Sample records for film gas sensor

  1. SAW Gas sensors with carbon nanotubes films

    Microsoft Academic Search

    M. Penza; R. Rossi; M. Alvisi; P. Aversa; G. Cassano; D. Suriano; M. Benetti; D. Cannata; F. Di Pietrantonio; E. Verona

    2008-01-01

    A surface acoustic wave (SAW) gas sensor with multiwalled carbon nanotubes (CNTs) layered films as chemically interactive nanomaterial is presented. A SAW two-port resonator integrated on ST-cut quartz substrate has been functionally characterized as oscillator in dual differential mode at the resonant frequency of 433.92 and 915 MHz. Nanocomposite layers based on filler of CNTs, grown by RF-plasma enhanced chemical

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

    PubMed

    Gaspera, Enrico Della; 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. SnO 2 thin film gas sensors for fire-alarm systems

    Microsoft Academic Search

    Ghennady Korotchenkov; Vladimir Brynzari; Serghei Dmitriev

    1999-01-01

    This paper presents results of studying of SnO2 thin films gas sensors (TFGS) sensitivity to the combustion products. The influence of operating temperature and the kind of a combustible material on TFGS sensitivity to the products of combustion and smouldering was considered. The kinetic characteristics of gas sensors as smoke sensors were determined. The specifics of a combustion products influence

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

    NASA Astrophysics Data System (ADS)

    Imai, Yuji; Kimura, Yasuo; Niwano, Michio

    2012-10-01

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

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

    Microsoft Academic Search

    Masahiko Matsumiya; Woosuck Shin; Noriya Izu; Norimitsu Murayama

    2003-01-01

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

  6. Nanostructured cobalt manganese ferrite thin films for gas sensor application

    Microsoft Academic Search

    Izabela Sandu; Lionel Presmanes; Pierre Alphonse; Philippe Tailhades

    2006-01-01

    Ferrite compounds are very important because of their optical, electrical or magnetic properties. Moreover, many papers relate to their development as possible gas sensor.In this study, we were interested in using cobalt–manganese–ferrite as sensitive layer for CO2 sensor devices. Such an application required a high surface activity, and consequently a small crystallite size and a large surface area. The physical

  7. High-temperature gas sensor using perovskite thin films on a suspended microheater

    NASA Astrophysics Data System (ADS)

    Grudin, O.; Marinescu, R.; Landsberger, L. M.; Kahrizi, M.; Frolov, G.; Cheeke, J. D. N.; Chehab, S.; Post, M.; Tunney, J.; Du, X.; Yang, D.; Segall, D.

    2002-05-01

    Suspended microstructures consisting of a thin oxide/nitride diaphragm with embedded polysilicon heaters were designed and fabricated using a standard complementary metal-oxide-semiconductor process and simple postprocessing. Thin films of gas sensitive materials based on the SrFeO2.5+x nonstoichiometric perovskite family were deposited onto the diaphragms by room-temperature pulsed excimer laser deposition. Successful chemical sensor functionality was demonstrated. With applied power up to 30 mW, estimated temperatures of the gas sensor film up to 900 °C were reached. When the device was exposed to volatile organic compounds (VOCs) such as acetone and methanol, a reversible ten to 100-fold increase in sensor film resistance was observed, with response times from less than 1 s to a few minutes. Sensor response sensitivity depended on applied power and on the nature of the VOC analyte. This sensor device has the potential for use in multiarray configurations such as in an electronic nose.

  8. Thermoelectric Thick-Film Hydrogen Gas Sensor Operating at Room Temperature

    Microsoft Academic Search

    Woosuck Shin; Kiyohisa Imai; Noriya Izu; Norimitsu Murayama

    2001-01-01

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

  9. Diamond Film Gas Sensors for Leak Detection of Semiconductor Doping Gases

    Microsoft Academic Search

    Kazushi Hayashi; Yoshihiro Yokota; Takeshi Tachibana; Koichi Miyata; Koji Kobashi; Tetsuya Fukunaga; Tadashi Takada

    2000-01-01

    Gas sensors for leak detection of toxic semiconductor doping gases such as PH3, B2H6, and AsH3 were fabricated using diamond films. The sensors have a double-layered structure composed of undoped and B-doped polycrystalline diamond layers with Pt electrodes. The relative changes in the resistance of the sensors were typically 10-20% for 0.2 ppm PH3 in air, and the highest value

  10. Classification of chemical warfare agents using thick film gas sensor array

    Microsoft Academic Search

    Nak-Jin Choi; Jun-Hyuk Kwak; Yeon-Tae Lim; Tae-Hyun Bahn; Ky-Yeol Yun; Jae-Chang Kim; Jeung-Soo Huh; Duk-Dong Lee

    2005-01-01

    Semiconductor thick film gas sensors based on tin oxide are fabricated and their gas response characteristics are examined for four simulant gases of chemical warfare agent (CWA)s. The sensing materials are prepared in three different sets such as impregnation, physical mixing (ball-milling) and co-precipitation method. Surface morphology, particle size, and specific surface area of fabricated sensing films are performed by

  11. An intelligent thick-film gas sensor: development and preliminary tests

    SciTech Connect

    Lauf, R.J.; Hoffheins, B.S.; Walls, C.A.

    1987-05-01

    Thick-film techniques were used to create a gas sensor that has a semiconducting oxide surface whose catalytic activity varies from point to point. An integral heater causes the oxide film to react with combustible gases; the electrical resistance of the oxide film is mapped through an array of electrodes to yield a 'signature' that depends on how a particular gas reacts to each of the different areas on the sensor. The catalytic activity can be varied by establishing a thermal gradient across the sensor, by distributing different catalysts in different areas, or by a combination of both effects. For simple cases, the signature can be related to the functional groups present in the gas. As an example, using a uniform distribution of platinum and a thermal gradient, alcohols, ketones, and alkanes have distinctly different signatures.

  12. An intelligent thick-film gas sensor: Development and preliminary tests

    NASA Astrophysics Data System (ADS)

    Lauf, R. J.; Hoffheins, B. S.; Walls, C. A.

    1987-05-01

    Thick-film techniques were used to create a gas sensor that has a semiconducting oxide surface whose catalytic activity varies from point to point. An integral heater causes the oxide film to react with combustible gases; the electrical resistance of the oxide film is mapped through an array of electrodes to yield a signature that depends on how a particular gas reacts to each of the different areas on the sensor. The catalytic activity can be varied by establishing a thermal gradient across the sensor, by distributing different catalysts in different areas, or by a combination of both effects. For simple cases, the signature can be related to the functional groups present in the gas. As an example, using a uniform distribution of platinum and a thermal gradient, alcohols, ketones, and alkanes have distinctly different signatures.

  13. Wide Bandgap Semiconductor Nanorod and Thin Film Gas Sensors

    PubMed Central

    Wang, Hung-Ta; Gila, Brent P.; Lin, Jenshan; Pearton, Stepehn J.

    2006-01-01

    In this review we discuss the advances in use of GaN and ZnO-based solid-state sensors for gas sensing applications. AlGaN/GaN high electron mobility transistors (HEMTs) show a strong dependence of source/drain current on the piezoelectric polarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous and piezoelectric polarization induced surface and interface charges can be used to develop very sensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc2O3/AlGaN/GaN metal-oxide semiconductor diodes also show large change in forward currents upon exposure to H2 containing ambients. Of particular interest are methods for detecting ethylene (C2H4), which offers problems because of its strong double bonds and hence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer large surface area, are bio-safe and offer excellent gas sensing characteristics.

  14. Room temperature pulsed laser deposited ZnO thin films as photoluminiscence gas sensors

    NASA Astrophysics Data System (ADS)

    Padilla-Rueda, D.; Vadillo, J. M.; Laserna, J. J.

    2012-10-01

    Zinc oxide thin films with optical sensing capabilities for NO2 have been elaborated by pulsed laser deposition (PLD) onto glass substrates at room temperature with Nd:YAG laser (1064 nm). Morphology, chemical composition and optical characteristics of the films were evaluated as a function of laser fluence, gas pressure and target-to-substrate distance. Films exhibit excellent morphological and optical (transmittance and photoluminescence) properties. The films have been evaluated as fluorescence sensors for NO2 in the concentration range between 26 and 200 ppm.

  15. Preparation of MEMS Thin Film Heater by All Dry Processes and Application to Gas Sensor

    NASA Astrophysics Data System (ADS)

    Yamadera, Hideya; Sugimoto, Noriaki; Kageyama, Yasuyuki

    The MEMS thin film heater was prepared by all dry processes and the heating properties of this heater were evaluated. The MEMS heaters were heated up to 400°C at consumed power of a few ten mW. The consumed power for heating was dependent on the heater area and the membrane size. Furthermore, 40 ppm ethanol gas was detected in smaller size and at lower-power consumption by the MEMS gas sensor utilizing this MEMS heater than by the conventional bulk gas sensor.

  16. NiO \\/ Fe 2O 3 polymer thick films as room temperature gas sensors

    Microsoft Academic Search

    K. Arshak; I. Gaidan

    2006-01-01

    This work investigates the use of NiO\\/Fe2O3 as a room temperature (RT) polymer thick film gas sensor. To find the optimum ratio of NiO to Fe2O3, three compositions were prepared using different molecular percentages (75\\/25, 50\\/50 and 25\\/75 M wt.%) and prepared as a thick film paste. These pastes were then screen-printed onto glass substrates with interdigitated silver (Ag) electrodes.

  17. Nanostructured thick-film gas sensors for atmospheric pollutant monitoring: quantitative analysis on field tests

    Microsoft Academic Search

    Maria Cristina Carotta; Giuliano Martinelli; Luigi Crema; Cesare Malagù; Marco Merli; Giovanna Ghiotti; Enrico Traversa

    2001-01-01

    Thick-film gas sensors were fabricated by screen-printing technology starting from different nanostructured semiconducting oxide powders both n-type and p-type; ultrafine and homogeneously sized ceramic powders were prepared using chemical methods such as sol–gel techniques and thermal decomposition of heteronuclear complexes. The temporal evolution of the conductivity changes in the various semiconducting oxide thick films were studied in comparison with the

  18. Design of auto control interface circuit for thick film heater gas sensor

    Microsoft Academic Search

    R. Khakpour; M. N. Hamidon; R. Wagiran; A. R. Bahadorimehr

    2010-01-01

    In this paper an automated control system of thick film resistive heater for gas sensor applications has been designed using low cost technologies. To control the desired temperature of heater, a programmable voltage with 12 bits resolution applies which can be adjusted to the appropriate temperature. The circuit consists of ADC, DAC, microcontroller, and current buffer. This circuit compensates dropt

  19. 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

  20. 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

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

    E-print Network

    . Sensitive vapor sensors are important for the development of noninvasive diagnostic breath analy- sis systemRoom-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide-film transistor TFT to form a hybrid sensor. The organic layer, served as a second gate, forms a p-n junction

  2. Gas sensitivity of ZnO based thick film sensor to NH 3 at room temperature

    Microsoft Academic Search

    G. S. Trivikrama Rao; D Tarakarama Rao

    1999-01-01

    Calcined powders of pure and doped ZnO have been prepared and characterized by XRD and scanning electron microscopy (SEM). Employing these powders ZnO, Pd–ZnO, Fe–ZnO and Ru–ZnO thick film sensor elements have been prepared and tested for specific sensitivity to ammonia gas in air at room temperature. Among all, Pd–ZnO showed high sensitivity to ammonia in the range 50–90 ppm

  3. 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.

  4. 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.

  5. Self-assembly of TiO2\\/polypyrrole nanocomposite ultrathin films and application for an NH3 gas sensor

    Microsoft Academic Search

    Huiling Tai; Yadong Jiang; Guangzhong Xie; Junsheng Yu; Mingjing Zhao

    2007-01-01

    TiO2\\/polypyrrole (PPy) nanocomposite ultrathin films for NH3 gas detection were fabricated by the in situ self-assembly technique. The films were characterized by UV–Vis absorption, FT–IR spectroscopy, and atomic force microscopy (AFM). The electrical properties of TiO2\\/PPy ultrathin film NH3 gas sensors, such as sensitivity, selectivity, reproducibility, and stability were investigated at room temperature in air as well as in N2.

  6. Hydrogen gas sensors using a thin Ta2O5 dielectric film

    NASA Astrophysics Data System (ADS)

    Kim, Seongjeen

    2014-12-01

    A capacitive-type hydrogen gas sensor with a MIS (metal-insulator-semiconductor) structure was investigated for high-temperature applications. In this work, a tantalum oxide (Ta2O5) layer of tens of nanometers in thickness formed by oxidizing tantalum film in rapid thermal processing (RTP) was exploited with the purpose of sensitivity improvement. Silicon carbide (SiC), which is good even at high temperatures over 500 °C, was used as the substrate. We fabricated sensors composed of Pd/Ta2O5/SiC, and the dependences of the capacitance response properties and the I-V characteristics on the hydrogen concentration were analyzed from the temperature range of room temperature to 500 °C. As a result, our hydrogen sensor showed promising performance with respect to the sensitivity and the adaptability at high temperature.

  7. Sensing properties to dilute chlorine gas of indium oxide based thin film sensors prepared by electron beam evaporation

    Microsoft Academic Search

    Jun Tamaki; Chizuko Naruo; Yoshifumi Yamamoto; Masao Matsuoka

    2002-01-01

    Indium oxide based thin film sensors have been prepared by means of an electron beam evaporation and subjected to the detection of dilute Cl2 gas less than ppm-level. Among various In2O3 based sensors tested, the In2O3 thin film modified with Fe2O3 (1wt.%) showed extremely high sensitivity to dilute Cl2 gas of 0.2–5ppm. The Fe2O3–In2O3 sensor showed the sensitivity as high

  8. 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

  9. 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.

  10. Optical fiber gas sensors based on hydrophobic alumina thin films formed by the electrostatic self-assembly monolayer process

    Microsoft Academic Search

    Francisco J. Arregui; Ignacio R. Matías; Richard O. Claus

    2003-01-01

    Optical fiber gas sensors have been fabricated by deposition of Al2O3 and polymer ultra-thin films on the ends of optical fibers using the electrostatic self assembly monolayer process. These sensors are designed to operate at the standard transmission wavelengths with no cross sensitivity to temperature from at least 10 to 70°C. Experimental results of the response of these sensors to

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

    Microsoft Academic Search

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

    2010-01-01

    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

  12. 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.

  13. Molecular Interactions Between Alcohols and Metal Phthalocyanine Thin Films for Optical Gas Sensor Applications

    NASA Astrophysics Data System (ADS)

    Uttiya, Sureeporn; Kladsomboon, Sumana; Chamlek, Onanong; Suwannet, Wiriya; Osotchan, Tanakorn; Kerdcharoen, Teerakiat; Brinkmann, Martin; Pratontep, Sirapat

    Optically active organic gas sensors represent a promising molecular sensing device with low power consumption. We report experimental and computational investigations into the molecular interactions of metal phthalocyanine thin films with alcohol vapor. In the gas-sensing regime, the interactions of zinc phthalocyanine and alcohol molecules were studied by the Density Functional Theory (DFT) calculations, in comparison to the x-ray absorption spectroscopy. The DFT results reveal a reversible charge interaction mechanism between the zinc atom and the oxygen atom in the alcohol OH group, which corresponds to a shift in the x-ray absorption edge of the zinc atom. In the irreversible interaction regime, the effect of saturated alcohol vapor on spin-coated zinc phthalocyanine films was studied by the phase contrast microscopy, the optical absorption spectroscopy, and the transmission electron microscopy. Annealing the spin-coated films in saturated methanol vapor was found to induce an irreversible structural transformation from an amorphous to a crystalline phase, similar to the effect of a thermal annealing process. These crystallization processes of the zinc phthalocyanine films were also found to enhance their stability and alcohol sensing performance.

  14. 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.

  15. The performance of fluorescence gas sensor using TiO2 coated dye-porphyrin nanocomposite thin films

    Microsoft Academic Search

    Nurul Huda Yusoff; Muhamad Mat Salleh; Muhammad Yahaya

    2008-01-01

    This paper reports the performance of fluorescence gas sensor to detect the presence of volatile organic compounds. Two thin films were prepared; TiO2 coated with iron (III) meso-tetraphenylporphine chloride (TiO2 coated IMTPPCl) and TiO2 coated with manganase (III) 5,10,15,20 tetra (4-pyridyl)-21 H, 23 H porphine chloride tetrakis (TiO2 coated MnTPCl). All the thin films were deposited on quartz substrate using

  16. Highly sensitive thin film NH 3 gas sensor operating at room temperature based on SnO 2\\/MWCNTs composite

    Microsoft Academic Search

    Nguyen Van Hieu; Luong Thi Bich Thuy; Nguyen Duc Chien

    2008-01-01

    A SnO2\\/MWCNTs composite-based NH3 sensor working at room temperature was fabricated by thin film microelectronic technique. The gas-sensitive composite thin film was prepared by using both commercially available multi-walled carbon nanotubes (MWCNTs) and nanosized SnO2 dispersion. Microstructure and surface morphology of the composite were investigated and they revealed that the MWCNTs were still present and well embedded by SnO2 particles

  17. Microfabricated gas sensor systems with sensitive nanocrystalline metal-oxide films

    Microsoft Academic Search

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

    2006-01-01

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

  18. Surface plasmon resonance-based fiber optic hydrogen sulphide gas sensor utilizing Cu-ZnO thin films.

    PubMed

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

    2013-07-28

    We report an experimental study on a surface plasmon resonance (SPR)-based fiber optic hydrogen sulphide gas sensor with a thin metal oxide (zinc oxide (ZnO)) layer as the additional layer. This zinc oxide layer is grown over the copper layer to support surface plasmons at the metal-dielectric interface at room temperature. The wavelength interrogation mode of operation has been used to characterize the sensor. The thin film of zinc oxide over the copper film was deposited on the unclad portion of the fiber by the thermal evaporation technique. Experiments were performed for the detection of concentrations of hydrogen sulphide gas varying from 0 to 100 ppm around the probe. The unpolarized light from a polychromatic source is launched from one end of the fiber and the corresponding SPR spectrum is recorded at the other end. The recorded SPR spectrum shows a shift in the resonance wavelength on a change in the hydrogen sulphide gas concentration, which is considered as a detectable signal for the characterization of the sensor. Further, the optimization of the performance of the sensor was achieved by varying the thickness of the zinc oxide film. The sensor possesses a very fast response time and high sensitivity. Since the sensor utilizes optical fibers it has additional advantages of remote sensing, online monitoring, light weight and low cost. PMID:23764905

  19. A microfabricated array of multiple thin film metal oxide sensors for multicomponent gas and vapor quantification

    Microsoft Academic Search

    Xiaodong Wang; Sinclair Yee; Patrick Carey

    1992-01-01

    The authors report on an integrated array consisting of eight thin film metal oxide sensors for analyzing mixtures of gases and vapors. The sensors were fabricated into a 3.1 mm×2.9 mm silicon chip in an eleven-mask process sequence. The sensing elements were constituted using single layers and bilayers of reactively sputtered thin films of SnO2, ZnO, TiO2 and WO3 with

  20. 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

  1. Fabrication of iron titanium oxide thin film and its application as opto-electronic humidity and liquefied petroleum gas sensors

    NASA Astrophysics Data System (ADS)

    Verma, Nidhi; Singh, Satyendra; Srivastava, Richa; Yadav, B. C.

    2014-04-01

    Present paper explores the synthesis, characterization, and opto-electronic humidity as well as liquefied petroleum gas (LPG) sensing applications of iron titanium oxide nanocomposite. Thin film of iron titanium oxide was deposited on an equilateral borosilicate glass prism using sol-gel spin coating process. X-ray diffraction reveals the formation of iron titanium oxide having minimum crystallite size 9 nm. The opto-electronic humidity sensing properties of the fabricated film were investigated at different angles of incidence of the light. It was observed that the intensity of reflected light increased with an increase in relative humidity (%RH) in the range 5-95. The fabricated film shows maximum sensitivity 4.5 ?W/%RH, which is quite significant for sensor fabrication purposes. The maximum percentage sensor response for LPG was found 2600 which is many folds more than the earlier reported titania based LPG sensor.

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

    Microsoft Academic Search

    Ralf Moos; Frank Rettig; Armin Hürland; Carsten Plog

    2003-01-01

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

  3. Study on a micro-gas sensor with SnO 2–NiO sensitive film for indoor formaldehyde detection

    Microsoft Academic Search

    Pin Lv; Zhen A. Tang; Jun Yu; Feng T. Zhang; Guang F. Wei; Zheng X. Huang; Yann Hu

    2008-01-01

    A micro-gas sensor is fabricated based on a micro-hotplate (MHP) with micromachining technology. The SnO2–NiO nanometer polycrystalline composite synthesized by a chemical co-precipitation method is coated onto a micro-hotplate as a sensitive film. The response and recovery time of the micro-gas sensor decrease rapidly with increasing the formaldehyde (HCHO) concentration at relatively low concentrations. The micro-gas sensor shows good stability,

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

    PubMed

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

    2010-11-01

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

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

    PubMed Central

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

    2004-01-01

    The paper presents results concerning the effect of spatial inhomogeneous operating temperature on the gas discrimination power of a gas-sensor microarray, with the latter based on a thin SnO2 film employed in the KAMINA electronic nose. Three different temperature distributions over the substrate are discussed: a nearly homogeneous one and two temperature gradients, equal to approx. 3.3 °C/mm and 6.7 °C/mm, applied across the sensor elements (segments) of the array. The gas discrimination power of the microarray is judged by using the Mahalanobis distance in the LDA (Linear Discrimination Analysis) coordinate system between the data clusters obtained by the response of the microarray to four target vapors: ethanol, acetone, propanol and ammonia. It is shown that the application of a temperature gradient increases the gas discrimination power of the microarray by up to 35 %.

  6. Thin-film calorimetric H 2O 2 gas sensor for the validation of germicidal effectivity in aseptic filling processes

    Microsoft Academic Search

    P. Kirchner; B. Li; H. Spelthahn; H. Henkel; A. Schneider; P. Friedrich; J. Kolstad; M. Keusgen; M. J. Schöning

    2009-01-01

    A novel thin-film gas sensor was realized to detect the H2O2 concentration up to 10 vol.-% during microbial reduction of carton packages by hydrogen peroxide vapor in aseptic filling processes. The calorimetric sensing device contains two meander-shaped platinum layers as temperature sensing elements, both have been passivated with perfluoralkoxy and one additionally covered with catalytically active manganese oxide particles. First

  7. 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.

  8. Zinc-oxide nanorod/copper-oxide thin-film heterojunction for a nitrogen-monoxide gas sensor

    NASA Astrophysics Data System (ADS)

    Yoo, Hwansu; Kim, Hyojin; Kim, Dojin

    2014-11-01

    A novel p- n oxide heterojunction structure was fabricated by employing n-type zinc-oxide (ZnO) nanorods grown on an indium-tin-oxide-coated glass substrate by using the hydrothermal method and a p-type copper-oxide (CuO) thin film deposited onto the ZnO nanorod array by using the sputtering method. The crystallinities and microstructures of the heterojunction materials were examined by using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p - n oxide heterojunction showed a nonlinear diode-like rectifying behavior. The effects of an oxidizing or electron acceptor gas, such as nitrogen monoxide (NO), on the ZnO nanorod/CuO thin-film heterojunction were investigated to determine the potential applications of the fabricated material for use in gas sensors. The forward current of the p - n heterojunction was remarkably reduced when NO gas was introduced into dry air at temperatures from 100 to 250 °C. The NO gas response of the oxide heterojunction reached a maximum value at an operating temperature of 180 °C and linearly increased as the NO gas concentration was increased from 5 to 30 ppm. The sensitivity value was observed to be as high as 170% at 180 °C when biased at 2 V in the presence of 20-ppm NO. The ZnO nanorod/CuO thin-film heterojunction also exhibited a stable and repeatable response to NO gas. The experimental results suggest that the ZnO nanorod/CuO thin-film heterojunction structure may be a novel candidate for gas sensors.

  9. ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor

    PubMed Central

    Chou, Shih Min; Teoh, Lay Gaik; Lai, Wei Hao; Su, Yen Hsun; Hon, Min Hsiung

    2006-01-01

    The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrate using Pt as interdigitated electrodes. The structure was characterized by XRD and SEM analyses, and the ethanol vapor gas sensing as well as electrical properties have been investigated and discussed. The gas sensing results show that the sensitivity for detecting 400 ppm ethanol vapor was ?20 at an operating temperature of 250°C. The high sensitivity, fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetron sputtering can be used for ethanol vapor gas sensing.

  10. Hydrogen-selective thermoelectric gas sensor

    Microsoft Academic Search

    Woosuck Shin; Masahiko Matsumiya; Noriya Izu; Norimitsu Murayama

    2003-01-01

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

  11. Discrimination of individual gas\\/odor using responses of integrated thick film tin oxide sensor array and fuzzy-neuro concept

    Microsoft Academic Search

    R. R. Das; K. K. Shukla; R. Dwivedi; A. R. Srivastava

    1999-01-01

    A new neural network classifier for an Intelligent Gas Sensor (IGS) application is presented. The classifier is trained on fuzzyfied training set. Its superior classification and learning performance is demonstrated for discrimination of alcohols and alcoholic beverages using published data of thick film tin oxide sensor array fabricated and characterized at our laboratory. The new model proposed in this article

  12. 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 ...

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  14. 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.

  15. Highly sensitive and selective ammonia gas sensor

    Microsoft Academic Search

    Dong Hyun Yun; Chul Han Kwon; Hyung-Ki Hong; Seung-Ryeol Kim; Kyuchung Lee; Ho Geun Song; Ji Eon Kim

    1997-01-01

    We have fabricated and examined an ammonia gas sensor with high sensitivity using thick-film technology. The sensing material of the gas sensor is FeOx-WO3-SnO2 oxide semiconductor. The sensor exhibits resistance increase upon exposure to low concentration of ammonia gas. The resistance of the sensor is decreased, on the other hand, for exposure to reducing gases such as ethyl alcohol, methane,

  16. Thick film hydrogen sensor

    DOEpatents

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

    1995-01-01

    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.

  17. 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

  18. Structural and optical characterization of WO3 thin films for gas sensor applications

    Microsoft Academic Search

    E. Gyoergy; G. Socol; I. N. Mihailescu; C. Ducu; S. Ciuca

    2005-01-01

    The structure, chemical composition, and optical properties of tungsten trioxide thin films grown by pulsed laser deposition were investigated. An ultraviolet KrF* excimer laser (lambda=248 nm, tauFWHM?20 ns, nu=2 Hz) was used for irradiation of tungsten trioxide targets in oxygen atmosphere. Our research focused on the effect of the ambient gas pressure and substrate temperature on the chemical composition, crystalline

  19. 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.

  20. 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.

  1. Sol-gel TiO2 films as NO2 gas sensors

    NASA Astrophysics Data System (ADS)

    Georgieva, V.; Gadjanova, V.; Grechnikov, A.; Donkov, N.; Sendova-Vassileva, M.; Stefanov, P.; Kirilov, R.

    2014-05-01

    TiO2 films were prepared by a sol-gel technique with commercial TiO2 powder as a source material (P25 Degussa AG). After a special treatment, printing paste was prepared. The TiO2 layers were formed by means of drop-coating on Si-control wafers and on the Au-electrodes of quartz resonators. The surface morphology of the films was examined by scanning electron microscopy (SEM). Their structure was studied by Raman spectroscopy and the surface composition was determined by X-ray photoelectron spectroscopy (XPS). The layers had a grain-like surface morphology and consisted mainly of anatase TiO2 phase. The sensitivity of the TiO2 films to NO2 was assessed by the quartz crystal microbalance (QCM) technique. To this end, the films were deposited on both sides of a 16-MHz QCM. The sensing characteristic of the TiO2-QCM structure was investigated by measuring the resonant frequency shift (?F) of the QCM due to the mass loading caused by NO2 adsorption. The Sauerbrey equation was applied to establish the correlation between the QCM frequency changes measured after exposure to different NO2 concentrations and the mass-loading of the QCM. The experiments were carried out in a dynamic mode on a special laboratory setup with complete control of the process parameters. The TiO2 films were tested in the NO2 concentration interval from 10 ppm to 5000 ppm. It was found that a TiO2 loading of the QCM by 5.76 kHz corresponded to a system sensitive to NO2 concentrations above 250 ppm. On the basis of the frequency-time characteristics (FTCs) measured, AF at different NO2 concentrations was defined, the adsorption/desorption cycles were studied and the response and recovery times were estimated. The results obtained show that the process is reversible in the NO2 interval investigated. The results further suggested that TiO2 films prepared by a sol-gel method on a QCM can be used as a sensor element for NO2 detection.

