| 1. |
- Nguyen Van, Toan, et al.
(författare)
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Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands
- 2016
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 0304-3894 .- 1873-3336. ; 301, s. 433-442
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasensitive and selective hydrogen gas sensor is vital component in safe use of hydrogen that requires a detection and alarm of leakage. Herein, we fabricated a H2 sensing devices by adopting a simple design of planar–type structure sensor in which the heater, electrode, and sensing layer were patterned on the front side of a silicon wafer. The SnO2 thin film–based sensors that were sensitized with microsized Pd islands were fabricated at a wafer–scale by using a sputtering system combined with micro–electronic techniques. The thicknesses of SnO2 thin film and microsized Pd islands were optimized to maximize the sensing performance of the devices. The optimized sensor could be used for monitoring hydrogen gas at low concentrations of 25–250 ppm, with a linear dependence to H2 concentration and a fast response and recovery time. The sensor also showed excellent selectivity for monitoring H2 among other gases, such as CO, NH3, and LPG, and satisfactory characteristics for ensuring safety in handling hydrogen. The hydrogen sensing characteristics of the sensors sensitized with Pt and Au islands were also studied to clarify the sensing mechanisms.
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| 2. |
- Duy, Nguyen Van, et al.
(författare)
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Design and fabrication of effective gradient temperature sensor array based on bilayer SnO2/Pt for gas classification
- 2022
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 351
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Tidskriftsartikel (refereegranskat)abstract
- Classification of different gases is important, and it is possible to use different gas sensors for this purpose. Electronic noses, for example, combine separated gas sensors into an array for detecting different gases. However, the use of separated sensors in an array suffers from being bulky, high-energy consumption and complex fabrication processes. Generally, gas sensing properties, including gas selectivity, of semiconductor gas sensors are strongly dependent on their working temperature. It is therefore feasible to use a single device composed of identical sensors arranged in a temperature gradient for classification of multiple gases. Herein, we introduce a design for simple fabrication of gas sensor array based on bilayer Pt/SnO2 for real-time monitoring and classification of multiple gases. The study includes design simulation of the sensor array to find an effective gradient temperature, fabrication of the sensors and test of their performance. The array, composed of five sensors, was fabricated on a glass substrate without the need of backside etching to reduce heat loss. A SnO2 thin film sensitized with Pt on top deposited by sputtering was used as sensing material. The sensor array was tested against different gases including ethanol, methanol, isopropanol, acetone, ammonia, and hydrogen. Radar plots and principal component analysis were used to visualize the distinction of the tested gases and to enable effective classification.
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| 3. |
- Jiao, Mingzhi, et al.
(författare)
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Comparison of NO2 Gas-Sensing Properties of Three Different ZnO Nanostructures Synthesized by On-Chip Low-Temperature Hydrothermal Growth
- 2018
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 47:1, s. 785-793
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Tidskriftsartikel (refereegranskat)abstract
- Three different ZnO nanostructures, dense nanorods, dense nanowires, and sparse nanowires, were synthesized between Pt electrodes by on-chip hydrothermal growth at 90°C and below. The three nanostructures were characterized by scanning electron microscopy and x-ray diffraction to identify their morphologies and crystal structures. The three ZnO nanostructures were confirmed to have the same crystal type, but their dimensions and densities differed. The NO2 gas-sensing performance of the three ZnO nanostructures was investigated at different operation temperatures. ZnO nanorods had the lowest response to NO2 along with the longest response/recovery time, whereas sparse ZnO nanowires had the highest response to NO2 and the shortest response/recovery time. Sparse ZnO nanowires also performed best at 300°C and still work well and fast at 200°C. The current–voltage curves of the three ZnO nanostructures were obtained at various temperatures, and the results clearly showed that sparse ZnO nanowires did not have the linear characteristics of the others. Analysis of this phenomenon in connection with the highly sensitive behavior of sparse ZnO nanowires is also presented.
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| 4. |
- Jiao, Mingzhi, et al.
(författare)
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Influence of annealing temperature on theperformance and stability of on-chip hydrothermally grown ZnO nanorod gassensor toward NO2
- 2018
-
Ingår i: Academia Journal of Scientific Research. - 2315-7712. ; 6:5, s. 180-189
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Tidskriftsartikel (refereegranskat)abstract
- Nanorod-based gas sensors synthesized at low temperature should generally be stabilized by anneling before usage. However, the influence of annealing on the sensing performance and stability of these nanorods is rarely reported. In this study, we first fabricated gas sensors based on ZnO nanorods grown on-chip on glass substrate using hydrothermal method. Subsequently, these sensors were annealed at either 400 °C, 500 °C, or 600 °C in air for 4 h. The gas-sensing performance of the ZnO nanorods toward NO2 was tested before and after annealing. The sensitivity of the gas sensors to NO2 decreased, but the stability increased with the increase in annealing temperature. Photoluminescence spectroscopy and X-ray diffraction were used to investigate the material structure of ZnO nanorods. Results revealed that the oxygen-atom-related defects in the ZnO lattice in the region close to the surface influenced by annealing process were the most significant factors on the sensing properties and stability of ZnO nanorods.
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| 5. |
- Jiao, Mingzhi, et al.
(författare)
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On-chip growth of patterned ZnO nanorod sensors with PdO decoration for enhancement of hydrogen-sensing performance
- 2017
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 42:25, s. 16294-16304
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we used a low-temperature hydrothermal technique to fabricate arrays of sensors with ZnO nanorods grown on-chip. The sensors on the glass substrate then were sputter decorated with Pd at thicknesses of 2, 4, and 8 nm and annealed at 650 °C in air for an hour. Scanning electron microscopy, high resolution transmission microscopy, X-ray diffraction, and surface analysis by X-ray photoelectron spectroscopy characterization demonstrated that decoration of homogenous PdO nanoparticles on the surface of ZnO nanorods had been achieved. The sensors were tested against three reducing gases, namely hydrogen, ethanol, and ammonia, at 350, 400, and 450 °C. The ZnO nanorods decorated with PdO particles from the 2 and 4 nm layers showed the highest responses to H2 at 450 and 350 °C, respectively. These samples also generally exhibited better selectivity for hydrogen than for ethanol and ammonia at the same concentrations and at all tested temperatures. However, the ZnO nanorods decorated with PdO particles from the 8 nm layer showed a reverse sensing behaviour compared with the first two. The sensing mechanism behind these phenomena is discussed in the light of the spillover effect of hydrogen in contact with the PdO particles as well as the negative competition of the PdO thin film formed between the sensor electrodes during sputter decoration, Pd-Zn heterojunction that forms at high temperature and thus influences the conductivity of the ZnO nanorods.
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| 6. |
- Ngoc, Trinh Minh, et al.
