Quantitative studies of long-term stable, top-down fabricated silicon nanowire pH sensors

We report a simple and effective method to develop long-term stable, top-down fabricated silicon nanowire (SiNW) pH sensors along with systematic studies on the performance of the sensors. In this work, we fabricated the SiNW pH sensors based on top-down fabrication processes. In order to improve the stability of the sensor performance, the sensors were coated with a passivation layer (PECVD-based silicon nitride) for effective electrical insulation and ion-blocking. The stability, pH sensitivity, and repeatability of the sensor response are critically analyzed with regard to the physics of sensing interface between sample liquid and the sensor surface. Also, trade-off between the stability and pH sensitivity of the sensor response is discussed.     

Incorporating Copper Nanoclusters into Metal‐Organic Frameworks: Confinement‐Assisted Emission Enhancement and Application for Trinitrotoluene Detection

Herein, a strategy for improving both the stability and the emission intensity of Cu nanoclusters based on their entrapment into metal‐organic frameworks (MOFs) is demonstrated. The latter effect reaches 20 times and is ascribed to a confinement‐assisted emission enhancement similar to the aggregation induced emission of fluorescent species in solution, evidenced by the prolonged emission lifetime. Cu nanoclusters are distributed homogeneously over the entire MOFs structure, as confirmed by combination of structural and elemental mapping studies. Toward potential applications of Cu nanocluster/MOF composites as chemical sensors, the authors demonstrate the selective quenching of their emission by 2,4,6‐trinitrotoluene attributed to specific electron‐withdrawing interactions with glutathione ligands on Cu clusters.     

一种新型微镜式光纤氢传感器的研究

介绍了光纤氢传感器的应用背景和工作原理,分析了其中的微镜式传感器。针对在垂直入射、单次反射方式下工作的微镜式光纤氢传感器,提出了多次反射的传感器模型。从金属光反射模型出发,研究了入射角、反射次数对探测灵敏度的影响。论证了通过多次反射来提高传感器探测灵敏度的可行性。     

Fiber ringdown pressure sensors

An exploratory study on a novel fiber ringdown pressure sensor is presented. With this technique, pressure measurements are achieved in a time domain by measurement of ringdown times. The proof-of-concept device consists of a diode laser light source, two 2 x 1 fiber couplers, a section of fused-silica single-mode fiber, a photodetector, and an electronic control. The sensor's performance in the areas of stability, repeatability, and dynamic range is explored. The results demonstrate the new concept of fiber pressure sensors and the technical feasibility of developing a new generation of fiber sensors for pressure measurements.     

Optical CO<Subscript>2</Subscript> Sensing with Ionic Liquid Doped Electrospun Nanofibers

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO₂ sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO₂ sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO₂ are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.     

Universal SAW gas sensor

A new principle of designing a SAW gas sensor is described. This sensor, being essentially of sorption type, also offers properties of thermometric SAW sensors. The basic idea here is that heat fluxes propagate between the SAW substrate and the working surface of the temperature-regulating system with some delay. A sensor based on this principle can detect not only the vapors of volatile substances but also gases by their thermal properties, retaining high temperature stability and speed of response unlike conventional SAW thermometric sensors. The design of this sensor built around a LiNbO₃ SAW delay line is described, and experiments on detecting a household propane-butane mixture with this sensor are reported. In particular, the responses of the sensor are measured at different gas-flow rates, two different SAW substrate temperatures, and two propane-butane concentrations. Ways of improving the sensor’s performance are discussed.     

Single and networked CuO nanowires for highly sensitive p‐type semiconductor gas sensor applications

Development of high‐performance p‐type semiconductor based gas sensors exhibiting fast‐response/recovery times with ultra‐high response are of major importance for gas sensing applications. Recent reports demonstrated the excellent properties of p‐type semiconducting oxide for various practical applications, especially for selective oxidation of volatile organic compounds (VOCs). In this work, sensors based on CuO nanowire (NW) networks have been successfully fabricated via a simple thermal oxidation process on pre‐patterned Au/Cr pads. Our investigation demonstrates high impact of the process temperature on aspect ratio and density of copper oxide NWs. An optimal temperature for growth of thin and densely packed NWs was found to be at 425 °C. The fabricated sensors demonstrated ultra‐high gas response by a factor of 313 to ethanol vapour (100 ppm) at an operating temperature of 250 °C. High stability and repeatability of these sensors indicate the efficiency of p‐type oxide based gas sensors for selective detection of VOCs. A high‐performance nanodevice was fabricated in a FIB‐SEM system using a single CuO NW, demonstrating an ethanol response of 202 and rapid response and recovery of ～198 ms at room temperature. The involved gas sensing mechanism of CuO NW networks has been described. We consider that the presented results will be of a great interest for the development of higher‐performance p‐type semiconductor based sensors and bottom‐up nanotechnologies. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Transparent ZnO/glass surface acoustic wave based high performance ultraviolet light sensors