  2. The Evolution of High Temperature Gas Sensors.

    SciTech Connect

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

    2001-01-01

    Gas sensor technology based on high temperature solid electrolytes is maturing rapidly. Recent advances in metal oxide catalysis and thin film materials science has enabled the design of new electrochemical sensors. We have demonstrated prototype amperometric oxygen sensors, nernstian potentiometric oxygen sensors that operate in high sulfur environments, and hydrocarbon and carbon monoxide sensing mixed potentials sensors. Many of these devices exhibit part per million sensitivities, response times on the order of seconds and excellent long-term stability.

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

    NASA Astrophysics Data System (ADS)

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

    1986-12-01

    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.

  4. A fully neural implementation of unitary response model for classification of gases\\/odors using the responses of thick film gas sensor array

    Microsoft Academic Search

    N. S. Rajput; R. R. Das; V. N. Mishra; K. P. Singh; R. Dwivedi

    2011-01-01

    In this paper, a classification scheme based on neurally implemented unitary response model (URM) for a gas\\/odor sensor array response has been presented. Thick-film tin-oxide sensor array responses for four gases\\/odors (viz. acetone, carbon tetra-chloride, ethyl methyl ketone and xylene) were first transformed into equivalent unitary responses. This transformation was carried out using a pre-trained neural ‘unitary response model pre-processor

  5. Acetone and ethanol solid-state gas sensors based on TiO 2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation

    Microsoft Academic Search

    R. Rella; J. Spadavecchia; M. G. Manera; S. Capone; A. Taurino; M. Martino; A. P. Caricato; T. Tunno

    2007-01-01

    Matrix assisted pulsed laser evaporation (MAPLE) is a new promising laser-based technique thought for polymer or biomaterial thin films deposition. In this work, the MAPLE technique has been used for the deposition of titania (TiO2) nanoparticle thin films to be used for gas sensor applications. For this purpose, an aqueous solution of TiO2 nanoparticles, synthesized by a novel chemical route,

  6. Identification of aromas from alcohols using a Japanese-lacquer-film-coated quartz resonator gas sensor in conjunction with pattern recognition analysis

    Microsoft Academic Search

    H Nanto; K Kondo; M Habara; Y Douguchi; R. I Waite; H Nakazumi

    1996-01-01

    Transient response curves for exposure to aromas from several kinds of alcohols are observed using a Japanese-lacquer-film-coated quartz resonator gas sensor. The shape of the transient response curves strongly depends on the ethanol concentration of alcohols. The pattern recognition analysis using principal component or neural network analysis is carried out using four parameters which characterize the shape of the transient

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

    E-print Network

    . Sensitive vapor sensors are important for the development of noninvasive diagnostic breath analy- sis systemRoom-temperature-operated sensitive hybrid gas sensor based on amorphous indium gallium zinc oxide Institute of Physics. Related Articles Semiconductor core-shell quantum dot: A low temperature nano-sensor

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  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. Indium tin oxide (ITO) thin film gas sensor for detection of methanol at room temperature

    Microsoft Academic Search

    N. G. Patel; P. D. Patel; V. S. Vaishnav

    2003-01-01

    Thin films of indium tin oxide (In2O3+SnO2) (ITO) were grown on alumina substrate using the direct evaporation method. The sensing characteristics of these films to methanol vapors were studied at room temperature. The effects of different concentrations of tin oxide in indium oxide and film thickness on sensitivity were studied. The effects of thin layers of noble metals—Au, Ag, Pt

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

    Microsoft Academic Search

    O. Lupan; L. Chow; S. Shishiyanu; E. Monaico; T. Shishiyanu; V. ?ontea; B. Roldan Cuenya; A. Naitabdi; A. Schulte

    2009-01-01

    Nanostructured ZnO thin films have been deposited using a successive chemical solution deposition method. The structural, morphological, electrical and sensing properties of the films were studied for different concentrations of Al-dopant and were analyzed as a function of rapid photothermal processing temperatures. The films were investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron and micro-Raman

  12. Spectral Investigations of Chemical Bath Deposited Zinc Oxide Thin Films - Ammonia Gas Sensor

    Microsoft Academic Search

    P. Kathirvel; D. Manoharan; S. M. Mohan; S. Kumar

    Zinc oxide thin films have been deposited on glass substrates at various bath temperatures (40ºC, 60 ºC and 80 ºC) by simple chemical bath deposition technique. The structure of the deposited ZnO films was determined by powder X-ray diffraction and it exhibits hexagonal structure along with c-axis orientation. The optical absorbance of the deposited films was characterized by UV-VIS-NIR spectrometry.

  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. Poisoning of platinum thin film catalyst by hexamethyldisiloxane (HMDS) for thermoelectric hydrogen gas sensor

    Microsoft Academic Search

    Masahiko Matsumiya; Woosuck Shin; Fabin Qiu; Noriya Izu; Ichiro Matsubara; Norimitsu Murayama

    2003-01-01

    The evolution of the catalytic activity of platinum (Pt) thin film towards hydrogen oxidation has been studied as a function of the exposure to hexamethyldisiloxane (HMDS) at various concentrations and temperatures. HMDS, decomposes by the thermally activated reaction and the catalyst surface, is progressively covered by silica and the number of active sites decreases. The interaction of Pt thin film

  15. 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.

  16. Hydrophobic alumina thin films formed by the electrostatic self-assembly monolayer process for the fabrication of optical fiber gas sensors

    Microsoft Academic Search

    Francisco J. Arregui; Ignacio R. Matias; Kristie L. Cooper; R. O. Claus

    2002-01-01

    Aluminum oxide thin films were formed by the electrostatic self-assembled monolayer (ESAM) method on optical fibers for the fabrication of gas sensors. Negligible sensitivity with humidity was achieved after thermal curing a variation of 1.5 dB at 1550 nm was achieved with the presence of ethanol. The coatings are also sensitive to other organic compound, this apparent lack of selectivity

  17. FLUORESCENCE GAS SENSOR USING TiO2 NANOPARTICLES COATED WITH PORPHYRIN DYE THIN FILMS

    Microsoft Academic Search

    Nurul Huda Yusoff; Muhamad Mat Salleh; Muhammad Yahaya

    This paper explores the possibility of using fluorescence technique to detect the presence of volatile organic compounds based on TiO2 nanoparticles coated with porphyrin dye thin films. Porphyrin dye used was Iron (III) meso-tetraphenylporphine chloride. The thin films were prepared with the variation of TiO2 and porphyrin ratio, i.e. 1:2, 1:3, 1:4 and 1:5 by volume. The purpose of this

  18. Gas Sensor Using a Rhodamine-6 G Doped TiO2 Film Deposited on an Optical Fiber to Detect Volatile Organic Compounds.

    NASA Astrophysics Data System (ADS)

    Aguirre, S. Muñoz; Hipatl, C. Martínez; Mixcóatl, J. Castillo; Pérez, G. Beltrán; Merino, R. Palomino

    2008-04-01

    The necessity of detection and recognition of different types of gases, such as simple volatile organic compounds or their mixtures, requires the development of different types of sensors and the study of different materials for sensing films. In this work, an application of an optical fiber to the detection of VOC is presented. The sensor was constructed removing a portion of the cladding of approximately 3 cm and depositing instead a sensing titanium dioxide (TiO2) film doped with an organic dye (rhodamine 6 G) by the sol-gel technique. The sensor operation principle is based on the absorption of evanescent wave when the sensing film interacts with the VOC molecules, which attenuates the output optical power. The difference between the output power with and without gas gives a measure of the concentration in the chamber. The results showed that for ethanol concentration from 0 to 10,000 ppm, the response of the sensor was approximately linear. The sensor responses to octane and ethyl acetate were also studied.

  19. 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

  20. 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.

  1. 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.

    2015-06-01

    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.

  2. Design interface circuits for thick film heater for a gas sensor resistor

    Microsoft Academic Search

    R. Khakpour; M. N. Hamidon; R. Wagiran

    2009-01-01

    In this paper an auto calibrated system of thick film resistive heater have been designed which can be adjusted to desired temperature. The circuit is consists of ADC, DAC, microcontroller, and current buffer. This circuit compensates dropt voltage across the heater which has been resulted from ambient temperature changes. Finally this circuit is able to control and adjust the heater's

  3. 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

  4. 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  6. 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

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

    PubMed

    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

  8. Thin-film Sensors for Space Propulsion Technology

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  9. 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.

  10. 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 ...

  11. 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

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

    PubMed

    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

  13. Thin Film Transistor Gas Sensors Incorporating High-Mobility Diketopyrrolopyrole-Based Polymeric Semiconductor Doped with Graphene Oxide.

    PubMed

    Cheon, Kwang Hee; Cho, Jangwhan; Kim, Yun-Hi; Chung, Dae Sung

    2015-07-01

    In this work, we fabricated a diketopyrrolopyrole-based donor-acceptor copolymer composite film. This is a high-mobility semiconductor component with a functionalized-graphene-oxide (GO) gas-adsorbing dopant, used as an active layer in gas-sensing organic-field-effect transistor (OFET) devices. The GO content of the composite film was carefully controlled so that the crystalline orientation of the semiconducting polymer could be conserved, without compromising its gas-adsorbing ability. The resulting optimized device exhibited high mobility (>1 cm(2) V(-1) s(-1)) and revealed sensitive response during programmed exposure to various polar organic molecules (i.e., ethanol, acetone, and acetonitrile). This can be attributed to the high mobility of polymeric semiconductors, and also to their high surface-to-volume ratio of GO. The operating mechanism of the gas sensing GO-OFET is fully discussed in conjunction with charge-carrier trap theory. It was found that each transistor parameter (e.g., mobility, threshold voltage), responds independently to each gas molecule, which enables high selectivity of GO-OFETs for various gases. Furthermore, we also demonstrated practical GO-OFET devices that operated at low voltage (<1.5 V), and which successfully responded to gas exposure. PMID:26068504

  14. DUAL GRADIENT THICK-FILM METAL OXIDE GAS SENSO

    Microsoft Academic Search

    M. W. Siegel; Lanwai Wong; R. J. Lauf; B. S. Hoffheins

    1987-01-01

    We describe the technology and characteristics of a family of thick-film gas sensors as simple to manufacture as a one- element sensor, but whose signal can be as rich as that of an array of twenty-five or more discrete sensors. This sensor design is particularly well adapted to using pattern recognition and related methods of analyte identification and quantitation based

  15. Thin film composite optical waveguides for sensor applications: a review.

    PubMed

    Yimit, Abliz; Rossberg, Axel G; Amemiya, Takashi; Itoh, Kiminori

    2005-03-15

    We review the design and fabrication of thin-film composite optical waveguides (OWG) with high refractive index for sensor applications. A highly sensitive optical sensor device has been developed on the basis of thin-film, composite OWG. The thin-film OWG was deposited onto the surface of a potassium-ion-exchanged (K(+)) glass OWG by sputtering or spin coating (5-9mm wide, and with tapers at both ends). By allowing an adiabatic transition of the guided light from the secondary OWG to the thin-film OWG, the electric field of the evanescent wave at the thin film was enhanced. The attenuation of the guided light in the thin film layer was small, and the guided light intensity changed sensitively with the refractive index of the cladding layer. Our experimental results demonstrate that thin-film, composite OWG gas sensors or immunosensors are much more sensitive than sensors based on other technologies. PMID:18969919

  16. Progress on thin-film sensors for space propulsion technology

    NASA Astrophysics Data System (ADS)

    Kim, Walter S.

    The objective is to develop thin-film thermocouples for Space Shuttle Main Engine (SSME) components. Thin-film thermocouples have been developed for aircraft gas turbine engines and are in use for temperature measurement on turbine blades to 1800 F. The technology established for aircraft gas turbine engines will be adapted to the materials and environment encountered in the SSME. Specific goals are to expand the existing in-house thin-film sensor technology and to test the survivability and durability of thin-film sensors in the SSME environment.

  17. Sensitivity Enhancement of ZnO Nanorod Gas Sensors with Surface Modification by an InSb Thin Film

    NASA Astrophysics Data System (ADS)

    Kakati, Nitul; Jee, Seung Hyun; Kim, Soo Ho; Lee, Hyun-Kwuon; Yoon, Young Soo

    2009-10-01

    Zinc oxide (ZnO) nanorods were prepared on sol-gel ZnO seed-coated alumina substrates by a hydrothermal method. A very thin layer of indium antimonite (InSb) was deposited on the ZnO nanorods by a thermal evaporation technique. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were applied to analyze the quality of the ZnO nanorods. XRD results showed that the as-synthesized ZnO nanorods were well crystallized in hexagonal wurzite ZnO. An X-ray photoelectron spectroscopy (XPS) study confirmed the deposition of InSb on the ZnO nanorods. The activation energies of sensors fabricated from ZnO nanorods and InSb-deposited ZnO nanorods were calculated. It was found that the activation energy of the InSb-deposited ZnO nanorods was very small. The sensitivity of the sensors towards acetone gas was measured at concentrations of 500-5,000 ppm and at operating temperatures ranging from 200 to 350 °C. The sensitivity of the InSb-deposited ZnO nanorod sensor was much higher than that of the ZnO nanorod sensor. The optimum temperature of the sensors was found to be 300 °C.

  18. 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.

  19. Bimodular high temperature planar oxygen gas sensor

    PubMed Central

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

    2014-01-01

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

  20. STW gas sensors using plasma-polymerized allylamine

    Microsoft Academic Search

    Hiromi Yatsuda; Makoto Nara; Takashi Kogai; Hidenobu Aizawa; Shigeru Kurosawa

    2007-01-01

    Gas sensors generally consist of two major components: a gas recognition element which provides the specificity and selectivity of the measurement and a physical transducer which translates the gas absorption or desorption event into electronic signal. In this paper, plasma polymerized allylamine (PPAa) film is used as a gas recognition element and a surface transverse wave (STW) device is used

  1. A neural net implementation of SPCA pre-processor for gas\\/odor classification using the responses of thick film gas sensor array

    Microsoft Academic Search

    N. S. Rajput; R. R. Das; V. N. Mishra; K. P. Singh; R. Dwivedi

    2010-01-01

    In this paper, an artificial neural net (ANN) implementation of SPCA pre-processing is presented for its use with a neural classifier trained with SPCA transformed data. Here, a SPCA transforming neural stage (Net ISPCA) is placed before a SPCA trained neural classifier stage (Net IISPCA). Accordingly, newer sensor array response of respective gas\\/odor can now be classified, more precisely, using

  2. Combustible gas sensor

    SciTech Connect

    Vaughn, E.D.; Creason, S.C.

    1993-07-06

    In a combustible gas sensor having a housing defining an interior containing an electrically conductive reference element and an electrically conducting measurement element coated with a catalyst for the catalytic combustion of a combustible gas and circuitry for measuring the difference in resistance between said measurement element and said reference element as they are heated by combustion of said combustible gas and means for measuring the difference in resistance between said measurement element and said reference element thereby to determine the quantity of combustible gas in a sample, the improvement is described comprising: maintaining said reference element and said measurement element in a common confined space for direct fluid communication therebetween wherein said reference element and said measurement element are disposed in one end of a housing member, a disk having an upper and a lower surface and a slot opening in said lower surface is disposed in said one end of said housing with said reference element and said measurement element being received in said slot and said disk having means for introducing gaseous sample to be tested into said slot whereby said gaseous sample freely communicates with both the said reference element and said measurement element.

  3. Combination of guided mode and photometric optical metrology methods for precise determination of refractive index dispersion: application to polymer blend and ceramic thin films for gas sensors

    NASA Astrophysics Data System (ADS)

    Wood, Thomas; Le Rouzo, Judikaël; Flory, François; Coudray, Paul; Mastelaro, Valmor Roberto; Pelissari, Pedro; Zilio, Sergio

    2013-09-01

    Two optical techniques, m-lines and spectroscopic ellipsometry, are compared for their suitability for obtaining the wavelength and the temperature dispersion of the refractive index of thin-film layers used in gas detector devices. Two types of materials that are often integrated into gas sensors are studied: a polymer organic-inorganic blend deposited by spin coating typically used in near-infrared waveguides and the ceramic semiconductor SrTi1-xFexO3 (strontium titanate) doped with iron at concentrations x=0.075 and 0.1 deposited by electron beam deposition. The refractive index dispersion obtained by m-lines and ellipsometry is compared, and the differences between the measured parameters for the two materials are discussed. The chromatic dispersion will be represented by a three-term Cauchy law. An intuitive method for verifying the measured indices using an integrating sphere and reflexion coefficient modeling techniques are also demonstrated. Thermo-optic coefficients in the order of -1×10-4/K for both materials are reported, and very low chromatic dispersions are also measured, thanks to the high sensitivity of the m-lines technique. The uniaxial anisotropic properties of the polymer-blend films are measured and discussed in the case of the semiconductor films.

  4. A rapid process for fabricating gas sensors.

    PubMed

    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

  5. High sensitivity chlorine gas sensors using CdIn{sub 2}O{sub 4} thick film prepared by co-precipitation method

    SciTech Connect

    Chu Xiangfeng

    2003-10-30

    Gas-sensing properties to dilute Cl{sub 2} have been investigated for CdIn{sub 2}O{sub 4} thick film sensors prepared by co-precipitation method. Cadmium nitrate and indium nitrate were mixed in de-ionized water. The 0.1 M NaOH was added to the mixed solution. The co-precipitate obtained was washed, filtered, dried, and calcined at 600-900 deg. C for 4 h. The CdIn{sub 2}O{sub 4} sensor prepared using the powder calcined at 600 deg. C showed high sensitivity (S=R{sub g}/R{sub a}) to dilute Cl{sub 2} at 250 deg. C. In particular, the CdIn{sub 2}O{sub 4} sensor showed the sensitivity as high as 1200 even to 0.2 ppm Cl{sub 2}. The crystal structure and surface morphology were examined by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.

  6. Development of thin film temperature sensor and its application

    NASA Astrophysics Data System (ADS)

    An, Baohe

    1992-02-01

    A new type of thin-film temperature sensor is discussed. The sensor is coated with a vacuum coating method on the surface of a turbine blade. Because both the sensor and the blade are combined, the sensor can measure accurately the surface temperature. It has the advantage of light weight, rapid response, and no interference in heat transfer within blade and gas flow over blade. The sensitive element of the sensor is the PtRh10/Pt thermocouple. The maximum temperature is up to 1000 C, and the accuracy is within +/-3 percent.

  7. 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

  8. Highly enhanced gas sensing in single-walled carbon nanotube-based thin-film transistor sensors by ultraviolet light irradiation.

    PubMed

    Chen, Tingting; Wei, Liangming; Zhou, Zhihua; Shi, Diwen; Wang, Jian; Zhao, Jiang; Yu, Yuan; Wang, Ying; Zhang, Yafei

    2012-01-01

    Single-walled carbon nanotube (SWCNT) random networks are easily fabricated on a wafer scale, which provides an attractive path to large-scale SWCNT-based thin-film transistor (TFT) manufacturing. However, the mixture of semiconducting SWCNTs and metallic SWCNTs (m-SWCNTs) in the networks significantly limits the TFT performance due to the m-SWCNTs dominating the charge transport. In this paper, we have achieved a uniform and high-density SWCNT network throughout a complete 3-in. Si/SiO2 wafer using a solution-based assembly method. We further utilized UV radiation to etch m-SWCNTs from the networks, and a remarkable increase in the channel current on/off ratio (Ion/Ioff) from 11 to 5.6 × 103 was observed. Furthermore, we used the SWCNT-TFTs as gas sensors to detect methyl methylphosphonate, a stimulant of benchmark threats. It was found that the SWCNT-TFT sensors treated with UV radiation show a much higher sensitivity and faster response to the analytes than those without treatment with UV radiation. PMID:23176557

  9. Surface silver clusters as oxidation catalysts on semiconductor gas sensors

    Microsoft Academic Search

    Jianping Zhang; Konrad Colbow

    1997-01-01

    We have investigated silver clusters on SnO2 thin-film surfaces by scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray diffraction (XRD). These clusters act as catalytic activators on SnO2 gas sensors and improve sensor performance for H2 detection compared to untreated surfaces. The sensitivity is found to be dependent on the operating temperature of the sensors and the amount

  10. 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.

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

    Microsoft Academic Search

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

    2000-01-01

    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

  12. 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.

  13. 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.

  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. Ultrafast response sensor to formaldehyde gas based on metal oxide.

    PubMed

    Choi, N-J; Lee, H-K; Moon, S E; Kim, J; Yang, W S

    2014-08-01

    Thick film semiconductor gas sensors based on indium oxide were fabricated on Si substrate. The sensing materials on Si substrate were characterized using optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM), and so on. They were very fine and uniform and we found out that particle sizes were about 20~30 nm through XRD analysis. Gas responses of fabricated sensors were measured in a chamber where gas flow was controlled by mass flow controller (MFC). Their resistance changes were monitored in real time by using data acquisition board and personal computer. Gas response characteristics were examined for formaldehyde (HCHO) gas which was known as the cause of sick building syndrome. Particularly, the sensors showed responses to formaldehyde gas at sub ppm (cf, standard of natural environment in building is about 80 ppb by ministry of environment in Korea), as a function of operating temperatures and gas concentrations. Also, we investigated sensitivity, repetition, selectivity, response speed and reproducibility of the sensors. The lowest detection limit is HCHO 25 ppb and sensitivity at 800 ppb is over 25% at 350 °C operating temperature. The response time (8 s) and recovery time (15 s) to HCHO gas at 200 ppb were very fast compared to other commercial products in flow type measurement condition. Repetition measurement was very good with ±3% in full measurement range. The fabricated metal oxide gas sensor showed good performance to HCHO gas and proved that it could be adaptable to indoor environment in building. PMID:25936006

  16. Surface morphology-dependent room-temperature LaFeO? nanostructure thin films as selective NO? gas sensor prepared by radio frequency magnetron sputtering.

    PubMed

    Thirumalairajan, S; Girija, K; Mastelaro, Valmor R; Ponpandian, N

    2014-08-27

    In the present work, perovskite LaFeO3 thin films with unique morphology were obtained on silicon substrate using radio frequency magnetron sputtering technique. The effect of thickness and temperature on the morphological and structural properties of LaFeO3 films was systematically studied. The X-ray diffraction pattern explored the highly oriented orthorhombic perovskite phase of the prepared thin films along [121]. Electron micrograph images exposed the network and nanocube surface morphology of LaFeO3 thin films with average sizes of ?90 and 70 nm, respectively. The developed LaFeO3 thin films not only possess unique morphology, but also influence the gas-sensing performance toward NO2. Among the two morphologies, nanocubes exhibited high sensitivity, good selectivity, fast response-recovery time, and excellent repeatability for 1 ppm level of NO2 gas at room temperature. The response time for nanocubes was 24-11 s with a recovery duration of 35-15 s less than the network structure. The sensitivity toward NO2 detection was found to be in the range 29.60-157.89. The enhancement in gas-sensing properties is attributed to their porous structure, surface morphology, numerous surface active sites, and the oxygen vacancies. The gas-sensing measurements demonstrate that the LaFeO3 sensing material is an outstanding candidate for NO2 detection. PMID:25029197

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

    Microsoft Academic Search

    Noriya Izu; Woosuck Shin; Norimitsu Murayama

    2003-01-01

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

  18. 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.

  19. Numerical analysis of response time for resistive oxygen gas sensors

    Microsoft Academic Search

    Noriya Izu; Woosuck Shin; Norimitsu Murayama

    2002-01-01

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

  20. A novel optical gas sensor based on sputtered In x O y N z films with gold-nano-dots

    Microsoft Academic Search

    H. Steffes; A. Schleunitz; U. Gernert; R. Chabicovsky; E. Obermeier

    2006-01-01

    In this paper we present new results achieved with a sputtered multilayer system consisting of InxOyNz and gold-nano-dots. This system shows not only electrical but also optical gas sensitivity. The optical sensing effect is enhanced by the gold-nano-dots which are randomly distributed on and inside each InxOyNz layer. The optical measuring system consists of a tuneable light source (or alternatively

  1. 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.

  2. 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.

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

    SciTech Connect

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

    1998-05-01

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

  4. CO Responses of Sensors Based on Cerium Oxide Thick Films Prepared from Clustered Spherical Nanoparticles

    PubMed Central

    Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2013-01-01

    Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors. PMID:23529123

  5. Selective modified SnO2-based materials for gas sensors arrays

    Microsoft Academic Search

    V. Krivetsky; A. Ponzoni; E. Comini; M. Rumyantseva; A. Gaskov

    2009-01-01

    An enhancement of selectivity of semiconductor gas sensors, based on nanocrystalline SnO2 is reported. It is shown that modification of the surface of crystallites, forming thick films of conductive sensor materials, with catalytic clusters of gold or oxides of ruthenium, nickel, copper and iron allows selective response of sensors to different gases, such as carbon monoxide, ammonia, hydrogen sulfide, nitrogen

  6. Fabrication of Thin Film Heat Flux Sensors

    NASA Technical Reports Server (NTRS)

    Will, Herbert A.

    1992-01-01

    Prototype thin film heat flux sensors have been constructed and tested. The sensors can be applied to propulsion system materials and components. The sensors can provide steady state and fast transient heat flux information. Fabrication of the sensor does not require any matching of the mounting surface. Heat flux is proportional to the temperature difference across the upper and lower surfaces of an insulation material. The sensor consists of an array of thermocouples on the upper and lower surfaces of a thin insulating layer. The thermocouples for the sensor are connected in a thermopile arrangement. A 100 thermocouple pair heat flux sensor has been fabricated on silicon wafers. The sensor produced an output voltage of 200-400 microvolts when exposed to a hot air heat gun. A 20 element thermocouple pair heat flux sensor has been fabricated on aluminum oxide sheet. Thermocouples are Pt-Pt/Rh with silicon dioxide as the insulating material. This sensor produced an output of 28 microvolts when exposed to the radiation of a furnace operating at 1000 C. Work is also underway to put this type of heat flux sensor on metal surfaces.

  7. Thin film thermal sensor fabrication and application

    NASA Astrophysics Data System (ADS)

    Gualous, Hamid

    1999-10-01

    This paper is about a gold palladium thin-film microthermocouple gate array. The gate array is fabricated by standard photolithography and sputtering technology. The sensor has been developed to characterize the energetic profile of laser power. The thermal sensor is a thin film thermocouple gate array with 16 sensing junctions per 288 micrometers . The response of Au/Pd thin-film thermocouple has been characterized, the time constant of thermocouple response is in order of 140 microsecond(s) . Furthermore, a linear graph giving the thermoelastic voltage versus the incident power laser has been obtained. Finally, the spot size and the intensity profile of laser beam have been estimated using the sensor.

  8. 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.

  9. Integrated interface circuit with multiplexed input and digital output for a 5 × 5 SnO 2 thick film gas-sensor matrix

    Microsoft Academic Search

    M. Grassi; P. Malcovati; L. Francioso; P. Siciliano; A. Baschirotto

    2008-01-01

    This paper presents the design and experimental results for a 5×5 tin-oxide gas-sensor array system with particular focus on the employed multiplexed-analog-input 0.35?m CMOS interface circuit chip. This interface circuit reads the electrical signal of all the elements of the array in time sharing by means of a solid-state selector, actually exploiting a row-column query technique and provides digital output

  10. Thick-film zinc-oxide gas sensor for the control of lean air-to-fuel ratio in domestic combustion systems

    Microsoft Academic Search

    Chul Han Kwon; Hyung-Ki Hong; Dong Hyun Yun; Kyuchung Lee; Sung-Tae Kim; Young-Hoon Roh; Byung-Hoon Lee

    1995-01-01

    We have investigated the sensing properties of Al2O3-doped ZnO for combustion control in lean-burn conditions. Planar-type sensing elements made of heater, electrode and sensing layer were formed on an alumina substrate using a screen-printing technique. Our exhaust-gas sensor exhibits significant resistance changes even under lean conditions, apparently due to the simultaneous functioning of bulk and surface conduction mechanisms. Utilizing the

  11. 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

  12. Thin-film temperature sensor

    NASA Technical Reports Server (NTRS)

    Maserjian, J.; Gatewood, J. R.

    1974-01-01

    Sensor measures rapid temperature changes in fluid streams. Sensor withstands contacts with various corrosive fluids, high fluid-flow rates, and turbulences caused by rapid changes in flow rates. Capacitor is part of resonant bridge circuit which produces ac voltage that is proportional to temperature.

  13. 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

  14. 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

  15. 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

  16. Vehicle exhaust gas chemical sensors using acoustic wave resonators

    SciTech Connect

    Cernosek, R.W.; Small, J.H.; Sawyer, P.S.; Bigbie, J.R. [Sandia National Labs., Albuquerque, NM (United States); Anderson, M.T. [3M Industrial and Consumer Sector Research Lab., St. Paul, MN (United States)

    1998-03-01

    Under Sandia`s Laboratory Directed Research and Development (LDRD) program, novel acoustic wave-based sensors were explored for detecting gaseous chemical species in vehicle exhaust streams. The need exists for on-line, real-time monitors to continuously analyze the toxic exhaust gases -- nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) -- for determining catalytic converter efficiency, documenting compliance to emission regulations, and optimizing engine performance through feedback control. In this project, the authors adapted existing acoustic wave chemical sensor technology to the high temperature environment and investigated new robust sensor materials for improving gas detection sensitivity and selectivity. This report describes one new sensor that has potential use as an exhaust stream residual hydrocarbon monitor. The sensor consists of a thickness shear mode (TSM) quartz resonator coated with a thin mesoporous silica layer ion-exchanged with palladium ions. When operated at temperatures above 300 C, the high surface area film catalyzes the combustion of the hydrocarbon vapors in the presence of oxygen. The sensor acts as a calorimeter as the exothermic reaction slightly increases the temperature, stressing the sensor surface, and producing a measurable deviation in the resonator frequency. Sensitivities as high as 0.44 (ppm-{Delta}f) and (ppm-gas) have been measured for propylene gas, with minimum detectable signals of < 50 ppm of propylene at 500 C.