(författare)
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Ultralow power consumption gas sensor based on a self- heated nanojunction of SnO2 nanowires
- 2018
-
Ingår i: RSC Advances. - : ROYAL SOC CHEMISTRY. - 2046-2069. ; 8:63, s. 36323-36330
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Tidskriftsartikel (refereegranskat)abstract
- The long duration of a working device with a limited battery capacity requires gas sensors with low power consumption. A self-heated gas sensor is a highly promising candidate to satisfy this requirement. In this study, two gas sensors with sparse and dense SnO2 nanowire (NW) networks were investigated under the Joule heating effect at the nanojunction. Results showed that the local heating nanojunction was effective for NO2 sensing but generally not for reduction gases. At 1 W, the sparse NW sensor showed a good sensing performance to the NO2 gas. The dense SnO2 NW network required a high-power supply for gas-sensitive activation, but was suitable for reduction gases. A power of approximately 500 W was also needed for a fast recovery time. Notably, the dense NW sensor can response to ethanol and H2S gases. Results also showed that the self-heated sensors were simple in design and reproducible in terms of the fabrication process.
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| 7. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Controllable growth of ZnO nanowires grown on discrete islands of Au catalyst for realization of planar-type micro gas sensors
- 2014
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 193, s. 888-894
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Tidskriftsartikel (refereegranskat)abstract
- The proper engineering design of gas sensors and the controlled synthesis of sensing materials for the high-performance detection of toxic gas are very important in the fabrication of handheld devices. In this study, an effective design for gas sensor chips is developed to control the formation of grown ZnO nanowires (NWs).The design utilizes the dendrite islands of Au catalyst deposited on and between Pt electrodes of a planar-type micro gas sensor so that NWs can grow on instead of a continuous Au seed layer. This method results in an increase of NW-NW junctions on the device and also eliminates current leakage through the seed layer, which results in a higher sensitivity. The results show that the developed gas-sensing devices could be used to monitor NO2 at moderate temperature (~250 °C) and/or ethanol at a high temperature (~400 °C).
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| 8. |
- Nguyen, Xuan Thai, et al.
(författare)
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Gas sensor array based on tin oxide nano structure for volatile organic compounds detection
- 2020
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Ingår i: Vietnam Journal of Science and Technology. - : Vietnam Academy of Science and Technology. - 2525-2518. ; 58:2, s. 189-196
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Tidskriftsartikel (refereegranskat)abstract
- The detection of volatile organic compounds (VOCs) is essential in practicalapplication in breath analysis. Thus, gas sensors based on metal oxide have been fabricated, butthey lacked selectivity. One approach to resolve this task is to use an array of highly sensitiveand selective sensors as an electronic nose. Here a gas sensor array based on Tin oxide nanostructurewith temperature modulation techniques was presented. A Platinum micro-heater isaccompanied with the array gas sensor. The gas sensor array was composed of five singlesensors, and that single sensor is located at different site from the micro heater and works atdifferent temperatures. The gas sensing properties of the gas array sensors were investigatedwith VOC gases such as Ethanol, Methanol, Iso-propanol, and Acetone as well as NH3, H2, andH2S. We also confirm the good selectivity of the array sensor for Ethanol, Methanol, Isopropanol,Acetone, NH3, H2, and H2S by using radar graphic method.
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| 9. |
- Nguyet, To Thi, et al.
(författare)
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Enhanced response characteristics of NO2 gas sensor based on ultrathin SnS2 nanoplates : Experimental and DFT study
- 2024
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier. - 0924-4247 .- 1873-3069. ; 373
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Tidskriftsartikel (refereegranskat)abstract
- Layered-metal dichalcogenides with extraordinary characteristics of vast surface area, tunable bandgap and superior adsorption capability enable the potential for application in gas sensors. However, the synthesis of effective material for enhanced response performance remains a challenge. Herein, we exploited a fascinating sensitivity and selectivity towards NO2 gas detection using SnS2 nanoflakes prepared via the hydrothermal method. SnS2 nanoflakes with a thickness of 25 nm and an average diameter of approximately 500 nm show the potential for the detection of NO2 gas at low concentrations of ppb levels. The sensing properties of the SnS2 sensors were investigated for different concentrations of NO2 at various operating temperatures. The sensor exhibits the highest gas-sensing response of 161 at 250 οC upon exposure to 5 ppm of NO2 gas with fast response and recovery times. In addition, the sensor shows excellent selectivity with a low detection limit of ppb level. The electronic structure and gas-sensing mechanism are elucidated via finding density of states, charge density, and band structure based on DFT study which is calculated by the Vienna ab-initio simulation package (VASP). The considerable small adsorption energy reveals a physisorption of the NO2 molecules on the SnS2 surface (-0.174 eV), indicating the SnS2 nanoflakes are intriguing candidates for the speedy detection of NO2 gas.
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| 10. |
- Son, Dang Ngoc, et al.
(författare)
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A novel design and fabrication of self-heated In2O3 nanowire gas sensor on for ethanol detection
- 2022
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Ingår i: Sensors and Actuators A-Physical. - : Elsevier. - 0924-4247 .- 1873-3069. ; 345
-
Tidskriftsartikel (refereegranskat)abstract
- Many attempts have been made on the design and fabrication of low-power consumption gas sensor for application on the Internet of Things and portable devices. The performance of gas sensors includes sensitivity, selectivity, and power consumption, which are strongly dependent on the configuration of the device such as the gap size between two electrodes, the sensing material, and operation principle. Here, self-heated In2O3 nanowire-based gas sensors were designed and fabricated by on-chip growth technique via thermal evaporation to work at room temperature. The effect of electrode gap (10-40 mu m) on the power consumption and gas sensing performance of the In2O3 nanowire sensors was studied. With the large gap of 40 mu m, the sensor exhibited excellent sensing characteristics of low power consumption (1.06 mW) with ability to detect ethanol gas down to 20 ppm effectively. We also examined the role of nanowire conductivity in the performance of the self-heated sensor in the detection of reducing gas. The sensor demonstrated rapid response and recovery times of less than a minute, exceptional stability, and remarkable recovery.
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| 11. |
- Thai, Nguyen Xuan, et al.
(författare)
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Prototype edge-grown nanowire sensor array for the real-time monitoring and classification of multiple gases
- 2020
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Ingår i: JOURNAL OF SCIENCE-ADVANCED MATERIALS AND DEVICES. - : VIETNAM NATL UNIV. - 2468-2284 .- 2468-2179. ; 5:3, s. 409-416
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Tidskriftsartikel (refereegranskat)abstract
- The monitoring and classification of different gases using a single resistive semiconductor sensor are challenging because of the similar response characteristics. An array of separated sensors can be used as an electronic nose, but such arrays have a bulky structure and complex fabrication processes. Herein, we easily fabricated a gas-sensor array based on edge-grown SnO2 nanowires for the real-time monitoring and classification of multiple gases. The array comprised four sensors and was designed on a glass substrate. SnO2 nanowires were grown on-chip from the edge of electrodes, made contact together, and acted as sensing elements. This method was advantageous over the post-synthesis technique because the SnO2 nanowires were directly grown from the edge of the electrodes rather than on the surface. Accordingly, damage to the electrode was avoided by alloying Sn with Pt at a high growth temperature. The sensing characteristics of the sensor array were further examined for different gases, including methanol, isopropanol, ethanol, ammonia, hydrogen sulphide and hydrogen. Radar plots were used to improve the selective detection of different gases and enable effective classification. (C) 2020 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.
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| 12. |
- Thai, Nguyen Xuan, et al.
