonstrated. The principle of the sensors is based on measuring the heat effect associated with the catalytic decomposition of explosive compounds present in the vapor phase. The decomposition mechanism is complicated and not well known, but it can be affected by many parameters including catalyst, reaction temperature and humidity. Explosives that have relatively high vapor pressure and readily sublime at room temperature, like TATP and 2, 6-DNT, are ideal candidate for vapor phase detection using the thermodynamic gas sensor. ZnO, W2O 3, V2O5 and SnO2 were employed as catalysts. This sensor exhibited promising sensitivity results for TATP, but poor selectivity among peroxide based compounds. In order to improve the sensitivity and selectivity of the thermodynamic sensor, a Pd:SnO2 nanocomposite was fabricated and tested as part of this dissertation. A combinatorial chemistry techniques were used for catalyst discovery. Specially, a series of tin oxide catalysts with continuous varying composition of palladium were fabricated to screen for the optimum Pd loading to maximize specificity. Experimental results suggested that sensors with a 12 wt.% palladium loading generated the highest sensitivity while a 8 wt.% palladium loading provided greatest selectivity. XPS and XRD were used to study how palladium doping level affects the oxidation state and crystal structure of the nanocomposite catalyst. As with any passive detection system, a necessary theme of this dissertation was the mitigation of false positive. Toward this end, an orthogonal detection system comprised of two independent sensing platforms sharing one catalyst was demonstrated using TATP, 2, 6-DNT and ammonium nitrate as target molecules. The orthogonal sensor incorporated a thermodynamic based sensing platform to measure the heat effect associated with the decomposition of explosive molecules, and a conductometric sensing platform that monitors the change in electrical conductivity of the same catalyst when exposed to the explosive substances. Results indicate that the orthogonal sensor generates an effective response to explosives presented at part per billion level. In addition, with two independent sensing platforms, a built-in redundancy of results could be expected to minimize false positive.

  13. Novel strategies for development of gas sensors for combustion and medical applications

    NASA Astrophysics Data System (ADS)

    Fulmer, Adam; Mullen, Max; Sun, Chenhu; Dutta, Prabir K.

    2014-06-01

    Chemical gas sensors can have an enormous impact on optimizing complex processes as well as facilitate disease diagnosis. In this article, we demonstrate how sensing of gas molecules is influencing the next generation of engines for transportation applications, as well as in disease diagnosis. In such applications, the demands on sensors are quite extreme. Not only does the device have to detect the gas of interest with high sensitivity, it also has to discriminate against other species present in a complex environment, such as combustion exhaust and human breath. In addition, the sensors will need to have as small a footprint as possible in size and power requirements. With these varied requirements in mind, only electrochemical sensors have the potential to be practical. This article focuses on nitric oxide (NOx) and ammonia (NH3) sensor necessary for emission control of next generation, high efficiency, lean burn engines and nitric oxide (NO) sensor for breath analysis for diagnosis of respiratory diseases. In all of these applications, there has been significant recent commercial activity. We indicate the electrochemical principles of these commercial sensors, and the development from our research group. We present potentiometric total NOx sensors that can operate in harsh environments, and impedance-based NH3 sensor for transportation industry. For detecting NO in human breath, we have demonstrated two strategies, the first using a resistive approach, and the second with an array of potentiometric sensors. Data from these sensors, their limitations as well as novel MEMS-based approaches for miniaturization is presented.

  14. In situ study of self-assembled nanocomposite films by spectral SPR sensor.

    PubMed

    Zhang, Zhe; Liu, Jie; Qi, Zhi-mei; Lu, Dan-feng

    2015-06-01

    Spectral surface plasmon resonance (SPR) sensor with a time-resolved charge-coupled device (CCD) detector is a powerful analytical tool for label-free detection of biomolecular interaction at the liquid/solid interface and for in situ study of molecular adsorption behavior. In this work, the layer-by-layer self-assembly processes for three nanocomposite films were monitored in real time using a broadband spectral SPR sensor with a large dynamic range. Kinetics studies suggest that cytochrome c (Cyt c) and deoxy ribonucleic acid (DNA) adsorptions obey the Langmuir-isotherm theory, while gold nanoparticle (GNP) adsorption follows the Diffusion-controlled model. Using poly(sodium 4-styrenesulfonate) (PSS) and poly(dimethyldiallylammonium chloride) (PDDA) as the positively charged agents, three kinds of multilayer films such as the PSS/Cyt c, GNP/Cyt c and PDDA/DNA binary nanocomposites were fabricated on the SPR chips by the electrostatic attraction based on self-assemble. The SPR response in terms of ??R was measured to linear increase with increasing the number of layers for a six-bilayer PSS/Cyt c nanocomposite film, indicating that every PSS/Cyt c layer has equal mass coverage. In contrast, the nonlinear dependences of ??R on the number of bilayers were observed for the GNP/Cyt c and PDDA/DNA nanocomposite multilayer films. PMID:25842131

  15. Flight Demonstration of a Shock Location Sensor Using Constant Voltage Hot-Film Anemometry

    NASA Technical Reports Server (NTRS)

    Moes, Timothy R.; Sarma, Garimella R.; Mangalam, Siva M.

    1997-01-01

    Flight tests have demonstrated the effectiveness of an array of hot-film sensors using constant voltage anemometry to determine shock position on a wing or aircraft surface at transonic speeds. Flights were conducted at the NASA Dryden Flight Research Center using the F-15B aircraft and Flight Test Fixture (FTF). A modified NACA 0021 airfoil was attached to the side of the FTF, and its upper surface was instrumented to correlate shock position with pressure and hot-film sensors. In the vicinity of the shock-induced pressure rise, test results consistently showed the presence of a minimum voltage in the hot-film anemometer outputs. Comparing these results with previous investigations indicate that hot-film anemometry can identify the location of the shock-induced boundary layer separation. The flow separation occurred slightly forward of the shock- induced pressure rise for a laminar boundary layer and slightly aft of the start of the pressure rise when the boundary layer was tripped near the airfoil leading edge. Both minimum mean output and phase reversal analyses were used to identify the shock location.

  16. Toward a chemiresistive ammonia (NH3) gas sensor based on viral-templated gold nanoparticles embedded in polypyrrole nanowires

    NASA Astrophysics Data System (ADS)

    Yan, Yiran; Zhang, Miluo; Su, Heng Chia; Myung, Nosang V.; Haberer, Elaine D.

