共查询到20条相似文献,搜索用时 15 毫秒
1.
Andrii BuvailoAuthor Vitae Yangjun XingAuthor VitaeJacqueline HinesAuthor Vitae Eric BorguetAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(1):444-449
Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) thin films, deposited on the surface of glass slides, were studied using transmission FTIR spectroscopy upon varying relative humidity (RH) from 2 to 70%. The obtained data revealed fast dynamics of water vapor adsorption-desorption with responses on the order of several seconds. Based on the fast FTIR signal intensity changes versus RH, it was proposed that a similar rapid response can be achieved for PVA and PVP coated SAW devices due to changes in mass-loading and film viscoelastic properties upon absorption of water vapor in the films. Sub-micron thickness films were spin-coated onto the surface of LiNbO3 SAW substrates. Both PVA and PVP based humidity sensors revealed prompt reversible response to variations in humidity, although PVP-based device demonstrated better sensor parameters with total insertion loss variation of about 50 dB over the studied RH range and response time 1.5 s for the humidity step 5-95% (recovery time - 2.5 s), representing one of the fastest SAW-based humidity sensors reported to date. 相似文献
2.
Lav R. KhotAuthor VitaeSuranjan PanigrahiAuthor Vitae Dongqing LinAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):1-10
In this study, the regioregular poly (3-hexyl thiophene) (rr-P3HT) based piezoelectric sensors were developed and evaluated to detect alcoholic volatile organic compounds (VOCs) associated with spoiled and Salmonella typhimurium contaminated packaged beef headspace. The drop coating technique was used to deposit thin films of rr-P3HT on both the sides of quartz crystal microbalance (QCM) electrode. The QCM polymer sensors were found to provide repeatable and reproducible sensor response to alcohol VOCs with a fast recovery (<2 min) at room temperature (25 °C). The principal component analysis on the sensors sensitivities was performed to discriminate the sensed alcohol VOCs, namely: 3-methyl-1-butanol from 1-hexanol. The QCM polymer sensors demonstrated selective response to low concentration of 3-methyl-1-butanol (average estimated lowest detection limit (LDL): 4.35 ppm) and to 1-hexanol (average estimated LDL: 3.20 ppm). The 30 days storage study performed on QCM sensors showed identical sensitivity responses for sensing 3-methyl-1-butanol and 1-hexanol at low concentrations. 相似文献
3.
Wan-Young Chung
Chang-Hyun Shim
Duk-Dong LeeSoon-Don Choi
《Sensors and actuators. B, Chemical》1994,20(2-3):139-143A silicon-based SnO2 gas sensor has been fabricated for monitoring liquified petroleum gas (LPG), commonly used as town gas. The gas sensor is made by silicon IC technology together with SnOf2 thin-film processing. The whole chip with a size of 9 mm x 9 mm consists of nine sensors (three by three array). each sensor is supported by a thin membrane of SiO2/Si3N4/SiO2 layers that provides a low thermal mass and prevents heat conduction through the surrounding substrate material. Tin oxide thin film is prepared by thermal evaporation of metallic tin granules and subsequent thermal oxidation of the metallic film at 600 °C. To form the SnO2(Pt) thin film, a layer of Pt with a thickness of several tens of angstroms is sputtered onto the tin oxide film and heat treated at 500 °C in air for several hours in order to stabilize its electrical response. The fabricated SnO2(Pt) microsensors exhibit about 85 and 92% sensitivities to 5000 ppm C3H8 and 5000 ppm C4H10 (the main components of LPG) at 250 °C, respectively, and show a rapid response time of less than 5 s. 相似文献
4.
Xiuming Changzhi Kemei Kun Zongbao K. Haiyang 《Sensors and actuators. B, Chemical》2008,134(1):258-265
Six imidazolium-based ionic liquids (ILs) were synthesized and employed as sensing materials coated on quartz crystal microbalance for the detection of organic vapors. Acetone, ethanol, dichloromethane, benzene, toluene and hexane were selected as representatives for common environmental pollutants, and good linear responses from 0 to 100% of concentrations were observed. The halogen-anion-containing imidazolium ILs-coated sensors showed fast response, excellent reversibility, and considerable sensitivity and selectivity towards alcohols, and the selective factors were up to 30 times for ethanol versus other VOCs. The existence of water vapor reduced the frequency response of the sensor, but a good linear relationship remained. 相似文献
5.