(författare)
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Realization of a portable H2S sensing instrument based on SnO2 nanowires
- 2020
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Ingår i: Journal of Science: Advanced Materials and Devices. - : Elsevier BV. - 2468-2284 .- 2468-2179. ; 5:1, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring of toxic gas in air is important because air pollution, especially in developing countries, has rapidly become severe. The high cost of installation and maintenance of a stationary analysis system by using methods such as gas chromatography limits its applications. Low-power, portable devices with relatively low-cost gas sensors are effective for mapping pollution levels in real-time in urban areas and in other living environmentts. Herein, the realization of a portable H2S sensing instrument based on SnO2 nanowires is reported. The sensor chip was prepared by the on-chip growth of SnO2 nanowires directly from the edges of Pt electrodes. The electronic system and software for signal acquisition, data processing, data storage, and output of the instrument were developed. A prototype for zero series of the instrument was also realized. The instrument is capable of monitoring H2S gas in air at ppm level and in biogas production with satisfation.
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| 13. |
- Duoc, Vo Thanh, et al.
(författare)
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New Design of ZnO Nanorod- and Nanowire-Based NO2 Room-Temperature Sensors Prepared by Hydrothermal Method
- 2019
-
Ingår i: Journal of Nanomaterials. - : HINDAWI LTD. - 1687-4110 .- 1687-4129.
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Tidskriftsartikel (refereegranskat)abstract
- Room-temperature gas sensors are attracting attention because of their low power consumption, safe operation, and long-term stability. Herein, ZnO nanorods (NRs) and nanowires (NWs) were on-chip grown via a facile hydrothermal method and used for room-temperature NO2 gas sensor applications. The ZnO NRs were obtained by a one-step hydrothermal process, whereas the NWs were obtained by a two-step hydrothermal process. To obtain ZnO NW sensor, the length of NRs was controlled short enough so that none of the nanorod-nanorod junction was made. Thereafter, the NWs were grown from the tips of no-contact NRs to form nanowire-nanowire junctions. The gas-sensing characteristics of ZnO NRs and NWs were tested against NO2 gas at room temperature for comparison. The gas-sensing characteristics of the sensors were also tested at different applied voltages to evaluate the effect of the self-activated gas-sensing performance. Results show that the diameter of ZnO NRs and NWs is the dominant parameter of their NO2 gas-sensing performance at room temperature. In addition, self-activation by local heating occurred for both sensors, but because the NWs were smaller and sparser than the NRs, local heating thus required a lower applied voltage with maximal response compared with the NRs.
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| 14. |
- Duoc, Vo Thanh, et al.
(författare)
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Room temperature highly toxic NO2 gas sensors based on rootstock/scion nanowires of SnO2/ZnO, ZnO/SnO2, SnO2/SnO2 and, ZnO/ZnO
- 2021
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 348
-
Tidskriftsartikel (refereegranskat)abstract
- Grafted structures between SnO2 and ZnO nanowires were realized in a two-step process of growth. First, the rootstocks of SnO2 or ZnO nanowires were synthesized by thermal evaporation technique. Second, a thin Au layer was sputter deposited on the sample and synthesis of nanowire scions of ZnO or SnO2, respectively, on the rootstocks was realized by thermal evaporation technique again. In both growth steps, SnO2 powder or a mixture of ZnO and carbon powders was use as source materials for the synthesis. Different rootstock/scion combinations of SnO2/ZnO, ZnO/SnO2 nanowires (called heterostructures) and ZnO/ZnO, SnO2/SnO2 nanowires (called homostructures) were synthesised. The fabricated grafted nanowires were examined by field-emission scanning electron microscope and their compositions were analyzed by energy dispersive spectroscopy and X-ray diffraction analysis. The test results indicate that this type of nanostructure material is very promising for NO2 gas sensing at ppt level at room temperature. Among the fabricated structures the SnO2/ZnO nanowires showed the best sensing performance with the high sensitivity and fast response and recovery time. We also discussed the gas sensing mechanism of the fabricated sensors based on the band diagram.
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| 15. |
- Tan, Ha Minh, 1989-, et al.
(författare)
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Novel Self-Heated Gas Sensors Using on-Chip Networked Nanowires with Ultralow Power Consumption
- 2017
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9, s. 6153-6162
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Tidskriftsartikel (refereegranskat)abstract
- The length of single crystalline nanowires (NWs) offers aperfect pathway for electron transfer, while the small diameter of the NWshampers thermal losses to tje environment, substrate, and metal electrodes.Therefore, Joule self-heating effect is nearly ideal for operating NW gassensors at ultralow power consumption, without additional heaters. Therealization of the self-heated NW sensors using the “pick and place”approach is complex, hardly reproducible, low yield, and not applicable formass production. Here, we present the sensing capability of the self-heatednetworked SnO2 NWs effectively prepared by on-chip growth. Ourdeveloped self-heated sensors exhibit a good response of 25.6 to 2.5 ppmNO2 gas, while the response to 500 ppm H2, 100 ppm NH3, 100 ppm H2S,and 500 ppm C2H5OH is very low, indicating the good selectivity of thesensors to NO2 gas. Furthermore, the detection limit is very low, down to 82parts-per-trillion. As-obtained sensing performance under self-heating modeis nearly identical to that under external heating mode. While the power consumption under self-heating mode is extremely low,around hundreds of microwatts, as scaled-down the size of the electrode is below 10 μm. The selectivity of the sensors can becontrolled simply by tuning the loading power that enables simple detection of NO2 in mixed gases. Remarkable performancetogether with a significantly facile fabrication process of the present sensors enhances the potential application of NW sensors innext generation technologies such as electronic noses, the Internet of Things, and smartphone sensing.
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| 16. |
- Thai, Nguyen Xuan, et al.
(författare)
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Multi gas sensors using one nanomaterial, temperature gradient, and machine learning algorithms for discrimination of gases and their concentration
- 2020
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Ingår i: Analytica Chimica Acta. - : ELSEVIER. - 0003-2670 .- 1873-4324. ; 1124, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- In this work, four identical micro sensors on the same chip with noble metal decorated tin oxide nanowires as gas sensing material were located at different distances from an integrated heater to work at different temperatures. Their responses are combined in highly informative 4D points that can qualitatively (gas recognition) and quantitatively (concentration estimate) discriminate all the tested gases. Two identical chips were fabricated with tin oxide (SnO2) nanowires decorated with different metal nanoparticles: one decorated with Ag nanoparticles and one with Pt nanoparticles. Support Vector Machine was used as the "brain" of the sensing system. The results show that the systems using these multisensor chips were capable of achieving perfect classification (100%) and good estimation of the concentration of tested gases (errors in the range 8-28%). The Ag decorated sensors did not have a preferential gas, while Pt decorated sensors showed a lower error towards acetone, hydrogen and ammonia. Combination of the two sensor chips improved the overall estimation of gas concentrations, but the individual sensor chips were better for some specific target gases. (C) 2020 Elsevier B.V. All rights reserved.
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| 17. |
- Tonezzer, Matteo, et al.
