压电传感器测定离子液体粘度温度系数

硅酸镧镓微天平是一种能在高粘度液体应用的新型压电传感器,可以用于液体粘度的快速传感监测.随着液体粘度增加,传感器的动态电阻增加,而谐振频率下降.采用该传感器实时监测离子液体的粘度随温度的变化曲线,结果表明:溴代1-甲基-3-正已辛基咪唑的粘度和粘度一温度系数均随温度升高呈指数下降,压电传感器为测定离子液体粘度提供了一种新的快速测量方法.     

阻抗法监测离子液体膜的吸附性能

采用高频阻抗计测定了离子液体与有机溶剂相互作用过程中的电阻抗变化,选用1-甲基-3-正辛基咪唑氟硼酸盐([C8Mim]][BF4])作为模型离子液体,所用有机溶剂包括乙醇、丙酮、乙酸乙酯、四氯化碳.结果表明,在[C8Mim][BF4]中加入丙酮或乙醇后,混合物的电导率和介电常数显著增加,而加入四氯化碳所引起的阻抗变化较小.根据离子液体膜的阻抗变化可以监测膜的吸附特性,该文采用阻抗法和对电导率和介电常数有频率响应的串联式压电传感器实时检测了[C8Mim][BF4]膜吸附有机溶剂蒸气的过程,为研究离子液体的吸附性能提供了一种新的测量方法.     

旋转式FBG粘度计设计与有限元分析

设计了一种用于测量液体粘度的旋转式光纤布拉格光栅(FBG)粘度计.对旋转式FBG粘度计的主体结构进行有限元分析,有限元分析表明:在转速同为44 r/min的条件下,当设置液体粘度参数分别为0.5,0.75,1.5Pa·s时,传感元件的最大应变量分别为2.578×10-6,3.836 × 10-6,7.502×10-6,扭转角度分别为1.32°,2.04°,3.83°.结果显示:改变液体的粘度值能够对测扭传感器扭转形变产生影响,并且呈一定的线性关系.有限元分析为研究传感器的工作原理和改进传感器的结构性能提供了依据.     

基于纳米金修饰丝网印刷电极的乙醇生物传感器

在丝网印刷电极上利用吸附法固定乙醇脱氢酶,并用纳米金进行修饰,以铁氰化钾为介体制作了用于酒精检测的一次性乙醇脱氢酶电极试纸.纳米金颗粒修饰酶电极,极大地改善了电极电流响应,提高了传感器的灵敏度.此乙醇传感器的响应时间仅为25 s,灵敏度为0.06 μA(mmol/L)~(-1),线性浓度测量范围为1.0 mmol/L至10 mmol/L.     

磁性液体的传感特性及原理应用研究

该文介绍了磁性液体应用在传感领域的独特性能,分析了磁性液体在传感器方面的各种应用研究.利用磁性液体的电磁响应和粘度等特性可开发出各种新型传感器.分析了各种磁性液体新型传感器的工作机理和应用方向,并对其应用前景进行了分析展望,指出其中有待研究的方向和意义.     

基于磁性液体粘度的水平磁性液体微压差传感器动态响应特性研究

微压差传感器在工业和民用领域有着广泛的应用。基于前期设计的水平磁性液体微压差传感器结构模型,着重探讨了磁性液体的粘度对该传感器结构模型动态响应特性的影响,并建立相关的理论模型。本文中的水平磁性液体微压差传感器能够用于静态和动态的微压差测量,根据理论推导和实验研究,可知在静态测量过程中,磁性液体的粘度和饱和磁化强度只影响水平磁性液体微压差传感器的测量范围,对其他的静态测量参数影响很小。然而在动态测量过程中,磁性液体的粘 度对水平磁性液体微压差传感器的动态参数将产生极大影响。例如上升时间、超调量、振荡次数、稳定时间等。通过本文的研究可知,当水平磁性液体微压差传感器同时用于静态测量和动态测量时,应采用粘度和饱和磁化强度适中的煤油基和机油基磁性液体。采用煤油基和机油基磁性液体的水平磁性液体微压差传感器在激励电压大小为 10Ｖ,激励频率为1000Hz的条件下,在500Pa以内的阶跃压强作用下该传感器系统的上升时间0.1S,超调量15％、振荡次数5、调节时间 0.7S。     

