多壁碳纳米管湿度传感器介电损耗模型（英文）

为揭示碳纳米管湿度传感器的介电损耗,制作了一种电阻型碳纳米管湿度传感器.使用介电损耗相关理论对其频率特性进行分析,并利用普适方程建立了传感器介电损耗模型.对实验数据与所建立模型进行拟合,得到拟合决定系数为0.994,表明可以使用普适方程对传感器介电损耗进行描述.由于测试频率引起的传感器电阻变化会改变传感器线性度,分析了不同测试频率下传感器的线性度,发现当测试频率为10 kHz时传感器的线性度最佳（1.52%）,此时传感器灵敏度为-7.83Ω/%RH.     

交流信号检测的多壁碳纳米管湿度传感器模型(英文)

为研究交流信号检测的多壁碳纳米管(MWCNTs)湿度传感器模型,通过扫描电子显微镜对传感器敏感薄膜(MWCNTs-SiO2薄膜)的孔隙结构进行观察,并使用表面积与孔隙(ASAP)分析系统对薄膜孔隙率进行分析.利用Debye方程对敏感薄膜中凝聚出液态水介电损耗的描述建立传感器模型.为了验证该传感器模型,制作了一种基于MWCNTs-SiO2的电导型湿度传感器,在100 kHz测试频率下,对不同相对湿度环境中的传感器电导值进行测试,利用测试结果与所建立模型进行拟合,发现R2大约为0.979,可见该模型可以用来描述传感器湿敏特性.     

涂敷ZnO纳米线的石英晶体微天平的湿度敏感特性

采用石英晶体微天平传感器电极上旋涂纳米氧化锌薄膜,构造湿度传感敏感元件,实现对湿度检测.介绍了检测系统的组成,纳米氧化锌的制备.通过DAQ数据采集卡和Labview软件实现数据的实时采集.实验结果表明旋涂纳米氧化锌薄膜的传感器频率随测试的相对湿度变化明显,用纳米氧化锌作为敏感元件检测湿度具有很高的灵敏度和重复性.     

基于电容检测MEMS磁传感器的设计与制作

为实现微型化、低功耗、低成本和高灵敏度的磁传感器,提出了一种基于微型磁扭摆结构的磁传感器,并利用对角度变化非常敏感的差分电容检测技术对磁扭摆的扭转角度进行检测．设计的磁传感器包括微扭摆结构、磁性敏感薄膜和差分检测电容等部分．分析了器件的磁敏感原理和电容检测原理,给出了器件的结构参数和综合设计考虑．利用体硅加工工艺成功制作出了磁传感器样品,并进行了实验测试．测试结果表明磁传感器有良好的线性度和重复性,其磁场检测的电容灵敏度可达到0．2fF／Gauss．根据对磁传感器的热噪声分析,可得到磁传感器最小可分辨的磁场为6．72μT．该磁传感器结构简凑、工艺简单,无需电流激励,大大降低了磁传感器功耗．     

侧壁四电极电容耦合非接触电导检测器(英文)

研制了一种集成于硅基电泳芯片分离沟道末端侧壁的新型四电极电容耦合非接触电导检测器.研究了该电导检测器的等效模型,对等效电路模型中的参数进行了公式推导,并讨论了影响电导检测响应灵敏度的相关因素.采用深刻蚀及离子注入加工技术制得了用于电导检测的立体电极.制作了基于锁相放大原理的信号处理电路,对该电导检测的频率响应及灵敏度进行了测试分析.实验结果表明,当激励信号频率为300 kHz时,该电导检测器具有最佳线性度;不同浓度Na+溶液响应电压差值为5 mV;检测限达到10-8mol/L;且成功实现了Na+和Li+混合无机阳离子的电泳分离在线检测.     

测量围护结构含水率的同面散射场式电容传感器设计

目前常用的测量含水率的方法有微波法、红外线法和电容法.由于基于电容法的传感器具有分辨力高、响应速度快、体积小、结构简单等优点,被广泛应用.针对围护结构含水率测试深度的要求和测试特点,本文通过仿真和实验,对同面电容传感器探头的结构尺寸进行了优化设计,并采取了保护电极以提高其抗干扰能力;运用改进的充放电电容检测电路,设计出一种测量围护结构含水率的新型同面散射场式电容传感器,该传感器具有宽范围的测试深度和较高的测试灵敏度.     

电容层析成像系统的仿真与研究

针对电容层析成像系统中的8电极电容传感器,通过电磁场有限元分析软件ANSYS建立了其仿真模型,实现了传感器电容值的快速获取,并分析了传感器的灵敏度特性.在此电容传感器结构下,对层流、核心流、泡流三种典型流型利用RBF神经网络进行了辨识.提出了以层流、核心流、泡流的特征参数作为BP神经网络图像重建的主要依据,实验结果表明利用特征值作为神经网络的输出可以重构出满意的图像.     