  17. Thin-film temperature sensor.

    NASA Technical Reports Server (NTRS)

    Maserjian, J.

    1972-01-01

    A new device has been developed for sensing small and rapid temperature changes accompanying biochemical reactions. The active element consists of an evaporated thin-film capacitor having a relatively strong temperature dependence. This dependence is derived from electron trapping effects in the thin amorphous dielectric film. A voltage output of at least 50 mV/deg can be obtained prior to amplification by using a resonant ac bridge circuit operating at 100 kHz. The corresponding noise output for a 10 kHz bandwidth can with an optimum circuit be as low as 4 microvolts. Therefore, the minimum detectable temperature change would be 80 microdegrees at 10 kHz. Rapid thermal response is assured by supporting the thin-film capacitor on a thin anodic tantalum oxide film suspended across an electrolytically etched window in a tantalum foil.

  18. Gas sensors based on semiconducting nanowire field-effect transistors.

    PubMed

    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

  19. 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

  20. A digital hygrometer using a polyimide film relative humidity sensor

    Microsoft Academic Search

    Hideo Shibata; Masahiro Ito; Masahiro Asakursa; K. Watanabe

    1996-01-01

    A digital hygrometer using a relative humidity sensor is developed. The sensor consists of a polyimide film spin-coated onto an Si substrate. The sensor model for signal processing, which describes the sensor capacitance in terms of relative humidity and temperature in closed form, is derived first. The interface appropriate for the sensor model, based on a relaxation oscillator, is designed

  1. 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.

  2. 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.

  3. Thermal Sensor Arrays for The Combinatorial Analysis of Thin Films

    E-print Network

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

  4. 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.

  5. Trial for simple gas sensor composed of as-grown carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kokabu, Takuya; Inoue, Shuhei; Matsumura, Yukihiko

    2015-05-01

    Carbon nanotube gas sensor does not require heat for detecting gas species unlike present semiconductor type; hence, it is expected to be commercially available. The detecting mechanisms are explained by both charge transfer and Schottky barrier, but its detail such as contribution of polar molecule and charge variation are not clear. In this study, we examined as-grown vertically aligned single-walled and dispersed multi-walled carbon nanotube as sensors without any micro/nanofabrication for realizing simple gas sensor. Both film showed obvious response to the air and, their detecting principle is explained only by charge transfer between carbon nanotube and absorbed gas molecules.

  6. Sol-gel synthesized semiconducting LaCo0.8Fe0.2O3-based powder for thick film NH3 gas sensor.

    PubMed

    Chaudhari, G N; Jagtap, S V; Gedam, N N; Pawar, M J; Sangawar, V S

    2009-05-15

    Perovskite type LaCo(x)Fe(1-x)O(3) nanoparticles was synthesized by a sol-gel citrate method. The structural, electrical and sensing characteristics of the LaCo(x)Fe(1-x)O(3) system were investigated. The structural characteristics were performed by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to examine the phase and morphology of the resultant powder. The XRD pattern shows nanocrystalline solid solution of LaCo(x)Fe(1-x)O(3) with perovskite phase. Electrical properties of synthesized nanoparticles are studied by DC conductivity measurement. The sensor shows high response towards ammonia gas in spite of other reducing gases when x=0.8. The effect of 0.3 wt.% Pd-doped LaCo(0.8)Fe(0.2)O(3) on the response and a recovery time was also addressed. PMID:19269483

  7. 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.

  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. 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

  10. Boundary layer measurements using hot-film sensors

    NASA Technical Reports Server (NTRS)

    Holmes, Harlan K.; Carraway, Debra L.

    1986-01-01

    Measurements in the aerodynamic boundary layer using heat transfer, hot-film sensors are receiving a significant amount of effort at the Langley Research Center. A description of the basic sensor, the signal conditioning employed, and several manifestations of the sensor are given. Results of a flow reversal sensor development are presented, and future work areas are outlined.

  11. Device optimization of CO2 gas sensor using planar technology.

    PubMed

    Lee, Woon Young; Choi, Yong Kook; Satyanarayana, L; Park, Jin Seong

    2007-11-01

    A planar type Li+ ion based potentiometric CO2 micro gas sensor of size 2 x 3 mm has been fabricated on alumina substrate by combining thin and thick film technology. The heater, electrodes and electrolyte were deposited by thin film deposition technique and the sensing and reference electrodes were printed by silk screen printing technology. The optimal thickness and sintering temperature of electrolyte are 1.2 microm and 775 degrees C. The sensor with Li2CO3 and 20 mol% BaCO3 not only exhibits a good Nernstian behavior but also consistent results over a long time at 450 degrees C in dry as well as 70% RH humidity condition between 160-5000 ppm CO2 concentrations. The spreading effect of the sensing and reference materials was controlled by the addition of Al2O3:B2O3 (1:2 mol%) glass. PMID:18047140

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

    Microsoft Academic Search

    W. Diehl

    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

  13. 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.

  14. ZnO thin film sensor

    Microsoft Academic Search

    P. Mitra; A. P. Chatterjee; H. S. Maiti

    1998-01-01

    The electrical and gas sensing properties of chemically deposited zinc oxide (ZnO) films were investigated. Two activation energy values, 0.3 eV and 0.8–0.9 eV, were determined in the temperature range 300–400 K which are attributed to oxygen vacancy (VO) donor and heat of chemisorption of the O2? species. The adsorption of oxygen on ZnO leads to a stable and highly

  15. Superconductive thin film makes convenient liquid helium level sensor

    NASA Technical Reports Server (NTRS)

    Becker, H. H.

    1968-01-01

    Sensor consisting of superconductive film mounted on a dipstick measures the level of liquid helium in a Dewar flask. The sensor is made by depositing a thin film of niobium metal to a thickness of 2000 angstroms on a quartz substrate, which is then mounted on a graduated dipstick.

  16. 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

  17. 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.

  18. Development of a thin film solid state gaseous HCl sensor

    NASA Technical Reports Server (NTRS)

    1975-01-01

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

  19. PALLADIUM DOPED TIN OXIDE BASED HYDROGEN GAS SENSORS FOR SAFETY APPLICATIONS

    SciTech Connect

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

    2010-04-09

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

  20. Polymer waveguide sensor with tin oxide thin film integrated onto optical-electrical printed circuit board

    NASA Astrophysics Data System (ADS)

    Lim, Jung Woon; Kim, Seon Hoon; Kim, Jong-Sup; Kim, Jeong Ho; Kim, Yune Hyoun; Lim, Ju Young; Im, Young-Eun; Park, Jong Bok; Hann, Swook

    2014-05-01

    In this study, we proposed and fabricated optical sensor module integrated onto optical-electrical printed circuit board (PCB) for gas detection based on polymer waveguide with tin oxide thin film. Their potential application as gas sensors are confirmed through computational simulation using the two dimensional finite-difference time-domain method (2DFDTD). Optical-electrical PCB was integrated into vertical cavity surface emitting laser (VCSEL), photodiode and polymeric sensing device was fabricated by the nano-imprint lithography technique. SnO2 thin film of 100nm thickness was placed on the surface of core layer exposed by removing the specific area of the upper cladding layer of 300 ?m length and 50 ?m width. The performance of the device was measured experimentally. Initial study on the sensor performance for carbon monoxide gas detection indicated good sensitivity.

  1. 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.

  2. 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. [Sandia National Labs., Albuquerque, NM (United States); Huber, R.J. [Utah Univ., Salt Lake City, UT (United States); Senturia, S.D. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

    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.

  3. Thermal Enzyme Sensor Utilizing Temperature-Sensitive Magnetic Thin Film

    Microsoft Academic Search

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

    2002-01-01

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

  4. 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.

  5. 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.

  6. A field effect transistor type gas sensor based on polyaniline

    Microsoft Academic Search

    Sang-Mun Lee; Sang-Jin Uhm; Jung-Il Bang; Kap-Duk Song; Byung-Su Joo; Yun-Su Lee; Duk-Dong Lee

    2005-01-01

    The researched sensor at this paper is based on gas sensitive conducting polymer. Some types of conducting polymer have gas sensitivity at room temperature (Matsuguchi et al., 2002). These conducting polymers have several shortages such as low sensitivity. The transistor type gas sensor has been studied for several decades. These sensors are based on metal oxide ceramics such as tin

  7. Colorimetric blood-gas monitoring sensors

    NASA Astrophysics Data System (ADS)

    Proctor, Keith J.; Seifert, George P.

    1993-05-01

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

  8. 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

  9. Graphene-based microfiber gas sensor

    NASA Astrophysics Data System (ADS)

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

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

  10. Improvement of long-term stability in SnO 2-based gas sensor for monitoring offensive odor

    Microsoft Academic Search

    Jong Hyun Park; Kwang Ho Kim

    1999-01-01

    WO3\\/SnO2 ceramics has been suggested as an effective sensing material for monitoring offensive odor or pollutant gases. This work was focused on improving long-term stability, which has been a principal problem generally associated with SnO2 semiconductor gas sensors. Miniaturized thick film gas sensors were fabricated by screen-printing technique. Two types of sensor materials, W-doped SnO2 and WO3-mixed SnO2, were comparatively

  11. Fabrication of resistive CO gas sensor based on SnO 2 nanopowders via low frequency AC electrophoretic deposition

    Microsoft Academic Search

    Amir Reza Gardeshzadeh; Babak Raissi; Ehsan Marzbanrad; Hamed Mohebbi

    2009-01-01

    A resistive CO gas sensor has been fabricated using AC electrophoretic deposition (ACEPD) technique. SnO2 thick films are deposited by applying low frequency (0.01–1,000 Hz) AC electric field to a stable suspension of SnO2 nanoparticles in acetyl acetone. A carbon film base electrode is used as deposit substrate. Effect of CO gas exposure on\\u000a conductivity of the SnO2 film at 300 °C

  12. Thin film polypyrrole\\/SWCNTs nanocomposites-based NH 3 sensor operated at room temperature

    Microsoft Academic Search

    Nguyen Van Hieu; Nguyen Quoc Dung; Phuong Dinh Tam; Tran Trung; Nguyen Duc Chien

    2009-01-01

    A PPY\\/SWCNTs nanocomposite-based sensor with relatively high sensitivity and fast response–recovery was developed for detection of NH3 gas at room temperature. The gas-sensitive composite thin film was prepared using chemical polymerization and spin-coating techniques, and characterized by Fourier transformed infrared spectra and field-emission scanning electron microscopy. The results reveal that the conjugated structure of the PPY layer was formed and

  13. 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.

  14. Nanoparticle SnO2 Gas Sensor with Circuit and Micro Heater on Chip Fabricated Using CMOS-MEMS Technique

    Microsoft Academic Search

    Ching-Liang Dai; Mao-Chen Liu

    2007-01-01

    The fabrication of a carbon monoxide (CO) micro gas sensor integrated with an inverting amplifier circuit and a micro heater on chip using the commercial 0.35mum complementary metal oxide semiconductor (CMOS) process and a post-process have been implemented. The gas sensor is composed of a polysilicon resistor and a CO gas sensing film. Tin dioxide prepared by the sol-gel method

  15. Laser Ablative Deposition of Polymer Films: A Promise for Sensor Fabrication

    NASA Astrophysics Data System (ADS)

    Blazevska-Gilev, Jadranka; Kup?ík, Jaroslav; Šubrt, Jan; Pola, Josef

    There is a continuing interest in the use of polymer films as insulating components of sensors; a number of such films have been prepared by polymer sputtering or vacuum deposition processes involving gas phase pyrolysis/photolysis and by plasma decomposition of monomers. An attractive and rather new technique for the deposition of novel polymer films is IR laser ablation of polymers containing polar groups. We have recently studied this process with poly(vinyl chloride) (PVC), poly(vinyl acetate) (PVAc) and poly(vinyl chloride-co-vinyl acetate) P(VC/VAc) to establish its specific features and differences to conventional pyrolysis.

  16. Nonlinear dynamics of a resonant gas sensor

    Microsoft Academic Search

    A. H. Nayfeh; H. M. Ouakad; F. Najar; S. Choura; E. M. Abdel-Rahman

    2010-01-01

    We develop a mathematical model for a resonant gas sensor made up of an microplate electrostatically actuated and attached\\u000a to the end of a cantilever microbeam. The model considers the microbeam as a continuous medium, the plate as a rigid body,\\u000a and the electrostatic force as a nonlinear function of the displacement and the voltage applied underneath the microplate.\\u000a We

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

    Microsoft Academic Search

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

    1997-01-01

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

  18. MWCNT-polymer composites as highly sensitive and selective room temperature gas sensors

    Microsoft Academic Search

    Raghu Mangu; Suresh Rajaputra; Vijay P. Singh

    2011-01-01

    Multi-walled carbon nanotubes (MWCNTs)-polymer composite-based hybrid sensors were fabricated and integrated into a resistive sensor design for gas sensing applications. Thin films of MWCNTs were grown onto Si\\/SiO2 substrates via xylene pyrolysis using the chemical vapor deposition technique. Polymers like PEDOT:PSS and polyaniline (PANI) mixed with various solvents like DMSO, DMF, 2-propanol and ethylene glycol were used to synthesize the

  19. 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...

  20. A novel thick-film ceramic humidity sensor

    Microsoft Academic Search

    Wenmin Qu; Jörg-Uwe Meyer

    1997-01-01

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

  1. A Novel Graphene-Based Inkjet-Printed WISP-Enabled Wireless Gas Sensor

    E-print Network

    Tentzeris, Manos

    . The sensor demonstrates good response to ammonia gas (NH3), yielding a 6% normalized resistance change within Georgia Institute of Technology Atlanta GA, USA Ziyin Lin, Ching-ping Wong School of Materials Science is achieved using the graphene thin films, with over 30% of material recovery observed within 5 minutes

  2. Metal oxide gas sensor array for the detection of diesel fuel in engine oil

    Microsoft Academic Search

    Simonetta Capone; Marzia Zuppa; Dominique S. Presicce; Luca Francioso; Flavio Casino; Pietro Siciliano

    2008-01-01

    We developed a novel method to detect the presence of unburned diesel fuel in lubricating oil for internal combustion engine. The method is based on the use of an array of different gas microsensors based on metal oxide thin films deposited by sol–gel technique on Si substrates. The sensor array, exposed to the volatile chemical species of different diesel fuel

  3. Temperature Compensation of Novel NDIR CO2 Gas Sensor

    Microsoft Academic Search

    SeungHwan Yi

    2006-01-01

    We have designed novel optical cavity and simulated it for NDIR gas sensor application. Novel optical cavity enhanced the light focusing effects. In this research, we developed the temperature compensated NDIR CO2 gas sensor for heat exchange system. The output characteristics of developed sensor module shows an exponentially decreasing property and all parameters are temperature dependent. The temperature compensated module

  4. 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.

  5. Optical hydrogen sensor using Pd/MoO{sub x} films

    SciTech Connect

    Hamagami, Jun-ichi; Huybrechts, Ben; Takata, Masasuke; Watanabe, Yuichi [Nagaoka Univ. of Technology, Niigata (Japan)

    1994-12-31

    An optical hydrogen sensor which colors under an H{sub 2}-atmosphere is prepared. The sensor consists of a molybdenum oxide (MoO{sub x}) layer (500-1300 nm) on a glass substrate covered with a very thin palladium layer of about 10 nm. Both layers are deposited by radio-frequency magnetron sputtering. The sputtering of the MoO{sub x} films is carried out in a mixed Ar-O{sub 2} atmosphere using a molybdenum metal plate as the target. The relationship between the hydrogen gas sensing properties and oxygen content in the MoO{sub x} film is examined. The oxygen content in the films, estimated by X-ray photoelectron spectroscopy (XPS), increases with the oxygen concentration in the sputtering gas. For amorphous MoO{sub x} films the initial coloration rate slightly increased with the oxygen concentration in the films. The initial coloration rate for the crystalline MoO{sub 3} film, obtained by sputtering in an oxygen atmosphere, was 7 times higher than the one for the amorphous MoO{sub x} films.

  6. A reusable smart interface for gas sensor resistance measurement

    Microsoft Academic Search

    Sebastiàn A. Bota; Raimon Casanova; Ángel Dieguez; Carles Cané; Josep Samitier

    2004-01-01

    The advances of the semiconductor industry enable microelectromechanical systems sensors, signal conditioning logic and network access to be integrated into a smart sensor node. In this framework, a mixed-mode interface circuit for monolithically integrated gas sensor arrays was developed with high-level design techniques. This interface system includes analog electronics for inspection of up to four sensor arrays and digital logic

  7. Investigations of optical interferometric structures applied in toxic gas sensors

    Microsoft Academic Search

    Z. OPILSKI; T. PUSTELNY; E. MACIAK; M. BEDNORZ; A. STOLARCZYK

    In recent years organic semiconductors have been given attention in the field of active materials for gas sensor applications. In the paper the investigations of the optoelectronic sensor structure of ammonia were presented. The sensor head consists of polyaniline and Nafion layers deposited on the face of the telecommunication optical fiber. The elaborated sensor structure in the form of Fabry-Perot

  8. A thin film, high sensitivity, two terminal, semiconductor strain sensor.

    NASA Technical Reports Server (NTRS)

    Mallon, J. R.

    1971-01-01

    A two terminal semiconductor strain sensor which makes use of an evaporated piezoelectric layer to modulate the forward current-voltage characteristics of a thin film diode is described. The physical mechanisms are discussed and compared to other types of semiconductor sensors. Application to the electromechanical design of ultraminiature pressure transducers is discussed.

  9. Augmenting Film and Video Footage with Sensor Data

    Microsoft Academic Search

    Norman Makoto Su; Eric Bostrom; Jeff Burke; Mani B. Srivastava; Deborah Estrin

    2004-01-01

    With the advent of tiny networked devices, Mark Weiser's vision of a world embedded with invisible computers is coming to age. Due to their small size and relative ease of deployment, sensor networks have been utilized by zoologists, seismologists and military personnel. In this paper, we investigate the novel application of sensor networks to the film industry. In particular, we

  10. 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.

  11. A novel thick film conductive type CO 2 sensor

    Microsoft Academic Search

    Andrea Haeusler; Jörg-Uwe Meyer

    1996-01-01

    A low-cost CO2 sensor in thick film technology has been developed using BaTiO3 and various semiconducting oxides. The sensing principle of this new CO2 sensor is based on changes in conductance of the metal oxides in the presence of carbon dioxide. In this report, effects of preparation parameters and effects of various additives on the sensitivity of the CO2 sensor

  12. SnO2 Highly Sensitive CO Gas Sensor Based on Quasi-Molecular-Imprinting Mechanism Design

    PubMed Central

    Li, Chenjia; Lv, Meng; Zuo, Jialin; Huang, Xintang

    2015-01-01

    Response of highly sensitive SnO2 semiconductor carbon monoxide (CO) gas sensors based on target gas CO quasi-molecular-imprinting mechanism design is investigated with gas concentrations varied from 50 to 3000 ppm. SnO2 nanoparticles prepared via hydrothermal method and gas sensor film devices SC (exposed to the target gas CO for 12 h after the suspension coating of SnO2 film to be fully dried, design of quasi-molecular-imprinting mechanism, the experiment group) and SA (exposed to air after the suspension coating of SnO2 film to be fully dried, the comparison group) made from SnO2 nanoparticles are all characterized by XRD, SEM and BET surface area techniques, respectively. The gas response experimental results reveal that the sensor SC demonstrates quicker response and higher sensitivity than the sensor SA does. The results suggest that in addition to the transformation of gas sensor materials, surface area, and porous membrane devices, the Molecular Imprinting Theory is proved to be another way to promote the performance of gas sensors. PMID:25664435

  13. 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.

  14. Study for Electrode Metals on Taste Sensor with LB film

    NASA Astrophysics Data System (ADS)

    Yokoya, Takahiro; Hirata, Takamichi; Akiya, Masahiro

    In this paper, sensor responses with only metal electrode as Au, Cr, Ti and more with LB film were described. LB film material was the Dioctadecyldimethylammonium bromide combined by PVSK as an underlayer. To detect five basic taste substances, sensor parameters were defined as maximum voltage change and response time. Response time for sourness and umami with Ti and Cr evaporated metal electrode was larger than that of usual Au electrode. LB film effect was finally found to increase response time for five basic taste materials.

  15. Gas detection by carbon nanotube gas-ionization sensor based on Lyapunov exponent

    Microsoft Academic Search

    Guohua Hui

    2010-01-01

    In this paper, a novel method utilizing a multi-walled carbon nanotube (MWNT) gas-ionization sensor based on Lyapunov exponent algorithm was proposed for argon, ethanol, acetone, and ammonia detection. The sensor was used as anodic sensor. Responses of MWNT sensor to four gases was measured and processed by Lyapunov exponent. Experimental results showed that the MWNT sensor array based on Lyapunov

  16. A sensitivity enhanced gas sensor based on carbon nanotubes around microfiber

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

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

  18. Room Temperature Ammonia Gas Sensor Based on Polyaniline-TiO$_{2}$ Nanocomposite

    Microsoft Academic Search

    S. G. Pawar; M. A. Chougule; S. L. Patil; B. T. Raut; P. R. Godse; Shashwati Sen; V. B. Patil

    2011-01-01

    In the present work, we report on the performance of room temperature ammonia gas sensor based on polyaniline-ti- tanium dioxide (PANi-TiO ) nanocomposite. The nanocomposite was fabricated using the spin coating method on glass substrates. PANi-TiO (0%-50%) nanocomposite films were characterized for their structural as well as surface morphologies, UV-Vis and various gas responses were studied. The XRD analysis showed

  19. Comparative studies on polymer coated SAW and STW resonators for chemical gas sensor applications

    Microsoft Academic Search

    I. D. Avramov; M. Rapp; A. Voigt; U. Stahl; M. Dirschka

    2000-01-01

    This paper presents and compares experimental data from performance tests on polymer coated 433 MHz surface acoustic wave (SAW) and 1 GHz surface transverse wave (STW) based two-port resonators for chemical gas sensor applications. The acoustic devices were coated with gas sensitive polymer films of different thickness' and viscoelastic properties as parylene C, poly-(2-hydroxyethylmethacrylate) (PHEMA) and poly-(n-butyl-methacrylate) (PBMA). Then they

  20. Polymeric foil optical waveguide with inkjet printed gas sensitive film for colorimetric sensing

    Microsoft Academic Search

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

    The design of low-cost and low-power optical transducers on plastic foil for colorimetric gas sensors is proposed. The transducer was fabricated from PET or PEN foil on which polymeric micro-mirrors and colorimetric film were patterned using additive techniques. It consisted of a planar optical waveguide that was covered with an inkjet printed ammonia sensitive film for its evaluation. A parametric

  1. Stagnation temperature measurement using thin-film platinum resistance sensors

    NASA Astrophysics Data System (ADS)

    Bonham, C.; Thorpe, S. J.; Erlund, M. N.; Stevenson, R. D.

    2014-01-01

    The measurement of stagnation temperature in high-speed flows is an important aspect of gas turbine engine testing. The ongoing requirement to improve the accuracy of such measurements has led to the development of probe systems that use a thin-film platinum resistance thermometer (PRT) as the sensing element. For certain aspects of engine testing this type of sensing device potentially offers superior measurement performance to the thermocouple, the temperature sensor of choice in most gas turbine applications. This paper considers the measurement performance of prototype PRT-based stagnation temperature probes, up to high-subsonic flow conditions, using passively aspirated probe heads. The relatively poor temperature recovery performance of a simply constructed probe has led to the development of a new design that is intended to reduce the impact of thermal conduction within the probe assembly. The performance of this so-called dual-skin probe has been measured through a series of tests at a range of Mach numbers, incidence angles and Reynolds numbers. The data reveal that a high probe recovery factor has been achieved with this device, and that the application of this design to engine tests would yield the measurement performance benefits of the PRT whilst requiring small levels of temperature recovery compensation.

  2. Graphene/mica based ammonia gas sensors

    NASA Astrophysics Data System (ADS)

    Ben Aziza, Zeineb; Zhang, Qing; Baillargeat, Dominique

    2014-12-01

    In this paper, graphene/mica and graphene/SiO2 based ammonia gas sensors are compared. It is found that adsorbed NH3 molecules result in up-shifting of the Fermi level in graphene, leading to a significant increase in graphene resistance. In comparison with SiO2 supporting substrate, the mica supporting substrate is found to induce more p-doping in graphene, in favour of NH3 molecule adsorption, yielding a high sensitivity. These findings suggest that the substrate plays an important role in mediating the interaction between graphene and NH3 molecules and that mica can be an excellent underlying substrate for graphene for ammonia gas detection.

  3. Humidity sensors based on polymer thin films

    Microsoft Academic Search

    Y Sakai; Y Sadaoka; M Matsuguchi

    1996-01-01

    Studies on humidity sensors fabricated with organic polymers for the last 10 years are reviewed. Several useful methods for improving the characteristics of humidity sensors based on polymers are proposed. In the case of a resistive-type sensor, cross-linking of hydrophilic polymers or formation of interpenetrated polymer networks with a hydrophobic polymer makes the hydrophilic polymers durable at high humidities. Graft

  4. Study of real-time visualization of gas\\/odor flow image using gas sensor array

    Microsoft Academic Search

    H Ishida; T Yamanaka; N Kushida; T Nakamoto; T Moriizumi

    2000-01-01

    A new method to find a gas\\/odor source is proposed. A portable homogeneous gas sensor array is used to visualize the flow of a target gas. The direction of a gas source is estimated using a real-time image processing algorithm, and the source is located by following the estimated direction. The design of the sensor array has been performed using

  5. Controlling a gas\\/odor plume-tracking robot based on transient responses of gas sensors

    Microsoft Academic Search

    Hiroshi Ishida; Gouki Nakayama; Takamichi Nakamoto; Toyosaka Moriizumi

    2005-01-01

    Gas sensors provide an artificial sense of smell for a mobile robot to track an airborne gas\\/odor plume and locate its source. However, a slow response of gas sensors has been the major factor limiting the development of plume-tracking robots. This paper describes a new control algorithm that breaks the limitation. The basic idea is to detect onsets of gas

  6. Detection of volatile organic compounds (VOCs) using SnO 2 gas-sensor array and artificial neural network

    Microsoft Academic Search

    A. K. Srivastava

    2003-01-01

    This paper presents design and development of an electronic nose system based on tin oxide gas-sensors array and artificial neural network (ANN) for the identification of some of the volatile organic compounds (VOCs) relevant to environmental monitoring such as propane-2-ol, methanol, acetone, ethyl methyl ketone, hexane, benzene and xylene. An array of SnO2-based thick-film gas sensors doped with Pd, Pt

  7. 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

  8. 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

  9. A micro-fabricated force sensor using an all thin film piezoelectric active sensor.

    PubMed

    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

  10. 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.

  11. 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.

  12. Conjugated polymer films for gas separations

    Microsoft Academic Search

    M. R. Anderson; B. R. Mattes; H. Reiss; R. B. Kaner

    1991-01-01

    Permeabilities for a series of gases through free-standing films of the conjugated polymer polyaniline are reported. A remarkable selectivity has been achieved for important gas pairs including hydrogen-nitrogen, oxygen-nitrogen, and carbon dioxide-methane. The selectivity values of 3,590 for Hâ\\/Nâ, 30 for Oâ\\/Nâ, and 336 for COâ\\/CHâsurpass the highest previously reported values of 313, 16, and 60 for the nonconjugated polymers

  13. Conjugated Polymer Films for Gas Separations

    Microsoft Academic Search

    Mark R. Anderson; Benjamin R. Mattes; Howard Reiss; Richard B. Kaner

    1991-01-01

    Permeabilities for a series of gases through free-standing films of the conjugated polymer polyaniline are reported. A remarkable selectivity has been achieved for important gas pairs including hydrogen-nitrogen, oxygen-nitrogen, and carbon dioxide-methane. The selectivity values of 3590 for H_2\\/N_2, 30 for O_2\\/N_2, and 336 for CO_2\\/CH_4 surpass the highest previously reported values of 313, 16, and 60 for the nonconjugated

  14. 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.

  15. TOPICAL REVIEW: Understanding the fundamental principles of metal oxide based gas sensors; the example of CO sensing with SnO2 sensors in the presence of humidity

    NASA Astrophysics Data System (ADS)

    Bârsan, N.; Weimar, U.