《Sensors and actuators. B, Chemical》2000,62(2):121-130
Preliminary testing of a prototype instrument employing an integrated array of six polymer-coated flexural plate wave (FPW) sensors and an adsorbent preconcentrator is described. Responses to thermally desorbed samples of individual organic solvent vapors and binary and ternary vapor mixtures are linear with concentration, and mixture responses are equivalent to the sums of the responses of the component vapors, which co-elute from the preconcentrator in most cases. Limits of detection as low as 0.3 ppm are achieved from a 60-s (34 cm3) air sample and peak widths at half-maximum range from 1 to 4 s. Tests at different flow rates suggest that the kinetics of vapor sorption in the sensor coating films may limit responses at higher flow rates, however, low data acquisition rates may also be contributory. Assessments of array performance using independent test data and Monte Carlo simulations with pattern recognition indicate that individual vapors and certain binary and ternary mixtures can be recognized/discriminated with very low error. More complex mixtures, and those containing homologous vapors, are problematic. This is the first report demonstrating multi-vapor analysis with an integrated FPW sensor array. 相似文献
6.
碳纳米管及其修饰物对挥发性有机物气敏性的研究 总被引:1,自引:0,他引:1
通过化学气相沉积(CVD)方法合成单壁碳纳米管(SWCNTs)和多壁碳纳米管(MWCNTs),并经过硝酸酸化预处理.在缩合剂N,N‘-二环己基碳化二亚胺(DCC)作用下,多壁碳纳米管经过乙二胺、十二胺和联苯胺的修饰生产新的纳米颗粒.将五种材料的悬浮液喷涂于Al2O3基底的金叉指电极上,构成气敏传感器,以甲醛、苯、甲苯、二甲苯作为测试气体,通过电化学分析仪测试他们在不同气体种类和浓度下的导电率.实验表面传感器在常温下具有较高的灵敏度和重复性,传感器之间有一定的选择性差异,可以构成传感器阵列,应用于具有复杂组分的挥发性有机气体定性和定量检测中. 相似文献
7.
Anna Sun Cui Li Chen Zhikuan Xu Hanying Zhou Qingzhong 《Sensors and actuators. B, Chemical》1994,20(2-3):151-158
Phosphatidylcholine (PC) and six other PC-similar lipids are coated on interdigital electrodes, IEs, as sensitive membranes. Eight alcohols (C1–C4) are tested in a flow system at room temperature. It is found that all responses are log(response)-log(concentration) linear relations. These results agree with Steven's law in psychophysics. Moreover, the thresholds of the sensors are coincident with human olfactory thresholds. The authors have analysed the data of the lipid hypothesis suggested by Kurihara et al. We have found that this hypothesis is also in agreement with Steven's law. Lipid microresistors are real mimicking olfactory sensors. A definition of an olfactory sensor is suggested. 相似文献
8.
Multiple conducting polymer microwire sensors 总被引:1,自引:1,他引:0
In this work, conducting polymer microwires of three commonly used conducting polymers were fabricated simultaneously on a common substrate using an intermediate-layer lithography (ILL) method. The three conducting polymers under consideration were polypyrrole (PPy), sulphonated polyaniline (SPANI) and poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT-PSS). The fabricated microwires were implemented as sensing elements in detecting humidity and two organic vapors (i.e., methanol and acetone). The sensitivity of a single PPy microwire was compared with a rectangular PPy film after both were exposed to 45–85% humidity. The microwire sensor, due to its higher surface-to-volume ratio, was found to be more sensitive than the film sensor at low levels of humidity (between 45 and 58%). Beyond 58% humidity, the responses of the film and microwire sensors were similar. Three different sets of conducting polymer microwires (of PPy, SPANI and PEDOT) were then fabricated and employed as sensors to detect methanol, acetone and their mixtures. These microwires exhibited wave-like responses when they were exposed to these targets. The PPy and PEDOT microwires showed higher sensitivities in detecting methanol and acetone, respectively. The SPANI microwires exhibited similar responses in detecting methanol and acetone. The results demonstrate that microwire sensors were more effective than film sensors in detecting little quantities of target molecules. A sensor platform which integrates multiple microwire detectors is promising to detect multiple targets, and it also provides more information in detecting and distinguishing targets. 相似文献
9.