基于超声反射法的液体粘度在线测量技术研究

传统的液体粘度测量方法如旋转法、落球法和毛细管法等需将传感器或装置浸入液体内部实现测量,然而在某些场景下这些方法无法适用,因此发展了一种基于超声横波反射的液体粘度测量方法,建立超声横波在固/液界面的反射模型,利用入射波、反射波的幅值与相位求解声波反射系数,再根据反射系数与液体声阻抗关系得到液体的粘度系数.引入固液声阻抗...     

溶菌酶在硅烷化石英表面吸附的压电传感监测

石英表面经硅烷修饰后 ,可通过憎水性相互作用吸附溶菌酶 ,该吸附动力学过程以压电传感器实时监测。结果表明溶菌酶以单分子层吸附 ,吸附仅部分可逆 ,吸附和解吸的速率常数分别为ka =36 .4mol-1.kg .s-1,kd =8.92 × 10 -3 s-1,且可逆吸附比及饱和单层的吸附密度随溶菌酶浓度增加而增加     

基于复合膜修饰ITO电极的乙醇传感器研究

利用羧基化的多壁碳纳米管(MWCNT)修饰氧化铟锡(ITO)电极,表面吸附一层普鲁士蓝(PB)作为电子介体制作一种新型的乙醇传感器.通过循环伏安法、计时电流法对传感器的性能进行表征和研究.结果表明:所制备传感器对乙醇具有明显的电化学活性,线性范围为0.5～10mmol/L,在S/N=3的情况下,检出限为0.07mmol/L(R=0.9968).该传感器制备简单、经济实用,具有良好的准确性、灵敏度及抗干扰能力.     

基于光纤光栅的液体粘度测量方法的研究

针对液体粘度在线测量问题,提出了一种基于光纤光栅的液体粘度测量方法,即通过检测光纤光栅中心波长的变化量测得液体自身的粘度值.这种依靠液体自身流动得到液体粘度的方法是对粘度在线测量问题的一种新的探索和突破.在液体流动过程中,利用光纤光栅感知阻流元件表面粘滞力引起的悬臂梁的应力变化,对解调出的波长变化量经过计算得到应力变化的大小,从而得到相对应的粘度值.通过实验研究,对于粘度标准液进行光纤光栅的标定,建立了中心波长变化量与粘度的数学模型.最终,进行验证性实验,测量一组液体的粘度值,并与标准粘度计测得的结果进行比对,证明了实验方法的可行性.     

硅酸镧镓晶体微天平测定石蜡膜的吸附特性

硅酸镧镓晶体微天平(LCM)是以硅酸镧镓晶体为压电材料研制的新型压电式传感器,对表面质量负载变化有灵敏的频率响应。在LCM表面浇铸石蜡薄膜,实时监测十二烷基苯磺酸钠在石蜡膜表面吸附过程中的质量变化,结果表明:其吸附过程呈现可逆吸附特征,并可以用Langmu ir等温线和动力学模型进行回归分析,获得吸附/脱附速率常数、平衡常数、饱和吸附量等参数,并讨论了盐浓度的影响。     

基于快速傅立叶变换的阻抗数据处理方法研究

根据阻抗频谱的特点,提出了基于快速傅立叶变换法(FFT)抑制压电传感器随机测量噪音的方法,结果表明,利用该法能对阻抗频谱进行有效平滑处理,滤噪效果明显,所得频率抗干扰能力大大增强。将该方法用于水中基线噪音消除,证明了其相对于其它方法的优越性。结合该文提出的数据处理方法,利用压电传感器研究了非离子表面活性剂TX-114在聚苯乙烯(PS)表面的吸附性能,得到了相关动力学、热力学参数,进一步证实了FFT法的可行性。     