    2014-08-01

    Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating of gold nanoparticles and PPy electrodeposition via cyclic voltammetry are the focus of this investigation. A gold-binding M13 bacteriophage was used as a bio-template to assemble continuous chains of gold nanoparticles on interdigitated Pt working electrodes. The dimensions of the resulting nanowire-like structures were examined and the electrical resistance measured. PPy films were electropolymerized using an interdigitated planar, Pt electrode integrated counter and reference electrode. Morphological characterization of the polymer films was completed.

  17. Improving the measurement accuracy of mixed gas by optimizing carbon nanotube sensor's electrode separation

    NASA Astrophysics Data System (ADS)

    Hao, Huimin; Zhang, Yong; Quan, Long

    2015-10-01

    Because of excellent superiorities, triple-electrode carbon nanotube sensor acts good in the detection of multi-component mixed gas. However, as one of the key factors affecting the accuracy of detection, the electrode separation of carbon nanotube gas sensor with triple-electrode structure is very difficult to decide. An optimization method is presented here to improve the mixed gas measurement accuracy. This method optimizes every separation between three electrodes of the carbon nanotube sensors in the sensor array when test the multi-component gas mixture. It collects the ionic current detected by sensor array composed of carbon nanotube sensors with different electrode separations, and creates the kernel partial least square regression (KPLSR) quantitative analysis model of detected gases. The optimum electrode separations come out when the root mean square error of prediction (RMSEP) of test samples reaches the minimum value. The gas mixtures of CO and NO2 are measured using sensor array composed of two carbon nanotube sensor with different electrode separations. And every electrode separation of two sensors is optimized by above-mentioned method. The experimental results show that the proposed method selects the optimal distances between electrodes effectively, and achieves higher measurement accuracy.

  18. Evaporation system and method for gas jet deposition of thin film materials

    DOEpatents

    Schmitt, Jerome J. (New Haven, CT); Halpern, Bret L. (Bethany, CT)

    1994-01-01

    A method and apparatus for depositing thin films of materials such as metals, oxides and nitrides at low temperature relies on a supersonic free jet of inert carrier gas to transport vapor species generated from an evaporation source to the surface of a substrate. Film deposition vapors are generated from solid film precursor materials, including those in the form of wires or powders. The vapor from these sources is carried downstream in a low pressure supersonic jet of inert gas to the surface of a substrate where the vapors deposit to form a thin film. A reactant gas can be introduced into the gas jet to form a reaction product with the evaporated material. The substrate can be moved from the gas jet past a gas jet containing a reactant gas in which a discharge has been generated, the speed of movement being sufficient to form a thin film which is chemically composed of the evaporated material and reactant gases.

  19. Chemical gas sensors and the characterization, monitoring and sensor technology needs of the US Department of Energy

    SciTech Connect

    Bastiaans, G.J.; Haas, W.J. Jr.; Junk, G.A.

    1993-10-01

    The Office of Technology Development within the Dept. of Energy (DOE) has the responsibility of providing new technologies to aid the environmental restoration and waste management (ER/WM) activities of the DOE. There is a perception that application and judicious development of chemical sensor technologies could result in large cost savings and reduced risk to the health and safety of ER/WM personnel. A number of potential gas sensor applications which exist within DOE ER/WM operations are described. The capabilities of several chemical sensor technologies and their potential to meet the needs of ER/WM applications in the present or near term future are discussed.

  20. The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh vacuum study

    E-print Network

    Ghosh, Ruby N.

    The role of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh of oxygen in hydrogen sensing by a platinum-gate silicon carbide gas sensor: An ultrahigh vacuum study Yung that elucidate the role of oxygen in the functioning of silicon carbide field-effect gas sensors with nonporous

  1. Highly sensitive gas sensor based on graphene/microfiber hybrid waveguide with Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Wu, Yu; Yao, Baicheng; Cheng, Yang; Zhang, Anqi; Gong, Yuan; Rao, Yun-Jiang

    2014-05-01

    A high sensitivity NH3 gas sensor based on graphene/microfiber hybrid waveguide (GMHW) is reported for the first time. Enhanced by the graphene, a very high sensitivity of 0.3ppm is achieved for GMHW-based NH3 gas sensing. This work may open a window for development of novel GMHW-based gas sensors with high sensitivity, small footprint, easy fabrication and low cost.

  2. Nanoporous Zeolite Thin Film-Based Fiber Intrinsic Fabry-Perot Interferometric Sensor for Detection of Dissolved Organics in Water

    PubMed Central

    Liu, Ning; Hui, Juan; Sun, Cunqiang; Dong, Junhang; Zhang, Luzheng; Xiao, Hai

    2006-01-01

    A fiber optic intrinsic Fabry-Perot interferometric (IFPI) chemical sensor was developed by fine-polishing a thin layer of polycrystalline nanoporous MFI zeolite synthesized on the cleaved endface of a single mode fiber. The sensor operated by monitoring the optical thickness changes of the zeolite thin film caused by the adsorption of organic molecules into the zeolite channels. The optical thickness of the zeolite thin film was measured by white light interferometry. Using methanol, 2-propanol, and toluene as the model chemicals, it was demonstrated that the zeolite IPFI sensor could detect dissolved organics in water with high sensitivity.

  3. Direct fabrication of thin film gold resistance temperature detection sensors on a curved surface using a flexible dry film photoresist and their calibration up to 450 °C

    NASA Astrophysics Data System (ADS)

    Ahn, C. H.; Park, H. W.; Kim, H. H.; Park, S. H.; Son, C.; Kim, M. C.; Lee, J. H.; Go, J. S.

    2013-06-01

    High efficiency heat exchangers, such as intercoolers and recuperators, are composed of complex and compact structures to enhance heat transfer. This limits the installation of conventional temperature sensors to measure the temperature inside the heat exchanger without flow disturbance. To overcome this limitation, we have developed a direct patterning method in which metal is sputtered onto a curved surface using film photoresist and the fabrication of thin film Au resistance temperature detection (RTD) temperature sensors. A photosensitive film resist has been used to overcome the difficulty of 3-dimensional photolithography on a curved surface. The film resist after 2-dimensional photolithography is laminated over an alumina rod which is deposited with Au as an RTD sensing material. The Au metal is etched chemically, and the film resist is removed to form the thin film Au-RTD temperature sensors. They are calibrated by measuring the resistance change against temperature in a thermally controlled furnace. The second order polynomial fit shows good agreement with the measured temperatures with a standard deviation of 0.02 for the temperature range of 20-450 °C. Finally, the performance of the Au-RTD temperature sensors was evaluated.