(författare)
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Miniaturized multisensor system with a thermal gradient : Performance beyond the calibration range
- 2023
-
Ingår i: Journal of Science: Advanced Materials and Devices. - : Elsevier BV. - 2468-2179. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Two microchips, each with four identical microstructured sensors using SnO2 nanowires as sensingmaterial (one chip decorated with Ag nanoparticles, the other with Pt nanoparticles), were used as anano-electronic nose to distinguish five different gases and estimate their concentrations. This innovativeapproach uses identical sensors working at different operating temperatures thanks to the thermalgradient created by an integrated microheater. A system with in-house developed hardware and softwarewas used to collect signals from the eight sensors and combine them into eight-dimensional data vectors. These vectors were processed with a support vector machine allowing for qualitative and quantitativediscrimination of all gases after calibration. The system worked perfectly within the calibrated range(100% correct classification, 6.9% average error on concentration value). This work focuses on minimizingthe number of points needed for calibration while maintaining good sensor performance, both forclassification and error in estimating concentration. Therefore, the calibration range (in terms of gasconcentration) was gradually reduced and further tests were performed with concentrations outsidethese new reduced limits. Although with only a few training points, down to just two per gas, the systemperformed well with 96% correct classifications and 31.7% average error for the gases at concentrationsup to 25 times higher than its calibration range. At very low concentrations, down to 20 times lower thanthe calibration range, the system worked less well, with 93% correct classifications and 38.6% averageerror, probably due to proximity to the limit of detection of the sensors.
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| 18. |
- Trinh, Minh Ngoc, 1978-, et al.
(författare)
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Effective design and fabrication of low-power-consumption self-heated SnO2 nanowire sensors for reducing gases
- 2019
-
Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 295, s. 144-152
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Tidskriftsartikel (refereegranskat)abstract
- Developing metal oxide gas sensors for internet-of-things (IoT) and portable applications require low-power consumption because of the limited battery in devices. This requirement is challenging because metal oxide sensors generally need high working temperatures, especially for reducing gases. Herein, we present an effective design and fabrication method of a SnO2 nanowire (NW) sensor for reducing gases by using the Joule heating effect at NW nanojunctions without needing an external or integrated heater. The sensor’s low-power consumption at around 4 mW was controlled by the size and nanojunction density of the device. The sensor has a simple design and is easy to fabricate. A proof-of-concept of a portable gas sensor module can be realised for monitoring highly toxic reducing gases, such as H 2S, NH3 and C2H5OH, by using the developed self-heated NWs.
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| 19. |
- Trinh, Minh Ngoc, 1978-, et al.
(författare)
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Self-heated Ag-decorated SnO2 nanowires with low power consumption used as a predictive virtual multisensor for H2S-selective sensing
- 2019
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 1069, s. 108-116
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Tidskriftsartikel (refereegranskat)abstract
- Multisensor systems with low-power consumption are emerging for the Internet of Things. In this work, we demonstrate the use of self-heated networked Ag-decorated SnO2 NW sensors integrated into a portable module for selective detection of H2S gas at low power consumption, and the integrated system is simulated as a virtual multisensor under varying heating powers for identifying and quantifying different reducing gases. The H2S gas-sensing characterisations at the different self-heating powers of 2–10 mW showed that the gas response significantly increased with the increase in Ag density decoration and the heated power strongly affected the gas-sensing performance and sensor stability. Excellent response of 21.2 to 0.5 ppm H2S gas was obtained at a low heating power of 2 mW with an acceptable response/recovery time of 18/980 s. The increase of the heating power over 20 mW can destroy the devices. The integrated system could selectively detect H2S at the heating power below 4 mW and H2, C2H5OH and NH3gases at the heating power upon 4 mW. The virtual multisensor could discriminate qualitatively (with an accuracy of 100%) and quantitatively H2S, H2, NH3, C2H5OH (Ethanol) and CH3COCH3 (Aceton) gases with average errors of 13.5%, 14.7%, 16.8%, 16.9%, and 14.8%, respectively. The proposed sensing platform is a promising candidate for selective detection of H2S gas and virtual multisensor with low power consumption for mobile or wireless network devices.
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| 20. |
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A design of high performance gas sensor array withdiscrete islands of Au catalyst for increasing of ZnO nanowire junctions
- 2013
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Proceedings (redaktörskap) (refereegranskat)abstract
- In this study, an effective design for growth of ZnO nanowires directly on gas sensor chips is introduced. The design utilizes the dendrite islands of Au catalyst deposited between and on the Pt electrodes for the nanowires to grow on instead of a continuous seed layer or Au film. This lead to an increase of the nanowirenanowire junctions in the devices, as well as a reduction of the leak current that would occur through the mentioned alternative seed layer; resulting in a higher sensitivity. The results showed that the developed gas sensors could be used for monitoring of NO2 at low concentration.
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| 21. |
- Chu Manh, Hung, et al.
(författare)
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ZnO coral-like nanoplates decorated with Pd nanoparticles for enhanced VOC gas sensing
- 2021
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Ingår i: Journal of Science: Advanced Materials and Devices. - Hanoi, Vietnam : Elsevier. - 2468-2284 .- 2468-2179. ; 6:3, s. 453-461
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Tidskriftsartikel (refereegranskat)abstract
- A high working temperature of the ZnO nanomaterial-based gas sensor could shorten the lifetime of the sensor and increase its power consumption. Enhancing the volatile organic compound (VOC) sensing performance of ZnO nanomaterial-based gas sensors in terms of gas response and temperature is vital for their practical application. Decoration of noble metals onto nanostructures is an effective approach for improving their sensing characteristics. Herein, hydrothermally synthesized ZnO coral-like nanoplates decorated with Pd nanoparticles are introduced to achieve the improved VOC sensing performance. The morphology, crystal structure, composition, atomic structure, and gas sensing properties of the synthesized pristine and Pd–ZnO coral-like nanoplates were investigated. The results showed a remarkable reduction of optimal working temperature from 450 °C for the pristine ZnO based sensor to 350 °C for the Pd–ZnO based sensor. The sensor response to acetone at the optimal operating temperature of 350 °C was improved three times by surface decoration with Pd nanoparticles. The response time and recovery time of the Pd–ZnO sensor were about three times faster than that of the pristine ZnO sensor. The Pd–ZnO sensor reached a theoretical detection limit of 17 ppt and a sensitivity of 3.5–2.5 ppm acetone at 350 °C. The sensor transient stability after several on/off switching cycles from air to gas revealed the effective reusability of the fabricated devices. A plausible mechanism for the VOC sensing of the porous Pd–ZnO coral-like nanoplate-based sensor is also discussed.
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| 22. |
- Chu Thi, Quy, et al.
(författare)
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Ethanol-Sensing Characteristics of Nanostructured ZnO: Nanorods, Nanowires, and Porous Nanoparticles
- 2017
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; , s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The morphology and crystalline size of metal oxide-sensing materials arebelieved to have a strong influence on the performance of gas sensors. In thispaper, we report a comparative study on the ethanol-sensing characteristics ofZnO nanorods, nanowires, and porous nanoparticles. The porous ZnOnanoparticles were prepared using a simple thermal decomposition of a sheetlikehydrozincite, whereas the nanorods and nanowires were grown byhydrothermal and chemical vapor deposition methods, respectively. Themorphology and crystal structure of the synthesized materials were characterizedby field-emission scanning electron microscopy and x-ray diffraction.Ethanol gas-sensing characteristics were systematically studied at differenttemperatures. Our findings show that for ethanol gas-sensing applications,ZnO porous nanoparticles exhibited the best sensitivity, followed by thenanowires and nanorods. Gas-sensing properties were also examined withrespect to the role of crystal growth orientation, crystal size, and porosity.