Surface acoustic wave(SAW) resonators are a type of ultraviolet(UV) light sensors with high sensitivity, and they have been extensively studied. Transparent SAW devices are very useful and can be developed into various sensors and microfluidics for sensing/monitoring and lab-on-chip applications. We report the fabrication of high sensitivity SAW UV sensors based on piezoelectric(PE) ZnO thin films deposited on glass substrates. The sensors were fabricated and their performances against the post-deposition annealing condition were investigated. It was found that the UV-light sensitivity is improved by more than one order of magnitude after annealing. The frequency response increases significantly and the response becomes much faster. The optimized devices also show a small temperature coefficient of frequency and excellent repeatability and stability, demonstrating its potential for UV-light sensing application.     

Dynamics Analysis of a Wireless Rechargeable Sensor Network for Virus Mutation Spreading

Virus spreading problems in wireless rechargeable sensor networks (WSNs) are becoming a hot topic, and the problem has been studied and discussed in recent years. Many epidemic spreading models have been introduced for revealing how a virus spreads and how a virus is suppressed. However, most of them assumed the sensors are not rechargeable sensors. In addition, most of existing works do not consider virus mutation problems. This paper proposes a novel epidemic model, including susceptible, infected, variant, low-energy and dead states, which considers the rechargeable sensors and the virus mutation factor. The stability of the proposed model is first analyzed by adopting the characteristic equation and constructing Lyapunov functions methods. Then, an optimal control problem is formulated to control the virus spread and decrease the cost of the networks by applying Pontryagin’s maximum principle. Finally, all of the theoretical results are confirmed by numerical simulation.     

反射相移对Faraday电流传感器灵敏度及稳定性影响的理论分析

光学法拉第电流传感器内的反射相移能降低传感器的灵敏度与稳定性。本文对此效应给予了定量的理论分析。     

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers

Surface plasmon resonance sensors based on Ag-metalized nanolayer in microstructured optical fibers are theoretically analyzed by using finite element method (FEM). In our simulations we use Drude-Lorentz model to describe the metal dielectric constant. The numerical results show that the sensitivity of Ag-metalized SPR sensor could reach 1167 nm/RIU and corresponding resolution is 8.57×10⁻⁵ RIU. Compared to conventional Au-metalized SPR sensors the performance of our device is obviously better.     

The distributed dynamic combined-stresses measurement of ship thruster inner-skin using fiber Bragg grating sensor rosette array

The use of a fiber Bragg grating (FBG) sensor array for the measurement of dynamic combined stress of ship thruster inner-skin is presented. The triaxial stress is detected using improved three-element rectangular rosette consisting of FBG sensors. Phase lag effect among triaxial stress sensor is considered and eliminated by employing multi-channel demodulation and improving the layout of sensor rosette array and connection layout. The tests are carried on to measure the distributed combined-stress change of ship thruster duct when ship thruster work at different rotate speed and pitch of angle. The test result are analyzed which show that measured stress are acceptable and in accord with predicted result.     

Sensors based on bulk soft magnetic materials: Advances and challenges

Sensors with cores, yokes or field concentrators made of bulk magnetic material are more sensitive and stable than thin-film sensors. Non-linearity and temperature dependence of sensitivity is often suppressed by a feedback. The common problem of these sensors is remanence, cross-field sensitivity and temperature stability of offset. The long-time effort to miniaturize the fluxgates led only to a few practical designs. For flat sensors (either pcb or CMOS) the core etched from amorphous tape gives better properties then electrodeposited or sputtered core. We compare traditional miniature fluxgates using wire cores based on longitudinal fluxgate effect with sensors using transverse fluxgate effect and GMI effect. Well-designed field concentrators or yokes can improve the parameters of any magnetic sensor. The achievable stable amplification factor is 10–100. Having a means to demagnetize the field concentrator is desirable. Overview of magnetic sensors for mechanical quantities is also given with special focus on torque sensors.     