    2003-05-01

    This paper investigates the effect of water vapour in CO sensing by using Pd doped SnO2 sensors realized in thick film technology as an example of the basic understanding of sensing mechanisms applied to sensors. The results of phenomenological and spectroscopic measurement techniques, all of them obtained under working conditions for sensors, were combined with modelling in order to derive conclusions able to be generalized to the field of metal oxide based gas sensors. The techniques employed were: dc conductance, ac impedance spectroscopy, work function (by using the Kelvin probe method), catalytic conversion and diffuse reflectance infrared Fourier transform measurements. The most important conclusion is that the different parts of the sensor (sensing layer, electrodes, substrate) are all influencing the gas detection and their role has to be taken into consideration when one attempts to understand how a sensor works.

  16. Mesoporous thin-film on highly-sensitive resonant chemical sensor for relative humidity and CO2 detection.

    PubMed

    Lee, Hyunjoo J; Park, Kwan Kyu; Kupnik, Mario; Melosh, Nicholas A; Khuri-Yakub, Butrus T

    2012-04-01

    Distributed sensing of gas-phase chemicals is a promising application for mesoporous materials when combined with highly sensitive miniaturized gas sensors. We present a direct application of a mesoporous silica thin film on a highly sensitive miniaturized resonant chemical sensor with a mass sensitivity at the zeptogram scale for relative humidity and CO(2) detection. Using mesoporous silica thin-film, we report one of the lowest volume resolutions and a sensitive detection of 5.1 × 10(-4)% RH/Hz to water vapor in N(2), which is 70 times higher than a device with a nontemplated silica layer. In addition, a mesoporous thin-film that is functionalized with an amino-group is directly applied on the resonant sensor, which exhibits a volume sensitivity of 1.6 × 10(-4)%/Hz and a volume resolution of 1.82 × 10(-4)% to CO(2) in N(2). PMID:22372606

  17. Characterization of polymer films for use in bimorph chemical sensors

    NASA Astrophysics Data System (ADS)

    Chatzandroulis, S.; Goustouridis, D.; Raptis, I.

    2005-01-01

    In the present work white light interferometry is applied for the characterization of polymer films commonly used in bimorph chemical sensors. The study focuses on methacrylate polymers with positive tone patterning capabilities. The behavior upon exposure to controlled concentrations volatile organic compound and water vapors of thin poly (hydroxy ethyl methacrylate) (PHEMA) and poly (methyl methacrylate) (PMMA) layers was evaluated. The normalized film expansion for PHEMA, compared to PMMA, is higher in the case of water and methanol vapors, almost equal for ethanol and significantly lower in the case of acetone. This behavior could be attributed to the combination of polarity and hydrogen bonding capability of the analytes. A wide polymer film thickness range was examined and it was revealed that the normalized film expansion in both PHEMA and PMMA is nearly constant for films thicker than 100 nm and increases for thinner films.

  18. CMOS Interfacing for Integrated Gas Sensors: A Review

    Microsoft Academic Search

    Julian W. Gardner; Prasanta K. Guha; Florin Udrea; James A. Covington

    2010-01-01

    Modern gas sensor technology is becoming an important part of our lives. It has been applied within the home (monitoring CO levels from boilers), the workplace (e.g., checking levels of toxic gases) to healthcare (monitoring gases in hospitals). However, historically the high price of gas sensors has limited market penetration to niche applications, such as safety in mines or petrochemical

  19. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

  20. 21 CFR 870.4410 - Cardiopulmonary bypass in-line blood gas sensor.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...false Cardiopulmonary bypass in-line blood gas sensor. 870.4410 Section...4410 Cardiopulmonary bypass in-line blood gas sensor. (a) Identification. A cardiopulmonary bypass in-line blood gas sensor is a transducer that...

  1. A film pressure sensor based on optical fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Zhichun; Deng, Gang; Dai, Yongbo; Liu, Yanju; Leng, Jinsong

    2010-03-01

    The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure, temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre to the thin sensing film.

  2. 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.

  3. Surface acoustic wave humidity sensor using polyvinyl-alcohol film

    Microsoft Academic Search

    M. Penza; V. I. Anisimkin

    1999-01-01

    A surface acoustic wave (SAW) sensor has been fabricated and used to study the hygroscopic properties of the polyvinyl-alcohol (PVA) polymer film as layer chemically sensitive to relative humidity (RH). A 42 MHz SAW device has been configured as delay line onto 128° YX-LiNbO3 substrate with the SAW path totally covered by the spin-coated PVA film. The SAW phase response

  4. Organic material as gas sensor for farm application

    Microsoft Academic Search

    M. P. Regaco; E. A. T. Dirani; F. J. Fonseca; A. M. de Andrade

    2005-01-01

    Polyaniline is a organic material with potential use in electronic nose sensors and has been shown to be highly sensitive to ammonia. This paper shows results of the characterization of ultra thin films of Polyaniline for applications as gaseous ammonia sensor at NH3 monitoring at chicken farms. A sensitive layer based on such material deposited on the top of interdigital

  5. Numerical analysis of the design parameters on the performance of thin film temperature sensors

    Microsoft Academic Search

    Yi Jia; Guillermo Araya

    2007-01-01

    An embedded thin film temperature sensor onto the surface of lubricated mechanical components is promising for real-time machine condition monitoring. The present study has been concerned with the performance of thin film temperature sensors due to the design parameters such as sensor film thickness, width, length, sensing materials, insulating and protecting layer. An improved three-dimensional heat conduction model has been

  6. 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.

  7. Metal Oxide Gas Sensors: Sensitivity and Influencing Factors

    PubMed Central

    Wang, Chengxiang; Yin, Longwei; Zhang, Luyuan; Xiang, Dong; Gao, Rui

    2010-01-01

    Conductometric semiconducting metal oxide gas sensors have been widely used and investigated in the detection of gases. Investigations have indicated that the gas sensing process is strongly related to surface reactions, so one of the important parameters of gas sensors, the sensitivity of the metal oxide based materials, will change with the factors influencing the surface reactions, such as chemical components, surface-modification and microstructures of sensing layers, temperature and humidity. In this brief review, attention will be focused on changes of sensitivity of conductometric semiconducting metal oxide gas sensors due to the five factors mentioned above. PMID:22294916

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    Barium titanate (BaTiO3) thick films were prepared from commercial powder to develop and optimize the film elaboration. Then, BaTiO3 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.

  9. Discrimination of acetone and ammonia vapor using an array of thin-film sensors of the same type

    Microsoft Academic Search

    V. V. Kisin; V. V. Sysoev; S. A. Voroshilov

    1999-01-01

    It is shown that a gas mixture can be discriminated by using an array of thin-film semiconductor sensors having variable internal\\u000a parameters. It is established that a multisensor system consisting of an array of sensors, fabricated by the same technological\\u000a process but having a spread of active-layer parameters, can discriminate between ammonia and acetone vapor impurities in air.

  10. Multi-Walled Carbon Nanotube-Doped Tungsten Oxide Thin Films for Hydrogen Gas Sensing

    PubMed Central

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

    2010-01-01

    In this work we have fabricated hydrogen gas sensors based on undoped and 1 wt% multi-walled carbon nanotube (MWCNT)-doped tungsten oxide (WO3) thin films by means of the powder mixing and electron beam (E-beam) evaporation technique. Hydrogen sensing properties of the thin films have been investigated at different operating temperatures and gas concentrations ranging from 100 ppm to 50,000 ppm. The results indicate that the MWCNT-doped WO3 thin film exhibits high sensitivity and selectivity to hydrogen. Thus, MWCNT doping based on E-beam co-evaporation was shown to be an effective means of preparing hydrogen gas sensors with enhanced sensing and reduced operating temperatures. Creation of nanochannels and formation of p-n heterojunctions were proposed as the sensing mechanism underlying the enhanced hydrogen sensitivity of this hybridized gas sensor. To our best knowledge, this is the first report on a MWCNT-doped WO3 hydrogen sensor prepared by the E-beam method. PMID:22163623

  11. 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.

  12. Controlling a gas\\/odor plume-tracking robot based on transient responses of gas sensors

    Microsoft Academic Search

    Hiroshi Ishida; Gouki Nakayama; Takamichi Nakamoto; Toyosaka Moriizumi

    2002-01-01

    Gas sensors provide the artificial sense of smell for a mobile robot to track an airborne gas\\/odor plume and to locate its source. However, a slow response of gas sensors has been the major factor limiting the development of plume-tracking robots. This paper describes a new control algorithm that overcomes the limitation. The basic idea is to detect the onset

  13. Rapid thermal processing of piezoresistive polycrystalline silicon films: An innovative technology for low cost pressure sensor fabrication

    Microsoft Academic Search

    B. Semmache; P. Kleimann; M. Le Berre; M. Lemiti; D. Barbier; P. Pinard

    1995-01-01

    Rapid thermal processing is evaluated as a low cost and flexible single wafer technology to develop SOI pressure sensors, allowing the fabrication of polycrystalline piezoresistors on thermally grown silicon dioxide with a turnaround time of a few minutes. The growth kinetics and the microstructure of polysilicon films obtained by rapid thermal chemical vapour deposition using an argon-silane gas mixture are

  14. 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

  15. Photonic bandgap fiber optical correlation spectroscopy gas sensor

    Microsoft Academic Search

    A. van Brakel; E. Austin; C. Grivas; M. N. Petrovich; D. J. Richardson

    2008-01-01

    We present results obtained from the first all-fiber, lensless, optical correlation spectroscopy gas sensor for acetylene (C2H2). In the reported sensing configuration, hollow-core photonic bandgap fiber (PBGF) is employed to contain all gas samples required for optical absorption measurements. This sensor relies upon comparison of the absorption spectrum of acetylene held in a 'reference gas cell' to that of a

  16. In-situ EXAFS analysis of the local environment of Pt particles incorporated in thin films of SnO 2 semi-conductor oxide used as gas-sensors

    Microsoft Academic Search

    M. Gaidi; M. Labeau; B. Chenevier; J. L. Hazemann

    1998-01-01

    A very fine and homogeneous dispersion of metallic nanoparticles (3–5 nm) inside polycrystalline SnO2 films was carried out by modified CVD co-deposition. It improves the sensitivity and selectivity for reducing gas detection. In order to verify and refine the models which can explain the role of metallic particles in the detection process, the environment of metallic nanoparticles were studied in

  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. 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.

  19. Thin Film Heat Flux Sensor of Improved Design

    NASA Technical Reports Server (NTRS)

    Fralick, Gus; Wrbanek, John; Blaha, Charles

    2002-01-01

    A new design for a thin film heat flux sensor is presented. It is easier to fabricate than previous designs, for a given heat flux has an order of magnitude larger signal, and is more easily scalable than previous designs. Transient and steady state data are also presented.

  20. Waveguide Zeeman interferometry for thin-film chemical sensors

    SciTech Connect

    Grace, K.M.; Shrouf, K.; Johnston, R.G.; Yang, X.; Swanson, B. [Los Alamos National Lab., NM (United States); Honkanen, S.; Ayras, P.; Peyghambarian, N. [Optical Sciences Center, Univ. of Arizona, Tucson, AZ (United States); Katila, P.; Leppihalme, M. [VTT Electronics (Finland)

    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. 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.

  2. Flexible PZT thin film tactile sensor for biomedical monitoring.

    PubMed

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

    2013-01-01

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

  3. Flexible PZT Thin Film Tactile Sensor for Biomedical Monitoring

    PubMed Central

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

    2013-01-01

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

  4. 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

  5. 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.

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

    PubMed

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

    2013-08-01

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

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

    E-print Network

    Gao, Zhihong

    2009-05-15

    The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern...

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

    E-print Network

    Gao, Zhihong

    2009-05-15

    The hot gas temperature in gas turbine engines is far above the permissible metal temperatures. Advanced cooling technologies must be applied to cool the blades, so they can withstand the extreme conditions. Film cooling is widely used in modern...

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

    Microsoft Academic Search

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

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

  10. 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

  11. A comparison of the gas sensing properties of solid state metal oxide semiconductor gas sensors produced by atmospheric pressure chemical vapour deposition and screen printing

    Microsoft Academic Search

    Russell Binions; Claire J Carmalt; Ivan P Parkin

    2007-01-01

    The reaction of metal chloride, MCln (where M = Ga, Sb or Sn) and ethyl acetate under atmospheric pressure chemical vapour deposition (APCVD) conditions leads to the production of metal oxide thin films on a variety of gas sensor substrates. Scanning electron microscopy indicated that an island growth mechanism predominated. X-ray photoelectron spectroscopy revealed binding energy shifts similar to previous

  12. 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.

  13. 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.

  14. Gas pressure feeds film into camera at high speed

    NASA Technical Reports Server (NTRS)

    Keigher, P. J.

    1966-01-01

    Blast of gas blows a loop of unexposed film as a wave across a vacuum platen to feed film smoothly into a camera so that 2 successive lengths can be exposed within 50 milliseconds. This technique can be readily applied to multiple aperture cameras as well as to various types of films.

  15. Thin-film optical sensors with silicon-compatible materials.

    PubMed

    Poenar, D P; Wolffenbuttel, R F

    1997-07-20

    Antireflection filters based on multilayer stacks of dielectric and polysilicon films on monocrystalline silicon combined with charge collection in different (poly)Si layers can be used to realize sensors with a programmable spectral response controlled by weighted summing of the photocurrents detected in the polysilicon and the substrate. Thus, employing both interference and selective absorption of light yields increased photoelectric efficiency and improved flexibility of spectral control and enables on-chip integration of the detector(s) with the signal conditioning and processing circuits. The potential of thin-film color sensors has been evaluated for this purpose. However, for practical implementation of such structures the problems associated with the realization of reliable photodetectors in polysilicon must also be considered. Phosphorus passivation of the grain-boundary states has been employed to yield polysilicon photodiodes with improved electrical characteristics and reliable light and color detection. We present the design methods of thin-film color sensors employing silicon-compatible materials only. The measurement results of a fabricated structure fully demonstrate that such sensors can be realized with good spectral selectivity. PMID:18259323

  16. 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.

  17. 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.

  18. Metal Oxide Semiconductor Gas Sensors and Neural Networks

    E-print Network

    Siegel, Mel

    Olfaction Metal Oxide Semiconductor Gas Sensors and Neural Networks M. W. Siegel Carnegie Mellon to motivate autonomous activity. #12;2 First, I describe the characteristics of metal oxide semiconductor (MOS

  19. Optimizing the performance of optical carbon dioxide gas sensors

    NASA Astrophysics Data System (ADS)

    Mills, Andrew; Chang, Qing; Wild, Lorraine

    1994-07-01

    The basic theory behind conventional colorimetric and fluorimetric optical sensors for CO2 is examined with respect to the effect on sensor response of the key parameters of initial base concentration and dye acid dissociation constant, KD. Experimental results obtained in aqueous solution using a variety of different dyes and initial base concentrations are reported and found to be consistent with the predictions made by the theoretical model. A series of model-generated pKD versus %CO2 curves for different initial base concentrations allow those interested in constructing an optical CO2 sensor to readily identify the optimum dye/initial base combination for their sensor; the response of the sensor can be subsequently fine-tuned through minor adjustment of the initial base concentration. The model appears also to apply to the new generation of plastic film CO2 sensor which have just been developed.

  20. Gas Sensor Based on Chalcohalide AgI-Containing Glasses

    NASA Astrophysics Data System (ADS)

    Monchev, Boris; Petkova, T.; Popov, Cyril; Petkov, Plamen

    Layered Ge-S-AgI material was used as a sensitive layer in cantilever gas sensors. The proposed sensor system was exposed to different vapour analytes: water, acetone, ammonia. The sensor studied works on the principle of a resonance microbalance and showed the best response to ammonia vapours. The chemisorbed ammonia on the surface of the exposed material caused an increased sensitivity towards water.

  1. Polyaniline as a Gas-Sensor Material

    Microsoft Academic Search

    Partha Pratim Sengupta; Satyananda Barik; Basudam Adhikari

    2006-01-01

    Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized

  2. Sensor validation and fusion for gas turbine vibration monitoring

    Microsoft Academic Search

    Weizhong Yan; Kai F. Goebel

    2003-01-01

    Vibration monitoring is an important practice throughout regular operation of gas turbine power systems and, even more so, during characterization tests. Vibration monitoring relies on accurate and reliable sensor readings. To obtain accurate readings, sensors are placed such that the signal is maximized. In the case of characterization tests, strain gauges are placed at the location of vibration modes on

  3. VOC gas leak detection using Pyroelectric Infrared sensors

    Microsoft Academic Search

    Fatih Erden; Emin Birey Soyer; B. Ugur Töreyin; A. Enis Çetin

    2010-01-01

    In this paper, we propose a novel method for detecting and monitoring Volatile Organic Compounds (VOC) gas leaks by using a Pyro-electric (or Passive) Infrared (PIR) sensor whose spectral range intersects with the absorption bands of VOC gases. A continuous time analog signal is obtained from the PIR sensor. This signal is discretized and analyzed in real time. Feature parameters

  4. 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.

  5. Research on gas diffusion mechanisms of limiting current oxygen sensor at low gas pressure

    Microsoft Academic Search

    Jiawen Jian; Jianyuan Gao; Jie Zhou

    2010-01-01

    In this article the gas diffusion mechanisms of the limiting current oxygen sensors was studied. For a limiting current oxygen sensor which the pore diameter d is about 30?m, the limiting current Il was quite linear with ln (1-X02) rather than X02 at 1 atm gas pressure, it showed the normal mechanism was more dominant than the Knudsen one. However

  6. Characterization of nano-dimensional thin-film elastic moduli using magnetoelastic sensors

    Microsoft Academic Search

    Stefan Schmidt; Craig A. Grimes

    2001-01-01

    Application of magnetoelastic thick-film sensors to the measurement of thin-film elastic moduli is described in this study. An analytical model is derived, that relates the resonant frequency of a magnetoelastic sensor to the elasticity and density of an applied thin-film. Limits of the model are analyzed, and related to experimental measurements using thin-films of silver and aluminum. For 500nm thick-films,

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  9. Nanostructured zinc oxide film for urea sensor

    Microsoft Academic Search

    Azahar Ali; Anees A. Ansari; Ajeet Kaushik; Pratima R. Solanki; A. Barik; M. K. Pandey; B. D. Malhotra

    2009-01-01

    Nanostructured zinc oxide (Nano-ZnO) film has been electrochemically deposited onto indium-tin-oxide (ITO) coated glass plate to co-immobilized urease (Urs) and glutamate dehydrogenase (GLDH) for urea detection. The observed reflection planes corresponding to wurtzite ZnO nanoparticles (~25nm) in XRD diffraction pattern and UV-visible absorption band at 338nm reveal the formation of Nano-ZnO. Urs-GLDH\\/Nano-ZnO\\/ITO bioelectrode shows high sensitivity for urea detection within

  10. Thick-film force, slip and temperature sensors for a prosthetic hand

    Microsoft Academic Search

    A Cranny; D P J Cotton; P H Chappell; S P Beeby; N M White

    2005-01-01

    Thick-film static and dynamic force sensors have been investigated for their suitability to measure the grip forces exerted upon an object held by a prosthetic hand, and to detect and correspondingly react to the possible slip of a gripped item. The static force sensors exploit the piezoresistive characteristics of commercially available thick-film pastes whilst the dynamic slip sensors utilize the

  11. 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

  12. The enhanced formaldehyde-sensing properties of P3HT-ZnO hybrid thin film OTFT sensor and further insight into its stability.

    PubMed

    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

  13. Thickness dependency of sol-gel derived ZnO thin films on gas sensing behaviors

    Microsoft Academic Search

    Nitul Kakati; Seung Hyun Jee; Su Hyun Kim; Jun Young Oh; Young Soo Yoon

    2010-01-01

    ZnO thin films were fabricated by a sol-gel method using Zn(CH3COO)2·2H2O as starting material in order to prepare an acetone gas sensor. A homogeneous and stable solution was prepared by dissolving the zinc acetate in a solution of ethanol and monoethanolamine. The sol-gel solution is coated on alumina substrates with various thicknesses by spin coating technique and heat treated to

  14. Development of gas sensors for environmental protection

    Microsoft Academic Search

    Noboru Yamazoe; Norio Miura

    1995-01-01

    Principles and materials for three types of ceramic sensors to detect gaseous components related to environmental problems are briefly reviewed. Newly developed sensors, based on solid electrolytes or semiconducting oxides, are demonstrated for detecting oxygenic gases (CO 2, NO, NO3, SOx, and O3) and offensive odorants (NH3 and H2S). Particularly emphasized is the importance of Type III solid electrolyte sensors

  15. An integrated optoelectronic CO2 gas sensor

    Microsoft Academic Search

    Catherine H. Morgan; Peter W. Cheung

    1991-01-01

    A novel CO2 sensor has been demonstrated that employs micromachined structures to produce a device that can be mass-produced with a high degree of integration of optoelectronic and chemical components. The sensor is designed to operate in a self-referencing mode that greatly minimizes short and long term drift of sensor response. Preliminary devices have been tested and exhibit a near-linear

  16. 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.

  17. Diamond thin film temperature and heat-flux sensors

    NASA Technical Reports Server (NTRS)

    Aslam, M.; Yang, G. S.; Masood, A.; Fredricks, R.

    1995-01-01

    Diamond film temperature and heat-flux sensors are developed using a technology compatible with silicon integrated circuit processing. The technology involves diamond nucleation, patterning, doping, and metallization. Multi-sensor test chips were designed and fabricated to study the thermistor behavior. The minimum feature size (device width) for 1st and 2nd generation chips are 160 and 5 micron, respectively. The p-type diamond thermistors on the 1st generation test chip show temperature and response time ranges of 80-1270 K and 0.29-25 microseconds, respectively. An array of diamond thermistors, acting as heat flux sensors, was successfully fabricated on an oxidized Si rod with a diameter of 1 cm. Some problems were encountered in the patterning of the Pt/Ti ohmic contacts on the rod, due mainly to the surface roughness of the diamond film. The use of thermistors with a minimum width of 5 micron (to improve the spatial resolution of measurement) resulted in lithographic problems related to surface roughness of diamond films. We improved the mean surface roughness from 124 nm to 30 nm by using an ultra high nucleation density of 10(exp 11)/sq cm. To deposit thermistors with such small dimensions on a curved surface, a new 3-D diamond patterning technique is currently under development. This involves writing a diamond seed pattern directly on the curved surface by a computer-controlled nozzle.

  18. Xerogel optical sensor films for quantitative detection of nitroxyl.

    PubMed

    Dobmeier, Kevin P; Riccio, Daniel A; Schoenfisch, Mark H

    2008-02-15

    Xerogel sensing films were synthesized via sol-gel chemistry were used to fabricate optical nitroxyl (HNO) sensors [corrected] Selective detection of HNO in solution was achieved by monitoring the rates of manganese(III) meso-tetrakis(4-sulfonatophenyl) porphyrinate (MnIIITPPS) reductive nitrosylation in the anaerobic interior of aminoalkoxysilane-derived xerogel films. Nitroxyl permeability in sensor films deposited in round-bottom 96-well plates was enhanced via incorporation of trimethoxysilyl-terminated poly(amidoamine-organosilicon) dendrimers in the xerogel network. The selectivity of MnIIITPPS for HNO, the overall sensitivity, and the working dynamic range of the resulting sensors were characterized. The HNO-sensing microtiter plates were used to quantify pH-dependent HNO generation by the recently described HNO-donor sodium 1-(isopropylamino)diazene-1-ium-1,2-diolate (IPA/NO), and compare HNO production efficiency between IPA/NO and Angeli's salt, a traditional HNO-donor. PMID:18197695

  19. A room temperature nitric oxide gas sensor based on a copper-ion-doped polyaniline/tungsten oxide nanocomposite.

    PubMed

    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 (Cu(2+)/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 Cu(2+)/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

  20. 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

  1. Corroles-Porphyrins: A Teamwork for Gas Sensor Arrays

    PubMed Central

    Capuano, Rosamaria; Pomarico, Giuseppe; Paolesse, Roberto; Di Natale, Corrado

    2015-01-01

    Porphyrins provide an excellent material for chemical sensors, and they have been used for sensing species both in air and solution. In the gas phase, the broad selectivity of porphyrins is largely dependant on molecular features, such as the metal ion complexed at the core of the aromatic ring and the peripheral substituents. Although these features have been largely exploited to design gas sensor arrays, so far, little attention has been devoted to modify the sensing properties of these macrocycles by variation of the molecular aromatic ring. In this paper, the gas sensing properties of a porphyrin analog, the corrole, are studied in comparison with those of the parent porphyrin. Results show that changes in the aromatic ring have important consequences on the sensitivity and selectivity of the sensors and that porphyrins and corroles can positively cooperate to enhance the performance of sensor arrays. PMID:25856324

  2. An optical gas sensor based on ellipsometric readout

    Microsoft Academic Search

    Guoliang Wang; Hans Arwin; Roger Jansson

    2003-01-01

    A gas sensor system based on ellipsometric readout is presented. It includes a gas chamber and a compact ellipsometer operated in off- mode. Small, low-cost optical components are used to demonstrate that this advanced methodology can be implemented in simplified instrumentation. The off- ellipsometric sensing principle and transducer mechanisms of the sensing layers, as well as the instrumentation, are described.

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

    Microsoft Academic Search

    Scott Phillips; Yefim Dain; Richard M. Lueptow

    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

  4. 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.

  5. 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.

  6. Application of a sensor array based on capillary-attached conductive gas sensors for odor identification

    Microsoft Academic Search

    Behzad Bahraminejad; Shahnor Basri; Maryam Isa; Zarida Hambali

    2010-01-01

    An electronic nose based on an array of capillary-attached conductive gas sensors was fabricated. The identification ability of the developed structure was investigated by employing different categories of simple and complex odor databases. Feature data sets were generated from the dynamic and steady state responses of the sensor array to the applied odor databases. Combinations of different feature extraction and

  7. Ultrathin porous carbon films as amperometric transducers for biocatalytic sensors

    SciTech Connect

    Wang, J.; Chen, Q. (New Mexico State Univ., Las Cruces, NM (United States)); Renschler, C.L.; White, C. (Sandia National Lab., Albuquerque, NM (United States))

    1994-07-01

    Novel ultrathin (0.4 [mu]m) porous carbon films are employed as transducers for amperometric biosensors. Such foamlike nanoscopic films couple the advantages of high enzyme loadings (within the micropore hosts) and large microscopic area with a small geometric area. Both electropolymerization and metalization are used to entrap the enzyme within the micropores. Scanning electron microscopy sheds useful insights into the unique morphology of the growing enzyme layer. The greatly enhanced sensitivity is coupled with a fast and stable response. Factors influencing the performance of porous-film-based biosensors are examined and discussed. The improved performance is illustrated in connection with glucose and phenol sensors. The latter offers a remarkably low detection limit of 2.5 x 10[sup [minus]8] M. The new nanoscopic foams should prove useful for many other electroanalytical applications. 11 refs., 7 figs.

  8. LaserSPECks: : laser SPECtroscopic trace-gas sensor networks - sensor integration and applications

    Microsoft Academic Search

    Stephen So; Farinaz Koushanfar; Anatoliy Kosterev; Frank Tittel

    2007-01-01

    We introduce a novel laser spectroscopic trace-gas sensor platform, LaserSPECks that integrates recently developed miniature quartz-enhanced photoacoustic spectroscopy (QE- PAS) gas sensing technology. This universal platform uses infrared laser spectroscopy detect and quantify numerous gas species at part-per-million to part-per-billion (ppm-ppb) concentrations (2). Traditional gas sensing devices capable of the same sensitivity and specificity are several orders of mag- nitude

  9. Nanocrystalline indium oxide-doped tin oxide thin film as low temperature hydrogen sensor

    Microsoft Academic Search

    S. Shukla; S. Seal; L. Ludwig; C Parish

    2004-01-01

    Hydrogen gas, within the concentration range of 100ppm–4vol.%, is successfully sensed at lower operating temperatures, 25 and 50°C, using the Pt-sputtered sol–gel dip-coated nanocrystalline (6–7nm) 6.5mol% In2O3-doped SnO2 semiconductor thin (100–150nm) film sensor. Typically, for 1000ppm of hydrogen, the maximum sensitivity values of 32 and 1600% are observed at 25 and 50°C, respectively; while for 2vol.% hydrogen, the maximum sensitivity

  10. Optimized temperature modulation of micro-hotplate gas sensors through pseudorandom binary sequences

    Microsoft Academic Search

    Alexander Vergara; Eduard Llobet; Jesús Brezmes; Xavier Vilanova; Peter Ivanov; Isabel Gràcia; Carles Cané; Xavier Correig

    2005-01-01

    In recent years, modulating the working temperature of metal-oxide gas sensors has been one of the most widely used methods to enhance sensor selectivity. When the working temperature of a gas sensor is modulated, the kinetics of the gas-sensor interaction are altered, and this leads to characteristic response patterns. Many works have shown that it is possible to identify and

  11. 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.