  4. Application of PIC microcontrollers in single-sensor dual gas-CO/CH4 detectors

    NASA Astrophysics Data System (ADS)

    Pietraszek, Stanislaw; Pachole, Aleksander

    2001-08-01

    The main aim of this work is to present an application of PIC16 microcontrollers in single sensor two gas - CO and CH4 detectors, using recently developed by FIS Incorporated, semiconductor sensor SB-95. Microcontroller is used not only for comparison the actual output signal from the sensor with the warning and alarm thresholds, but also provides control and self diagnostic functions. Output logic signals allow user to check the level of gas concentration and detect the improper operation of sensor and electronics circuits.

  5. Strain sensor using stress-magnetoresistance effect of Ni-Fe/Mn-Ir exchange-coupled magnetic film

    NASA Astrophysics Data System (ADS)

    Sonehara, M.; Shinohara, T.; Sato, T.; Yamasawa, K.; Miura, Y.

    2010-05-01

    A strain sensor using a stress-magnetoresistance effect of a Ni-Fe/Mn-Ir exchange-coupled magnetic film was fabricated and evaluated. The stress magnetoresistance is used in the inverse magnetostrictive effect and the magnetoresistance effect in the magnetic film since an external stress is changed into an electric resistance in it. A compressive stress was measured by the strain sensor with a Mn-Ir (10 nm)/Ni-Fe (50 nm)/Ru (1 nm) exchange-coupled film. The change in resistivity ?? /? is proportional to the applied compressive stress ? for ? ?50 MPa in the strain sensor. When increasing Ni-Fe layer thickness in the strain sensor, a gauge factor increased.

  6. Thermal characterization of austenite stainless steel (304) and CNT films of varying thickness using micropipette thermal sensors

    NASA Astrophysics Data System (ADS)

    Dangol, Ashesh

    Thermal transport behavior of austenite stainless steel stripe (304) and the carbon nano-tubes (CNTs) films of varying thickness are studied using a micropipette thermal sensor. Micropipette sensors of various tip sizes were fabricated and tested for the sensitivity and reliability. The sensitivity deviated by 0.11 for a batch of pipette coated under same physical vapor deposition (PVD) setting without being affected by a tip size. Annealing, rubber coating and the vertical landing test of the pipette sensor proved to be promising in increasing the reliability and durability of the pipette sensors. A micro stripe (80microm x 6microm x 0.6microm) of stainless steel, fabricated using focused ion beam (FIB) machining, was characterized whose thermal conductivity was determined to be 14.9 W/m-K at room temperature. Similarly, the thermal characterization of CNT films showed the decreasing tendency in the thermal transport behavior with the increase in the film thickness.

  7. An ultra-sensitive resistive pressure sensor based on hollow-sphere microstructure induced elasticity in conducting polymer film

    NASA Astrophysics Data System (ADS)

    Pan, Lijia; Chortos, Alex; Yu, Guihua; Wang, Yaqun; Isaacson, Scott; Allen, Ranulfo; Shi, Yi; Dauskardt, Reinhold; Bao, Zhenan

    2014-01-01

    Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultra-sensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1?Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.

  8. Sensor Selection for Aircraft Engine Performance Estimation and Gas Path Fault Diagnostics

    NASA Technical Reports Server (NTRS)

    Simon, Donald L.; Rinehart, Aidan W.

    2015-01-01

    This paper presents analytical techniques for aiding system designers in making aircraft engine health management sensor selection decisions. The presented techniques, which are based on linear estimation and probability theory, are tailored for gas turbine engine performance estimation and gas path fault diagnostics applications. They enable quantification of the performance estimation and diagnostic accuracy offered by different candidate sensor suites. For performance estimation, sensor selection metrics are presented for two types of estimators including a Kalman filter and a maximum a posteriori estimator. For each type of performance estimator, sensor selection is based on minimizing the theoretical sum of squared estimation errors in health parameters representing performance deterioration in the major rotating modules of the engine. For gas path fault diagnostics, the sensor selection metric is set up to maximize correct classification rate for a diagnostic strategy that performs fault classification by identifying the fault type that most closely matches the observed measurement signature in a weighted least squares sense. Results from the application of the sensor selection metrics to a linear engine model are presented and discussed. Given a baseline sensor suite and a candidate list of optional sensors, an exhaustive search is performed to determine the optimal sensor suites for performance estimation and fault diagnostics. For any given sensor suite, Monte Carlo simulation results are found to exhibit good agreement with theoretical predictions of estimation and diagnostic accuracies.

  9. Wireless biomedical signal monitoring device on wheelchair using noncontact electro-mechanical film sensor.

    PubMed

    Kim, Jong-Myoung; Hong, Joo-Hyun; Cho, Myeong-Chan; Cha, Eun-Jong; Lee, Tae-Soo

    2007-01-01

    The present study purposed to measure the BCG (Ballistocardiogram) of subjects on a wheelchair using a noncontact electro-mechanical film sensor (EMFi sensor) and detect the respiratory rate from BCG in real-time while the subjects are moving. In order to measure wirelessly the BCG of subjects moving on a wheelchair, we made a seat-type noncontact EMFi sensor and developed a transmitter and a receiver using Zigbee wireless RF communication technology. The sensor is embedded with a 3-axis accelerometer to remove the noise of wheelchair vibration from BCG signal. Signal obtained from each sensor goes through the A/D converter and is recorded in the SD (Secure Digital) card in PDA (Personal Digital Assistance) with a receiving part. We also developed a PC (Personal Computer) data analysis program, analyzed data recorded in the SD card using the program, and presented the results in graph. Lastly, this study demonstrated that a warning message can be sent from PDA to the remote server via a CDMA (Code Division Multiple Access) network in case the person on wheelchair falls in emergency. Our experiment was carried out with healthy male and female adults in their 20s who volunteered to help this research. The results of analyzing collected data will show that the respiratory rate can be measured in real-time on a moving wheelchair. PMID:18002021

  10. Insights into the reactive ion etching mechanism of nanocrystalline diamond films as a function of film microstructure and the presence of fluorine gas

    SciTech Connect

    Yoon, Ju-Heon; Lee, Wook-Seong; Park, Jong-Keuk; Hwang, Gyu Weon; Baik, Young-Joon; Jeong, Jeung-hyun; Seong, Tae-Yeon