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| 23. |
- Duoc, Vo Thanh, et al.
(författare)
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Hydrogen gas sensor based on self-heating effect of SnO2/Pt thin film with ultralow power consumption
- 2024
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Ingår i: International journal of hydrogen energy. - : Elsevier. - 0360-3199 .- 1879-3487. ; 61, s. 774-782
-
Tidskriftsartikel (refereegranskat)abstract
- Self-heating of sensing elements on gas sensors is an effective solution to avoid using external heaters. In this paper, a self-heated hydrogen gas sensor is presented. The sensor was created using the DC sputtering method, which involved fabricating it on a thermal-insulating Kapton flexible substrate. This process utilized a thin film of SnO2 with thick 50 nm that was modified with nanoclusters of Pt, serving as the sensing material. The SnO2/Pt material film was analyzed for microstructure and composition by SEM, XRD, and XPS analysis. Infrared images show that the self-heating effect is mainly concentrated in the strip of gas-sensitive material. It showed many good performances, such as high sensitivity (able to detect down to 50 ppm of H2), good selectivity (poor response to CO, NH3, H2S, and NO2), the sensor's performance is little changed by environmental humidity, and low power consumption (89 μW at 5V). The sensor is also stable and low-cost, suitable for portable H2 detection devices due to its low generated heat and small size.
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| 24. |
- Duy, Nguyen Van, et al.
(författare)
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Enhancement of NH3 gas sensing with Ag-Pt co-catalyst on SnO2 nanofilm towards medical diagnosis
- 2023
-
Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 767
-
Tidskriftsartikel (refereegranskat)abstract
- Exhaled breath analysis is a noninvasive diagnostic method for fatal disease monitoring and screening, which is recently gained extensive interest of researchers worldwide emphasizing on the development of effective chemiresistive gas sensor for practical application. Here, the Ag-Pt bimetallic nanoparticles were used to deco-rate nanofilms of SnO2 making different gas sensors with high performance. We found that the bimetal alloy improved the sensor performance significantly with super sensitivity as compared with the separate Ag and Pt catalyst. The right ratio of the bimetal made the sensor very sensitive to NH3, so that it was able to quickly (12 s) detect 1 parts-per-million of NH3 with a response of 4.31 at a temperature of 250 degrees C. The sensor limit of detection for NH3 was less than 10 parts-per-billion. The response of the sensor was negligibly affected by humidity and interfering gases. The results showed that the tiny, robust, and inexpensive sensor developed in this work can be used in breath analysis for early diagnosis via NH3 monitoring.
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| 25. |
- Ngoc, Trinh Minh, 1978-, et al.
(författare)
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H2S Sensing Characteristics of Self-heated Ag-coated SnO2 nanowires
- 2017
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Ingår i: Proceeding of the 12th Asian Conference on Chemical Sensors (ACCS2017). - Hanoi. ; , s. 350-353
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The H2S gas sensing characterization of gas sensors based on the SnO2 nanowires network has been reported by several research groups. However, the self-heated gas sensor using Ag-coated SnO2 nanowires network for sensing H2S was investigated the first times. In this study, we will report on the effected of density SnO2 nanowires network on H2S sensitivity. The SnO2 nanowires network density can be controlled bythe distance between sensor electrodes. After SnO2 nanowires decorated with Ag, the results showt hat the H2S gas sensing properties depend on the density of the SnO2 nanowires network. Asthe density of SnO2 nanowires network increases, the response of sensors decreases. Thesensor can operate at as low power as 2 mW to H2S gas concentration of 0.25 ppm. The responseand recovery times of sensor are about 200 s. Moreover, working at low operating power gives us the benefit of energy saving as well as the elongation of lifetime.
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| 26. |
- Nguyen, Thi Quynh Hoa, et al.
(författare)
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Numerical study of a broadband metamaterial absorber using a single split circle ring and lumped resistors for X-band applications
- 2020
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- We report a numerical study on the design of a broadband metamaterial absorber (MMA) with a single layer of metal-dielectric-metal based on an FR-4 substrate for X-band applications. The MMA structure consists of a periodic array of a split circle ring and lumped resistors coupled within split segments. The MMA structure achieves a broadband absorption response in the frequency range of 7.8-12.6 GHz with an absorptivity of above 90% under normal incidence for all polarization angles. The absorptivity remains above 70% in the frequency range of 6.8-11.8 GHz at wide incident angles from 0 degrees to 30 degrees for both transverse electric and transverse magnetic polarizations. The physical mechanism of the absorber is explained by the electric and the surface current distributions that, in turn, are significantly affected by magnetic resonance.
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| 27. |
- Nguyen, Thi Quynh Hoa, et al.
(författare)
-
Numerical study of a wide incident angle- and polarisation-insensitive microwave metamaterial absorber based on a symmetric flower structure
- 2019
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, we propose a wide incident angle- and polarisation-insensitive metamaterial absorber covered with structures comprising a metallic flower shape layer, a dielectric layer and a metallic ground plane. The influences of the structural parameters on the absorptivity are investigated numerically. The proposed absorber exhibits polarisation insensitivity as the number of symmetric petals of a flower shape reaches as high as 4, 6 and 8. Particularly, the absorber based on 8 petals shows an absorptivity of above 90% for wide incident angles up to 70° under transverse electric and transverse magnetic polarisations. The physical mechanism of these observations is clarified by investigating the electric, power loss density and induced current distributions, which is also supported by the retrieved constitutive electromagnetic parameters. That is, the absorption phenomenon is considerably affected by magnetic resonance. By modifying the petals into hollow shapes, the absorber becomes effective in confining the magnetic resonance and can thus minimise the resonant frequency variation to 0.22% without affecting the absorption performance. In comparison with other reported metamaterial absorbers, our design shows considerable practical feasibility in terms of resonant frequency stability, wide incident angle and polarisation insensitivity, thereby making it suitable for various applications in microwave frequency region.
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| 28. |
- Tan, Ha Minh, 1989-, et al.
(författare)
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Self-heating Effect on Tin Oxide Nanowire Network Gas Sensor
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Self-heated gas sensors have attracted much of interests owing to the ultra-low power consumption as well as simple device fabrication. However, it still requires further improvement to overcome some technical difficulties such as high operation voltage, long-term stability, and mass production. In this work, we propose a nanowire nework structure to solve these problems. The self-heating effect on fabricated structures was tested and working temperature was evaluated by base resistance measurement and infrared emission microscopy methods. The fabricated sensor consumed an electric power of about 40 mW to reach the working temperature up to 250 oC. The NO2 sensing properties were initially studied on this sensor structure.
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| 29. |
- Van Duy, Lai, et al.