  12. Development of micro engine oil condition sensor using multi-wall carbon nanotube films

    Microsoft Academic Search

    Dae Seok Na; James Jung-Ho Pak; Jai Kyeong Kim

    2007-01-01

    A new interdigit-type micro oil condition sensor was designed and fabricated for monitoring the deterioration of lubricating and insulating oils. The designed sensor operates based on the change of the dielectric constant and electrical conductivity. In order to improve sensor performance, an oil condition sensor was fabricated using MEMS technology and multi-wall carbon nanotube film. The experiment was performed with

  13. Improving the functionality of a prosthetic hand through the use of thick film force sensors

    Microsoft Academic Search

    A. Cranny; P. H. Chappell; S. P. Beeby; N. M. White

    with the primary objectives of detecting touch and the onset of slippage of an item grasped by the hand. Two types of sensor have been used for this purpose: piezoresistive sensors to measure and monitor static forces and piezoelectric sensors to measure and monitor dynamic forces. All sensors have been fabricated using thick film printing techniques and their location and

  14. Thick-film intelligent sensors using new Du Pont and ESL high technology materials

    Microsoft Academic Search

    J. Fitt; J. J. Gondek; Z. Parzelka; W. Zaraska

    1997-01-01

    The paper presents the design and technology of production of thick-film intelligent sensors (TF-ASIC), their characteristics and applications. The novel hybrid sensors and application specific integrated sensors were made with the use of high technology materials manufactured by Du Pont Nemours Co. (USA) and ESL (USA). The authors also discuss the prospects of industrial and other applications of such sensors

  15. 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

  16. 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

  17. 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.

  18. 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, ...

  19. Temperature-Programmed Gas-Sensing With Microhotplates: an Opportunity to Enhance Microelectronic Gas Sensor Metrology

    NASA Astrophysics Data System (ADS)

    Geist, Jon; Afridi, Muhammad

    2009-09-01

    It is only recently that the ITRS (International Technical Roadmap for Semiconductors) has identified functional diversification through heterogeneous integration as a key enabler of future industry growth. This paper describes a powerful temperature-programmed gas-sensing technique that has the potential to convert low-cost, integrated, microhotplate-based non-selective, metal-oxide gas sensors into stable, sensitive, and highly selective gas-sensor systems. The paper also points out the importance of heterogeneous integration and temperature sensor stability to support this measurement technique.

  20. 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.

  1. A study on transient and steady state sensor data for identification of individual gas concentrations in their gas mixtures

    Microsoft Academic Search

    Ali Gulbag; Fevzullah Temurtas

    2007-01-01

    In this study, a comparative study was performed for the quantitative identification of individual gas concentrations (trichloroethylene and acetone) in their gas mixtures using transient and steady state sensor responses. For this purpose, three neural network (NN) structures were used. The quartz crystal microbalance (QCM) type sensors were selected as gas sensors. One of the neural networks was used for

  2. H 2 gas-sensing characteristics of SnO x sensors fabricated by a reactive ion-assisted deposition with\\/without an activator layer

    Microsoft Academic Search

    W. K. Choi; S. K. Song; J. S. Cho; Y. S. Yoon; D. Choi; H.-J. Jung; S. K. Koh

    1997-01-01

    SnOx-based gas-sensor devices have been fabricated by a reactive ion-assisted deposition technique. SnOx films of 400 Å thickness are deposited on sputtered amorphous SiO2 substrates and then Pt films (600 Å) are sputtered on top of them as upper electrodes. From XRD and TEM studies, as-deposited SnOx films are seen to be amorphous and become polycrystalline after annealing at 500°C

  3. Comparative study on micromorphology and humidity sensitive properties of thin-film and thick-film humidity sensors based on semiconducting MnWO 4

    Microsoft Academic Search

    Wenmin Qu; Wojtek Wlodarski; Jörg-Uwe Meyer

    2000-01-01

    Based on our experience of developing thick-film MnWO4 humidity sensors, a thin-film humidity sensor with nano-sized MnWO4 grains has been fabricated using the sol–gel technique. The thin-film sensor shows smaller humidity sensitivity than that compared to a thick-film sensor. However, it exhibits a fast response to humidity change and also has a very low temperature coefficient within the temperature range

  4. Photonic bandgap fiber optical correlation spectroscopy gas sensor

    NASA Astrophysics Data System (ADS)

    van Brakel, A.; Austin, E.; Grivas, C.; Petrovich, M. N.; Richardson, D. J.

    2008-04-01

    We present results obtained from the first all-fiber, lensless, optical correlation spectroscopy gas sensor for acetylene (C2H2). In the reported sensing configuration, hollow-core photonic bandgap fiber (PBGF) is employed to contain all gas samples required for optical absorption measurements. This sensor relies upon comparison of the absorption spectrum of acetylene held in a 'reference gas cell' to that of a gas sample under test, which is contained in the 'measurement gas cell'. Ingress of the test gas mixture into the measurement cell is achieved via femtosecond laser-machined micro-channels running from the surface of the PBGF to its hollow core. Stable, lensless optical interrogation of the measurement cell is guaranteed by means of arc fusion splices to standard (solid-core) single-mode fiber (SMF). The reference cell is filled with acetylene at atmospheric pressure, and is permanently sealed at both ends by splices to SMF. Therefore, being constructed entirely from optical fiber, both the reference and measurement gas cells are inherently compact and coilable, and dispense with the need for lenses or other free-space optics for connection to the correlation spectroscopy system. We quantify the acetylene concentration of various test gas mixtures and compare our sensor's measured results with computer simulations.

  5. Processing and Gas Barrier Behavior of Multilayer Thin Nanocomposite Films

    E-print Network

    Yang, You-Hao

    2012-10-19

    Thin films with the ability to impart oxygen and other types of gas barrier are crucial to commercial packaging applications. Commodity polymers, such as polyethylene (PE), polycarbonate (PC) and polyethylene terephthalate (PET), have insufficient...

  6. Pattern recognition for selective odor detection with gas sensor arrays.

    PubMed

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

    2012-01-01

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

  7. Pattern Recognition for Selective Odor Detection with Gas Sensor Arrays

    PubMed Central

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

    2012-01-01

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

  8. Polymer coating behavior of Rayleigh-SAW resonators with gold electrode structure for gas sensor applications.

    PubMed

    Avramov, Ivan D; Länge, Kerstin; Rupp, Swen; Rapp, Bastian; Rapp, Michael

    2007-01-01

    Results from systematic polymer coating experiments on surface acoustic wave (SAW) resonators and coupled resonator filters (CRF) on ST-cut quartz with a corrosion-proof electrode structure entirely made of gold (Au) are presented and compared with data from similar SAW devices using aluminium (Al) electrodes. The recently developed Au devices are intended to replace their earlier Al counterparts in sensor systems operating in highly reactive chemical gas environments. Solid parylene C and soft poly[chlorotrifluoroethylene-co-vinylidene fluoride] (PCFV) polymer films are deposited under identical conditions onto the surface of Al and Au devices. The electrical performance of the Parylene C coated devices is monitored online during film deposition. The PCVF coated devices are evaluated after film deposition. The experimental data show that the Au devices can stand up to 40% thicker solid films for the same amount of loss increase than the Al devices and retain better resonance and phase characteristics. The frequency sensitivities of Au and Al devices to parylene C deposition are nearly identical. After coating with soft PCFV sensing film, the Au devices provide up to two times higher gas sensitivity when probed with cooling agent, octane, or tetrachloroethylene. PMID:17225810

  9. Theoretical analysis of sensing character of long period fiber grating coated with gas-sensitive film

    NASA Astrophysics Data System (ADS)

    Peng, Yong; Wang, Yizhuo

    2005-12-01

    Firstly we studied the sensitivity of long-period fiber gratings (LPFG) to the refractive index of ambient medium using the coupled modes theory. Then we presented numerical calculation based on long period fiber grating to show the relationship between the resonant wavelength of transmission spectrum and the ambient refractive index. Secondly we analyzed the optical mechanics of the semiconductor oxide film with gas-sensitivity and found that when touching the thin film gas can make its extinction coefficient, absorption coefficient and corresponding refractive index change. Thus we can coat the grating surface with gas-sensitive film and make use of the character that the refractive index will change with the component and density of ambient gas. Furthermore the change will influence the resonant wavelength of transmission spectrum of LPFG therefore we can get information about the gas component and density by way of monitoring changes of wavelength. The LPFG is more sensitive to ambient refractive index than fiber and the sensed signal is wavelength-modulated so the signal is not reflected by the fluctuation of light intensity and the fiber loss. Therefore the LPFG is more sensitive than intensity-type fiber gas sensor.

  10. 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.

  11. 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.

  12. Fiber optic gas sensor with nanocrystalline ZnO

    NASA Astrophysics Data System (ADS)

    Renganathan, B.; Ganesan, A. R.

    2014-01-01

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

  13. A novel humidity sensor based on alumina nanowire films

    NASA Astrophysics Data System (ADS)

    Feng, Zhe-sheng; Chen, Xin-Jie; Chen, Jin-ju; Hu, Jing

    2012-06-01

    Alumina nanowire (ANW) films were prepared by etching porous anodic aluminium oxide (AAO), and then humidity sensors with coplanar interdigitated electrodes based on ANWs were fabricated. The ANWs not only present tremendous surface area for water molecule adsorption but also provide efficient sites for attracting water molecules at low relative humidity (RH) levels. The sensors based on the particular morphology of ANWs with large open voids show high sensitivity and small hysteresis, and have fast response and recovery time to humidity. The capacitance rises slowly at a lower RH and increases rapidly after 70% RH, which is associated with the humidity mechanism of chemisorption at lower RH and physisorption at higher RH levels. The impendence analysis suggests that the ANWs are the main factor for sensing humidity, and AAO also contributes to humidity sensing. This study demonstrates that ANWs have promising applications in humidity monitoring.

  14. ?-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

  15. Thin-film sensors for reusable space propulsion systems

    NASA Technical Reports Server (NTRS)

    Hepp, Aloysius F.; Kim, Walter S.

    1989-01-01

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

  16. New potentiomentric dissolved oxygen sensors in thick film technology

    Microsoft Academic Search

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

    2004-01-01

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

  17. 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

  18. New remote gas infrared optical fiber sensor

    Microsoft Academic Search

    Yasser Alayli; Sofiane Bendamardji; Serge J. Huard

    1996-01-01

    A new remote optical fiber sensor is presented for the detection of carbon dioxide by molecular absorption in the near infrared corresponding to fundamental mode v3 equals 2349 cm-1 (4.257 micrometers ). To overcome this problem of the strong attenuation signal of optical fibers in the infrared, the opto power supply, technique is used which changes the working wavelength from

  19. Gas-leak localization using distributed ultrasonic sensors

    Microsoft Academic Search

    Javid Huseynov; Shankar Baliga; Michael Dillencourt; Lubomir Bic; Nader Bagherzadeh

    2009-01-01

    We propose an ultrasonic gas leak localization system based on a distributed network of sensors. The system deploys highly sensitive miniature Micro-Electro-Mechanical Systems (MEMS) microphones and uses a suite of energy-decay (ED) and time-delay of arrival (TDOA) algorithms for localizing a source of a gas leak. Statistical tools such as the maximum likelihood (ML) and the least squares (LS) estimators

  20. Pt\\/graphene nano-sheet based hydrogen gas sensor

    Microsoft Academic Search

    M. Shafiei; R. Arsat; J. Yu; K. Kalantar-zadeh; W. Wlodarski; S. Dubin; R. B. Kaner

    2009-01-01

    In this paper, we present gas sensing properties of Pt\\/graphene-like nano-sheets towards hydrogen gas. The graphene-like nano-sheets were produced via the reduction of spray-coated graphite oxide deposited on SiC substrates by hydrazine vapor. Structural and morphological characterizations of the graphene sheets were analyzed by scanning electron and atomic force microscopy. Current-voltage and dynamic responses of the sensors were investigated towards

  1. Dome Shaped Touch Sensor Using PZT Thin Film made by Hydrothermal Method

    Microsoft Academic Search

    Fumihito Arai; Toshio Fukuda; Kouichi Itoigawa; Yasunori Thukahara

    2001-01-01

    We propose a dome shaped touch sensor unit, which is small and is applicable in high temperature environment. The PZT thin film was made on the half- round Ti substrate, and the electrodes were deposited on its surface to form the sensor and driving actuator. The PZT thin film was made on the curved surface of the substrate by the

  2. Film-Type Sensor Materials PVDF and EMFi in Measurement of Cardiorespiratory Signals— A Review

    Microsoft Academic Search

    Satu Rajala; Jukka Lekkala

    2012-01-01

    In this paper, some recent results obtained with film-type sensor materials polyvinylidenefluoride (PVDF) and electromechanical film (EMFi) are presented. The materials generate a voltage when they are mechanically deformed, however, because of their capacitive nature only the change of an external force can be measured. Hence, the sensors made of these materials are useful especially in the measurements of physiological

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

    Microsoft Academic Search

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

    2005-01-01

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

  4. Fiber optic sensor based on surface plasmon resonance with nanoparticle films

    Microsoft Academic Search

    Anuj K. Sharma; B. D. Gupta

    2005-01-01

    This paper reports on a novel design of a fiber optic surface plasmon resonance (SPR) sensor based on nanoparticle metal film. The performance of the proposed sensor in terms of its signal-to-noise ratio (SNR) and sensitivity under different conditions related to the film with spherical gold nanoparticles embedded in a host material is theoretically analyzed. In particular, the effect of

  5. 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.

  6. Al-doped ZnO Thin Films for Ethanol Sensors

    NASA Astrophysics Data System (ADS)

    Nulhakim, Lukman; Nugraha; Nuruddin, Ahmad; Suyatman; Yuliarto, Brian

    2011-12-01

    Al doped ZnO (AZO) is done to understand the effect of Al dopant on ZnO. The sensor response condition will be analyzed for ethanol detection. Chemical Bath Deposition (CBD) method is used to fabrication pure ZnO and AZO thin films. Al dopant concentrations used in this study is 2.9 at% Al. The crystallinity, composition and morphology were investigated by using XRD, EDS and SEM. The ZnO and AZO gas sensors were exposed to different concentrations of ethanol at room temperature, 2.5%, 5% and 7.5% volume ethanol, respectively. The sensor response at low concentrations (2.5% V) for pure ZnO sample is 70.88% and 88.57% for high concentrations of ethanol (7.5% V). The highest sensor response for AZO sample is 95.29% at low concentrations (2.5% V) and 96.68% V at the high concentration (7.5% V).

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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.

  8. 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.

  9. 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.

  10. Biochemical sensor using polyaniline nanofibers for sensing amino-group type of gas

    Microsoft Academic Search

    Da-Jeng Yao; Yong-Ruei Yang

    2005-01-01

    Traditionally, polyaniline was used for sensing ammonia (NH3 ) gas due to the change of conductivity. By integrated with surface acoustic wave sensor (SAW) for sensing the amino-group type of gas, a novel bio-chemical sensor had been developed. The mechanism of the SAW sensor is that the change of gravity results in the change of physical characteristics of SAW sensor.

  11. A High-Precision NDIR Gas Sensor for Automotive Applications

    Microsoft Academic Search

    Robert Frodl; Thomas Tille

    2006-01-01

    A new high-precision spectroscopic gas sensor measuring carbon dioxide (CO2) for harsh environmental conditions of automotive applications is presented. The carbon dioxide concentration is the primary parameter for sensing in cabin air quality, as well as an important safety parameter when R744 (carbon dioxide) is used as the refrigerant in the air conditioning system. The automotive environment challenges the potential

  12. Harmful gas recognition exploiting a CTL sensor array.

    PubMed

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

    2013-01-01

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

  13. Conduction and Gas–Surface Reaction Modeling in Metal Oxide Gas Sensors

    Microsoft Academic Search

    Brian Chwieroth; Bruce R. Patton; Yunzhi Wang

    2001-01-01

    A phenomenological approach to the operation of metal oxide gas sensors, the Integrated Reaction Conduction (IRC) model, is proposed which integrates the gas-surface reactions with the electrical conduction process in a weakly sintered, porous metal oxide. An effective medium approximation is employed to relate the mesoscopic microstructure and the carrier depletion at the granular surface to the macroscopic electrical conduction.

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

    PubMed Central

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

    2012-01-01

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

  15. Improvement of porous silicon based gas sensors by polymer modification

    Microsoft Academic Search

    J. W. P. Bakker; H. Arwin; G. Wang; K. Järrendahl

    2003-01-01

    Gas sensing was performed using spectroscopic ellipsometry and porous silicon films. Modification of the porous layer by polymer deposition showed an increase in sensitivity to organic solvent vapor of up to 135%. The increase in sensitivity is strongly dependent on polymer concentration. At high concentrations, too much polymer is deposited, presumably blocking the pores, causing a decrease in sensitivity. At

  16. 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. Index Terms--Hard disk drive (HDD), piezoelectric thin films, smart structures, vibration control. I. INTRODUCTION HARD disk drives (HDDs) are among the most complex electro-mechanical systems encountered in daily

  17. Chemical discrimination in turbulent gas mixtures with MOX sensors validated by gas chromatography-mass spectrometry.

    PubMed

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

    2014-01-01

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

  18. Gas sensors based on Paschen's law using carbon nanotubes as electron emitters

    Microsoft Academic Search

    S J Kim

    2006-01-01

    In the case of typical gas sensors responding by gas adsorption on the surface, it is very difficult to detect inert gases which have low chemical adsorption energies under normal conditions. Carbon nanotubes (CNTs) are well known as electron emitters in applications like field emission displays. In this work, we fabricate a physical gas sensor (or vacuum sensor) using CNTs

  19. FLUORESCENCE AND FIBER-OPTICS BASED REAL-TIME THICKNESS SENSOR FOR DYNAMIC LIQUID FILMS

    E-print Network

    Narain, Amitabh

    1 FLUORESCENCE AND FIBER-OPTICS BASED REAL-TIME THICKNESS SENSOR FOR DYNAMIC LIQUID FILMS T. W. Ng phenomena and fiber-optic technology has been developed and reported here. Measurements from this sensor research and development fields. This paper focuses on a sensor capable of measuring interfacial wave

  20. Metal Oxide Semiconductor Nanoparticles for Chemical Gas Sensors

    NASA Astrophysics Data System (ADS)

    Baraton, Marie-Isabelle

    During the recent years, it has been widely recognized that the use of semiconductor nanoparticles for the fabrication of chemical gas sensors by screen-printing technology definitely improves the sensor performance. In this paper, we review the possibilities offered by Fourier transform infrared (FTIR) spectroscopy for the study of semiconductor nanoparticles. Thanks to FTIR spectroscopy, it is possible to identify the surface chemical groups, to characterize the surface reactivity, to monitor the surface functionalization, to investigate the surface reactions at the origin of the gas detection, and to evaluate the gas sensing potentiality of the nanoparticles before the device fabrication. All these steps are critical for the optimization of nanoparticle-based gas sensors because they ensure i) the reproducibility of the surface chemical composition and of the surface chemistry, ii) the control of the surface modifications to decrease cross-sensitivity, particularly to humidity, iii) the investigation of the gas detection mechanism to properly tailor the surface structure, iv) the selection of the best nanoparticles batches for further processing. Examples of tin oxide and titanium oxide nanoparticles are discussed with regards to CO and NOx detection.

  1. [Design of non-dispersed infrared (NDIR) methane gas sensor].

    PubMed

    Zhao, Zheng-Jie; Liu, Dong-Xu; Zhang, Ji-Long; Wang, Zhi-Bin; Li, Xiao; Tian, Er-Ming

    2011-02-01

    A non-dispersed infrared (NDIR) methane gas sensors system based on infrared absorption spectrum theory was designed according to single light beam and double wavelengths technology. In the system, an infrared LED IRL715 serving as the light power, a absorptive gas cell with the function of dust-proof and damp-proof and a pyroelectric detector LIM-262 are composed of optical probe. Signal condition uses active filter circuit and differential amplifier, and binomial expression fits the relation curve between methane concentration and voltage, which realizes accurate detection of gas concentration. Experiment approved that the sensor system with good consistency and applicability can detect the range of 5% methane reliably and have 0.5% of the sensitivity, possessing the conditions for industrial applications initially. PMID:21510429

  2. 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.

  3. SEMICONDUCTOR LASER BASED TRACE GAS SENSOR TECHNOLOGY: RECENT ADVANCES AND APPLICATIONS Laser Based Trace Gas Sensor Technology

    Microsoft Academic Search

    FRANK K. TITTEL; GERARD WYSOCKI

    Recent advances in the development of sensors based on infrared diode and quantum cascade lasers for the detection of trace gas species is reported. Several examples of applications in environmental and industrial process monitoring as well as in medical diagnostics using quartz enhanced photoacoustic spectroscopy and laser absorption spectroscopy will be described.

  4. 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.

  5. Numerical simulation of a new generation of high-temperature micropower gas and odor sensors based on SOI technology

    Microsoft Academic Search

    Julian W. Gardner; Florin Udrea; Bill Milne

    1999-01-01

    Gas sensors fabricated using conventional silicon microtechnology can suffer from a number of significant disadvantages when compared with commercially available thick-film, screen-printed devices. For example, platinum gate MOSFET devices normally operate only at a temperature of up to 180 degree(s)C and this limits the catalyst activity, and hence their sensitivity and response time. In addition, the fabrication of an integrated,

  6. Gas transport and sorption in polyaniline thin film

    Microsoft Academic Search

    H. L. Wang; B. R. Mattes

    1999-01-01

    The permeability of gases through thin polyaniline EB film depends upon the combined mobility and solubility of the gases at a given temperature and pressure. The gas transport behavior of an emeraldine base (EB) film was studied in detail. Permeability measurements were made using the manometric time-lag method of analysis for He, H2, CO2, O2, N2 and CH4, all as

  7. Optical-fibre sensor system for monitoring the performance of the gas propellant centrifuge separator of a spacecraft

    NASA Astrophysics Data System (ADS)

    Romo-Medrano, Katya E.; Khotiaintsev, Sergei N.; García-Garduño, Victor

    2004-08-01

    An optical-fibre sensor system is presented for monitoring void fraction distribution in a spacecraft's gas and propellant centrifuge separator. The system could be used at the separator development stage or for monitoring, during ground tests, the elements of the spacecraft propulsion system. Our sensor system employs an array of point optical-fibre refractometric transducers installed in the form of several linear radial arrays on the separator rotating blades. We employed a small-size hemispherical optical detection element as the transducer and we optimized its parameters through numerical ray-tracing. The aim is to minimize the effect of the thin film of liquid that forms on the transducer's surface in this application. The features of this sensor system are: (1) an efficient matrix-type multiplexing scheme, (2) the installation of the main optoelectronic unit of the sensor in a hermetically sealed container inside the separator tank located on the rotating shaft and (3) the spark-proof and explosion-proof design of the sensor circuits and elements. The sensor is simple, reliable, low-cost and is capable of withstanding the factors involved during operation of the propulsion system such as cryogenic temperatures and chemically aggressive liquids. The novel elements and design concepts implemented in this sensor system can also find applications in other sensors for spacecraft propulsion systems and also in a variety of optical-fibre sensors used in scientific research and industry.

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

    PubMed

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

    2011-01-01

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

  9. Sensors control gas metal arc welding

    SciTech Connect

    Siewert, T.A.; Madigan, R.B.; Quinn, T.P. [National Inst. of Standards and Technology, Boulder, CO (United States)

    1997-04-01

    The response time of a trained welder from the time a weld problem is identified to the time action is taken is about one second--especially after a long, uneventful period of welding. This is acceptable for manual welding because it is close to the time it takes for the weld pool to solidify. If human response time were any slower, manual welding would not be possible. However, human response time is too slow to respond to some weld events, such as melting of the contact tube in gas metal arc welding (GMAW), and only automated intelligent control systems can react fast enough to correct or avoid these problems. Control systems incorporate welding knowledge that enables intelligent decisions to be made about weld quality and, ultimately, to keep welding parameters in the range where only high-quality welds are produced. This article discusses the correlation of electrical signals with contact-tube wear, changes in shielding gas, changes in arc length, and other weld process data.

  10. Characterization of Mixed xWO3(1-x)Y2O3 Nanoparticle Thick Film for Gas Sensing Application

    PubMed Central

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

    2010-01-01

    Microstructural, topology, inner morphology, and gas-sensitivity of mixed xWO3(1-x)Y2O3 nanoparticles (x = 1, 0.95, 0.9, 0.85, 0.8) thick-film semiconductor gas sensors were studied. The surface topography and inner morphological properties of the mixed powder and sensing film were characterized with X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Also, gas sensitivity properties of the printed films were evaluated in the presence of methane (CH4) and butane (C4H10) at up to 500 °C operating temperature of the sensor. The results show that the doping agent can modify some structural properties and gas sensitivity of the mixed powder. PMID:22399925

  11. Current conduction mechanism and gas adsorption effects on device parameters of the Pt\\/SnOx\\/diamond gas sensor

    Microsoft Academic Search

    Yasar Gurbuz; Weng Poo Kang; Jim L. Davidson; David V. Kerns

    1999-01-01

    This paper presents the results from analysis and modeling of the gas sensing performance, current conduction and gas detection mechanisms, and adsorption effects on device parameters of a Pt\\/SnOx\\/diamond-based gas sensor. The sensor is sensitive and demonstrates high, repeatable, and reproducible reaction. The sensor response in seconds to small concentrations of O2, CO, and H 2 gases. The current conduction

  12. 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.

  13. Steady state model of electrochemical gas sensors with multiple reactions

    SciTech Connect

    Brailsford, A.D.; Yussouff, M.; Logothetis, E.M. [Ford Motor Co., Dearborn, MI (United States)

    1996-12-31

    A general first-principles model of the steady state response of metal oxide gas sensors was developed by the authors and applied to the case of both electrochemical and resistive type oxygen sensors. It can describe many features of the experimentally observed response of commercial electrochemical zirconia sensors exposed to non-equilibrium gas mixtures consisting of O{sub 2} and one or more reducing species (CO, H{sub 2} , etc). However, the calculated sensor emf as a function of R`= 2p{sub O2}/P{sub CO} (or 2p{sub O2}/P{sub H2}) always showed a sharp transition from high to low values at some R` value and had a small value for R` >> 1. These results do not agree with the broad transitions and relatively high emf values for large R`, as observed experimentally at low temperatures. This paper discusses an extension of the model which is able to describe all aspects of the observed response.

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

    NASA Astrophysics Data System (ADS)

    Kumar, Shailesh

    2014-04-01

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

  15. Development of a high resolution human breath gas sensor considering application for rescue robotics in disaster zones

    Microsoft Academic Search

    Hideki Toda; Genci Capi

    2010-01-01

    This paper presents a new type of ultrasonic gas molecule concentration sensor for rescue robotics. This devise can measure the change of the gas concentration with a sampling rate of over 400 kHz. The performance of developed sensor is investigated by applying as human breath gas measurement sensor. Ideal gas experiment results show that the proposed sensor could detect the

  16. Characterization of gas-phase adsorption on metal oxide thin films using a magnetoelastic resonance microbalance.

    PubMed

    Zorn, Michael E; Rahne, Kari A; Tejedor-Tejedor, M Isabel; Anderson, Marc A; Grimes, Craig A

    2003-11-15

    In this study, a magnetoelastic resonance microbalance (MERM) was used to directly measure the gas-phase adsorption behavior of water vapor, isopropyl alcohol, and acetone on a sol-gel-derived titanium dioxide sensor coating. The nature of the MERM platform enables chemical measurements in situations in which wires or physical connections are undesired (or not possible) or in which sensor cost is a major issue. The underlying MERM technique (with an uncoated sensor) showed excellent day-to-day stability, a linear calibration over a 1 kHz change in frequency (or a 1.5-mg change in mass), and the ability to detect a mass change of 15 microg without any efforts at sensitivity optimization. The titanium dioxide coated sensor yielded excellent response to each of the analytes; however, the response did not follow a simple linear calibration function. A more complex calibration model or utilization of the coated sensor in a limited concentration range would be required for quantitative analysis. The process of applying the metal oxide coatings onto the magnetic substrate altered the structure of the thin film layer, resulting in a relatively loose packing of the porous primary titanium dioxide particles to create an open overall honeycomb structure, thereby affecting the adsorption behavior at high relative concentration. PMID:14616005

  17. Analysis of Face Deformation Effects on Gas Film Seal Performance

    Microsoft Academic Search

    John Zuk

    1973-01-01

    Analyses are presented for compressible fluid flow across shaft face seals with face deformation. The solutions are obtained from an approximate integral analysis. The models, used in this analysis, can predict gas film seal behavior operating at subsonic or choked flow conditions. The flow regime can either be laminar or turbulent. Entrance losses can also be accounted for. When fluid

  18. 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.

