Flexible strain sensors fabricated using carbon-based nanomaterials: A review

Flexible strain sensors have experienced growing demand due to their several potential applications, such as personalized health monitoring, human motion detection, structural health monitoring, smart garments, and robots. Recently, several academic results have been reported concerning flexible and stretchable strain sensors. These reports indicate that the materials and design methods have an important influence on the performance of strain sensors. Carbon-based nanomaterials including carbon-based nanofibers, carbon nanotubes, graphene, and carbon black nanoparticles play a key role in the fabrication of flexible strain sensors with excellent properties. In terms of design, carbon-based nanomaterials are generally combined with polymers to maintain the flexibility and stability of a strain sensor. Various combined methods were successfully developed using different assembly structures of carbon-based nanomaterials in polymers, such as uniform mixing and ordered structures, including films, fibers, nanofiber membranes, yarns, foams, and fabrics. The working mechanisms of the flexible strain sensors, including changing the conductive network between overlapped nanomaterials, tunneling effect, and crack propagation, are also different compared with that of traditional semiconductor and metal sensors. The effects of the carbon-based nanomaterial structures in polymers on the strain sensing performance have been comprehensively studied and analyzed. The potential applications of flexible strain sensors and current challenges have been summarized and evaluated. This review provides some suggestions for further development of flexible and stretchable strain sensors with outstanding performance.     

STW gas sensors using plasma-polymerized allylamine

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 as a physical transducer. It is confirmed that STW sensor devices coated with PPAa films provide high sensitivity for moisture. The STW sensor device with a 63 nm PPAa film provided twenty four times higher sensitivity than that of a non-coated STW device. In addition, the chemical structure of PPAa films is characterized by the FT-IR and the contact angle measurement.     

电纺In2O3纳米材料在气体传感器中的应用研究进展

In2O3纳米材料因其具有载流子的量子限域效应而表现出新颖的电学、光学性质,在超灵敏气体传感器研究领域具备潜在的应用价值。静电纺丝技术被广泛应用于纳米材料的制备,是制备In2O3纳米材料最有效的方法之一。本文综述了静电纺丝In2O3纳米材料在气体传感器中的应用现状,并提出了今后的研究方向。     

MEMS气敏传感器

随着MEMS技术的飞速发展，各种MEMS器件和系统相继问世，MEMS气敏传感器是其中之一。本文重点介绍了7种MEMS气敏传感器。     

Semiconductor gas sensors

Abstract

The technology associated with the use of semiconductors in monitoring the composition of the atmosphere has been advancing rapidly in recent years. The twin demands of remote process control and concern for the environment have produced requirements for sensing different gases in a wide range of applications. In this paper the authors review the state of the art of semiconductor gas sensor development and anticipate the directions in which future progress is likely to be made.

MST/221     

Trace detection and discrimination of explosives using electrochemical potentiometric gas sensors

In this article, selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors based on lanthanum strontium chromite and Pt electrodes with yttria stabilized zirconia (YSZ) solid electrolyte were used to capture the signature of the explosives. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (1-3 μg). Moreover, the results showed that PETN, TNT, and RDX samples could be discriminated from each other by calculating the ratio of nitrogen oxides to hydrocarbon integrated area under the peak. Further, the use of front-end technology to collect and concentrate the high explosive (HE) vapors make intrinsically low vapor pressure of the HE less of an obstacle for detection while ensuring higher sensitivity levels. In addition, the ability to use multiple sensors each tuned to basic chemical structures (e.g., nitro, amino, peroxide, and hydrocarbon groups) in HE materials will permit the construction of low-cost detector systems for screening a wide spectrum of explosives with lower false positives than present-day technologies.     