    2010-02-15

    Inhomogeneous etching of nanocrystalline diamond (NCD) films, which produces nanopillars during reactive ion etching process, is problematic to the microfabrication of NCD films for the sensor and actuator applications. Thus, its origin was investigated for various initial microstructures of the NCD films, SF{sub 6}/O{sub 2} gas ratios during etching, and plasma powers. The etched NCD film surface roughness became more pronounced (leading to larger pillar diameters and heights) for larger initial microstructural features (larger grain and cluster sizes), particularly at low plasma powers. The surface roughening was significantly reduced with the addition of SF{sub 6}, almost disappearing at SF{sub 6}/O{sub 2} of 5% to 10%. These results indicate that the etch rate was locally enhanced at the interfaces between grains or clusters, and the etch rate disparity between intragranular and intergranular (or cluster) carbons increased with decreasing ion energy, implying a chemical reaction rate-limited etching mechanism. The role of SF{sub 6} could be explained to reduce the energy barrier for the chemical reaction of intragranular carbons. Here we suggest that the etching rate is limited by an energy barrier that could be reduced by defect generation during ion bombardment or by catalytic radicals.

  11. ZnO-nanowires modified polypyrrole films as highly selective and sensitive chlorine sensors

    NASA Astrophysics Data System (ADS)

    Joshi, Aditee; Aswal, D. K.; Gupta, S. K.; Yakhmi, J. V.; Gangal, S. A.

    2009-03-01

    Room temperature sensing characteristics of the polypyrrole (PPy) films modified with different weight percentages of ZnO nanowires (ZnO-NWs) have been studied for various oxidizing (NO2 and Cl2) as well as reducing (H2S, NH3, CH4, and CO) gases. We demonstrate that ZnO-NW (50 wt %):PPy composite films are highly selective to Cl2 along with high-sensitivity (40 at 10 ppm), fast-response (55 s), and highly reproducible response curves. It has been shown that negatively charged O2- surfaces of ZnO-NW transfer electrons to PPy, making it in a highly reduced form. A strong localization of charge carriers in the reduced PPy makes composite film highly resistive (>1010 ? cm) as well insensitive to interaction with most of the gases except Cl2. Cl2 being highly oxidizing gas interacts with composite films and causes a sharp reduction in its resistivity.

  12. Experimental study of rotordynamic coefficients of squeeze film dampers of an aircraft gas turbine engine 

    E-print Network

    Na, Uhn Joo

    1996-01-01

    The rotordynamic coefficients of squeeze film dampers of an aircraft gas turbine engine were investigated experimentally. Rotordynamic model(XLROTOR) for Gas Generator and Power Turbine were constructed. The XLROTOR response plots with changing...

  13. Gas Sensing Mechanism in Chemiresistive Cobalt and Metal-Free Phthalocyanine Thin Films

    E-print Network

    Kummel, Andrew C.

    Gas Sensing Mechanism in Chemiresistive Cobalt and Metal-Free Phthalocyanine Thin Films Forest I@ucsd.edu; wtrogler@ucsd.edu Abstract: The gas sensing behaviors of cobalt phthalocyanine (CoPc) and metal

  14. Characteristic responses of a semiconductor gas sensor depending on the frequency of a periodic temperature change

    NASA Astrophysics Data System (ADS)

    Nakata, Satoshi; Okunishi, Hirokazu

    2005-02-01

    A novel gas-sensing system based on a dynamic nonlinear response is reported to enhance the selectivity toward sample gases using a single detector. A periodic temperature change was applied to a semiconductor gas sensor and the resulting conductance of the sensor was evaluated by fast Fourier transformation (FFT). The dynamic nonlinear response to the sample gases was further characterized depending on the frequency of the temperature change. The characteristic sensor response under the application of a temperature change was theoretically simulated by considering the kinetics of gas molecules on the semiconductor surface.

  15. A novel compact design of calibration equipment for gas and thermal sensors

    SciTech Connect

    Feng, P. X.; Zhang, H. X.; Peng, X. Y.; Sajjad, M.; Chu, J.

    2011-04-15

    A novel design of calibration equipment has been developed for static and dynamic calibrations of gas and thermal sensors. This system is cheap, compact, and easily adjustable, which is also combined with a plasma surface modification source for tailoring the surface of sensors to ensure the sensitivity and selectivity. The main advantage of this equipment is that the operating temperature, bias voltage, types of plasma source (for surface modification), types of feeding gases, and gas flow rate (for calibrations), etc., can be independently controlled. This novel system provides a highly reliable, reproducible, and economical method of calibrations for various gas and thermal sensors.

  16. Crack-free periodic porous thin films assisted by plasma irradiation at low temperature and their enhanced gas-sensing performance.

    PubMed

    Dai, Zhengfei; Jia, Lichao; Duan, Guotao; Li, Yue; Zhang, Hongwen; Wang, Jingjing; Hu, Jinlian; Cai, Weiping

    2013-09-27

    Homogenous thin films are preferable for high-performance gas sensors because of their remarkable reproducibility and long-term stability. In this work, a low-temperature fabrication route is presented to prepare crack-free and homogenous metal oxide periodic porous thin films by oxygen plasma irradiation instead of high temperature annealing by using a sacrificial colloidal template. Rutile SnO2 is taken as an example to demonstrate the validity of this route. The crack-free and homogenous porous thin films are successfully synthesized on the substrates in situ with electrodes. The SnO2 porous thin film obtained by plasma irradiation is rich in surface OH groups and hence superhydrophilic. It exhibits a more homogenous structure and lower resistance than porous films generated by annealing. More importantly, such thin films display higher sensitivity, a lower detection threshold (100 ppb to acetone) and better durability than those that have been directly annealed, resulting in enhanced gas-sensing performance. The presented method could be applied to synthesize other metal oxide homogenous thin films and to fabricate gas-sensing devices with high performances. PMID:24026905