  19. Nano-clay/poly(vinylidene fluoride) composite films as sensor and actuator element

    NASA Astrophysics Data System (ADS)

    Murasawa, Go; Wakabayashi, Daisuke; Yamada, Eiji; Nishioka, Akihiro; Miyata, Ken; Koda, Tomonori

    2010-04-01

    Poly(vinylidene fluoride) (PVDF) is a piezoelectric polymer material. In general, it is necessary to give large stretch to PVDF film when PVDF film is used as sensor or actuator element. However, we recently found that PVDF shows piezoelectricity without large stretch if nano-clays are uniformly dispersed into it. The aim of present study is to investigate the possibilities of nano-clay/PVDF composite film as sensor and actuator element. Firstly, PVDF films and nano-clay/PVDF composite film are fabricated by solvent casting. Also, commercial PVDF film is prepared as comparative material. Secondarily, we investigate the change of electrical displacement according to the input voltage of triangle wave by using Sawyer-tower bridge circuit for PVDF films and nano-clay/PVDF composite film. Then, the change of impedance is also measured at broad frequency by using impedance analyzer. Thirdly, we apply the voltage of sine wave to fabricated films, and measure the output oscillation generated from films. Finally, we discuss the possibilities of nano-clay/PVDF composite film as sensor and actuator element.

  20. Hollow Waveguide Gas Sensor for Mid-Infrared Trace Gas Analysis

    Microsoft Academic Search

    Seong-Soo Kim; Christina Young; James Chan; Chance Carter; Boris Mizaikoff

    2007-01-01

    A hollow waveguide mid-infrared gas sensor operating from 1000 cm-1 to 4000 cm-1 has been developed, optimized, and its performance characterized by combining a FT-IR spectrometer with Ag\\/Ag-halide hollow core optical fibers. The hollow core waveguide simultaneously serves as a light guide and miniature gas cell. CH-4 was used as test analyte during exponential dilution experiments for accurate determination of

  1. Development of a micro-thermal flow sensor with thin-film thermocouples

    NASA Astrophysics Data System (ADS)

    Kim, Tae Hoon; Kim, Sung Jin

    2006-11-01

    A micro-thermal flow sensor is developed using thin-film thermocouples as temperature sensors. A micro-thermal flow sensor consists of a heater and thin-film thermocouples which are deposited on a quartz wafer using stainless steel masks. Thin-film thermocouples are made of standard K-type thermocouple materials. The mass flow rate is measured by detecting the temperature difference of the thin-film thermocouples located in the upstream and downstream sections relative to a heater. The performance of the micro-thermal flow sensor is experimentally evaluated. In addition, a numerical model is presented and verified by experimental results. The effects of mass flow rate, input power, and position of temperature sensors on the performance of the micro-thermal flow sensor are experimentally investigated. At low values, the mass flow rate varies linearly with the temperature difference. The linearity of the micro-thermal flow sensor is shown to be independent of the input power. Finally, the position of the temperature sensors is shown to affect both the sensitivity and the linearity of the micro-thermal flow sensor.

  2. Application of the laser scanning confocal microscope in fluorescent film sensor research

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyan; Liu, Wei-Min; Zhao, Wen-Wen; Dai, Qing; Wang, Peng-Fei

    2010-10-01

    Confocal microscopy offers several advantages over conventional optical microscopy; we show an experimental investigation laser scanning confocal microscope as a tool to be used in cubic boron nitride (cBN) film-based fluorescent sensor research. Cubic boron nitride cBN film sensors are modified with dansyl chloride and rhodamine B isothiocyanate respectively. Fluorescent modification quality on the cubic boron nitride film is clearly express and the sensor ability to Hg2+ cations and pH are investigated in detail. We evidence the rhodamine B isothiocyanate modified quality on cBN surface is much better than that of dansyl chloride. And laser scanning confocal microscope has potential application lighttight fundus film fluorescent sensor research.

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

    NASA Astrophysics Data System (ADS)

    Kim, Walter S.; Barrows, Richard F.

    1988-03-01

    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.

  4. Sensing behaviors of the electrochemically co-deposited polypyrrole–poly(vinyl alcohol) thin film exposed to ammonia gas

    Microsoft Academic Search

    C. W. Lin; B. J. Hwang; C. R. Lee

    1999-01-01

    The polypyrrole–poly(vinyl alcohol)(PPy–PVA) composite thin films were prepared electrochemically by means of co-deposition at a constant potential. The behaviors, including sensitivity, response speed and recovery speed, to various ammonia gas concentrations ranging from 50 to 150ppm were investigated. The response speeds and recovery speeds of the PPy–PVA composite sensors increased as ammonia concentration increased. The ammonia-sensing behaviors of the composite

  5. Semiconductor TiO 2 Gas Sensor for Controlling Nitrocarburizing Processes

    Microsoft Academic Search

    H. Klümper-Westkamp; S. Beling; A. Mehner; F. Hoffmann; P. Mayr

    2004-01-01

    TiO2 films can serve as oxygen sensors for controlling the nitrogen potential in the process of nitrocarburizing. In contrast to conventional semiconductor-base oxygen sensors that lose stability under extreme thermal and chemical conditions in nitriding and carburizing atmospheres, TiO2 films obtained by the sol-gel method offer a promising alternative. In the present work TiO2 films with a density of about

  6. Scanning electron microscopy to probe working nanowire gas sensors

    NASA Astrophysics Data System (ADS)

    Liu, Yangmingyue

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

  7. Fiber-optic Fabry-Perot hydrogen sensor coated with Pd-Y film

    NASA Astrophysics Data System (ADS)

    Yu, Caibin; Liu, Li; Chen, Xiaoxiao; Liu, Qunfeng; Gong, Yuan

    2015-06-01

    A fiber-optic Fabry-Perot hydrogen sensor was developed by measuring the fringe contrast changes at different hydrogen concentrations. The experimental results indicated that the sensing performance with the Pd-Y film was better than that with the Pd film. A fringe contrast with a decrease of 0.5 dB was detected with a hydrogen concentration change from 0% to 5.5%. The temperature response of the sensor was also measured.

  8. Room-temperature anisotropic magnetoresistive sensor based on manganese perovskite thick films

    Microsoft Academic Search

    Ll. Balcells; E. Calvo; J. Fontcuberta

    2002-01-01

    Manganese perovskites, having the ferromagnetic transition above room temperature, are good candidates for use as a magnetoresistive sensor. In the previous works, some potential applications using thick films (Appl. Phys. Lett. 69 (1996) 1486; Sensors Actuators 81 (2000) 64) were presented. In this paper, the role of the anisotropic magnetoresistance (MR) has been explored in La2\\/3Sr1\\/3MnO3 thick films on polycrystalline

  9. Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures

    PubMed Central

    Huang, Jin; Wan, Qing

    2009-01-01

    This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. PMID:22303154

  10. New method for selectivity enhancement of SiC field effect gas sensors for quantification of NOx

    NASA Astrophysics Data System (ADS)

    Bur, Christian; Reimann, Peter; Andersson, Mike; Lloyd Spetz, Anita; Schütze, Andreas

    2011-06-01

    A Silicon Carbide based enhancement type field effect transistor with porous films of Iridium and Platinum as gate metallization has been investigated as a total NOx sensor operated in a temperature cycling mode. This operating mode is quite new for gas sensors based on the field effect but promising results have been reported earlier. Based on static investigations we have developed a suitable T-cycle for NOx detection in a mixture of typical exhaust gases (CO, C2H4, and NH3). Significant features describing the shape of the sensor response have been extracted allowing determination of NOx concentrations in gas mixtures. Multivariate statistics (e.g. Linear Discriminant Analysis) have been used to evaluate the multidimensional data. With this kind of advanced signal processing the influence of sensor drift and cross sensitivity to ambient gases can effectively be reduced. Thereby, we were able to detect NOx and furthermore determine different concentrations of NOx even in mixtures with typical exhaust gases. It can be concluded that the performance of field effect gas sensors for NOx determination can be enhanced considerably.

  11. Sub-ppm multi-gas photoacoustic sensor

    NASA Astrophysics Data System (ADS)

    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 2O and 30 ppb at 1737.9 for HCl have been demonstrated.

  12. Factors affecting PD detection in GIS using a carbon nanotube gas sensor

    Microsoft Academic Search

    Weidong Ding; Kohei Ochi; Junya Suehiro; Kiminobu Imasaka; Ryota Hayashi; Masanori Hara

    2007-01-01

    The authors have previously demonstrated that a carbon nanotube (CNT) gas sensor can detect SF6 decomposition byproducts generated by partial discharges (PDs). There are several factors to be considered, however, before applying the CNT gas sensor to practical diagnosis of a gas-insulated switchgear (GIS). In this paper, three major factors, namely, the effects of operating temperature and installation location of

  13. The effect of multiwalled carbon nanotube doping on the CO gas sensitivity of TiO2 xerogel composite film

    NASA Astrophysics Data System (ADS)

    Lee, Jin-Seok; Ha, Tae-Jung; Hong, Min-Hee; Park, Chang-Sun; Park, Hyung-Ho

    2013-03-01

    A simple sol-gel method was applied for the synthesis of 0.01 wt% multiwalled carbon nanotubes (MWCNTs)-doped TiO2 xerogel composite film. The film's CO gas sensing properties were then evaluated. Doped MWCNTs were coated with TiO2 and distributed on a TiO2 xerogel matrix. The TiO2 xerogel showed an anatase structure after heat treatment at 450 °C under vacuum. The specific surface area of the composite material was larger than the pure TiO2 xerogel material. The CO gas sensitivity of the MWCNTs(0.01 wt%)-doped TiO2 xerogel composite film was found to be seven times higher than that of pure TiO2 xerogel film and to have good stability. This higher gas-sensing property of the composite film was due to both an increase of specific surface area and the n-p junction structure of the TiO2 xerogel coated on MWCNTs. The electrons generated from TiO2 after adsorption of CO gas induces electron transfer from the TiO2 to the MWCNTs. This induces a characteristic change in the MWCNTs from p-type to n-type, and the resistance of MWCNTs-doped TiO2 xerogel composite sensor is therefore decreased.

  14. Thin film dissolved oxygen sensor based on platinum octaethylporphyrin encapsulated in an elastic fluorinated polymer

    Microsoft Academic Search

    R. N. Gillanders; M. C. Tedford; P. J. Crilly; R. T. Bailey

    2004-01-01

    A robust thin film dissolved oxygen sensor was fabricated by encapsulating platinum octaethylporphyrin (PtOEP) in an oxygen permeable elastic fluorinated co-polymer matrix. Phosphorescence, which was partially quenched by dissolved oxygen, was observed when the sensor was immersed in water. Aggregation of the dye was observed at elevated temperatures. Dye aggregate phosphorescence was not or only partially quenched by dissolved oxygen.

  15. Thin FeC Alloy Solid Film Based Fiber Optic Corrosion Sensor

    Microsoft Academic Search

    Guofu Qiao; Zhi Zhou; Jinping Ou

    2006-01-01

    In last few years, some transmitted type fiber optic corrosion sensors (FOCS) have emerged, but the fragile character makes them difficultly use in practice. In this paper, a novel thin Fe-C alloy solid film based fiber optic corrosion sensor has been developed. The sensing section is located at one end of the fiber. A double layer classic slab model has

  16. Thick-film force and slip sensors for a prosthetic hand

    Microsoft Academic Search

    A. Cranny; D. P. J. Cotton; P. H. Chappell; S. P. Beeby; N. M. White

    2005-01-01

    In an attempt to improve the functionality of a prosthetic hand device, a new fingertip has been developed that incorporates sensors to measure temperature and grip force and to detect the onset of object slip from the hand. The sensors have been implemented using thick-film printing technology and exploit the piezoresistive characteristics of commercially available screen printing resistor pastes and

  17. Metallo-porphyrins as gas sensing material for colorimetric gas sensors on planar optical waveguides

    NASA Astrophysics Data System (ADS)

    Peter, Carolin; Schmitt, Katrin; Schiel, Martin; Wöllenstein, Jürgen

    2011-06-01

    The work presented here focuses on the investigations of metallo-porphyrins and their gasochromic behavior. Gasochromic materials change their color while they are exposed to a certain gas. So they offer the possibility to develop very selective chemical gas sensors. In the focus of this work is the metallo-porphyrin 5, 10, 15, 20- tetraphenylporphyrin-zinc (ZnTPP). When embedded into a polymeric matrix (PVC) the color change to the toxic gas NO2 can be detected. During exposure to NO2 the dye changes its color from bright purple to yellow. To develop a standalone gas sensor, the ZnTPP/PVC matrix is deposited onto a planar optical waveguide. The color change of the porphyrin dye, due to the gas exposure, can be detected in the evanescent field of the optical waveguide. Therefore the light of a high power LED is coupled into the waveguide. The color change of the porphyrin is detectable with photodiodes as variations of the decoupled light intensity. The sensor shows no cross-sensitivities to other gases like CO2, NH3, EtOH, CO or water vapor. NO2 is detectable with a limit of 1 ppm.

  18. Field-test system for underground fire detection based on semiconductor gas sensor

    Microsoft Academic Search

    Peter Reimann; Stephan Horras; Andreas Schütze

    2009-01-01

    Based on a single semiconductor (sc) gas sensor and sensors for temperature, relative humidity and gas flow we developed a system for fire detection in coal mines. These sensors are read-out by a high-dynamic-range hardware control and data acquisition platform, in which the sc-sensor is operated with an application-optimized temperature cycle to improve the stability and selectivity. A hierarchical evaluation

  19. Lubricant film thickness measurement using fiber-optic Michelson interferometer and fiber-optic displacement sensor

    Microsoft Academic Search

    Yuping Chen; Xiaodong Zhang; Ping Zhang; Chunxiang Liu

    2009-01-01

    How to accurately measure the lubricant film thickness of the hydrodynamic slide bearings has been an important research field in the condition monitor and fault diagnosis of large rotary machinery. This paper focus on a new detection approach using a fiber-optical Michelson Interferometer combined with a fiber-optical displacement sensor for the lubricant film thickness measurement. After introducing the fundamental principle,

  20. Corrosion behaviors of sputter-deposited steel thin film for electrical resistance sensor material

    Microsoft Academic Search

    Young-Geun Kim; SeonYeob Li; Sungwon Jung; Seong-Min Lee; Jiyoung Kim; Young-Tai Kho

    2006-01-01

    This paper describes an experimental approach for the study of electrochemical characteristics of the steel thin film with a thickness of 600 nm as an electrical resistance sensor material with an improved sensitivity for the corrosion rate measurement. The thin film was deposited onto the glass by magnetron-sputtering using carbon steel targets in an Ar atmosphere. The physical properties of fabricated

  1. Utilizing the response patterns of a temperature modulated chemoresistive gas sensor for gas diagnosis

    NASA Astrophysics Data System (ADS)

    Amini, Amir; Ghafarinia, Vahid

    2011-02-01

    The observed features in the temporal response patterns of a temperature-modulated chemoresistive gas sensor were used for gas diagnosis. The patterns were recorded for clean air and air contaminated with different levels of some volatile organic compounds while a staircase heating voltage waveform had been applied to the microheater of a tin oxide gas sensor that modulated its operating temperature. Combining the steady-state and transient parameters of the recorded responses in the 50-400°C range resulted in discriminatory feature vectors which were utilized for contaminant classification. The information content of these feature vectors was proved sufficient for discrimination of methanol, ethanol, 1-butanol, and acetone contaminations in a wide concentration range.

  2. Room temperature ammonia sensor based on copper nanoparticle intercalated polyaniline nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Patil, U. V.; Ramgir, Niranjan S.; Karmakar, N.; Bhogale, A.; Debnath, A. K.; Aswal, D. K.; Gupta, S. K.; Kothari, D. C.

    2015-06-01

    Thin films of copper nanoparticles intercalated-polyaniline nanocomposites (NC) have been deposited at room temperatures by in situ oxidative polymerization of aniline in the presence of different concentrations of Cu nanoparticles. The response characteristics of the NC thin films toward different gases namely NH3, CO, CO2, NO and CH4 were examined at room temperature. Both pure polyaniline (PANI) and NC films exhibited a selective response toward NH3. Incorporation of Cu nanoparticles resulted in an improvement of the sensors response and response kinetics. The response and the recovery times of composite film toward 50 ppm of NH3 were 7 and 160 s, respectively. Additionally, the NC sensor film could reversibly detect as low as 1 ppm of NH3 concentrations. The enhanced response of NC films toward NH3 is attributed to the deprotonation and reprotonation processes as also supported by Raman investigations.

  3. A composite thin film optical sensor for dissolved oxygen in contaminated aqueous environments

    Microsoft Academic Search

    R. N. Gillanders; M. C. Tedford; P. J. Crilly; R. T. Bailey

    2005-01-01

    A robust optical composite thin film dissolved oxygen sensor was fabricated by ionically trapping the dye ruthenium(II) tris(4,7-diphenyl-1,10-phenanthroline) dichloride in a blended fluoropolymer matrix consisting of Nafion® and Aflas®. Strong phosphorescence, which was strongly quenched by dissolved oxygen (DO), was observed when the sensor was immersed in water. The sensor was robust, optically transparent, with good mechanical properties. Fast response,

  4. Thin As-Se-Sb Films as Potential Medium for Optics and Sensor Application

    NASA Astrophysics Data System (ADS)

    Ilcheva, Vania; Boev, V.; Petkova, T.; Petkov, Plamen; Petkov, Emil; Socol, G.; Mihailescu, I. N.

    Thin films have been deposited onto quartz substrates by the pulsed laser deposition (PLD) method from the corresponding glassy bulk As-Se-Sb chalcogenide materials. Photoinduced changes have been observed after illumination of the films with a Xe lamp. The transmission spectra of the thin films have been measured before and after irradiation and the optical constants have been derived by the Swanepoel method. The results suggest feasible applications of these materials for waveguide-sensors.

  5. Pressure sensor using polycrystalline germanium films prepared by plasma assisted chemical vapor deposition

    Microsoft Academic Search

    K. Kamimura; N. Kimura; S. Miyashita; Y. Onuma; T. Homma

    1989-01-01

    Pressure sensors were fabricated using polycrystalline germanium films on a stainless steel diaphragm covered with an insulating layer. The polycrystalline germanium films, the sensing part of this device, were prepared by plasma-assisted chemical vapor deposition (plasma-CVD) at temperatures between 200°C and 500°C. The gauge factor of these films was about 20-60. The values were two times larger than those of

  6. A Quartz tuning fork-based humidity sensor using Nanocrystalline Zinc oxide thin film coatings

    Microsoft Academic Search

    Xiaofeng Zhou; Tao Jiang; Jian Zhang; Jianzhong Zhu; Xiaohua Wang; Ziqiang Zhu

    2006-01-01

    This paper describes an application of quartz tuning forks (QTF) coated with nanocrystalline ZnO films used as relative humidity sensors. The nanocrystalline ZnO thin films were deposited on the QTF by sol-gel method. The film was characterized by X-Ray Diffraction (XRD) and Atomic Force Microscope (AFM) to obtain the information on the structural and morphological properties. And the humidity sensitivity

  7. Piezoelectric thin films formed by MOD on cantilever beams for micro sensors and actuators

    Microsoft Academic Search

    T. Cui; D. Markus; S. Zurn; D. L. Polla

    2004-01-01

    Novel piezoelectric cantilever beams for micro sensors and actuators based on PZT thin films have been batch fabricated by surface micromachining. Lead zirconate titanate (PZT) thin film is formed by metalorganic deposition (MOD) on Pt\\/Ti\\/SiO 2\\/Si (1 0 0) substrates and Pt\\/Ti\\/LTO\\/Si 3N 4 cantilever beams and then annealed at 700 °C in air. The PZT thin film is 0.5

  8. Gas sensor selectivity enhancement by noise spectroscopy: a model of adsorption-desorption noise

    Microsoft Academic Search

    Sami Gomri; Jean-Luc Seguin; Khalifa Aguir

    2005-01-01

    Metal oxide gas sensors present an inherent lack of selectivity. Some experimental results revealed that noise spectroscopy could be considered as a method for improving gas sensors selectivity. In order to confirm this idea, we propose, as a first step towards an overall model, a theoretical description of adsorption-desorption noise in metal oxide gas sensors. Using Langmuir’s and Wolkenstein’s isotherms

  9. 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. .

  10. A cubic boron nitride film-based fluorescent sensor for detecting Hg2+

    NASA Astrophysics Data System (ADS)

    Liu, W. M.; Zhao, W. W.; Zhang, H. Y.; Wang, P. F.; Chong, Y. M.; Ye, Q.; Zou, Y. S.; Zhang, W. J.; Zapien, J. A.; Bello, I.; Lee, S. T.

    2009-05-01

    Cubic boron nitride (cBN) film-based sensors for detecting Hg2+ ions were developed by surface functionalization with dansyl chloride. To immobilize dansyl chloride, 3-aminopropyltriethoxy silane was modified on hydroxylated cBN surfaces to form an amino-group-terminated self-assembled monolayer. The covalent attachment of the amino groups was confirmed by x-ray photoelectron spectroscopy. The selectivity and sensitivity of the sensors to detect diverse metal cations in ethanol solutions were studied by using fluorescence spectroscopy, revealing a great selectivity to Hg2+ ions. Significantly, the dansyl-chloride-functionalized cBN film sensors were recyclable after the sensing test.

  11. 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.

  12. Integrated CNTs thin film for MEMS mechanical sensors

    Microsoft Academic Search

    Van Thanh Dau; Takeo Yamada; Dzung Viet Dao; Bui Thanh Tung; Kenji Hata; Susumu Sugiyama

    2010-01-01

    This paper reports the top-down fabrication of CNTs thin film on MEMS structure, and characterization of piezoresistive coefficients of aligned single wall carbon nanotube (SWNT) forest film. The film was synthesized by water-assisted chemical vapor deposition (CVD), a process known as “super growth”. CNTs film was condensed, manually maneuvered and conveniently patterned by EB lithography to form desirable shapes. The

  13. 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.

  14. Analysis of face deformation effects on gas film seal performance

    NASA Technical Reports Server (NTRS)

    Zuk, J.

    1972-01-01

    Analyses are presented for compressible fluid flow across shaft face seals with face deformation. The solutions are obtained from an approximate integral analysis. The models, used in this analysis, can predict gas film seal behavior operating at subsonic or choked flow conditions. The flow regime can either be laminar or turbulent. Entrance losses can also be accounted for. When fluid inertia effects are negligible and the sealing faces are slightly deformed, the following results are found for both laminar and turbulent flows: (1) The pressure profiles are independent of fluid properties; and (2) the parallel film leakage equation can be used, provided a characteristic film thickness is used. Pressure profiles are presented for both divergent and convergent seal faces under choked flow conditions.

  15. 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

  16. Applied analysis of lacquer films based on pyrolysis-gas chromatography\\/mass spectrometry

    Microsoft Academic Search

    Rong Lu; Yukio Kamiya; Tetsuo Miyakoshi

    2006-01-01

    Ancient lacquer film, a Nanban lacquer film, an old lacquer-ware object imported from an Asian country, and the Baroque and Rococo lacquer films were analyzed by pyrolysis-gas chromatography\\/mass spectrometry. Compared with the results of the natural lacquer film, it was revealed that the ancient lacquer film and Nanban lacquer film were made from Rhus vernicifera, and the old lacquer-ware imported

  17. Study of robust thin film PT-1000 temperature sensors for cryogenic process control applications

    NASA Astrophysics Data System (ADS)

    Ramalingam, R.; Boguhn, D.; Fillinger, H.; Schlachter, S. I.; Süßer, M.

    2014-01-01

    In some cryogenic process measurement applications, for example, in hydrogen technology and in high temperature superconductor based generators, there is a need of robust temperature sensors. These sensors should be able to measure the large temperature range of 20 - 500 K with reasonable resolution and accuracy. Thin film PT 1000 sensors could be a choice to cover this large temperature range. Twenty one sensors selected from the same production batch were tested for their temperature sensitivity which was then compared with different batch sensors. Furthermore, the sensor's stability was studied by subjecting the sensors to repeated temperature cycles of 78-525 K. Deviations in the resistance were investigated using ice point calibration and water triple point calibration methods. Also the study of directional oriented intense static magnetic field effects up to 8 Oersted (Oe) were conducted to understand its magneto resistance behaviour in the cryogenic temperature range from 77 K - 15 K. This paper reports all investigation results in detail.

  18. Altering the Flow of Gas through Modification of Surface Films

    NASA Astrophysics Data System (ADS)

    Seo, Dongjin; Ducker, William

    2013-11-01

    Normally the flow of gas in a channel is considered to be a function of the pressure difference between the ends of the channel and the geometry. For high Knudsen numbers, the flow also depends on the tangential momentum accommodation coefficients (TMAC). Here we consider methods of altering the TMAC, and thus the flow of gas at 1 atm through a narrow channel, by the use of surface films that alter the TMAC. Gas flow was determined by measuring the damping on a glass sphere as a function of separation from a flat plate. The solids were coated with octadecyltrichlorosilane (OTS), which undergoes a melting-like transition near room temperature. The measured damping passes through a maximum in the temperature range of 9 - 42 °C and thus the TMAC also passes through a maximum. We attribute this maximum to competing effects due to the decrease in surface roughness and the decrease in stiffness as a function of temperature. Control of flow via alteration of a surface film should also be possible using other methods of altering the state of surface films.

  19. Experimental and Analytical Investigation of a Dynamic Gas Squeeze Film Bearing Including Asperity Contact Effects

    Microsoft Academic Search

    Manoj Mahajan; Robert Jackson; George Flowers

    2008-01-01

    This work presents a theoretical and experimental investigation of a flat circular gas squeeze film bearing. The thickness and the pressure profile of the gas squeeze film are obtained by simultaneously solving the Reynolds equation and the equation of motion for the squeeze film bearing. This work also accounts for the force due to asperity contact in the equation of

  20. 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.

  1. Developed quasi-harmonic motions of a fluid film in a gas flow

    Microsoft Academic Search

    L. N. Maurin; G. E. Odishariia; A. A. Tochigin

    1976-01-01

    Quasi-harmonic wave motions of a thin fluid film flowing along a vertical surface under the action of gravity, capillary forces, and shear stress acting on the film-gas boundary are analyzed. Region of existence and spectral characteristics of quasi-harmonic wave solutions are found for various flow regimes of the film (e.g., with and against the gas flow).

  2. A micro force sensor based on a single ZnO belt coated with chromium film.

    PubMed

    Ren, Xiaoyan; Yang, Xing; Zhou, Zhaoying; Li, Jinming; Liu, Jing

    2010-11-01

    A micro force sensor was fabricated using a single ZnO belt coated with ultra thin Cr film. As a result of the piezoresistive effect of the ultra thin (in nano-scale) Cr film, the bending of the belt led to the change in the resistance of ultra thin Cr film. Based on the mechanics of the materials, the relationship between the deformation and the force was calculated, and a linear relationship between the bending force and the resistance of Cr thin film was deduced at small bending regions. Dielectrophoresis, focused ion beam (FIB) and sputtering were used in the process of the micro force sensor. The experimental results show that the resistance of Cr film is sensitive to the bending force and demonstrate the potential for developing a new class of stable and sensitive nano-sized structures for force sensing. PMID:21137908

  3. 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

  4. Bipolar strain sensor based on an ultra-thin film of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Park, Dong-Won; Kim, Beom Soo; Park, Serin; Choi, Won-Jin; Yang, Cheol-Soo; Lee, Jeong-O.

    2014-02-01

    A bipolar strain sensor based on an ultra-thin film of single-walled carbon nanotubes (SWNTs) has been fabricated. First, a random network of SWNTs was grown on a Si substrate with thermal oxide by using chemical vapor deposition and then transferred to a transparent poly(dimethyl)siloxane (PDMS) film. A mechanical load was applied by pressing the PDMS-SWNT film with a blunt micrometer tip, and its electrical conductance was found to decrease linearly with increasing pressure. Upward bending of the flexible PDMS-SWNT film was found to yield increases in conductance whereas downward bending of the film was found to result in decreases in the conductance. We modeled the SWNT network on the PDMS film with a two-dimensional percolation system, and found that the increases (decreases) in the conductance of the film upon bending could be explained in terms of stick-density changes in the 2-D percolation system. Finally, because PDMS swells with certain organic vapors, a PDMS-SWNT film can be used as a chemical sensor for volatile organic compounds. Unlike for three-dimensional composites of SWNTs and polymers, the bipolar response upon bending and simple fabrication process for the system introduced here mean that it is an attractive candidate for tactile and motion sensor applications.

  5. Nanocrystalline SnO gas sensors in view of surface reactions and modifications

    Microsoft Academic Search

    S. Seal; S. Shukla

    2002-01-01

    The gas-sensing mechanism of an n-type semiconductor (tin dioxide) gas sensor is reviewed in this paper. It is demonstrated\\u000a that very high sensitivity can be obtained only when the crystallite size is less than -10 nm. Various mechanisms involving\\u000a the surface and the bulk modifications of the semiconductor oxide gas sensors are discussed to improve the gas sensitivity.\\u000a Current challenges

  6. 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.