(författare)
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Room Temperature Ammonia Gas Sensor Based on p-Type-like V2O5 Nanosheets towards Food Spoilage Monitoring
- 2023
-
Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 13:1, s. 146-146
-
Tidskriftsartikel (refereegranskat)abstract
- Gas sensors play an important role in many areas of human life, including the monitoring of production processes, occupational safety, food quality assessment, and air pollution monitoring. Therefore, the need for gas sensors to monitor hazardous gases, such as ammonia, at low operating temperatures has become increasingly important in many fields. Sensitivity, selectivity, low cost, and ease of production are crucial characteristics for creating a capillary network of sensors for the protection of the environment and human health. However, developing gas sensors that are not only efficient but also small and inexpensive and therefore integrable into everyday life is a difficult challenge. In this paper, we report on a resistive sensor for ammonia detection based on thin V2O5 nanosheets operating at room temperature. The small thickness and porosity of the V2O5 nanosheets give the sensors good performance for sensing ammonia at room temperature (RT), with a relative change of resistance of 9.4% to 5 ppm ammonia (NH3) and an estimated detection limit of 0.4 ppm. The sensor is selective with respect to the seven interferents tested; it is repeatable and stable over the long term (four months). Although V2O5 is generally an n-type semiconductor, in this case the nanosheets show a p-type semiconductor behavior, and thus a possible sensing mechanism is proposed. The device’s performance, along with its size, low cost, and low power consumption, makes it a good candidate for monitoring freshness and spoilage along the food supply chain.Keywords: gas sensor; vanadium pentoxide; ammonia; nanosheet; room temperature; food quality
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| 30. |
- Hoa, Nguyen Thi Quynh, et al.
(författare)
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Numerical Study of a Wide-Angle and Polarization-Insensitive Ultrabroadband Metamaterial Absorber in Visible and Near-Infrared Region
- 2019
-
Ingår i: IEEE Photonics Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1943-0655. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- An ultrabroadband metamaterial absorber structure based on a periodic array of metallic-dielectric multilayered conical frustums is numerically investigated and proposed. The metamaterial absorber indicated an absorptivity of higher than 90%, which covered the visible and near-infrared region at 480-1480 nm, and a relative absorption bandwidth of 102%. The high absorptivity can be maintained with large incident angles up to 60 degrees under both transverse electric and transverse magnetic polarizations. Furthermore, the proposed absorber exhibits polarization insensitivity owing to its rotational symmetry structure. Compared with the previously reported ultrabroadband metamaterial absorbers, the design in this work indicates high practical feasibility in terms of a compact structure for a large bandwidth, a wide incident angle, and polarization insensitivity, thereby suggesting its promising application, for example, in solar cells and thermal emitters.
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| 31. |
- Vu Trong, Thu, 1982-, et al.
(författare)
-
Tiềm năng lớn của vệ tinh siêu nhỏ đáp ứng nhu cầuquản lý hàng hải của Việt Nam
- 2011
-
Ingår i: REV/ComNaVi-11, Workshop on Communications and Navigations for the Development of Vietnam's Marine Economy, Da Nang city Vietnam, August 2-4, 2011.
-
Konferensbidrag (refereegranskat)abstract
- Trong 10 năm gần đây, loại vệ tinh siêu nhỏ có kích thước 10x10x10 cm và trọng lượng 1 kg với tên gọi CubeSat từ công cụ thực hành của sinh viên đại học đang dần trở thành nền tảng cho những vệ tinh có khả năng ứng dụng trong thực tiễn. Ngày nay, người sử dụng có thể tự thiết kế hoặc mua sẵn linh kiện điện tử và cơ khí lắp thành vệ tinh cỡ 1, 2, 3... kg với các tính năng mong muốn. Ưu điểm của loại vệ tinh siêu nhỏ này là thời gian chế tạo ngắn, chi phí thấp và càng phát huy năng lực khi sử dụng cả một chùm vệ tinh. Nhờ có thể thích hợp hóa dễ dàng với từng nhu cầu thực tiễn và nhờ những tiến bộ nhanh chóng trong lĩnh vực điện tử và công nghệ thu nhỏ các hệ thống cảm ứng, nhiều nhu cầu quản lý hàng hải của Việt Nam được đánh giá là khả thi ngay trong thời điểm hiện tại. Nhiều trường đại học trên thế giới đã sử dụng thành công vệ tinh siêu nhỏ trong các chương trình viễn thám và khoa học vũ trụ. Gần đây, Trường đại học FPT cộng tác với Đại học Uppsala Thụy Điển đã đưa ra ý tưởng sử dụng loại vệ tinh này trong công tác quản lý hàng hải Việt Nam và đã được Trường đại học Tokyo, Nhật Bản tuyển chọn, mời sang trình bày đề án tại hội thảo “2nd Nano-satellite symposium” ngày 13-15/3/2011. Nói tóm tắt, đây là đề án dùng chùm vệ tinh siêu nhỏ loại 3kg có trang bị máy thu tín hiệu định vị (AIS) của tàu thuyền lưu thông trên biển, nhằm hỗ trợ công tác quản lý hàng hải và tìm kiếm, cứu nạn. Bài viết này đề cập đến loại vệ tinh siêu nhỏ CubeSat có thể áp dụng cho các nhu cầu thiết thực của Việt Nam, đồng thời cũng trình bày về đề án theo dõi sự di chuyển của tàu biển từ vệ tinh làm ví dụ điển hình cho thấy tiềm năng lớn của vệ tinh siêu nhỏ đáp ứng nhu cầu quản lý hàng hải hiện nay của đất nước.
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| 32. |
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| 33. |
- Carter, Sarah-Sophia, 1994-, et al.
(författare)
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Medical grade titanium on-chip : assessing the biological properties of biomaterials for bone regeneration
- 2019
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Medical grade titanium on-chip: assessing the biological properties of biomaterials for bone regeneration Sarah-Sophia D. Carter1, Hugo Nguyen2, Milena Moreira1, Maria Tenje1, and Gemma Mestres11Department of Engineering Sciences, Science for Life Laboratory, Uppsala University, Sweden2Department of Engineering Sciences, Uppsala University, Sweden IntroductionBefore entering the clinic, biomaterials need to be thoroughly evaluated, which requires accurate in vitro models. In this work, we have developed a microfluidic device that could be used to assess the biological properties of biomaterials, in a more in vivo-like environment than what is currently possible. MethodsOur device consists of a polydimethylsiloxane (PDMS, Sylgard 184) microfluidic channel (l= 6 mm, w= 2 mm, h= 200 µm) and a titanium disc (Ti6Al4V, at bottom), held together by an additively manufactured fixture (Fig. 1A). PDMS was cured overnight at 65°C on a silicon wafer master. Once the microchannel and titanium disc were positioned, MC3T3-E1 pre-osteoblast-like cells were seeded (50,000 cells/cm2). After 5 hours incubation under standard culture conditions, flow was started (2 μl/min). As a control, MC3T3-E1 cells were seeded onto plain titanium discs off-chip. Cell viability and morphology were assessed after 20 hours by calcein-AM/propidium iodide (PI), staining live and dead cells respectively. Results and discussionFigure 1B and 1C show calcein-AM/PI stained MC3T3-E1 cells cultured on-chip and figure 1D shows the control, MC3T3-E1 cells cultured off-chip. The potential to culture cells in our chip was confirmed by the presence of a majority of viable cells (green) with a similar morphology as the control sample. The reason for the increased amount of dead cells (red) on-chip compared to the control needs to be further examined, which requires longer-term experiments.ConclusionWe have set the first steps towards a microfluidic tool for the assessment of biological properties of biomaterials.