Lateral field excited Y-cut langasite bulk acoustic wave sensor

Previous studies have shown that lateral field excited (LFE) devices on AT-cut quartz are sensitive to liquid electrical property changes. AT-cut quartz LFE devices have low piezoelectric coupling factors. To further improve electrical sensitivities of LFE sensors, it is necessary to study LFE sensors based on other piezoelectric materials with higher coupling factors. In this paper, LFE sensors on Y-cut langasite, which has twice the higher piezoelectric coupling factor of AT-cut quartz, are investigated. Several Y-cut langasite LFE sensors are designed, fabricated, and tested. The experimental results show that the devices are over 6 times more sensitive to liquid conductivity changes and about 2.5 times more sensitive to liquid permittivity changes compared to AT-cut quartz LFE devices. It was also found that the Y-cut langasite LFE devices are about 1.3 times more sensitive to changes in liquid acoustic viscosity compared to the AT-cut quartz LFE devices.     

Micromachined Acoustic Resonant Mass Sensor

This paper describes a highly sensitive, film bulk acoustic resonator (FBAR) mass sensor (built on a micromachined silicon-nitride diaphragm with a piezoelectric thin film and Al electrodes) that can operate in vapor and liquid. The sensitivity of the device to mass change on its surface has been investigated by having various thicknesses of silicon-nitride support layer and also of Al layer. The sensor is measured to have a mass sensitivity of 726 cm$^2$/g, which is about 50 times that of a typical quartz crystal microbalance (QCM). In vapor, the sensor (operating at around 1 GHz and having a relatively high quality (Q) factor of 200–300) shows a minimum detectable frequency shift of about 400 Hz, which corresponds to a mass change of$10^-9$g/cm$^2$on the sensor surface, comparable with that detectable by a QCM. In liquid, though the Q usually drops more than an order of magnitude, we obtain a Q of 40 at 2 GHz by using a second harmonic resonance of the resonator. And with the Q, a minimum 5 ppm resonant frequency shift can be detected, which corresponds to$10^- 8$g/cm$^2$change on the sensor surface.hfillhbox[1374]     

Piezoelectric Disk Resonators Based on Epitaxial AlGaAs Films

A new design for anisotropic piezoelectric disk resonators is demonstrated using single-crystal Al_0.3Ga_0.7As films. The shape of the disk resonator is based on the velocity propagation profile of the elastic wave in the plane of the piezoelectric film, with lateral dimensions scaled to the half wavelength of the desired resonance frequency. The resonators are designed with supports which emulate free-free boundary conditions. Prototype resonators are fabricated using a three-layer Al_0.3Ga_0.7As heterostructure containing silicon-doped electrodes and an undoped piezoelectric Al_0.3Ga _0.7As layer. Quality factors as high as 11 200 are measured in air for a 23.25 MHz fundamental resonant mode, with a corresponding motional resistance of 1.67 kOmega. A finite-element model for the resonator design is also described. Simulation results agree well with both theoretical calculations and experimental data     

A piezoelectric micro-cantilever bio-sensor using the mass-micro-balancing technique with self-excitation

A biosensor was developed for using in a Lab-On-a-Chip (LOC). The sensor detects the change in the resonance frequency of a micro-cantilever with a piezoelectric film. This is the mass micro-balancing technique, which has been successfully used for detecting bio-materials in the quartz crystal microbalance (QCM). The PZT film, a piezoelectric film, is designed to act as both sensor and actuator. The geometry of the micro cantilever is optimized to maximize the sensitivity and minimize the environmental effects such as viscous damping and added mass effect in liquid. The fabricated sensor is composed of a 100 μm long, 30 μm wide, and 5 μm thick cantilever with a 2.5 μm thick piezoelectric (PZT) layer on it. The ratio of thickness to length of the micro cantilever is very high compared to others in micro cantilever-based studies. This high aspect ratio is the key to maximize the sensitivity and minimize the environmental effects. The fabricated micro sensor was tested by detecting the mussel gluing protein, the insulin-anti insulin binding protein and the poly T-sequence DNA.     