  7. Crack identification based on thin-film full-bridge strain sensors

    NASA Astrophysics Data System (ADS)

    Tung, Shue-Ting E.; Yao, Yao; Glisic, Branko

    2014-04-01

    A sensing sheet based on large-area electronics consists of a dense array of discrete short-gauge sensor units, integrated circuits for collecting, analyzing and communicating data, and a flexible photovoltaic system that serves as both a power harvester and a protective layer. We investigated the sensitivity of thin-film full-bridge strain sensors to cracks, and the effect of crack position with respect to the sensor. In general, the results of this research show that full-bridge strain sensors can successfully detect and characterize cracks in structural materials and are therefore good candidates to utilize in a sensing sheet.

  8. Thick-Film Carbon Dioxide Sensor via Anodic Adsorbate Stripping Technique and Its Structural Dependence

    PubMed Central

    Photinon, Kanokorn; Wang, Shih-Han; Liu, Chung-Chiun

    2009-01-01

    A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the platinum nanoparticles. The sensing output was linearly related to the CO2 presented. Stability measurements demonstrated that the decline of the active surface area and the sensitivity of the sensor were 8% and 13%, respectively, over a two week period of time. The sensor response appeared to be a structural dependence of the crystallographic orientation of platinum electrode. PMID:22399993

  9. Scalable fabrication of SnO2 thin films sensitized with CuO islands for enhanced H2S gas sensing performance

    NASA Astrophysics Data System (ADS)

    Van Toan, Nguyen; Chien, Nguyen Viet; Van Duy, Nguyen; Vuong, Dang Duc; Lam, Nguyen Huu; Hoa, Nguyen Duc; Van Hieu, Nguyen; Chien, Nguyen Duc

    2015-01-01

    The detection of H2S, an important gaseous molecule that has been recently marked as a highly toxic environmental pollutant, has attracted increasing attention. We fabricate a wafer-scale SnO2 thin film sensitized with CuO islands using microelectronic technology for the improved detection of the highly toxic H2S gas. The SnO2-CuO island sensor exhibits significantly enhanced H2S gas response and reduced operating temperature. The thickness of CuO islands strongly influences H2S sensing characteristics, and the highest H2S gas response is observed with 20 nm-thick CuO islands. The response value (Ra/Rg) of the SnO2-CuO island sensor to 5 ppm H2S is as high as 128 at 200 °C and increases nearly 55-fold compared with that of the bare SnO2 thin film sensor. Meanwhile, the response of the SnO2-CuO island sensor to H2 (250 ppm), NH3 (250 ppm), CO (250 ppm), and LPG (1000 ppm) are low (1.3-2.5). The enhanced gas response and selectivity of the SnO2-CuO island sensor to H2S gas is explained by the sensitizing effect of CuO islands and the extension of electron depletion regions because of the formation of p-n junctions.

  10. Electrochemical sensor for paracetamol recognition and detection based on catalytic and imprinted composite film.

    PubMed

    Teng, Ying; Fan, Limei; Dai, Yunlong; Zhong, Min; Lu, Xiaojing; Kan, Xianwen

    2015-09-15

    A new strategy for a composite film based electrochemical sensor was developed in this work. A layer of conductive film of poly(p-aminobenzene sulfonic acid) (pABSA) was electropolymerized onto glassy carbon electrode surface and exhibited a high electrocatalytic active for paracetamol (PR) redox. The subsequent formation of a layer of molecular imprinted polymer (MIP) film on pABSA modified electrode endowed the sensor with plentiful imprinted cavities for PR specific adsorption. The advantages of the composite film made the prepared sensor display high sensitivity and good selectivity for PR detection and recognition. Under the optimal conditions, the sensor could recognize PR from its interferents. A linear ranging from 5.0×10(-8) to 1.0×10(-4)mol/L for PR detection was obtained with a detection limit of 4.3×10(-8)mol/L. The sensor has been applied to analyze PR in tablets and human urine samples with satisfactory results. The simple, low cost, and efficient strategy reported here can be further used to prepare electrochemical sensors for other compounds recognition and detection. PMID:25897883

  11. Reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes.

    PubMed

    Yim, H S; Meyerhoff, M E

    1992-09-01

    Various materials and sensor configurations that exhibit reversible potentiometric responses to the partial pressure of oxygen at room temperature in neutral pH solution are examined. In one arrangement, platinum electrodes are coated with plasticized poly(vinyl chloride) films doped with a cobalt(II) tetraethylene pentamine complex. For such sensors, potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as a change in redox potential of the Co(II)-tetren-doped film as the complex binds oxygen reversibly. The response due to the platinum surface is prolonged by the presence of the Co(II)-tetren/PVC film. Alternately, thin films of metallic copper, electrochemically deposited on platinum and/or sputtered or vapor deposited on a single crystal silicon substrate, may be used for reversible oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to 1 month) by preventing the formation of cuprous oxide on the surfaces via the application of an external nonpolarizing cathodic current through the working electrode or by specifically using sputtered copper films that have [100] preferred crystal structures as determined by X-ray diffraction. The implications of these findings in relation to fabricating analytically useful potentiometric oxygen sensors are discussed. PMID:1416035

  12. Temperature-programmed technique accompanied with high-throughput methodology for rapidly searching the optimal operating temperature of MOX gas sensors.

    PubMed

    Zhang, Guozhu; Xie, Changsheng; Zhang, Shunping; Zhao, Jianwei; Lei, Tao; Zeng, Dawen

    2014-09-01

    A combinatorial high-throughput temperature-programmed method to obtain the optimal operating temperature (OOT) of gas sensor materials is demonstrated here for the first time. A material library consisting of SnO2, ZnO, WO3, and In2O3 sensor films was fabricated by screen printing. Temperature-dependent conductivity curves were obtained by scanning this gas sensor library from 300 to 700 K in different atmospheres (dry air, formaldehyde, carbon monoxide, nitrogen dioxide, toluene and ammonia), giving the OOT of each sensor formulation as a function of the carrier and analyte gases. A comparative study of the temperature-programmed method and a conventional method showed good agreement in measured OOT. PMID:25090138

  13. Deodorant Characteristics of Breath Odor Occurred from Favorite Foods Using Metal Oxide Gas Sensors

    Microsoft Academic Search

    Shuichi Seto; Takashi Oyabu; Kuiqian Cai; Teruaki Katsube

    2003-01-01

    Three types of metal oxide gas sensors were adopted to detect the degree of breath odor. Various sorts of information are included in the odor. Each sensor has different sensitivities to gaseous chemical substances and the sensitivities also differ according to human behaviors, for example taking a meal, teeth-brushing and drinking something. There is also a possibility that the sensor

  14. Minimum Film Thickness in a Gas Foil Journal Bearing with an Unbalanced Rotor

    Microsoft Academic Search

    Marc Carpino; Gita Talmage

    2010-01-01

    A gas-lubricated foil journal bearing consists of a compliant metal shell structure that supports a rigid journal or rotor by means of a gas film. The response of this system to the periodic forces of an unbalanced rotor supported by a single bearing is predicted using perturbation analysis. The foil structure and the gas film are modeled with an analytically

  15. Limiting-current type surface modified gas sensor based on ??-alumina fast solid ionic conductor

    Microsoft Academic Search

    J. Liu; W. Weppner

    1991-01-01

    A new type of limiting current solid state ionic gas sensor is presented. The sensor is based on the reaction of the gaseous species with the electroactive component under the condition of limited access of the gas by a kinetic barrier. This allows one to employ the available fast solid alkali metal, silver and copper ionic conductors at ambient, and

  16. Limiting-current type surface modified gas sensor based on beta

    Microsoft Academic Search

    J. Liu; W. Weppner

    1991-01-01

    A new type of limiting current solid state ionic gas sensor is presented. The sensor is based on the reaction of the gaseous species with the electroactive component under the condition of limited access of the gas by a kinetic barrier. This allows one to employ the available fast solid alkali metal, silver and copper ionic conductors at ambient, and

  17. A versatile SAW-based sensor system for investigating gas-sensitive coatings

    Microsoft Academic Search

    R. S. Falconer

    1995-01-01

    Surface acoustic wave (SAW) technology is an extremely versatile technique for the development of gas sensors because of the SAW device's sensitivity to a wide variety of material properties that can change with gas concentration. In the present work, a SAW sensor oscillator is described, which allows both of the important SAW properties, velocity and attenuation, to be easily measured.

  18. RAPID COMMUNICATION CW DFB RT diode laser-based sensor for trace-gas detection

    E-print Network

    RAPID COMMUNICATION CW DFB RT diode laser-based sensor for trace-gas detection of ethane using- moelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy

  19. Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts

    E-print Network

    Wang, Zhong L.

    Stable and highly sensitive gas sensors based on semiconducting oxide nanobelts E. Comini, G for publication 16 July 2002 Gas sensors have been fabricated using the single-crystalline SnO2 nanobelts to environmental polluting species like CO and NO2 , as well as to ethanol for breath analyzers and food control

  20. Glassy spectral gas sensors based on the immobilized indicators

    NASA Astrophysics Data System (ADS)

    Novikov, Alexander F.; Zemskii, Vladimir I.

    1995-09-01

    A number of color absorption and luminescence indicators being dispersed within a porous matrix have been investigated by means of spectral techniques. As a support for the indicator molecules served a mesoporous silica glass of Vycor type (pore size of 7.5 nm) which was transparent to the light and permeable to the ambient gases and vapors. The selected immobilized indicators have revealed the well-defined spectral sensitivity to certain components of an atmosphere or other gas mixture. After a proper chemical and thermal treatment these indicators have gained high selectivity of spectral response on an individual gas appearing in the ambients, the observed spectral changes have demonstrated its reversibility. The indicators immobilized within the porous glass turned out to be mostly advantageous as applied in the colorimetric sensors and anlyzyers, sepcifically in the automated remote air monitoring systems. Some of the essential parameters of the developed portable individual gas analyzers and remote multicomponent monitoring systems with use of fiber optic guides are reported.

  1. An arrayed hot-film sensor for detection of laminar boundary-layer flow disturbance spatial characteristics

    NASA Technical Reports Server (NTRS)

    Wusk, M. S.; Carraway, D. L.; Holmes, B. J.

    1988-01-01

    An arrayed hot-film sensor has been developed for use in laminar boundary-layer research for the detection of crossflow or Goertler vortices. This sensor has been developed to detect spatial variations in heat transfer which are characteristic of crossflow or Goertler vortices. The sensor is ultimately intended for flight research applications. This paper describes the sensor, its priciples of operation, signal analysis techniques, and experimental results illustrating the spatial detection capabilities of this specialized hot-film device. Discretely placed spheres placed in the boundary layer created alternating regions of undisturbed and disturbed laminar flow over a prototype sensor. Flow visualization results were correlated with the sensor output to demonstrate the ability of the sensor to determine the spatial boundaries of localized disturbances in laminar flow. This work represents the initial steps toward the validation and calibration of an arrayed hot-film sensor for the detection of crossflow or Goertler vorticity wavelength and/or wave frequency.

  2. Taxonomy of Wireless Sensor Network Cyber Security Attacks in the Oil and Gas Industries

    Microsoft Academic Search

    Pedram Radmand; Alex Talevski; Stig Petersen; Simon Carlsen

    2010-01-01

    The monitoring of oil and gas plants using sensors allows for greater insight into safety and operational performance. However, as a result of strict installation regulations of powered sensors near oil and gas fittings, the introduction of new wired sensors to optimize end-of-lifecycle plants has been expensive, complex and time consuming. Recent advances in wireless technology have enabled low-cost Wireless

  3. Application of semiconductor gas sensor to quality control of meat freshness in food industry

    Microsoft Academic Search

    Naomi Funazaki; Akihide Hemmi; Satoshi Ito; Yasukazu Asano; Yukio Yano; Norio Miura; Noboru Yamazoe

    1995-01-01

    We have investigated the possibility of utilizng a semiconductor gas sensor for quality control of meat freshness in the food industry. A semiconductor gas sensor based on In2O3 is exploited for detecting ethyl acetate, a typical flavour volatile component produced in the initial bacterial putrefaction of meat. Of the sensor elements examined, Rh-La2O3-In2O3 is found to show excellent sensitivity and

  4. SnO2\\/PPy Screen-Printed Multilayer CO2 Gas Sensor

    Microsoft Academic Search

    S. A. WAGHULEY; S. M. YENORKAR; S. S. YAWALE; S. P. YAWALE

    Tin dioxide (SnO2) plays a dominant role in solid state gas sensors and exhibit sensitivity towards oxidizing and reducing gases by a variation of its electrical properties. The electrical conducting polymer-polypyrrole (PPy) has high anisotropy of electrical conduction and used as a gas sensor. SnO2\\/PPy multilayer, pure SnO2, pure PPy sensors were prepared by screen-printing method on Al2O3 layer followed

  5. Thin-Film Magnetic-Field-Response Fluid-Level Sensor for Non-Viscous Fluids

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Shams, Qamar A.; Fox, Robert L.; Taylor, Bryant D.

    2008-01-01

    An innovative method has been developed for acquiring fluid-level measurements. This method eliminates the need for the fluid-level sensor to have a physical connection to a power source or to data acquisition equipment. The complete system consists of a lightweight, thin-film magnetic-field-response fluid-level sensor (see Figure 1) and a magnetic field response recorder that was described in Magnetic-Field-Response Measurement-Acquisition System (LAR-16908-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 28. The sensor circuit is a capacitor connected to an inductor. The response recorder powers the sensor using a series of oscillating magnetic fields. Once electrically active, the sensor responds with its own harmonic magnetic field. The sensor will oscillate at its resonant electrical frequency, which is dependent upon the capacitance and inductance values of the circuit.

  6. 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

  7. Humidity sensor composed of a microporous film of polyethylene-graft-poly-(2-acrylamido-2-methylpropane sulfonate)

    Microsoft Academic Search

    Y. Sakai; V. L. Rao; Y. Sadaoka; M. Matsuguchi

    1987-01-01

    Inside a microporous polyethylene film, 2-acrylamido-2-methylpropane sulfonic acid was graft polymerized by ultraviolet irradiation. A humidity sensor was fabricated by depositing gold electrodes on both sides of the grafted film. The impedance was measured as a function of humidity for the acid and alkali salts of sulfonate. The sensor has long term stability and is resistant to water.

  8. 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.

  9. Characterization of the gas sensors based on polymer-coated resonant microcantilevers for the detection of volatile organic compounds

    Microsoft Academic Search

    Ying Dong; Wei Gao; Qin Zhou; Yi Zheng; Zheng You

    2010-01-01

    The gas sensors based on polymer-coated resonant microcantilevers for volatile organic compounds (VOCs) detection are investigated. A method to characterize the gas sensors through sensor calibration is proposed. The expressions for the estimation of the characteristic parameters are derived. The effect of the polymer coating location on the sensor's sensitivity is investigated and the formula to calculate the polymer–analyte partition

  10. Fiber-optic interferometric sensor for gas flow measurements

    SciTech Connect

    Kaminski, W.R. [Central Washington Univ., Ellensburg, WA (United States); Griffin, J.W.; Bates, J.M. [Pacific Northwest Lab., Richland, WA (United States)

    1991-12-01

    This paper presents the results of an investigation to determine the feasibility of a novel approach to measuring gas flow in a pipe. An optical fiber is stretched across a pipe and serves as a sensor which is based upon the well-established principle of vortex shedding of a cylinder in cross-flow. The resulting time varying optical signal produces a frequency component proportional to the average velocity in the pipe which is in turn proportional to volumetric flow. A Mach-Zehnder interferometer is used to enhance the accuracy of the vortex shedding frequency signal. The analytical and experimental effort discussed herein shows that the concept is feasible and holds promise for a sensitive and accurate flow measuring technique.

  11. SnO2 thick films for room temperature gas sensing applications

    NASA Astrophysics Data System (ADS)

    Khun Khun, Kamalpreet; Mahajan, Aman; Bedi, R. K.

    2009-12-01

    Porous nanosized SnO2 powder has been synthesized by a simple nonaqueous sol gel method using SnCl2?2H2O and C2H5OH as precursors. Thermal stabilization of the gel is investigated by thermogravimetric/differential thermal analysis. SnO2 powder has been obtained by calcining the gel at 500°C for 3h and studied for its structural properties using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). XRD observations confirm the formation of rutile structured SnO2. On an average, 35nm size particles have been found in TEM micrographs of SnO2 powder. FESEM of the powder reveals the formation of a porous network formed by weak aggregation of nanoparticles. An attempt has been made to fabricate gas sensor by depositing thick SnO2 films on glass substrate. Gas sensing studies show that the sensing response of SnO2 sensor toward ammonia is comparatively higher at room temperature as compared to that toward acetone and ethanol.

  12. 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.

  13. Potentiometric CO2 Sensor Using Li+ Ion Conducting Li3PO4 Thin Film Electrolyte

    PubMed Central

    Noh, Whyo Sub; Satyanarayana, L.; Park, Jin Seong

    2005-01-01

    Li+ ion conducting Li3PO4 thin film electrolytes with thickness 300nm, 650nm and 1.2?m were deposited on Al2O3 substrate at room temperature by thermal evaporation method. Reference and sensing electrodes were printed on Au interfaces by conventional screen printing technique. The overall dimension of the sensor was 3 × 3 mm and of electrodes were 1 × 1.5 mm each. The fabricated solid state potentiometric CO2 sensors of type: CO2, O2, Au, Li2TiO3-TiO2| Li3PO4 |Li2CO3, Au, CO2, O2 have been investigated for CO2 sensing properties. The electromotive force (emf) and ?emf/dec values of the sensors are dependent on the thickness of the electrolyte film. 1.2?m thickness deposited sensor has shown good sensing behavior than the sensors with less thickness. The ?emf values of the sensor are linearly increased up to 460°C operating temperature and became stable above 460°C. Between 460-500°C temperatures region the sensor has reached an equilibrium state and the experimentally obtained ?emf values are about 80% of the theoretically calculated values. A Nernst's slope of -61mV/decade has been obtained between 250 to 5000 ppm of CO2 concentration at 500°C temperature. The sensor is suitable for ease of mass production in view of its miniaturization and cost effectiveness after some further improvement.

  14. Synthesis and Characterization of Carbon Nitride Films for Micro Humidity Sensors

    PubMed Central

    Lee, Sung Pil

    2008-01-01

    Nano-structured carbon nitride (CNx) films were synthesized by a reactive RF magnetron sputtering system with a DC bias under various deposition conditions, and their physical and electrical properties were investigated with a view to using them for micro humidity sensors. The FTIR spectra of the deposited films showed a C=N stretching band in the range of 1600?1700 cm-1, depending on the amount of nitrogen incorporation. The carbon nitride films deposited on the Si substrate had a nano-structured surface morphology with a grain size of about 20 nm, and their deposition rate was 1.5 ?m/hr. The synthesized films had a high electrical resistivity in the range of 108 to 109 ?·cm, depending on the deposition conditions. The micro humidity sensors showed a good linearity and low hysteresis between 5 ? 95 %RH.

  15. Enhancement of evanescent fluorescence from fiber optic sensors by thin film sol gel coatings

    SciTech Connect

    Kao, H.P.; Yang, N.; Schoeniger, J.S.

    1997-09-01

    A theoretical analysis and experimental demonstration of the increase in collected evanescent fluorescence for a fiber optic sensor having a high refractive index, titanium sol gel, thin film coating is presented. Collected fluorescence increased by up to 6 X over that from a bare fiber having a numerical aperture of 0.60. The maximum collected fluorescence increased and shifted to smaller film thicknesses as the film refractive index increased. The simulations and experimental data are consistent with a decrease in the effective refractive index of the sol gel as the film thickness increased. Electron micrographs of the sol gel structure support this observation, and show that the sol gel structure is significantly different from those on a planar glass substrate. The sol gel technique is a potentially inexpensive approach to increase the signal from fiber sensors but higher photobleaching rates at the surface are predicted.

  16. 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.

  17. Manganese perovskites: Thick-film based position sensors fabrication

    Microsoft Academic Search

    Ll. Balcells; R. Enrich; J. Mora; A. Calleja; J. Fontcuberta; X. Obradors

    1996-01-01

    In this letter we report on the growth of thick films of magnetoresistive La2\\/3Sr1\\/3MnO3 films using a spray printing technique. The as-prepared films display a room-temperature magnetoresistance of 0.0012%\\/Oe in the 1 kOe field region. We will show that this field sensitivity is high enough to fabricate devices which, operated under a bias magnetic field, can be used as a

  18. Robotic tactile sensor array fabricated from a piezoelectric polyvinylidene fluoride film

    Microsoft Academic Search

    R. R. Reston; E. S. Kolesar

    1990-01-01

    A robotic tactile sensor comprised of 25 discrete sensor electrodes arranged in a 5×5 grid was designed and fabricated from a piezoelectric polyvinylidene fluoride (PVDF) film coupled to an integrated circuit (IC). Each of the 25 sensing electrodes in the IC grid were connected to metal-oxide-semiconductor field effect transistor (MOSFET) amplifiers which provided sufficient gain to generate usable response signal

  19. High Pulsed Magnetic Field Sensor Based on La-Ca-Mn-O Thin Polycrystalline Films

    Microsoft Academic Search

    S. Balevicius; N. Zurauskiene; V. Stankevic; S. Kersulis; J. Novickij; L. L. Altgilbers; F. Clarke

    2005-01-01

    It is demonstrated that polycrystalline La0.33Ca0.67MnO3 thin film sensors can be used to measure pulsed strong magnetic fields with microsecond duration rise and decay times. The response characteristics of these sensors were investigated using 0.7-1.0 ms duration bell-shaped magnetic field pulses of 10-20 T amplitudes and by using special waveform magnetic field pulses with amplitudes of 40 T and decay

  20. Breath-by-breath measurement of carbon dioxide using a plastic film optical sensor

    Microsoft Academic Search

    Andrew Mills; Anne Lepre; Lorraine Wild

    1997-01-01

    An optical sensor has been developed for breath-by-breath gaseous CO2 analysis. The detector is based on a general formulation described in previous work where a phase-transfer agent, tetraoctyl ammonium hydroxide, is used to incorporate a hydrophilic pH-sensitive dye into a hydrophobic plastic film to create an effectively solid-state colorimetric sensor. In this work the formulation has been modified to yield

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

    SciTech Connect

    Kassas, Ahmad, E-mail: a.kassas.mcema@ul.edu.lb [Faculty of Agricultural Engineering and Veterinary Medicine, Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences and Doctoral School of Sciences and Technology (EDST), Lebanese University, Hariri Campus, Hadath, Beirut (Lebanon); Laboratoire Universitaire des Sciences Appliquées de Cherbourg (LUSAC), 50130 Cherbourg-Octeville (France); Bernard, Jérôme; Lelièvre, Céline; Besq, Anthony; Guhel, Yannick; Houivet, David; Boudart, Bertrand [Laboratoire Universitaire des Sciences Appliquées de Cherbourg (LUSAC), 50130 Cherbourg-Octeville (France); Lakiss, Hassan [Faculty of Agricultural Engineering and Veterinary Medicine, Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences and Doctoral School of Sciences and Technology (EDST), Lebanese University, Hariri Campus, Hadath, Beirut (Lebanon); Faculty of Engineering, Section III, Hariri Campus, Hadath, Beirut (Lebanon); Hamieh, Tayssir [Faculty of Agricultural Engineering and Veterinary Medicine, Laboratory of Materials, Catalysis, Environment and Analytical Methods (MCEMA), Faculty of Sciences and Doctoral School of Sciences and Technology (EDST), Lebanese University, Hariri Campus, Hadath, Beirut (Lebanon)

    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.

  2. Ceramic thin films by sol-gel processing as novel materials for integrated humidity sensors

    Microsoft Academic Search

    Enrico Traversa; Guglielmina Gnappi; Angelo Montenero; Gualtiero Gusmano

    1996-01-01

    Thin films based on 10 at% alkali-doped TiO2 and on iron with very large humidity sensitivity were prepared using a sol-gel technique. Prototype humidity sensors were prepared by depositing metal alkoxide solutions onto Al2O3 substrates with comb-type Au electrodes, by dip-coating and heating in air. Heating to 300°C produces continuous films, free of porosity, which appear as layers covering the

  3. Sol—gel processed TiO 2-based thin films as innovative humidity sensors

    Microsoft Academic Search

    Giampiero Montesperelli; Antonio Pumo; Enrico Traversa; Gusmano; Andrea Bearzotti; Angelo Montenero; Guglielmina Gnappi

    1995-01-01

    Active elements for humidity sensors based on alkali-doped and undoped TiO2 films have been prepared by the sol-—gel technique. TiO2-based films are deposited onto Al2O3 substrates with comb-type Au electrodes by dip-coating, from the appropriate solutions, to obtain four different compositions of 1, 3, 6, and 10 at.% Li and K, with respect to the alkali metal\\/Ti system. The humidity-sensing

  4. Effects of palladium coatings on oxygen sensors of titanium dioxide thin films

    Microsoft Academic Search

    L. Castañeda

    2007-01-01

    Titanium dioxide (TiO2-anatase phase) thin films were deposited by the ultrasonic spray pyrolysis technique employing titanium (IV) oxide acetylacetonate (TiO(acac)2) dissolved in pure methanol as a source material. In order to prepare oxygen sensors, TiO2 thin films were deposited on interdigitated gold electrodes with contacted alumina substrates. Palladium (Pd) coatings were carried out by vacuum thermal evaporation through a metallic

  5. Dual-mode surface-plasmon sensor based on bimetallic film.

    PubMed

    Dyankov, G; Zekriti, M; Bousmina, M

    2012-05-01

    We propose a plasmonic structure, based on a silver-gold two-layered metallic film, where two surface plasmons (SPs) with equal propagation constants are excited simultaneously at different wavelengths. We show theoretically that the bimetallic film provides unique opportunities for manipulation of plasmons and optimization of the accuracy and cross-sensitivity. The structure can be used as an effective self-reference SP sensor in wavelength-interrogated design. PMID:22614425

  6. NTCDA organic thin-film-transistor as humidity sensor: weaknesses and strengths

    Microsoft Academic Search

    L Torsi; A Dodabalapur; N Cioffi; L Sabbatini; P. G Zambonin

    2001-01-01

    1,4,5,8-Naphthalene-tetracarboxylic-dianhydride (NTCDA) organic thin-film-transistors employed as humidity sensors exhibit higher performance level compared to NTCDA chemiresitors. In particular, the transistor on-current exhibits higher values and a larger dynamic range as well as a better reversibility, compared to the response of an NTCDA resistor. On the basis of the FT-IR spectra of NTCDA humid and anhydrous thin-films, a model for the

  7. CdO-based nanostructures as novel CO2 gas sensors

    NASA Astrophysics Data System (ADS)

    Krishnakumar, T.; Jayaprakash, R.; Prakash, T.; Sathyaraj, D.; Donato, N.; Licoccia, S.; Latino, M.; Stassi, A.; Neri, G.

    2011-08-01

    Crystalline Cd(OH)2/CdCO3 nanowires, having lengths in the range from 0.3 up to several microns and 5-30 nm in diameter, were synthesized by a microwave-assisted wet chemical route and used as a precursor to obtain CdO nanostructures after a suitable thermal treatment in air. The morphology and microstructure of the as-synthesized and annealed materials have been investigated by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and thermogravimetry-differential scanning calorimetry. The change in morphology and electrical properties with temperature has revealed a wire-to-rod transformation along with a decreases of electrical resistance. Annealed samples were printed on a ceramic substrate with interdigitated contacts to fabricate resistive solid state sensors. Gas sensing properties were explored by monitoring CO2 in synthetic air in the concentration range 0.2-5 v/v% (2000-50 000 ppm). The effect of annealing temperature, working temperature and CO2 concentration on sensing properties (sensitivity, response/recovery time and stability) were investigated. The results obtained demonstrate that CdO-based thick films have good potential as novel CO2 sensors for practical applications.

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

    E-print Network

    Dutta, Prabir K.

    Mixed Ionic and Electronic Conduction in Li3PO4 Electrolyte for a CO2 Gas Sensor Chonghoon Lee and Measurements, The Ohio State University, Columbus, Ohio 43210, USA An electrochemical CO2 gas sensor using Li2 as the electrolyte is the subject of this paper. The sensor response to CO2 gas showed a systematic deviation from

  9. Thermal and flow analysis of SiC-based gas sensors for automotive applications

    Microsoft Academic Search

    Ilja Belov; Helena Wingbrant; Anita Lloyd Spetz; Hans Sundgren; B. Thuner; H. Svenningstorp; P. Leisner

    2004-01-01

    Different block and tube mounting alternatives for SiC-based gas sensors were studied by means of temperature measurements and simulation of heat transfer and gas flow for steady state conditions. The most preferable tube mounting design was determined. Simulation-based guidelines were developed for designing tube-mounted gas sensors in the exhaust pipes of diesel and petrol engines, taking into account thermal constraints

  10. Experimental demonstration of a fiber-optic gas sensor network addressed by FMCW

    Microsoft Academic Search

    H. L. Ho; W. Jin; H. B. Yu; K. C. Chan; C. C. Chan; M. S. Demokan

    2000-01-01

    We report on the use of frequency-modulated continuous-wave and wavelength modulation spectroscopy techniques for addressing a multipoint gas sensor network. A three-sensor network of ladder topology is experimentally demonstrated for the detection of acetylene gas. A minimum detectable concentration of 270 ppm\\/?Hz is obtained with 25-mm gas cells under atmospheric pressure which corresponds to a minimum detectable absorbance of 3.40×10-4.