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| 34. |
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| 35. |
- Nguyen, Hugo, 1955-, et al.
(författare)
-
A heavily miniaturized submersible : a terrestrial kickoff
- 2008
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Ingår i: Proceedings of ASTRA 2008. ; , s. 1-9
-
Konferensbidrag (refereegranskat)abstract
- The vision of exploring extraterrestrial water findings employing a remotely operated submersible, as proposed by JPL/NASA for the investigation of the possible ocean underneath the frozen crust of Jupiter’s moon Europa, is now taking a step further into fulfilment. The Ångström Space Technology Centre has developed a sophisticated vehicle concept based on microtechnology for most of the navigational systems and payload systems. This enables a high function density, and a compact vehicle with a diameter of 50 mm and length of 200 mm, i.e. an overall size allowing the vehicle to be deployed through a borehole like that typical for arctic drilling.Here, the system architecture of the vehicle complying with the requirements on manoeuvrability, operational functions, and mission objectives is presented. In short, the vehicle in the first version will operate in deep and narrow waters, and will be equipped with a camera, sonar imaging system, an electronic tongue for chemical sampling, and a Conductivity-Temperature-Depth (CTD) sensor. Although the vehicle will be given certain autonomy in later versions, the first edition will rely on remote manual guidance. Commands for this, as well as power download, and data upload will be communicated through an optic fibre.The objective of this contribution is to present, for the first time, the status of the project including, briefly, the first results from miniaturized sonar, the vehicle bus design, and the design, realization and testing of the propulsion and attitude control systems differing in manoeuvrability, weight/volume, redundancy and efficiency.
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| 36. |
- Nguyen, Hugo, 1955-, et al.
(författare)
-
Heavily Miniaturized Submersible – A Terrestrial Kickoff
- 2008
-
Ingår i: Heavily Miniaturized Submersible – A Terrestrial Kickoff. ; , s. S14-01
-
Konferensbidrag (refereegranskat)abstract
- The vision of exploring extraterrestrial water findings employing a remotely operated submersible, as proposed by JPL/NASA for the investigation of the possible ocean underneath the frozen crust of Jupiter’s moon Europa, is now taking a step further into fulfilment. The Ångström Space Technology Centre has developed a sophisticated vehicle concept based on microtechnology for most of the navigational systems and payload systems. This enables a high function density, and a compact vehicle with a diameter of 50 mm and length of 200 mm, i.e. an overall size allowing the vehicle to be deployed through a borehole like that typical for arctic drilling.Here, the system architecture of the vehicle complying with the requirements on manoeuvrability, operational functions, and mission objectives is presented. In short, the vehicle in the first version will operate in deep and narrow waters, and will be equipped with a camera, sonar imaging system, an electronic tongue for chemical sampling, and a Conductivity-Temperature-Depth (CTD) sensor. Although the vehicle will be given certain autonomy in later versions, the first edition will rely on remote manual guidance. Commands for this, as well as power download, and data upload will be communicated through an optic fibre.The objective of this contribution is to present, for the first time, the status of the project including, briefly, the first results from miniaturized sonar, the vehicle bus design, and the design, realization and testing of the propulsion and attitude control systems differing in manoeuvrability, weight/volume, redundancy and efficiency.
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| 37. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Material- and fabrication-governed performance of a tunnelling magnetometer
- 2010
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Ingår i: Advances in Natural Sciences. - : Institute of Physics (IOP). - 2043-6254 .- 2043-6262. ; 1:4, s. 045006-
-
Tidskriftsartikel (refereegranskat)abstract
- Miniaturization of sensitive magnetic sensors for nano- and picosatellites has come to the point where the traditional sensors with magnetic coils soon can be replaced. Thin film technology offers the possibility of making extremely small magnetic field sensors that employ the effect of anisotropic, giant and tunneling magnetoresistance (AMR, GMR and TMR). In this paper, the development status of sensors based on microelectromechanical systems technology (MEMS), starting from a TMR layer structure is presented. The sensors have been successfully fabricated and integrated onto an electronic circuit designed for space application. The system as a whole, and the sensors in particular, have not only been characterized with respect to sensitivity, resolution, and noise level, but also to launch vibration and space radiation. The sensor performance and limitations are strongly dependent on the deposited materials, sensor design, and fabrication process. Since the sensor elements are small and sensitive (with lateral dimensions of some tens of micrometres, and resolution of 100 pT at frequencies of MHz), they are also promising for other MEMS applications.
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| 38. |
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| 39. |
- Nguyen, Hugo, 1955-
(författare)
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Microsystem Interfaces for Space
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microsystem interfaces to the macroscopic surroundings and within the microsystems themselves are formidable challenges that this thesis makes an effort to overcome, specifically for enabling a spacecraft based entirely on microsystems. The NanoSpace-1 nanospacecraft is a full-fledged satellite design with mass below 10 kg. The high performance with respect to mass is enabled by a massive implementation of microsystem technology – the entire spacecraft structure is built from square silicon panels that allow for efficient microsystem integration. The panels comprise bonded silicon wafers, fitted with silicone rubber gaskets into aluminium frames. Each module of the spacecraft is added in a way that strengthens and stiffens the overall spacecraft structure. The structural integrity of the silicon module as a generic building block has been successfully proven. The basic design (silicon, silicone, aluminium) survived considerable mechanical loads, where the silicon material contributed significantly to the strength of the structural element. Structural modeling of the silicon building blocks enables rapid iterative design of e.g. spacecraft structures by the use of pertinent model simplifications. Other microsystem interfaces treats fluidic, thermal, and mechanical functions. First, solder sealing of microsystem cavities was demonstrated, using screen-printed solder and localized resistive heating in the microsystem interface. Second, a dismountable fluidic microsystem connector, using a ridged silicon membrane, intended for monopropellant thruster systems, was developed. Third, a thermally regulated microvalve for minute flows, made by a silicon ridge imprint in a stainless steel nipple, was investigated. Finally, particle filters for gas interfaces to microsystems, or between parts of fluidic microsystems, were made from sets of crossed v-grooves in the interface of a bonded silicon wafer stack. Filter manufacture, mass flow and pressure drop characterization, together with numeric modeling for filter design, was performed. All in all this reduces the weight and volume when microsystems are interfaced in their applications.
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| 40. |
- Nguyen, Hugo, 1955-, et al.
(författare)
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Tailoring the properties of a magnetic tunnel junction to be used as a magnetic field sensor
- 2011
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Ingår i: Conf. on solid state physics and materials VII (SPMS 2011), Ho Chi Minh, 7-9 November 2011.