Conductive polymer composite sensors have shown great potential in identifying gaseous analytes. To more thoroughly understand the physical and chemical mechanisms of this type of sensor, a mathematical model was developed by combining two sub-models: a conductivity model and a thermodynamic model, which gives a relationship between the vapor concentration of analyte(s) and the change of the sensor signals. In this work, 64 chemiresistors representing eight different carbon concentrations (8-60 vol% carbon) were constructed by depositing thin films of a carbon-black/polyisobutylene composite onto concentric spiral platinum electrodes on a silicon chip. The responses of the sensors were measured in dry air and at various vapor pressures of toluene and trichloroethylene. Three parameters in the conductivity model were determined by fitting the experimental data. It was shown that by applying this model, the sensor responses can be adequately predicted for given vapor pressures; furthermore the analyte vapor concentrations can be estimated based on the sensor responses. This model will guide the improvement of the design and fabrication of conductive polymer composite sensors for detecting and identifying mixtures of organic vapors. 相似文献
10.
《Sensors and actuators. B, Chemical》2006,113(1):94-99
Cross-linked polymers made of methyl methacrylate (MMA) as a monomer and divinylbenzene (DVB) as a cross-linking agent were prepared in the presence of toluene or p-xylene as a solvent. The cross-linked polymer prepared in toluene tended to sorb toluene vapor preferably, while the cross-linked polymer prepared in p-xylene sorbed p-xylene vapor preferably. The observed molecular recognition ability can be explained on the bases of an imprinting effect by solvent molecules. Molecularly imprinted polymer (MIP) powders were blended with PMMA, and the blended films were coated on a piezoelectric quartz crystal with a view to preparing QCM-based VOC sensors. The imprint effect was clearly observed, even in these blended films. The response of the sensor towards toluene or p-xylene vapor was reversible; however, the response time was slow due to the existence of the matrix polymer around the MIP particles. 相似文献
11.
Lazarus N. Bedair S. S. Lo C.-C. Fedder G. K. 《Journal of microelectromechanical systems》2010,19(1):183-191
12.
Humidity sensors were fabricated using ZnO thin films synthesized on a Si wafer substrate. The ZnO thin films were grown via a vapor solid (VS) approach at temperatures ranging from 400 to 700 °C. Experiments were executed to observe the relationships between the relative humidity (RH) and resistance of these devices fabricated under various VS temperatures. Experimental results show that the ZnO thin films grown at a temperature of 700 °C using the VS approach exhibits an optimum sensitivity to humidity. The measured sensor resistance ranges from 495 × 106 to 46 × 103 Ω for RH ranging from 11 to 95 % at room temperature. The variance of sensor resistance exceeds 104 times, indicating that the proposed method can produce a highly sensitive humidity sensor. 相似文献
13.
The feasibility of utilizing chemical sensor arrays and multivariable analyses as the basis for an early-warning combustion alarm for electrical fires was evaluated. During the pre-combustion phase of electrical fires, electronic components will heat up, resulting in an out-gassing of chemical vapors, which generally will precede the formation of smoke, scorching and fire. A variety of materials (PVC, Teflon®, Kapton®, and silicone rubber) that are frequently used as wire insulation were subjected to electrically induced thermal excursions, thereby simulating an electrical failure and possible pre-combustion condition. The off-gassing vapors from the various coatings can serve as chemical signatures for a pending fire and were detected by an array of chemical sensors (e.g., an electronic nose). Principal component analyses and KNN identification algorithms applied to the sensor response patterns successfully identified the various vapor sources. A 20-sensor array including electrochemical sensors, quartz microbalance (QMB) sensors with different polymer coatings, and heated metal oxide sensors (MOXs) was evaluated and the optimal performance was obtained using the electrochemical and MOXs. The use of heterogeneous orthogonal sensors increased the information content of sensor array signals and a diminutive array can still identify fire materials and extent of damage. The small, lightweight, inexpensive and low power sensors used to detect vapors during pre-fire conditions were ideal for space or commercial aircraft applications. 相似文献
14.