  11. Dansyl-based fluorescent film sensor for nitroaromatics in aqueous solution

    NASA Astrophysics Data System (ADS)

    Kang, Jianping; Ding, Liping; Lü, Fengting; Zhang, Shujuan; Fang, Yu

    2006-12-01

    We demonstrate the preparation, characterization and performance evaluation of a fluorescent film sensor for the specific detection of nitroaromatics in aqueous solution. The film sensor was fabricated by covalent immobilization of a fluorophore, dansyl, on a glass slide surface via reaction with diaminopropane and then with an epoxide-terminated self-assembled monolayer. Nitroaromatics like nitrobenzene, 4-nitrotoluene, 3, 5-dinitrotoluene, and 2,4,6-trinitrotoluene, etc were found to strongly quench the fluorescence emission of the film while some other commonly-used quenchers like nitromethane, KI, acrylamide, etc showed no or slight quenching effect on the emission. The quenching mechanism was examined through fluorescence lifetime measurements and it was proved that the quenching is static in nature and may be caused by electron transfer from the fluorophore to the nitroaromatics. The presence of other aromatics like benzene, toluene, etc had little effect upon the sensing performance of the film to nitroaromatics. Solvent effect studies revealed that the conformations adopted by the spacer connecting the fluorophore and the substrate played a crucial role in the performance of the film sensor. Furthermore, the response of the film to nitroaromatics is fast and reversible.

  12. Heat flux sensor research and development: The cool film calorimeter

    NASA Technical Reports Server (NTRS)

    Abtahi, A.; Dean, P.

    1990-01-01

    The goal was to meet the measurement requirement of the NASP program for a gauge capable of measuring heat flux into a 'typical' structure in a 'typical' hypersonic flight environment. A device is conceptually described that has fast response times and is small enough to fit in leading edge or cowl lip structures. The device relies heavily on thin film technology. The main conclusion is the description of the limitations of thin film technology both in the art of fabrication and in the assumption that thin films have the same material properties as the original bulk material. Three gauges were designed and fabricated. Thin film deposition processes were evaluated. The effect of different thin film materials on the performance and fabrication of the gauge was studied. The gauges were tested in an arcjet facility. Survivability and accuracy were determined under various hostile environment conditions.

  13. Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors

    Microsoft Academic Search

    Craig A. Grimes; Dimitris Kouzoudis

    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

  14. Solid-state potentiometric CO2-sensor in thick film technology for breath analysis

    Microsoft Academic Search

    S. Wiegartner; G. Hagen; J. Kita; R. Moos; M. Seufert; E. Glaser; K. Grimmel; A. Bolz; C. Schmaus; A. Kiessig

    2011-01-01

    A solid-state potentiometric CO2-sensor of the type CO2, O2, Au, Li2CO3-BaCO3 | Nasicon | Na2Ti6O13-TiO2, Au, O2, CO2 was fully manufactured in planar thick-film technology. Due to an integrated screen-printed heater on the rear side, the sensor can be applied in a small tube for breath analysis, despite its high working temperature of 525 °C. The sensor is insensitive to

  15. 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.

  16. Designing and testing of a sensor based on a magnetoresistive manganese perovskite thick film

    Microsoft Academic Search

    Ll. Balcells; R. Enrich; A. Calleja; J. Fontcuberta; X. Obradors

    1997-01-01

    In this paper we report on the growth of thick films of magnetoresistive La2\\/3Sr1\\/3MnO3 by using spray and screen printing techniques on various substrates (Al2O3 and ZrO2). The growth conditions are explored in order to optimize the microstructure of the films. The films display a room-temperature magnetoresistance of 0.0012%\\/Oe in the 1 kOe field region. A magnetic sensor is described

  17. Development of Micro-Heaters with Optimized Temperature Compensation Design for Gas Sensors

    PubMed Central

    Hwang, Woo-Jin; Shin, Kyu-Sik; Roh, Ji-Hyoung; Lee, Dae-Sung; Choa, Sung-Hoon

    2011-01-01

    One of the key components of a chemical gas sensor is a MEMS micro-heater. Micro-heaters are used in both semiconductor gas sensors and NDIR gas sensors; however they each require different heat dissipation characteristics. For the semiconductor gas sensors, a uniform temperature is required over a wide area of the heater. On the other hand, for the NDIR gas sensor, the micro-heater needs high levels of infrared radiation in order to increase sensitivity. In this study, a novel design of a poly-Si micro-heater is proposed to improve the uniformity of heat dissipation on the heating plate. Temperature uniformity of the micro-heater is achieved by compensating for the variation in power consumption around the perimeter of the heater. With the power compensated design, the uniform heating area is increased by 2.5 times and the average temperature goes up by 40 °C. Therefore, this power compensated micro-heater design is suitable for a semiconductor gas sensor. Meanwhile, the poly-Si micro-heater without compensation shows a higher level of infrared radiation under equal power consumption conditions. This indicates that the micro-heater without compensation is more suitable for a NDIR gas sensor. Furthermore, the micro-heater shows a short response time of less than 20ms, indicating a very high efficiency of pulse driving. PMID:22163756

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

    E-print Network

    Mench, Matthew M.

    2006-01-01

    reserved. Keywords: Thin film thermistor; MEMS; Microstructure; Polymer electrolyte fuel cell; Solid of electrolyte temperature in a polymer electrolyte fuel cell Suhao Hea, Matthew M. Mencha, Srinivas Tadigadapab electrolyte fuel cell (PEFC). A patterned thin film gold thermistor embedded in a 16 m thick parylene film

  19. Sensitive gas sensor embedded in a vertical polymer space-charge-limited transistor

    NASA Astrophysics Data System (ADS)

    Zan, Hsiao-Wen; Li, Chang-Hung; Yu, Chih-Kuan; Meng, Hsin-Fei

    2012-07-01

    We report a very sensitive gas sensor embedded in a vertical polymer space-charge-limited transistor. The oxidizing and reducing gases act as electron dedoping and electron doping agents on the transistor active layer to change the potential distribution in the vertical channel and hence to change the output current density. With a 30-ppb detection limit to ammonia, the sensor can be used for non-invasive breath monitor in point-of-care applications. The integration of a sensitive gas sensor and a low-operation-voltage transistor in one single device also facilitates the development of low-cost and low-power-consumption sensor array.

  20. 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.

  1. Development of thermal sensor based on PbTe thin films in MEMS design

    NASA Astrophysics Data System (ADS)

    Dashevsky, Zinovi; Rabih, Eli; Dariel, Moshe

    2005-08-01

    The work of a MEMS-technology compatible thin-film thermoelectric IR radiation sensor with multiple PbTe thermocouples is simulated. The sensitivity up to 350 V/W is predicted. PbTe thin films are grown on the BaF2(111) buffered Si(111) substrates, using the hot-wall-beam epitaxy technique. Indium and zinc ion implantation is applied to transform the as-grown p-PbTe films into the n-type thermocouple counterpart films. With a dose of 10l6 cm-2 and exposition time of 3-4 h, a 4-pm-thick film is homogeneously reversed, retaining the high epitaxial quality.

  2. Membrane-based characterization of a gas component--a transient sensor theory.

    PubMed

    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

  3. 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

  4. 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.

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

    E-print Network

    Cai, Long

    . Therefore, the online monitoring of alpha radiation from a nuclear facility using conventional detectors nuclear track detector CR-39 film by low level alpha radiation to changes in optical properties like be one of promising candidates for the development of online radiation sensors. T he Fukushima nuclear

  6. Enhancement of evanescent fluorescence from fiber optic sensors by thin film sol gel coatings

    Microsoft Academic Search

    H. P. Kao; N. Yang; J. S. Schoeniger

    1997-01-01

    A theoretical analysis and experimental demonstration of the increase in collected evanescent fluorescence for a fiber optic sensor having a high refractive index, titanium sol gel, thin film coating is presented. Collected fluorescence increased by up to 6 X over that from a bare fiber having a numerical aperture of 0.60. The maximum collected fluorescence increased and shifted to smaller

  7. 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

  8. Reactive Ion Etching of Columnar Nanostructured Thin Films for Modified Relative Humidity Sensor Response Time

    Microsoft Academic Search

    Martin R. Kupsta; Michael T. Taschuk; Michael J. Brett; Jeremy C. Sit

    2009-01-01

    A CF4 dry etch recipe for TiO2 was optimized for nanostructured thin films. The impact of our etching process and ultraviolet irradiation of nanostructured relative humidity (RH) sensors was studied. Reactive ion etching of titanium dioxide decreased device adsorption response time by opening high diffusivity channels while retaining the high surface area and high dynamic range of the interdigitated electrode

  9. 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.

  10. 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.

  11. Fabry-Pérot cavity sensors for multipoint on-column micro gas chromatography detection.

    PubMed

    Liu, Jing; Sun, Yuze; Howard, Daniel J; Frye-Mason, Greg; Thompson, Aaron K; Ja, Shiou-Jyh; Wang, Siao-Kwan; Bai, Mengjun; Taub, Haskell; Almasri, Mahmoud; Fan, Xudong

    2010-06-01

    We developed and characterized a Fabry-Pérot (FP) sensor module based micro gas chromatography (microGC) detector for multipoint on-column detection. The FP sensor was fabricated by depositing a thin layer of metal and a layer of gas-sensitive polymer consecutively on the endface of an optical fiber, which formed the FP cavity. Light partially reflected from the metal layer and the polymer-air interface generated an interference spectrum, which shifted as the polymer layer absorbed the gas analyte. The FP sensor module was then assembled by inserting the FP sensor into a hole drilled in the wall of a fused-silica capillary, which can be easily connected to the conventional gas chromatography (GC) column through a universal quick seal column connector, thus enabling on-column real-time detection. We characterized the FP sensor module based microGC detector. Sensitive detection of various gas analytes was achieved with subnanogram detection limits. The rapid separation capability of the FP sensor module assembled with both single- and tandem-column systems was demonstrated, in which gas analytes having a wide range of polarities and volatilities were well-resolved. The tandem-column system obtained increased sensitivity and selectivity by employing two FP sensor modules coated with different polymers, showing great system versatility. PMID:20441156

  12. Thin-film temperature sensors deposited by radio frequency cathodic sputtering

    NASA Astrophysics Data System (ADS)

    Godefroy, J. C.; Gageant, C.; Francois, D.; Portat, M.

    1987-10-01

    In order to gain better knowledge of the heat exchanges occurring in aircraft turbines, ONERA is presently developing thin-film heat sensors capable of operating up to a maximum temperature of 1100 C. These high-temperature sensors are surface thermometers and fluxmeters of the gradient type. They consist of metal films forming thermocouples and insulating films such as alumina or zircon stabilized by yttrium oxide. These layers are deposited by RF cathodic sputtering on substrates such as IN100, DS200, and CMSX2 superalloys which are either aluminized or coated with an NiCoCrAlY alloy. The present state of development of the thermometers is described as well as the first results obtained.

  13. Flexible high-resolution film recorder system. [in NASA image processing facility for remote sensor data

    NASA Technical Reports Server (NTRS)

    Heffner, P.; Connell, E.

    1980-01-01

    The paper describes a high-resolution film recorder (HRFR) system capable of meeting the requirements of all of the imaging sensors for the recording support of NASA missions. The technical requirements imposed by sensor constraints and end users of the film product are examined, along with the implementation techniques to satisfy these requirements. The recorder can produce annotated imagery with array sizes ranging from 1 to 400 million picture elements and a programmable radiometric transfer function provided by the recorder. The HRFR requirements were grouped into three categories: (1) front end (input) requirements defined by the input medium, (2) operational requirements based on the volume, throughput, and changeover time from one mode to another, and (3) film product requirements determined by the needs of the end product user.

  14. 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.

  15. 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

  16. Integrating Metal-Oxide-Decorated CNT Networks with a CMOS Readout in a Gas Sensor

    PubMed Central

    Lee, Hyunjoong; Lee, Sanghoon; Kim, Dai-Hong; Perello, David; Park, Young June; Hong, Seong-Hyeon; Yun, Minhee; Kim, Suhwan

    2012-01-01

    We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 ?m CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures. PMID:22736966

  17. Sol–gel processed Al 2O 3 thick film template as sensitive capacitive trace moisture sensor

    Microsoft Academic Search

    Kalyan Kumar Mistry; Debdulal Saha; Kamalendu Sengupta

    2005-01-01

    Sol–gel processed Al2O3 thick film template has been tested for the first time to fabricate a trace moisture sensor. The device consists of a thick film nano porous ?-Al2O3 film, electrodes coated by silver palladium (AgPd) conductive past on both sides of the film forming a parallel plate capacitor. A high change in capacitance was observed with increasing ppmV moisture

  18. A wearable oxygen sensor for transcutaneous blood gas monitoring at the conjunctiva

    Microsoft Academic Search

    Shigehito Iguchi; Kohji Mitsubayashi; Takayuki Uehara; Mitsuhiro Ogawa

    2005-01-01

    A thinner and flexible oxygen sensor as one of the Soft-MEMS devices was developed in order to monitor transcutaneous oxygen tension from conjunctiva. The wearable oxygen sensor with membrane structure was constructed by pouching KCl electrolyte solution by nonpermeable membrane and gas-permeable membrane with Pt- and Ag\\/AgCl electrode patterned by using photolithography and sputtering methods. The wearable oxygen sensor (width:

  19. 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.

  20. SEMICONDUCTOR LASER BASED TRACE GAS SENSOR TECHNOLOGY: RECENT ADVANCES AND APPLICATIONS

    E-print Network

    SEMICONDUCTOR LASER BASED TRACE GAS SENSOR TECHNOLOGY: RECENT ADVANCES AND APPLICATIONS Laser Based University, 6100 Main Street, Electrical and Computer Engineering Department ­ MS 366, Houston, TX, 77005, USA Abstract. Recent advances in the development of sensors based on infrared diode and quantum

  1. Design of a hybrid modular sensor system for gas and odor analysis

    Microsoft Academic Search

    J. Mitrovics; H. Ulmer; G. Noetzel; U. Weimar; W. Gopel

    1997-01-01

    We present a new very flexible design of a sensor system for gas and odor analysis, which may easily be optimized for specific applications. The core part contains a digital bus system that connects individual sensor modules with a central processor. By using dedicated microcontrollers onboard the modules it is possible to use any kind of transduction principles (“hybrid system”),

  2. Functional design of semiconductor gas sensors for measurement of smell and freshness

    Microsoft Academic Search

    M. Egashira

    1997-01-01

    Some important results of our research on semiconductor gas\\/odor sensors are reviewed. Our research is focused on observation of nonlinear I-V characteristics of sensors, elucidation of influences of reactivity and diffusivity of both objective and oxygen gases in a porous sensing layer, optimization of catalytic activity of sensing materials to objective gases, control of oxygen readsorption, and so on. Based

  3. A NASICON CO2 gas sensor with drift-detection electrode

    Microsoft Academic Search

    Song Chen; Hironori Hadano; Yoshiaki Ishiguro; Masakatsu Nakayama; Kenzo Watanabe

    2002-01-01

    A Nasicon (sodium super ion conductor) CO2 gas sensor with a new structure is developed for monitoring CO2 level in the atmospheric air. In addition to the sensing and reference electrodes of a conventional Nasicon sensor, an auxiliary electrode, referred to as the base electrode, is provided with the new structure. Characterization has revealed that the output voltage at the

  4. A Nasicon CO2 gas sensor with drift-detection electrode

    Microsoft Academic Search

    Song Chen; De-Yin Jeng; Hironori Hadano; Yoshiaki Ishiguro; Masakatsu Nakayama; Kenzo Watanabe

    2003-01-01

    A Nasicon (sodium super ion conductor) CO2 gas sensor with a new structure is developed for monitoring CO2 levels in the atmospheric air. In addition to the sensing and reference electrodes of a conventional Nasicon sensor, an auxiliary electrode, referred to as the base electrode, is provided with the new structure. The principle of CO2 detection is the same as

  5. Evaluation of the sensidyne toxic gas sensor for HF (Hydrogen Fluoride) vapor

    Microsoft Academic Search

    W. D. Bostick; E. C. Angel; T. H. Hamilton

    1987-01-01

    A diffusion-type electrochemical sensor is evaluated for the detection of hydrogen fluoride (HF) vapor, both for use as an area monitor safety device and as a stack gas monitor. Response characteristics of individual sensor assemblies are variable, but with frequent, proper calibration, the Sensidyne HF Toxic Alert device is demonstrated to provide accurate, sensitive, and relatively rapid response to this

  6. Nano Sensor Networks for Tailored Operation of Highly Efficient Gas-To-Liquid Fuels Catalysts

    E-print Network

    New South Wales, University of

    Nano Sensor Networks for Tailored Operation of Highly Efficient Gas-To-Liquid Fuels Catalysts Eisa surface processes can be controlled via Nano Sensor Network (NSN) involving the turning on or off to the wanted products. The overall effect of this nano-level communications will lead to superior selectivity

  7. Thin-film gas sensors based on semiconducting metal oxides

    Microsoft Academic Search

    H Meixner; J Gerblinger; U Lampe; M Fleischer

    1995-01-01

    In recent years, there has been a gradual realization that an intact environment and properly functioning ecosystems are essential to the continuance of human life; this has led to the tightening up of environmental legislation. As far as air pollution is concerned, gases like sulfur dioxide, the oxides of nitrogen (NOx), carbon monoxide and carbon dioxide are considered to be

  8. Doped-vanadium oxides as sensing materials for high temperature operative selective ammonia gas sensors

    Microsoft Academic Search

    Ken-ichi Shimizu; Isao Chinzei; Hiroyuki Nishiyama; Shiro Kakimoto; Satoshi Sugaya; Wataru Matsutani; Atsushi Satsuma

    2009-01-01

    Resistive electrochemical sensors based on vanadium oxides equipped with a pair of interdigital Au electrodes can detect NH3 gas selectively at high temperature (500°C). NH3 addition in a base gas increased the relative conductance (?\\/?0). Addition of less electronegative cation (Ce, Zr, Mg) to V2O5 increased the response and recovery rates, while electronegative cation (Al, Fe, Ni) increased sensor response

  9. Fabrication and characteristics of SnO 2 gas sensor array for volatile organic compounds recognition

    Microsoft Academic Search

    Dae-Sik Lee; Youn Tae Kim; Jeung-Soo Huh; Duk-Dong Lee

    2002-01-01

    Ten different gas sensors were integrated as an array on a substrate to identify various kinds and quantities of volatile organic compounds (VOCs), such as benzene, toluene, ethyl alcohol, methyl alcohol, and acetone. The sensor array consists of gas-sensing materials with SnO2 as the base material and a platinum heater and is fabricated using silk printing methods on an alumina

  10. Sensors

    NSDL National Science Digital Library

    Leske, Cavin.

    2003-01-01

    Electronic sensors exist in many facets of our lives, from measuring operating conditions of our vehicles to adjusting the temperature of our homes. They can even mean the difference between life and death when used to monitor patients in emergency rooms. Even though sensors work transparently in their multitude of functions, their importance cannot be understated.Sensorland (1) has basic descriptions of a wide variety of sensors and related concepts. Out of the 50 items in the list, some have full technical reports that explain physical processes, while others consist of succinct explanations of a device's operation. The site covers sensors that measure everything from atmospheric pressure to the pH value of liquid solutions. In September 2002, the US Army conducted exercises using the zNose, a sensor that can quickly and quantitatively analyze any smell or vapor. This paper (2) provides a complete technical description of the zNose. Several more documents, including the press release of the Army's use of the device, can be found on the Electronic Sensor Technology homepage. In a related story from Sandia National Laboratories, the SnifferSTAR (3) could be especially useful in case of a terrorist gas attack. The short article briefly discusses how the invention works, with an emphasis on its characteristics of low power consumption and rapid analysis. Environmental Research Aircraft and Sensor Technology (4) is a NASA program to develop unmanned aerial vehicles capable of conducting advanced scientific studies. A number of aircraft are highlighted on the program's Web site, many of which are designed for long-term flights or potentially dangerous missions. The February 2003 cover story of Sensors magazine (5) is inertial sensing technology made from microelectromechanical systems (MEMS). The article discusses the applications of MEMS in accelerometers and gyroscopes, as well as explaining some of the theory behind these devices. A streaming video presentation, given in May 2002, can be viewed from this site (6). The hour-long talk introduces Sensor Webs, a network of tiny sensors connected by wireless technology that can be scattered over a large area to gather scientific data. Sensors can even be used in performing arts, as is shown in this paper from the Massachusetts Institute of Technology Media Lab (7). The authors propose using motion sensors to monitor hundreds of performers simultaneously, thereby allowing for much improved lighting and music responses. In the wake of the Space Shuttle Columbia tragedy, a great deal of attention was given to the intermittent and failing sensors on the shuttle minutes before it broke apart. This document from NASA shows the status of several sensors at various intervals in the shuttle's decent (8).

  11. 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.

  12. Polymer waveguide grating sensor integrated with a thin-film photodetector

    PubMed Central

    Song, Fuchuan; Xiao, Jing; Xie, Antonio Jou; Seo, Sang-Woo

    2014-01-01

    This paper presents a planar waveguide grating sensor integrated with a photodetector (PD) for on-chip optical sensing systems which are suitable for diagnostics in the field and in-situ measurements. III–V semiconductor-based thin-film PD is integrated with a polymer based waveguide grating device on a silicon platform. The fabricated optical sensor successfully discriminates optical spectral characteristics of the polymer waveguide grating from the on-chip PD. In addition, its potential use as a refractive index sensor is demonstrated. Based on a planar waveguide structure, the demonstrated sensor chip may incorporate multiple grating waveguide sensing regions with their own optical detection PDs. In addition, the demonstrated processing is based on a post-integration process which is compatible with silicon complementary metal-oxide semiconductor (CMOS) electronics. Potentially, this leads a compact, chip-scale optical sensing system which can monitor multiple physical parameters simultaneously without need for external signal processing. PMID:24466407

  13. A polymer waveguide grating sensor integrated with a thin-film photodetector

    NASA Astrophysics Data System (ADS)

    Song, Fuchuan; Xiao, Jing; Jou Xie, Antonio; Seo, Sang-Woo

    2014-01-01

    This paper presents a planar waveguide grating sensor integrated with a photodetector (PD) for on-chip optical sensing systems which are suitable for diagnostics in the field and in situ measurements. A III-V semiconductor-based thin-film PD is integrated with a polymer-based waveguide grating device on a silicon platform. The fabricated optical sensor successfully discriminates optical spectral characteristics of the polymer waveguide grating from the on-chip PD. In addition, its potential use as a refractive index sensor is demonstrated. Based on a planar waveguide structure, the demonstrated sensor chip may incorporate multiple grating waveguide sensing regions with their own optical detection PDs. In addition, the demonstrated processing is based on a post-integration process which is compatible with silicon complementary metal-oxide-semiconductor electronics. Potentially, this leads to a compact, chip-scale optical sensing system which can monitor multiple physical parameters simultaneously without the need for external signal processing.

  14. Electrochemical sensor with polymer thick film printed electrodes

    Microsoft Academic Search

    C. Bala; L. Rotariu; C. Ionescu; P. Svasta

    2009-01-01

    The assurance of a high level of safety regarding the food market has been one of the main concern issues of the European Commission. In this sense the affirmed documents name the pesticides as a major hazard factor. For these residuals the maximum quantity is strictly limited, especially for children. A sensor with detection capabilities in this sense will be

  15. Mass sensitivity of multilayer thin film resonant BAW sensors

    Microsoft Academic Search

    G. Wingqvist; V. Yantchev; I. Katardjiev

    2008-01-01

    A systematic study of the mass sensitivity and its dependence on the material's properties and thicknesses in composite multilayer Thin Film Bulk Acoustic Resonators (FBAR) is presented. The Mason transmission line model has been employed in combination with the acoustic energy balance principle for the determination of the FBAR mass sensitivity. The results have been experimentally verified. Further, the mass

  16. Optical properties of porous chalcogenide films for sensor application

    NASA Astrophysics Data System (ADS)

    Lalova, A.; Todorov, R.

    2012-12-01

    The object of the present work is investigation of the optical properties of obliquely deposited thin films from As - S - Ge system. Aiming to obtain high porous coatings the deposition rate was varied in the range of 0.05-10 nm/s. The conditions for deposition of thin As - S - Ge films with columnar structure and high porosity were established. The role of the actual deposition conditions on the optical properties is examined. The optical constants (refractive index, n and absorption coefficient, ?) and thickness, d as well as the optical band gap, Eg, and slope parameter B in dependence of the deposition angle and rate are determined from specrophotometric measurements in the spectral range 400-2000 nm applying the Swanepoel's envelope method and Tauc's procedure. Increasing of the value of n from 2.40 to 1.83 for thin film with composition As10Ge30S60 with increasing deposition angle from 0° to 75° is observed. The possibility of using the thin films for optical sensing of SO2 and H2S was examined. Reversible changes of the refractive index, ?n = 0.015 were observed as a consequence of treatment virgin - exposure to H2SO4 vapors- annealing at 120 °C.

  17. TiAgx thin films for lower limb prosthesis pressure sensors: effect of composition and structural changes in the electrical and thermal response of the films

    E-print Network

    Paris-Sud XI, Université de

    changes in the electrical and thermal response of the films C. Lopes1 , P. Pedrosa1,2,3 , F. Macedo1 , E silicon, glass and polished high-speed steel substrates by DC magnetron sputtering from a pure Ti target1 TiAgx thin films for lower limb prosthesis pressure sensors: effect of composition and structural

  18. High sensitivity gas sensor based on high-Q suspended polymer photonic crystal nanocavity

    SciTech Connect

    Clevenson, Hannah, E-mail: hannahac@mit.edu; Desjardins, Pierre; Gan, Xuetao; Englund, Dirk, E-mail: englund@mit.edu [Department of Electrical Engineering and Computer Science, Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2014-06-16

    We present high-sensitivity, multi-use optical gas sensors based on a one-dimensional photonic crystal cavity. These devices are implemented in versatile, flexible polymer materials which swell when in contact with a target gas, causing a measurable cavity length change. This change causes a shift in the cavity resonance, allowing precision measurements of gas concentration. We demonstrate suspended polymer nanocavity sensors and the recovery of sensors after the removal of stimulant gas from the system. With a measured quality factor exceeding 10{sup 4}, we show measurements of gas concentration as low as 600 parts per million (ppm) and an experimental sensitivity of 10?ppm; furthermore, we predict detection levels in the parts-per-billion range for a variety of gases.

  19. Ultrasensitive and highly selective graphene-based single yarn for use in wearable gas sensor.

    PubMed

    Ju Yun, Yong; Hong, Won G; Choi, Nak-Jin; Hoon Kim, Byung; Jun, Yongseok; Lee, Hyung-Kun

    2015-01-01

    Electric components based on fibers or textiles have been investigated owing to their potential applications in wearable devices. High performance on response to gas, drape-ability and washing durability are of important for gas sensors based on fiber substrates. In this report, we demonstrate the bendable and washable electronic textile (e-textile) gas sensors composed of reduced graphene oxides (RGOs) using commercially available yarn and molecular glue through an electrostatic self-assembly. The e-textile gas sensor possesses chemical durability to several detergent washing treatments and mechanical stability under 1,000 bending tests at an extreme bending radius of 1?mm as well as a high response to NO2 gas at room temperature with selectivity to other gases such as acetone, ethanol, ethylene, and CO2. PMID:26043109

  20. Ultrasensitive and Highly Selective Graphene-Based Single Yarn for Use in Wearable Gas Sensor

    PubMed Central

    Ju Yun, Yong; Hong, Won G.; Choi, Nak-Jin; Hoon Kim, Byung; Jun, Yongseok; Lee, Hyung-Kun

    2015-01-01

    Electric components based on fibers or textiles have been investigated owing to their potential applications in wearable devices. High performance on response to gas, drape-ability and washing durability are of important for gas sensors based on fiber substrates. In this report, we demonstrate the bendable and washable electronic textile (e-textile) gas sensors composed of reduced graphene oxides (RGOs) using commercially available yarn and molecular glue through an electrostatic self-assembly. The e-textile gas sensor possesses chemical durability to several detergent washing treatments and mechanical stability under 1,000 bending tests at an extreme bending radius of 1?mm as well as a high response to NO2 gas at room temperature with selectivity to other gases such as acetone, ethanol, ethylene, and CO2. PMID:26043109