碳纳米管及其掺杂氧化物半导体气敏传感器

碳纳米管气敏传感器以其工作温度低和最低检出限较低等优点而备受关注,而碳纳米管掺杂氧化物半导体气敏传感器兼备了氧化物半导体气敏传感器和碳纳米管气敏传感器二者的优点,具有灵敏度较高、最低检出限低和工作温度低等特性。综述了这两类传感器的研究进展,介绍了其气敏机理,并对相应存在的问题及今后的发展趋势进行了概述。     

Interaction of thermally pretreated carbon nanomaterials with water vapor

We used temperature-programmed desorption-mass spectrometry to verify whether low-molecular-weight products can form by reacting thermally pretreated single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs, respectively) with water vapor. The reactivity of MWNTs toward water is similar to the reactivity of graphite, whereas acid-oxidized SWNTs behave like polymerized C60 fullerene. We think the main factors influencing the reactivity are molecular surface curvature and the presence of pyrolyzable defect groups, which create highly strained bonds upon their elimination.     

基于碳纳米材料的肾上腺素电化学传感器研究进展

肾上腺素(AD)作为一种神经递质在人体内扮演重要角色,其含量的高低直接影响人体身体健康,因此对AD进行快速检测具有重要的实际意义。其检测方法中电化学方法具有灵敏度高、检测速度快、操作简便的优点,因而构建性能优异的肾上腺素电化学传感器成为研究热点。为提高传感器的电化学性能,碳纳米材料被采纳作为修饰传感器的新型材料而广泛应用,取得了检测限低、灵敏度高并有希望应用于临床检测的巨大进步。本文从碳点、石墨烯、碳纳米颗粒等碳纳米材料出发,分析AD在电极表面的电氧化还原机制,对近年来基于碳纳米材料的肾上腺素电化学传感器制备方法及检测结果进行分类统计,并对今后的检测提出展望,以期获得更有效的肾上腺素电化学传感器。     

利用纳米ZnO粉制备厚膜气敏传感器的研究

以ZnO纳米粉(平均粒径30nm)为原料,利用水热热压方法制备了ZnO多孔纳米固体,同时用通常的水热法对ZnO纳米粉进行了预处理(预处理ZnO纳米粉)。然后,分别以ZnO多孔纳米固体和预处理ZnO纳米粉为原料,制备了厚膜气敏传感器。本征电阻的测试结果表明,这两种厚膜气敏传感器的本征电阻比用未经处理的ZnO纳米粉(以下简称“原料ZnO纳米粉”)制备的厚膜气敏传感器大大降低并很快达到稳定状态。有效地改善了器件工作的稳定性。结合对三种传感器的显微结构分析,对出现上述差异的原因进行了讨论。     

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

It is shown that a gas mixture can be discriminated by using an array of thin-film semiconductor sensors having variable internal parameters. It is established that a multisensor system consisting of an array of sensors, fabricated by the same technological process but having a spread of active-layer parameters, can discriminate between ammonia and acetone vapor impurities in air. Pis’ma Zh. Tekh. Fiz. 25, 54–58 (August 26, 1999)     

Odour measurement using conducting polymer gas sensors and anartificial neural network decision system

The conventional way of assessing the magnitude of nuisance odours using an olfactometer and a sensory panel is costly. This paper describes experiments that have been conducted into matching the results from trained sensory panellists to those from a conducting polymer-based electronic nose. By taking the data from the electronic nose and applying them to a trained neural network, it has been shown that the data can be manipulated to give rise to results that are within a few percent of those from the sensory panellists. This is the first time that an electronic nose has been calibrated in terms of odour intensity measurements and it points the way forward to more objective measurements of nuisance odours     