基于ANSYS的同面多电极电容传感器仿真研究

同面多电极电容传感器是一种新的飞机复合材料构件损伤检测技术,该检测技术的正问题中敏感场分布函数的计算要涉及到静电场中电容计算问题。在仿真研究中,电容要通过场的数值计算方法来求得。本文介绍了如何使用ANSYS有限元分析计算同面多电极电容传感器中的各电极对之间的电容,对检测材料发生异常及传感器参数改变时电容的变化进行了分析,为损伤检测的特征提取和逆问题图像重构提供了仿真数据。     

激励功率对微机械谐振梁谐振频率的影响

对谐振式微机械传感器的敏感元件——微机械谐振梁的谐振频率特性进行了详细的实验研究，并从理论上分析了激励功率对谐振频率的影响．实验结果表明，谐振频率随着激励功率的增加而近似线性减小，当激励功率从1．1mW提高到10．1mW时，谐振梁的谐振频率降低了1．609kHz，灵敏度为0．179kHz／mW．实验结论与理论分析的结果基本一致．若要使激励功率对谐振频率的影响减小，则要求降低激励功率并减小梁的长度，增大梁的厚度和宽度．上述研究结论对优化谐振式微机械传感器敏感元件结构尺寸的设计有指导意义．     

基于均匀设计及非线性偏最小二乘法的非闭合电极ECT传感器参数优化设计

提出了一种非闭合电极电容层析成像(ECT)传感器结构参数的优化方法.采用均匀设计结合非线性偏最小二乘(NPLS)回归,提取传感器结构参数(电极极板的宽度 L、绝缘外壳的壁厚δ1.、屏蔽罩与绝缘外壳间距δ2及绝缘外壳材料的相对介电常数ε)与待优化指标(敏感场的均匀度及灵敏度指标p1、最大与最小电容的比值 K)间的函数关系,建立相应的优化目标泛函,通过对优化目标泛函的求解,最终获得传感器结构参数的最优值.并以 10 电极非闭合电极 ECT 传感器为研究对象,进行了结构参数的优化设计,根据优化结果设计制作了非闭合电极 ECT 传感器,对其成像进行了仿真与实测.结果表明,参数优化后的传感器图像重建质量优于未优化的传感器.     

钒钛酸掺杂聚苯胺的制备与湿敏性能

采用沉淀聚合法,在聚乙二醇的乙醇溶液中制备了钒钛酸掺杂的聚苯胺,并对其进行红外表征和灵敏度、湿滞、电阻特性、电容特性和响应-恢复等湿敏特性研究。结果表明,钒钛酸已掺杂到聚苯胺中,且钒钛酸掺杂聚苯胺的湿敏性能明显优于聚苯胺。当频率为1kHz时该湿敏元件的线性度较好。在11%~97%相对湿度(RH)范围内,电阻变化了3个数量级、灵敏度较高、湿滞回差为5%RH,响应时间为5s,恢复时间为19s,是一种良好的湿敏材料。     

Effect of crystallization on humidity sensing properties of sol-gel derived nanocrystalline TiO2 thin films

In the present work, we describe the effect of crystallization on humidity sensing properties of nanocrystalline TiO₂ thin films prepared by sol-gel techniques. Here, we report an enhancement in the relative humidity (RH) sensitivity just after the crystallization at 375 °C, which is attributed to increased surface activity near crystallization and lower crystallite size. After crystallization, the RH sensitivity was found to decrease with increasing grain size. The complex impedance of the sensor, measured using impedance spectroscopy, fits well with an equivalent circuit consisting of inter-granular resistance and capacitance in parallel. It was found that with the change in RH, only resistance changes significantly, when compared with the capacitance.     

A surface acoustic wave humidity sensor with high sensitivity based on electrospun MWCNT/Nafion nanofiber films

Humidity detection has been widely used in a variety of fields. A humidity sensor with high sensitivity is reported in this paper. A surface acoustic wave resonator (SAWR) with high resonance frequency was fabricated as a basic sensitive component. Various nanotechnologies were used to improve the sensor's performance. A multi-walled carbon nanotube/Nafion (MWCNT/Nafion) composite material was prepared as humidity-sensitive films, deposited on the surface of an SAWR by the electrospinning method. The electrospun MWCNT/Nafion nanofiber films showed a three-dimensional (3D) porous structure, which was profitable for improving the sensor's performance. The new nano-water-channel model of Nafion was also applied in the humidity sensing process. Compared to other research, the present sensor showed excellent sensitivity (above 400 kHz/% relative humidity (RH) in the range from 10% RH to 80% RH), good linearity (R(2) > 0.98) and a short response time (～3 s@63%).     