-
Konferensbidrag (refereegranskat)abstract
- A magnetic tunnel junction (MTJ) can be used as an effective magnetic field sensor thank to its high magnetoresistance ratio. To be used as a magnetic field sensor in different applications, the possibility of tuning the performance of the MTJ is important. Different means of tuning, such as voltage and magnetic field biasing, can be used. In this work, an external magnetic field from a permanent magnet was used to bias the sensing layer of a MTJ along its hard axis, and the effect of the biasing on the sensitivity, detection limit, and hysteresis of the MTJ was investigated. The experiments showed that the hysteresis of the MTJ languished away at a certain applied magnetic field. Moreover, the sensitivity and noise level decreased, whereas the detection limit increased with increasing bias field strength. The motivation of this experiment is not only to find a power- and cost-effective method of tuning the MTJ, but also to study what happens with the sensing layer, and with electron transport within the MTJ when an external magnetic field is applied.
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| 41. |
- Persson, Anders, et al.
(författare)
-
Changing the attitude towards magnetoresistance
- 2011
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Ingår i: Changing the attitude towards magnetoresistance.
-
Konferensbidrag (refereegranskat)abstract
- Magnetometers are one of the most common instruments on spacecrafts. They are used for both satellite attitude determination and for scientific purposes, such as mapping of Earth’s magnetic field. The most common magnetometer for low-frequency applications is the fluxgate. High-end fluxgates are generally quite bulky, with a mass of around 1 kg, but there exist miniature version, weighing only around 100 g, but with worse noise figure. Interest in such miniature models has increased with the adaption of the Faster-Better-Cheaper philosophy, and the introduction of small satellite classes. However, downscaling of fluxgates beyond the present 100 g has proven difficult, wherefore other technologies have earned more and more interest, especially those employing different kinds of magnetoresistance.Here, a review of different magnetoresistive techniques, and their past, present and potential use in space is presented. Magnetoresistive sensors based on anisotropic, giant, and tunneling magnetoresistance is covered, and extra attention is directed towards sensors based on the planar Hall effect. The latter have the potential of overcoming some of the major disadvantages of other magnetoresistive sensors, such as poor detectivity at low frequencies, and the need for external biasing coils to improve linearity and reduce hysteresis by, e.g., set-reset protocols and magnetic feedback.Moreover, the design of two such planar Hall effect sensors is tailored to meet the requirements set on a magnetometer aimed for, firstly, attitude determination and, secondly, mapping of Earth’s magnetic field. It is concluded that planar Hall effect sensors is one of the prime candidates for the next generation of miniaturized low-frequency space magnetometers.
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| 42. |
- Persson, Anders, 1982-, et al.
(författare)
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Micro- and nanostructured magnetic field sensor for space applications
- 2009
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Ingår i: 15th International Conference on Solid-State SensorsTransducers 2009. ; , s. 1190-1193
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Konferensbidrag (refereegranskat)abstract
- Magnetometers are popular payloads on scientific space missions. Here, the design and fabrication process of a miniaturized magnetometer based on tunneling magnetoresistance is presented. The process is capable of making magnetic tunnel junctions in a wide size range, by employing both UV lithography and focused ion beam milling and deposition. Ga implantation in the ferromagnetic electrodes of the junction is studied in more detail. It was shown that Ga implantation may harm the magnetometer if the irradiation dose exceeds 1014 Ga+ cm-2.
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| 43. |
- Sahlberg, Arne, et al.
(författare)
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High-Resolution Liquid Alloy Patterning for Small Stretchable Strain Sensor Arrays
- 2018
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Ingår i: Advanced Materials Technologies. - : Wiley. - 2365-709X. ; 3:4
-
Tidskriftsartikel (refereegranskat)abstract
- Soft material applied technology has in recent years become more advanced, enabling for, e.g., soft robotics, skin electronics, and wearable systems. Yet, the processing technology of soft materials has not been sufficiently developed to create high performance in soft and stretchable systems, as compared to the processing technology of conventional electronics or electromechanical systems. Liquid alloys have shown excellent properties for soft and stretchable electrical interconnectors and conductors, which is a basic building block to produce electric or electromechanical systems. In order to overcome the limited resolution of previously developed liquid alloy patterning methods for large-area printed circuits, this work explores the possibility of employing shrinking substrates. By utilizing the characteristics of liquid alloys and elastomers the pattern resolution is improved through a stretch-shrink patterning (SSP) process. The process provides highly conductive liquid conductors of high resolution and can be combined with existing printing techniques for liquid alloys. The SSP process increases design flexibility of soft and stretchable systems that use liquid alloys and enables designs with finer and denser patterns, and cost-effective production for small scale systems.
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| 44. |
- Thorslund, Sara, et al.
(författare)
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A disposable and multifunctional capsule for easy operation of microfluidic elastomer systems
- 2011
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Ingår i: Journal of Micromechanics and Microengineering. - : Institute of Physics (IOP). - 0960-1317 .- 1361-6439. ; 21:12, s. 127001-
-
Tidskriftsartikel (refereegranskat)abstract
- The global lab-on-chip and microfluidic markets for cell-based assays have been predicted to grow considerably, as novel microfluidic systems enable cell biologists to perform in vitro experiments at an unprecedented level of experimental control. Nevertheless, microfluidic assays must, in order to compete with conventional assays, be made available at easily affordable costs, and in addition be made simple to operate for users having no previous experience with microfluidics. We have to this end developed a multifunctional microfluidic capsule that can be mass-produced at low cost in thermoplastic material. The capsule enables straightforward operation of elastomer inserts of optional design, here exemplified with insert designs for molecular gradient formation in microfluidic cell culture systems. The integrated macro–micro interface of the capsule ensures reliable connection of the elastomer fluidic structures to an external perfusion system. A separate compartment in the capsule filled with superabsorbent material is used for internal waste absorption. The capsule assembly process is made easy by integrated snap-fits, and samples within the closed capsule can be analyzed using both inverted and upright microscopes. Taken together, the capsule concept presented here could help accelerate the use of microfluidic-based biological assays in the life science sector.
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| 45. |
- Vu Trong, Thu, 1982-, et al.
(författare)
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Constellation of small quick-launch and self-deorbiting nano-satellites with AIS receivers for global ship traffic monitoring
- 2011
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Ingår i: 2nd Nano-Satellite Symposium, Tokyo, Japan, Mars 2011.
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Konferensbidrag (refereegranskat)abstract
- Since December 2004 the International Maritime Organization's International Convention for the Safety of Life at Sea requires that Automatic Identification System (AIS) has to be implemented on all international voyaging ships with gross tonnage of 300 or more tons, and on all passenger ships regardless of size. This stems from the need of collision avoidance, search-and-rescue operations and other maritime purposes. Ground-based AIS receiving station usually cannot cover ships over the horizon, but with space-based AIS signal receivers, the global ship monitoring became possible, providing data service for maritime administrations, cargo liners, and even navies. Since 2007, a number micro-satellites and nano-satellites have been launched for technical demonstration in this respect. However, at present the space-based global AIS data service is not fully operational and international cooperation is limited. In this paper, a constellation of 3 self-deorbiting nano-satellites, with a mass equivalent to 3U cubesats, carrying AIS receivers is proposed to complement the existing systems. The feasible study presented here showed that this mission can be realized at very low cost, and quick-launched. Three other important features of the mission are: international cooperation, making a practical use of smaller nano-satellites and taking the responsibility for deorbiting the satellites at the end of mission. It is also the hope that this mission will become a milestone that marks the maturity of smaller nanosats, and give the "student satellite" projects around the world a new dimension for real application and sustainable business application.
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