Ehsan DaneshAuthor VitaeSeyed Reza GhaffarianAuthor Vitae Payam Molla-AbbasiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,155(2):562-567
The fabrication of novel porous conductive composite vapor sensors characterized by different porosities and specific surface areas is described in this study. These samples were obtained by the dry-cast non-solvent induced phase separation (NIPS) method. Porous composite structures have been studied by the SEM, BET and water evaporation methods. Testing different concentrations of several organic vapors, the porous sensors showed improved sensitivities and response times as compared to their dense counterpart. Improved characteristics of the sensor response were correlated to better sorption and diffusion properties of sensing film due to increased porosity and specific surface area obtained by this method of film fabrication. A competition theory was proposed that describes the optimum porosity and thickness of sensing films in which the highest sensitivities were observed. 相似文献
15.
16.
A composite thin film was fabricated by coating nanocrystal magnetite (nc-Fe3O4) on silicon nanoporous pillar array (Si-NPA), which shows a regular hierarchical structure composed by the pillar array in micron dimension and the nanoporous structure in the film of Fe3O4. Capacitive humidity sensors were made based on nc-Fe3O4/Si-NPA and the corresponding sensing properties were investigated. The experimental results disclosed that nc-Fe3O4/Si-NPA sensor exhibits high sensitivity, strong output signal intensity, and short response times. These high performances of nc-Fe3O4/Si-NPA sensor are explained on the basis of the structural and compositional factors of nc-Fe3O4/Si-NPA. 相似文献
17.
Flexible micro temperature and humidity sensors on parylene thin films were designed and fabricated using a micro-electro-mechanical-systems (MEMS) process. Based on the principles of the thermistor and the ability of a polymer to absorb moisture, the sensing device comprised gold wire and polyimide film. The flexible micro sensors were patterned between two pieces of parylene thin film that had been etched using O2 plasma to open the contact pads. The sacrificial Cr spacer layer was removed from the Cr etchant to release the flexible temperature and humidity sensors from the silicon substrate. Au was used to form the sensing electrode of the sensors while Ti formed the adhesion layer between the parylene and Au. The thickness of the device was 7 ± 1 μm, so the sensors attached easily to highly curved surfaces. The sensitivities of the temperature and humidity sensor were 4.81 × 10−3 °C−1 and 0.03 pF/%RH, respectively. This work demonstrates the feasibility and compatibility of thin film sensor applications based on flexible parylene. The sensor can be applied to fuel cells or components that must be compressed. 相似文献
18.
用于食品气味快速检测的可视传感器特性研究 总被引:2,自引:0,他引:2
针对食品品质快速检测的需求和人工嗅觉技术存在的检测范围窄、受环境湿度影响大等缺陷,根据金属卟啉化合物与有机小分子气体反应后发生颜色变化的原理,筛选二十多种对食品常见气味成分响应的金属卟啉制成可视传感器阵列.以食品腐败的常见特征气体为研究对象,对传感器阵列的选择性、检测范围、水蒸气对传感器的影响等特性进行初步研究.试验结果表明,设计的可视传感器阵列具有良好的选择性、灵敏性、重现性和稳定性,且受环境湿度影响不大,在食品品质的快速检测方面有广泛的应用前景. 相似文献
19.
In this work, vacuum deposited thin films of PbPc, NiPc, VOPc, TiOPc and CoPc were employed as gas sensor to detect NO2 and NO. Data collected from sensor responses were used to train a back-propagation network (BPN) for identifying the gas species and quantifying its concentration. The results show that among the metallophthalocyanines tested, PbPc and NiPc have better sensing characteristics towards NO2 and NO. In BPN training, maximum error occurs for data collected by the TiOPc sensor, and minimum error occurs for array of PbPc and NiPc sensors. In the concentration prediction of NO or NO2, the maximum predicted error is 6.94%. When Two-Stage BPN or Single-Stage BPN was use to identify and quantify a single gas (NO2 or NO), the accuracy of recognition approaches 100% and the maximum error for concentration prediction is 7.45%. 相似文献
20.
针对目前PVDF体积位移传感器的研究主要集中在经典边界条件(如简支、固定、自由等)、需要预知精确的边界条件等不足,提出通过伪逆方法结合Tikhonov正则化方法设计振动梁在任意未知边界条件下的压电式体积位移传感器的通用设计模型。以一未知边界条件的振动梁为例,用一组PVDF阵列测量其体积位移。在该梁表面均匀粘贴一组相同形状的矩形PVDF薄膜,然后通过所提出的新方法设计这组PVDF输出信号的加权系数,从而得到体积位移。实验结果表明这种传感器设计方法是可行的,并且不需要预知振动梁的边界条件或模态信息。 相似文献