  17. Optical Thin Films for Gas Sensing in Advanced Coal Fired Power Plants

    SciTech Connect

    Ohodnicki, Paul; Brown, Thomas; Baltrus John; Chorpening, Benjamin

    2012-08-09

    Even for existing coal based plants, the opportunity for sensors and controls to improve efficiency is great. A wide range of gas species are of interest for relevant applications. Functional sensor layers for embedded sensing must be compatible with extreme conditions (temperature, pressure, corrosive). Au incorporated metal oxides have been looked at by a number of other authors previously for gas sensing, but have often focused on temperatures below 500{degree}C. Au nanoparticle incorporated metal oxide thin films have shown enhanced gas sensing response. In prior work, we have demonstrated that material systems such as Au nanoparticle incorporated TiO{sub 2} films exhibit a potentially useful optical response to changing gas atmospheres at temperatures up to ~800-850{degree}C. Current work is focused on sputter-deposited Au/TiO{sub 2} films. Au and Ti are multi-layered sputter deposited, followed by a 950{degree}C oxidation step. Increasing Au layer thickness yields larger particles. Interband electronic transitions significantly modify the optical constants of Au as compared to the damped free electron theory. A high temperature oxidation (20%O{sub 2}/N{sub 2}) treatment was performed at 700{degree}C followed by a reduction (4%H{sub 2}/N{sub 2}) treatment to illustrate the shift in both absorption and scattering with exposure to reducing gases. Shift of localized surface plasmon resonance (LSPR) absorption peak in changing gas atmospheres is well documented, but shift in the peak associated with diffuse scattering is a new observation. Increasing Au layer-thickness results in an increase in LSPR absorption and a shift to longer wavelengths. Diffuse scattering associated with the LSPR resonance of Au shows a similar trend with increasing Au thickness. To model the temperature dependence of LSPR, the modification to the plasmon frequency, the damping frequency, and the dielectric constant of the oxide matrix must be accounted for. Thermal expansion of Au causes a decrease in free-carrier concentration and plasmon frequency with increasing temperature. Increased scattering of electrons with increasing temperatures results in an increased damping frequency for free carriers. The thermo-optic coefficient of TiO{sub 2} is assumed to be constant or decreasing with increasing temperature. A Custom Designed System Can Be Used to Monitor Optical Transmission and Reflection of Films at Elevated Temperatures and Upon Exposure to Changing Ambient Gas Atmospheres. The calculated extinction peak broadens and reduces peak height with increasing temperature. Extinction spectra measured using the elevated temperature system deviate from measurements performed with an integrating sphere. Modifications to measured transmittance and reflectance spectra are observed with increasing temperatures. Optical constants of Au nanoparticles were measured for elevated temperature. The thermo-optic coefficient of TiO{sub 2} strongly affects the shift in LSPR absorption peak. Peak broadening is dictated by the increased damping frequency of Au. In all cases of the theoretical modeling, we are assuming a particle of Au embedded in a TiO{sub 2} matrix without any interparticle interaction. Localized surface plasmon resonance in noble metal nanoparticles is associated with the free electrons. Surface charges create an internal field that acts as a restoring force on displaced charge carriers resulting in an oscillation with an associated resonance. An estimate of the sensitivity as a function of wavelength for sensing done using a single wavelength transmission measurement can be derived by focusing on the partial derivative of Q{sub abs} with respect to the material parameter that we assume is changing during the experiment. We focus on the free carrier density. However, other material parameters may also change in some cases. Peak sensitivity for transmission or absorption based sensing occurs on either side of the LSPR absorption peak maximum. Theoretically predicted wavelength dependence is consistent with the literature. The wavelength of LSPR ab

  18. Membrane-Based Characterization of a Gas Component — A Transient Sensor Theory

    PubMed Central

    Lazik, Detlef

    2014-01-01

    Based on a multi-gas solution-diffusion problem for a dense symmetrical membrane this paper presents a transient theory of a planar, membrane-based sensor cell for measuring gas from both initial conditions: dynamic and thermodynamic equilibrium. Using this theory, the ranges for which previously developed, simpler approaches are valid will be discussed; these approaches are of vital interest for membrane-based gas sensor applications. Finally, a new theoretical approach is introduced to identify varying gas components by arranging sensor cell pairs resulting in a concentration independent gas-specific critical time. Literature data for the N2, O2, Ar, CH4, CO2, H2 and C4H10 diffusion coefficients and solubilities for a polydimethylsiloxane membrane were used to simulate gas specific sensor responses. The results demonstrate the influence of (i) the operational mode; (ii) sensor geometry and (iii) gas matrices (air, Ar) on that critical time. Based on the developed theory the case-specific suitable membrane materials can be determined and both operation and design options for these sensors can be optimized for individual applications. The results of mixing experiments for different gases (O2, CO2) in a gas matrix of air confirmed the theoretical predictions. PMID:24608004

  19. Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors

    NASA Technical Reports Server (NTRS)

    Grimes, C. A.; Kouzoudis, D.

    2000-01-01

    Free-standing magnetoelastic thick-film sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted from the sensor in response to a time varying magnetic field. This property allows the sensors to be monitored remotely without the use of direct physical connections, such as wires, enabling measurement of environmental parameters from within sealed, opaque containers. In this work, we report on application of magnetoelastic sensors to measurement of atmospheric pressure, fluid-flow velocity, temperature, and mass load. Mass loading effects are demonstrated by fabrication of a remote query humidity sensor, made by coating the magnetoelastic thick film with a thin layer of solgel deposited Al2O3 that reversibly changes mass in response to humidity. c2000 Elsevier Science S.A. All rights reserved.

  20. Multifunctional Polypeptide EQCN Sensors: Probing the Cysteamine-Glutathione Film Permeability with Hg(II) Ions

    PubMed Central

    Hepel, Maria; Dallas, Julia

    2008-01-01

    Multifunctional films are the basis of biosensors and play an important role in the emerging field of nanobioelectronics. In this work, films of a tripeptide glutathione (GSH) immobilized on a self-assembled monolayer of cysteamine (CA-SAM) on a quartz crystal Au piezosensor have been synthesized and characterized using electrochemical quartz crystal nanogravimetry (EQCN) with a Hg(II) ion probe. It has been found that in contrast to previously studied Au/GSH films, the Au/CA-GSH films strongly hinder the formation of Hg0 with bulk properties while still allowing for relatively easy permeation by Hg(II) ions. This results in complete disappearance of the sharp Hg0 electrodissolution peak which is observed on bare Au and Au/GSH piezosensors. The multiple-peak anodic behavior of Au/CA and bare Au is replaced by a single high-field anodic peak of mercury reoxidation in the case of Au/CA-GSH sensors. The mass-to-charge plots indicate predominant ingress/egress of Hg(II) to/from the film. The strong hindrance of CA-SAM to bulk-Hg0 formation is attributed to film-stabilizing formation of surface (CA)2Hg2+ complexes with conformation evaluated by ab initio quantum mechanical calculations of electronic structure using Hartree-Fock methods. The associates CA-GSH provide an additional functionality of the side sulfhydryl group which is free for interactions, e.g. with heavy metals. It is proposed that in the film, the CA-GSH molecules can assume open (extended) conformation or bent hydrogen-bonded conformation with up to four possible internal hydrogen bonds.