反射相差对光学玻璃电流传感器测量灵敏度和稳定性的影响

在光学玻璃电流传感器中，如果在光线反射转向时的光的ｐ，ｓ分量之间引入反射相差，则会降低传感器的测量灵敏度和稳定性，本文对这种影响进行了理论上的分析，并给出了数值模拟的结果。     

Optimal locations and orientations of piezoelectric transducers on cylindrical shell based on gramians of contributed and undesired Rayleigh–Ritz modes using genetic algorithm

In this study, the active vibration control and configurational optimization of a cylindrical shell are analyzed by using piezoelectric transducers. The piezoelectric patches are attached to the surface of the cylindrical shell. The Rayleigh–Ritz method is used for deriving dynamic modeling of cylindrical shell and piezoelectric sensors and actuators based on the Donnel–Mushtari shell theory. The major goal of this study is to find the optimal locations and orientations of piezoelectric sensors and actuators on the cylindrical shell. The optimization procedure is designed based on desired controllability and observability of each contributed and undesired mode. Further, in order to limit spillover effects, the residual modes are taken into consideration. The optimization variables are the positions and orientations of piezoelectric patches. Genetic algorithm is utilized to evaluate the optimal configurations. In this article, for improving the maximum power and capacity of actuators for amplitude depreciation of negative velocity feedback strategy, we have proposed a new control strategy, called “Saturated Negative Velocity Feedback Rule (SNVF)”. The numerical results show that the optimization procedure is effective for vibration reduction, and specifically, by locating actuators and sensors in their optimal locations and orientations, the vibrations of cylindrical shell are suppressed more quickly.     

光纤光栅传感技术在成桥检测中的应用研究

在分析的基础上,通过等强度梁试验具体验证了光纤Bragg光栅波长变化与应变的关系,研究了光纤Bragg光栅传感器的布设工艺,并在某大桥的成桥检测过程中成功地布设了36个光纤Bragg光栅应变传感器与5个温度传感器,布设的传感器在成桥检测过程中监测结构层状态。监测结果表明：埋入的光纤Bragg光栅传感器具有很好的传感性能,可以很方便地监测桥梁结构,为桥梁结构的健康诊断提供可靠的依据。     

偏心测量系统驱动机构的改进设计

偏心距是弹箭飞行稳定性的重要影响因素,其精确测量是保证弹道计算正确性的关键。为了解决某些特殊外形的弹体,在利用偏心测量系统测量偏心时,驱动弹体精确转动的机构出现卡滞、打滑等现象,导致无法自动测量的问题。本文结合系统偏心距测量的原理和试验操作步骤,分析了测量过程设备存在的不足及产生原因,提出了改进支撑和用减速伺服电机增加旋转力矩的方案,并进行了详细地设计及计算。验证结果表明,改进后的系统可以有效解决电机直驱不规则弹体时出现的问题,测量精度提高了4.15倍。扩大了测量范围,提高了驱动精度和测量效率,具有很好的应用价值。     

Excellent acetone sensing properties of porous ZnO

Porous Zn O was obtained by hydrothermal method.The results of scanning electron microscope revealed the porous structure in the as-prepared materials.The acetone sensing test results of porous Zn O show that porous Zn O possesses excellent acetone gas sensing properties.The response is 35.5 at the optimum operating temperature of 320?C to 100 ppm acetone.The response and recovery times to 50 ppm acetone are 2 s and 8 s,respectively.The lowest detecting limit to acetone is 0.25 ppm,and the response value is 3.8.Moreover,the sensors also exhibit excellent selectivity and long-time stability to acetone.     

Investigation of stability of ITER candidate Hall sensors under neutron irradiation

Hall sensors offer an attractive true non-inductive method of magnetic field measurements for fusion reactors. Their use for steady state magnetic diagnostics of ITER is presently limited by their questionable radiation and thermal stability. Issues of stable and reliable operation in ITER like radiation and thermal environment are addressed by the contribution. Recently, novel Hall sensors, compatible with temperatures up to 200°C, were developed and their radiation stability was tested at LVR-15 experimental fission reactor. Overview of the experimental set-up on LVR-15 reactor is given. Degradation of the sensor’s sensitivity by several tens of percents was observed after neutron irradiation by the total neutron fluence of 2 × 10¹⁷ n/cm² in LVR-15. This level of neutron fluence is comparable to that expected to occur over the whole ITER life time for a sensor location just outside the ITER vessel. The in-situ recalibration techniques are expected to handle the observed degree of Hall sensors performance degradation in ITER environment.     

Improved performance of SPR sensors by a chemical etching of tapered optical fibers

We present the results of a chemical attack on the optical fiber surface previous to the deposition of the double layer (metal plus dielectric) in Double-layer uniform-waist tapered fibers (DLUWTs) used for the development of SPR sensors. It is shown how this simple chemical treatment increases the roughness of the surface and permits improvement of the stability of the deposits and the general performance of the sensors. The obtained devices are robust and very compact, their sensitivity is good and repeatability of the measurements is remarkably increased. The procedure can be useful for any fiber-optic sensor.