基于正弦力激励的预紧压电式力传感器的研究

为了校准预紧的压电式力传感器动态灵敏度并研究其频响特性和预紧结构的设计,首先介绍了正弦力激励的方法并建立校准数学模型。分别在传感器正立和倒立安装方式下进行测试,通过对比试验研究传感器端部等效质量引入的惯性力对传感器动态灵敏度的影响。然后根据传感器固有频率的落球测试方法,将传感器和附加质量块安装于振动系统。通过白噪声激励得到系统安装谐振频率,进而研究传感器有效频率范围和测量精度与安装谐振频率的关系。最后通过理论分析,说明传感器非对称设计的原因。试验结果表明,当附加质量块质量约为传感器质量的121倍时,可忽略端部等效质量对灵敏度标定的影响;压电式力传感器固有频率高达46kHz,但其有效使用频率范围受安装谐振频率限制,当试验频率与安装谐振频率比 时,压电式传感器精度等级为1%;传感器两端等效质量不同,预紧结构是非对称的,用于动态测试时要将端部等效质量轻的一端连接到被测物体。本研究结果可为开展传感器的现场标定和预紧结构的设计提供理论依据。     

Finite element analysis and experiments on a silicon membrane actuated by an epitaxial PZT thin film for localized-mass sensing applications

In this paper, we investigate the performance of a piezoelectric membrane actuated by an epitaxial piezoelectric Pb(Zr_0.2Ti_0.8)O₃ (PZT) thin film for localized-mass sensing applications. The fabrication and characterization of piezoelectric circular membranes based on epitaxial thin films prepared on a silicon wafer are presented. The dynamic behavior and mass sensing performance of the proposed structure are experimentally investigated and compared to numerical analyses. A 1500 μm diameter silicon membrane actuated by a 150 nm thick epitaxial PZT film exhibits a strong harmonic oscillation response with a high quality factor of 110-144 depending on the resonant mode at atmospheric pressure. Different aspects related to the effect of the mass position and of the resonant mode on the mass sensitivity as well as the minimum detectable mass are evaluated. The operation of the epitaxial PZT membrane as a mass sensor is determined by loading polystyrene microspheres. The mass sensitivity is a function of the mass position, which is the highest at the antinodal points. The epitaxial PZT membrane exhibits a mass sensitivity in the order of 10⁻¹² g/Hz with a minimum detectable mass of 5 ng. The results reveal that the mass sensor realized with the epitaxial PZT thin film, which is capable of generating a high actuating force, is a promising candidate for the development of high performance mass sensors. Such devices can be applied for various biological and chemical sensing applications.     

Effect of surface roughness on liquid property measurements using mechanically oscillating sensors

The resonant frequency and quality factor Q of a liquid immersed magnetoelastic sensor are shown to shift linearly with the liquid viscosity and density product. Measurements using different grade oils, organic chemicals, and glycerol-water mixtures show that the surface roughness of the sensor in combination with the molecular size of the liquid play important roles in determining measurement sensitivity, which can be controlled through adjusting the surface roughness of the sensor surface. A theoretical model describing the sensor resonant frequency and quality factor Q as a function of liquid properties is developed using a novel equivalent circuit approach. Experimental results are in agreement with theory when the liquid molecule size is larger than the average surface roughness. However, when the molecular size of the liquid is small relative to the surface roughness features molecules are trapped, and the trapped molecules act both as a mass load and viscous load; the result is higher viscous damping of the sensor than expected.     

提高液体中石英晶体传感器频率稳定度的方法

石英晶体传感器的动态阻抗显著增大,品质因数下降是液体阻尼负载作用的主要效果。本文从分析液体中石英晶体谐振器的相位平衡条件出发,研究了影响传感器频率稳定度的因素;由石英晶体谐振器的能量局部化效应,分析了传感器液体测头设计中的问题,并由此设计出在液体中工作的石英晶体传感器。实验结果表明,此传感器在液体中具有较高的频率稳定度。