  1. Sensors and Actuators B xxx (2006) xxxxxx Contrast enhancement of gas sensor array patterns with

    E-print Network

    Raman, Barani

    2006-01-01

    a fiber-optic sensor array. Pearce et al. [11] investigated the issue of concen- tration hyperacuity sensor arrays has traditionally relied on statistical or artificial neural network techniques [1­3]. Much

  2. Gas and flame detection and identification using uncooled MWIR imaging sensors

    NASA Astrophysics Data System (ADS)

    Linares, Rodrigo; Vergara, Germán.; Gutiérrez, Raúl; Fernández, Carlos; Villamayor, Víctor; Gómez, Luis; González-Camino, María.; Baldasano, Arturo

    2015-05-01

    Gas detectors are nowadays widely spread for safety purposes in industrial facilities. They are categorized by the type of gas they detect: combustible and/or toxic. Whereas electrochemical sensors have limited lifetime and maintenance issues, infrared sensors are reliable and free of maintenance devices used for detecting a wide variety of VOCs and inflammable gases such as hydrocarbon vapors. They usually work via a system of transmitters (light sources) which power is interfered when a gas is present in the optical path. A spectral analysis of this optical interference allows the gas detection and identification. Optical flame detectors are sensors intended to sight and respond to the presence of a flame, faster than a smoke detector or a heat detector would do. Many of these systems operate in the infrared band in order to detect the heat radiation, most of the times by comparison of three specific wavelength bands. Most of the present infrared gas and optical flame detectors traditionally make use of MWIR single point sensors rather than imaging sensors; this is mainly due to the lack of affordable imaging sensing technologies in this band of the infrared spectrum. However, the appearance of uncooled imaging MWIR sensors made of VPD PbSe, with spectral detection range from 1 to 5 microns, opens the possibility to incorporate these sensors into gas and flame detection systems to allow area monitoring.

  3. Gas assisted thin-film evaporation from confined spaces

    NASA Astrophysics Data System (ADS)

    Narayanan, Shankar

    A novel cooling mechanism based on evaporation of thin liquid films is presented for thermal management of confined heat sources, such as microprocessor hotspots, high power light emitting diodes and RF packages with a high operational frequency. A thin nanoporous membrane (˜1--5microm) is utilized to maintain microscopically thin liquid films (˜1--5microm) by capillary action, while providing a pathway for the vapor generated due to evaporation at the liquid-vapor interface. The vapor generated by evaporation is continuously removed by using a dry sweeping gas, keeping the membrane outlet dry. This thesis presents a detailed theoretical, computational and experimental investigation of the heat and mass transfer mechanisms that result in cooling the confined heat sources. Performance analysis of this cooling mechanism demonstrates heat fluxes over 600W/cm2 for sufficiently thin membrane and film thicknesses (˜1--5microm) and by using air jet impingement for advection of vapor from the membrane surface. Based on the results from this performance analysis, a monolithic micro-fluidic device is designed and fabricated incorporating micro and nanoscale features. This MEMS/NEMS device serves multiple functionalities of hotspot simulation, temperature sensing, and evaporative cooling. Subsequent experimental investigations using this microfluidic device demonstrate heat fluxes in excess of 600W/cm2 at 90 °C using water as the evaporating coolant. In order to further enhance the device performance, a comprehensive theoretical and computational analysis of heat and mass transfer at micro and nanoscales is carried out. Since the coolant is confined using a nanoporous membrane, a detailed study of evaporation inside a nanoscale cylindrical pore is performed. The continuum analysis of water confined within a cylindrical nanopore determines the effect of electrostatic interaction and Van der Waals forces in addition to capillarity on the interfacial transport characteristics during evaporation. The detailed analysis demonstrates that the effective thermal resistance offered by the interface is negligible in comparison to the thermal resistance due to the thin film and vapor advection. In order to determine the factors limiting the performance of the MEMS device on a micro-scale, a device-level detailed computational analysis of heat and mass transfer is carried out, which is supported by experimental investigation. Identifying the contribution of various simultaneously occurring cooling mechanisms at different operating conditions, this analysis proposes utilization of hydrophilic membranes for maintaining very thin liquid films and further enhancement in vapor advection at the membrane outlet to achieve higher heat fluxes.

  4. One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection

    PubMed Central

    Zhao, Xiaoli; Cai, Bin; Tang, Qingxin; Tong, Yanhong; Liu, Yichun

    2014-01-01

    Recently; one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio; which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime. This article reviews the recent developments in the field of 1D nanostructure FET for gas detection. The sensor configuration; the performance as well as their sensing mechanism are evaluated. PMID:25090418

  5. Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lipomi, Darren J.; Vosgueritchian, Michael; Tee, Benjamin C.-K.; Hellstrom, Sondra L.; Lee, Jennifer A.; Fox, Courtney H.; Bao, Zhenan

    2011-12-01

    Transparent, elastic conductors are essential components of electronic and optoelectronic devices that facilitate human interaction and biofeedback, such as interactive electronics, implantable medical devices and robotic systems with human-like sensing capabilities. The availability of conducting thin films with these properties could lead to the development of skin-like sensors that stretch reversibly, sense pressure (not just touch), bend into hairpin turns, integrate with collapsible, stretchable and mechanically robust displays and solar cells, and also wrap around non-planar and biological surfaces such as skin and organs, without wrinkling. We report transparent, conducting spray-deposited films of single-walled carbon nanotubes that can be rendered stretchable by applying strain along each axis, and then releasing this strain. This process produces spring-like structures in the nanotubes that accommodate strains of up to 150% and demonstrate conductivities as high as 2,200 S cm-1 in the stretched state. We also use the nanotube films as electrodes in arrays of transparent, stretchable capacitors, which behave as pressure and strain sensors.

  6. Development of Microfabricated Chemical Gas Sensors and Sensor Arrays for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Hunter, G. W.; Neudeck, P. G.; Fralick, G.; Thomas, V.; Liu, C. C.; Wu, W. H.; Ward, B.; Makel, D.

    2002-01-01

    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, fire detection, and environmental monitoring. 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. However, due to issues of selectivity and cross-sensitivity, individual sensors are limited in the amount of information that they can provide in environments that contain multiple chemical species. Thus, sensor arrays are being developed to address detection needs in such multi-species environments. This paper 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, hydrazine, 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.