Development and application of mass sensors based on flexuralresonances in alumina beams

New mass sensors are described, which are based on the change in the flexural resonant frequencies of ceramic cantilever beams subject to piezoelectric excitation. The devices have been fabricated by screen-printing and firing a PZT-based paste on 96% alumina substrates with the methods of thick film technology and are, therefore, low cost and easy to manufacture. Inserted in an electronic feedback loop sustaining and tracking oscillations at one of the resonant frequencies, the sensors work as resonant microbalances with frequency output and can be employed for gravimetric chemical measurements. The beams have been implemented in two different sizes and, as a consequence, operated at different frequencies (about 82 and 149 kHz), in order to vary the mass sensitivity. The sensors' manufacturing and theory of operation are illustrated, and experimental results on their characterization are reported. For the two sensor sizes, mass sensitivities of about -280 and -1200 Hz/mg have been measured, in agreement with theoretical predictions. The influence of temperature has been investigated showing that, for slow thermal drifts, a satisfying degree of compensation can be achieved with a differential configuration. The devices have been successfully applied as sorption sensors for the measurement of air relative humidity (RH) by sensitizing the beams' surface with hydrophilic polymeric coatings. On the basis of past investigations, poly(N-vinylpyrrolidinone) and poly(ethyleneglycol) have been adopted as coating materials, obtaining respective frequency shifts of about 500 and 1400 Hz for RH ranging from 12 to 85%     

Zn_2SnO_4-LiZnVO_4系厚膜湿敏元件的制备和性能研究

采用溶胶凝胶法制备 Zn2SnO4-LiZnVO4系陶瓷纳米粉体,用平面丝网印刷工艺在氧化铝基片上制备厚膜湿敏元件。与普通陶瓷粉体制备的元件相比,该元件低湿电阻小,长期稳定性较好。 测量不同工作频率时的湿敏特性表明,元件在 1kHz频率范围感湿线性最佳。复阻抗分析表明,采用溶胶凝胶法制备纳米粉体并控制烧结温度,可获得良好的微结构,是改善元件感湿特性的原因。     

Capacitive humidity-sensitivity of carbonized silicon nanoporous pillar array

The synthesis and application of silicon carbide (SiC) electronic devices have been studied broadly. In this letter, we report that by a thermal treatment process, the surface of silicon nanoporous pillar array (Si-NPA) could be carbonized in a graphite vacuum furnace. The composition and the morphology of the carbonized Si-NPA (SiC/Si-NPA) were characterized by X-ray diffractometer and scanning electron microscope. The humidity-sensing properties of SiC/Si-NPA were measured at room temperature. The result shows that with the relative humidity (RH) being changed from 11 to 95%, the capacitance of the sensor increased from 7.65 to 145.94 nF at the testing frequency of 20 Hz, and a capacitance increment over 1900% was achieved. The response and recovery times were determined to be ∼ 10 s by carrying out vapor adsorption and desorption dynamic cycle experiment. The sensing performances are attributed to the unique surface structure, morphology and chemical characteristics of SiC/Si-NPA.     

Surface-type multifunctional sensor based on 5,10,15,20-tetrakis(4′-isopropylphenyl) porphyrin

In this study, an organic semiconductor 5,10,15,20-tetrakis(4′-isopropylphenyl) porphyrin (TIPP) was synthesized and investigated as an active material in surface-type multifunctional sensor. As electrodes, 100 nm thick Ag films were deposited on 25 mm × 25 mm glass substrate with 40 μm gap between them. Thin film of TIPP of area 15 mm × 15 mm was thermally sublimed to cover the gap between the silver electrodes. Thickness of TIPP film was 100 nm. A change in electrical resistance and capacitance of the fabricated device was observed with the increase in relative humidity (RH), temperature, and illumination. Hysteresis, response, and recovery times were investigated over a wide range of RH (0–94%). Activation energy of the TIPP was estimated. An equivalent circuit of the Ag/TIPP/Ag humidity, temperature, and illumination sensor was developed. Humidity, temperature, illumination dependent capacitive, and resistive properties of this sensor make it promising for use in a humidity, temperature, and lux multi-meters.     

Y5U multilayer ceramic capacitors with high-specific capacitance and low-equivalent series resistance

A dielectric powder material, for Y5U multilayer ceramic capacitors was developed in the Pb(Mg(1/3)Nb(2/3))O (3)-Pb(Ni(1/3)Nb(2/3))O(3)-PbTiO (3) ternary system by using an alkoxide process. Multilayer ceramic chip capacitors (10 muF) with high specific capacitances were fabricated using this powder. A Ag80%-Pd20% alloy was used for the internal electrodes. The alkoxide-derived capacitor had an extremely high specific capacitance of about 500 muF/cm(3) and a small temperature dependence meeting Y5U specifications of the EIA standard. The equivalent series resistance was approximately 20 mOmega at 500 kHz. The breakdown voltages of the capacitor were 300 V or higher. In accelerated load life tests and load humidity tests, no degradation of insulation resistance was found during 1000 h of testing.