Single-walled carbon nanotubes nanocomposite microacoustic organic vapor sensors

We have developed highly sensitive microacoustic vapor sensors based on surface acoustic waves (SAWs) configured as oscillators using a two-port resonator 315, 433 and 915 MHz device. A nanocomposite film of single-walled carbon nanotubes (SWCNTs) embedded in a cadmium arachidate (CdA) amphiphilic organic matrix was prepared by Langmuir–Blodgett technique with a different SWCNTs weight filler content onto SAW transducers as nanosensing interface for vapor detection, at room temperature. The structural properties and surface morphology of the nanocomposite have been examined by X-ray diffraction, transmission and scanning electron microscopy, respectively. The sensing properties of SWCNTs nanocomposite LB films consisting of tangled nanotubules have been also investigated by using Quartz Crystal Microbalance 10 MHz AT-cut quartz resonators. The measured acoustic sensing characteristics indicate that the room-temperature SAW sensitivity to polar and nonpolar tested organic molecules (ethanol, ethylacetate, toluene) of the SWCNTs-in-CdA nanocomposite increases with the filler content of SWCNTs incorporated in the nanocomposite; also the SWCNTs-in-CdA nanocomposite vapor sensitivity results significantly enhanced with respect to traditional organic molecular cavities materials with a linearity in the frequency change response for a given nanocomposite weight composition and a very low sub-ppm limit of detection.     

Capacitive sensors for in-vivo measurements of the dielectricproperties of biological materials

Two open-ended coaxial sensors for in vivo measurements of the dielectric properties of biological tissues at low radio frequencies are described. The high fringing-field capacitance of these sensors allows accurate measurements of high-water-content tissues at frequencies as low as 10 kHz. Each sensor is represented by two capacitances, which are calculated using the method of moments. Theoretical and experimental results for experimental sensors terminating a standard 14-mm coaxial line with a GR900 connector are presented     

Organic vapor sensors based on SAW resonator and organic films

The majority of investigations of SAW devices used as chemical sensors are based on delay line oscillators. However, SAW resonator oscillator offers some advantages over the SAW delay line oscillator for its higher stability. In the incipient stage of fabricating gas sensors based upon SAW resonator, taking detection of organic vapor as an example, the analysis method that combines the SAW theory with organic film technology has been adopted to give an intensive insight into the responses of two-port SAW resonator coated with LB-film and cast-film after exposure to organic vapors.     

Tin oxide based gas sensors

The key parameters on which the function of resistance-modulating tin dioxide gas sensors depends nave been studied. A model based on the controlling influence of chemisorbed oxygen molecules is supported by electrical conductivity measurements performed both in air and in vacuo and by measurements of surface state energies evaluated by a novel method involving a solid electrolyte. It has been shown that water vapour behaves as an interference in the detection of gases over the whole range between room temperature and 600°C and as a sensor poison at temperatures below around 300°C. The application of fine particles of precious metals to the surface of the tin dioxide introduces the possibility of an oxygen-independent influence on surface energetics and this is found to substantially modify the gas sensing properties of the material.     

Comparisons of polymer/gas partition coefficients calculated from responses of thickness shear mode and surface acoustic wave vapor sensors

Apparent partition coefficients, K, for the sorption of toluene by four different polymer thin films on thickness shear mode (TSM) and surface acoustic wave (SAW) devices are compared. The polymers examined were poly(isobutylene) (PIB), poly(epichlorohydrin) (PECH), poly(butadiene) (PBD), and poly(dimethylsiloxane) (PDMS). Independent data on partition coefficients for toluene in these polymers were compiled for comparison, and TSM sensor measurements were made using both oscillator and impedance analysis methods. K values from SAW sensor measurements were about twice those calculated from TSM sensor measurements when the polymers were PIB and PECH, and they were also at least twice the values of the independent partition coefficient data, which is interpreted as indicating that the SAW sensor responds to polymer modulus changes as well as to mass changes. K values from SAW and TSM measurements were in agreement with each other and with independent data when the polymer was PBD. Similarly, K values from the PDMS-coated SAW sensor were not much larger than values from independent measurements. These results indicate that modulus effects were not contributing to the SAW sensor responses in the cases of PBD and PDMS. However, K values from the PDMS-coated TSM device were larger than the values from the SAW device or independent measurements, and the impedance analyzer results indicated that this sensor using our sample of PDMS at the applied thickness did not behave as a simple mass sensor. Differences in behavior among the test polymers on SAW devices are interpreted in terms of their differing viscoelastic properties.