  7. Aircraft aerodynamic parameter detection using micro hot-film flow sensor array and BP neural network identification.

    PubMed

    Que, Ruiyi; Zhu, Rong

    2012-01-01

    Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic parameters are inferred using a micro hot-film flow sensor array mounted on the surface of the wing is proposed. A back-propagation neural network is used to model the coupling relationship between readings of the sensor array and aerodynamic parameters. Two different sensor arrangements are tested in wind tunnel experiments and dependence of the system performance on the sensor arrangement is analyzed. PMID:23112638

  8. Aircraft Aerodynamic Parameter Detection Using Micro Hot-Film Flow Sensor Array and BP Neural Network Identification

    PubMed Central

    Que, Ruiyi; Zhu, Rong

    2012-01-01

    Air speed, angle of sideslip and angle of attack are fundamental aerodynamic parameters for controlling most aircraft. For small aircraft for which conventional detecting devices are too bulky and heavy to be utilized, a novel and practical methodology by which the aerodynamic parameters are inferred using a micro hot-film flow sensor array mounted on the surface of the wing is proposed. A back-propagation neural network is used to model the coupling relationship between readings of the sensor array and aerodynamic parameters. Two different sensor arrangements are tested in wind tunnel experiments and dependence of the system performance on the sensor arrangement is analyzed. PMID:23112638

  9. The mechanism of improved aeration due to gas films on leaves of submerged rice.

    PubMed

    Verboven, Pieter; Pedersen, Ole; Ho, Quang Tri; Nicolai, Bart M; Colmer, Timothy D

    2014-10-01

    Some terrestrial wetland plants, such as rice, have super-hydrophobic leaf surfaces which retain a gas film when submerged. O2 movement through the diffusive boundary layer (DBL) of floodwater, gas film and stomata into leaf mesophyll was explored by means of a reaction-diffusion model that was solved in a three-dimensional leaf anatomy model. The anatomy and dark respiration of leaves of rice (Oryza sativa?L.) were measured and used to compute O2 fluxes and partial pressure of O2 (pO2 ) in the DBL, gas film and leaf when submerged. The effects of floodwater pO2 , DBL thickness, cuticle permeability, presence of gas film and stomatal opening were explored. Under O2 -limiting conditions of the bulk water (pO2 ?gas film significantly increases the O2 flux into submerged leaves regardless of whether stomata are fully or partly open. With a gas film, tissue pO2 substantially increases, even for the slightest stomatal opening, but not when stomata are completely closed. The effect of gas films increases with decreasing cuticle permeability. O2 flux and tissue pO2 decrease with increasing DBL thickness. The present modelling analysis provides a mechanistic understanding of how leaf gas films facilitate O2 entry into submerged plants. PMID:24548021

  10. Microwave plasma assisted supersonic gas jet deposition of thin film materials

    DOEpatents

    Schmitt, J.J. III; Halpern, B.L.

    1993-10-26

    An apparatus for fabricating thin film materials utilizing high speed gas dynamics relies on supersonic free jets of carrier gas to transport depositing vapor species generated in a microwave discharge to the surface of a prepared substrate where the vapor deposits to form a thin film. The present invention generates high rates of deposition and thin films of unforeseen high quality at low temperatures. 5 figures.

  11. Redesigned Gas Mass Flow Sensors for Space Shuttle Pressure Control System and Fuel Cell System

    NASA Technical Reports Server (NTRS)

    1996-01-01

    A program was conducted to determine if a state of the art micro-machined silicon solid state flow sensor could be used to replace the existing space shuttle orbiter flow sensors. The rather aggressive goal was to obtain a new sensor which would also be a multi-gas sensor and operate over a much wider flow range and with a higher degree of accuracy than the existing sensors. Two types of sensors were tested. The first type was a venturi throat design and the second was a bypass design. The accuracy of venturi design was found to be marginally acceptable. The bypass sensor was much better although it still did not fully reach the accuracy goal. Two main problems were identified which would require further work.

  12. Apparatus to characterize gas sensor response under real-world conditions in the lab.

    PubMed

    Kneer, J; Eberhardt, A; Walden, P; Ortiz Pérez, A; Wöllenstein, J; Palzer, S

    2014-05-01

    The use of semiconducting metal-oxide (MOX) based gas sensors in demanding applications such as climate and environmental research as well as industrial applications is currently hindered by their poor reproducibility, selectivity, and sensitivity. This is mainly due to the sensing mechanism which relies on the change of conductivity of the metal-oxide layer. To be of use for advanced applications metal-oxide (MOX) gas sensors need to be carefully prepared and characterized in laboratory environments prior to deployment. This paper describes the working principle, design, and use of a new apparatus that can emulate real-world conditions in the laboratory and characterize the MOX gas sensor signal in tailor-made atmospheres. In particular, this includes the control of trace gas concentrations and the control of oxygen and humidity levels which are important for the surface chemistry of metal-oxide based sensors. Furthermore, the sensor temperature can be precisely controlled, which is a key parameter of semiconducting, sensitive layers, and their response to particular gas compositions. The setup also allows to determine the power consumption of each device individually which may be used for performance benchmarking or monitoring changes of the temperature of the gas composition. Both, the working principle and the capabilities of the gas measurement chamber are presented in this paper employing tin dioxide (SnO2) based micro sensors as exemplary devices. PMID:24880407

  13. CNT-based RFID Passive Gas Sensor Cecilia Occhiuzzi, Amin Rida , Gaetano Marrocco, Manos M. Tentzeris

    E-print Network

    Tentzeris, Manos

    CNT-based RFID Passive Gas Sensor Cecilia Occhiuzzi, Amin Rida , Gaetano Marrocco, Manos M-Wall Carbon Nanotube (CNT) are examined for the design of a passive and maintenance-free wireless RFID sensor way, by using antenna measurement and simulations in a controlled medium. A CNT-based prototype RFID

  14. Mid-Infrared Laser based Gas Sensor Technologies for Environmental Monitoring,

    E-print Network

    Chapter XX Mid-Infrared Laser based Gas Sensor Technologies for Environmental Monitoring, Medical Electronics Group, Wroclaw University of Technology, Wybrzeze Wyspi- anskiego 27, 50-370 Wroclaw, Poland Abstract Recent advances in the development of compact sensors based on mid- infrared continuous wave (CW

  15. H2S gas sensing mechanism of SnO2 films with ultrathin CuO dotted islands

    NASA Astrophysics Data System (ADS)

    Chowdhuri, Arijit; Sharma, Parmanand; Gupta, Vinay; Sreenivas, K.; Rao, K. V.

    2002-08-01

    H2S gas interaction mechanisms of sputtered SnO2 and SnO2-CuO bilayer sensors with a varying distribution of the Cu catalyst on SnO2 are studied using Pt interdigital electrodes within the sensing film. Sensitivity to H2S gas is investigated in the range 20-1200 ppm. Changes induced on the surface, the SnO2-CuO interface, and the internal bulk region of the sensing SnO2 film upon exposure to H2S have been analyzed to explain the increasing sensitivity of three different sensors SnO2, SnO2-CuO, and SnO2 with CuO islands. SnO2 film covered with 0.6 mm diameter ultrathin (approx10 nm) CuO dots is found to exhibit a high sensitivity of 7.3 x103 at a low operating temperature of 150 degC. A response speed of 14 s for 20 ppm of H2S, and a fast recovery time of 118 s in flowing air have been measured. The presence of ultrathin CuO dotted islands allow effective removal of adsorbed oxygen from the uncovered SnO2 surface due to spillover of hydrogen dissociated from the H2S-CuO interaction, and the spillover mechanism is sensed through the observed fast response characteristics, and the high sensitivity of the SnO2-CuO-dot sensor.

  16. Electrical resistivity response of amorphous carbon nitride thin films in various gas atmospheres

    NASA Astrophysics Data System (ADS)

    Tamura, Naoyuki; Aono, Masami; Abe, Hiroshi; Kitazawa, Nobuaki; Watanabe, Yoshihisa

    2015-04-01

    Electrical behaviors of amorphous carbon nitride (a-CNx) films following exposure to various gas species were investigated. The a-CNx film was prepared by reactive RF magnetron sputtering at 873 K. The resistivity of the film was measured in flowing He, N2, O2, Ar, and CO2. Regardless of gas species, the electrical resistivity of the a-CNx film dropped rapidly following gas injection and recovered in the evacuation process. This phenomenon is closely related to the changes in the film microstructure and electrical state. The response time in the adsorption process decreased with increasing gas pressure. The variation range of the electrical resistivity changed depending on the gas species.

  17. Highly sensitive room-temperature surface acoustic wave (SAW) ammonia sensors based on Co?O?/SiO? composite films.

    PubMed

    Tang, Yong-Liang; Li, Zhi-Jie; Ma, Jin-Yi; Su, Hai-Qiao; Guo, Yuan-Jun; Wang, Lu; Du, Bo; Chen, Jia-Jun; Zhou, Weilie; Yu, Qing-Kai; Zu, Xiao-Tao

    2014-09-15

    Surface acoustic wave (SAW) sensors based on Co3O4/SiO2 composite sensing films for ammonia detection were investigated at room temperature. The Co3O4/SiO2 composite films were deposited onto ST-cut quartz SAW resonators by a sol-gel method. SEM and AFM characterizations showed that the films had porous structures. The existence of SiO2 was found to enhance the ammonia sensing property of the sensor significantly. The sensor based on a Co3O4/SiO2 composite film, with 50% Co3O4 loading, which had the highest RMS value (3.72), showed the best sensing property. It exhibited a positive frequency shift of 3500 Hz to 1 ppm ammonia as well as excellent selectivity, stability and reproducibility at room temperature. Moreover, a 37% decrease in the conductance of the composite film as well as a positive frequency shift of 12,500 Hz were observed when the sensor was exposed to 20 ppm ammonia, indicating the positive frequency shift was derived from the decrease in film conductance. PMID:25151235

  18. Determination of gas composition in a biogas plant using a Raman-based sensor system

    NASA Astrophysics Data System (ADS)

    Eichmann, S. C.; Kiefer, J.; Benz, J.; Kempf, T.; Leipertz, A.; Seeger, T.

    2014-07-01

    We propose a gas sensor, based on spontaneous Raman scattering, for the compositional analysis of typical biogas mixtures and present a description of the sensor, as well as of the calibration procedure, which allows the quantification of condensable gases. Moreover, we carry out a comprehensive characterization of the system, in order to determine the measurement uncertainty, as well as influences of temperature and pressure fluctuation. Finally, the sensor is applied at different locations inside a plant in which biogas is produced from renewable raw materials. The composition is monitored after fermenting, after purification and after the final conditioning, where natural gas is added. The Raman sensor is able to detect all the relevant gas components, i.e. CH4, CO2, N2 and H2O, and report their individual concentrations over time. The results were compared to reference data from a conventional gas analyzer and good agreement was obtained.

  19. Electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines

    SciTech Connect

    Holcomb, Gordon R.; Bullard, Sophie J.; Covino, Bernard S., Jr.; Cramer, Stephen D.; Russell, James H.; Ziomek-Moroz, Margaret

    2002-09-01

    The U.S. Department of Energy, National Energy Technology Laboratory funded a Natural Gas Infrastructure Reliability program directed at increasing and enhancing research and development activities in topics such as remote leak detection, pipe inspection, and repair technologies and materials. The Albany Research Center (ARC), U.S. Department of Energy was funded to study the use of electrochemical noise sensors for detection of localized and general corrosion of natural gas transmission pipelines. As part of this, ARC entered into a collaborative effort with the corrosion sensor industry to demonstrate the capabilities of commercially available remote corrosion sensors for use with the Nation's Gas Transmission Pipeline Infrastructure needs. The goal of the research was to develop an emerging corrosion sensor technology into a monitor for the type and degree of corrosion occurring at key locations in gas transmission pipelines.

  20. A 3D scaffold for ultra-sensitive reduced graphene oxide gas sensors

    NASA Astrophysics Data System (ADS)

    Yun, Yong Ju; Hong, Won G.; Choi, Nak-Jin; Park, Hyung Ju; Moon, Seung Eon; Kim, Byung Hoon; Song, Ki-Bong; Jun, Yongseok; Lee, Hyung-Kun

    2014-05-01

    An ultra-sensitive gas sensor based on a reduced graphene oxide nanofiber mat was successfully fabricated using a combination of an electrospinning method and graphene oxide wrapping through an electrostatic self-assembly, followed by a low-temperature chemical reduction. The sensor showed excellent sensitivity to NO2 gas.An ultra-sensitive gas sensor based on a reduced graphene oxide nanofiber mat was successfully fabricated using a combination of an electrospinning method and graphene oxide wrapping through an electrostatic self-assembly, followed by a low-temperature chemical reduction. The sensor showed excellent sensitivity to NO2 gas. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00332b