An Unexpected Frequency Response of A Piezoelectric Quartz Crystal Sensor to the Density and Viscosity of the Liquid

An unexpected frequency response for a piezoelectric quartz crystal (PQC) sensor to liquid density and viscosity was reported. For a PQC oscillating in a liquid phase, the frequency shifts (?f ) show a wave-shape response to liquid density (ρ) and viscosity (η) in fine structure, if the longitudinal wave effect was not eliminated. This result is different from the well-known linear relationship between of ?f and (ρη)1/2. An oscillating frequency-temperature curve of the sensor was observed and explained.

Application of modified quartz crystal sensors:Detection of isobutyl alcohol,ethyl acetate and ethylene

Aroma volatilization is one of the very important attributes of agricultural products during ripening.Ingredients of aroma compounds experience changes over products’different ripening stages.This paper aimed to develop a detection system based on modified quartz crystal sensors to detect volatile organic compounds(VOCs).By drop-coating on sensors’surface,four sensors were made using quartz crystal resonators coated with four different absorbable materials:ethyl cellulose,cellulose acetate,1,2-dioleoyl-sn-glycero-3-[phosphor-L-serine],and galactosyl ceramide.With the diversely coated sensors,three VOCs:isobutyl alcohol,ethyl acetate and ethylene were detected at ppm level.To investigate the structure influence of the coated sensing films on VOCs absorption,the topography of films was imaged in 3D using atomic force microscopy(AFM)in tap mode for qualitative analysis of gas absorption.The selectivity and sensitivity were investigated when sensors were exposed to VOCs with increasing concentrations.The results showed that the frequency shift of sensors was linear to the concentrations of all three VOCs in the range of 5-25 ppm.With values reaching over 4.5 Hz/ppm,the sensitivity of cellulose acetate coated sensor to three VOCs was similar,higher than that of sensors with other coatings.The high sensitivity of the cellulose acetate coated sensor might be due to the film’s rough surface and porous structure.The results may help further research on detection of fruits’organic volatiles during the ripening stage.

Vibration analysis of a new polymer quartz piezoelectric crystal sensor for detecting characteristic materials of volatility liquid

We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance(QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fspof 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fspwas found and subsequently became one of the most important parameters in the new sensor design.

High sensitive piezoelectric quartz crystal liquid density sensor

We report for the first time a cleavage phenomenon in the resonant peak of a piezoelectric quartz crystal(PQC) in liquid phase.In the presence of a strong longitudinal wave effect,an additional resonant peak appears in the conductance-frequency curve.With gradually increasing liquid density,the additional peak moves from low to high frequency region then disappears.The frequency of the additional resonant peak is sensitive to the change in liquid density.The frequency shift of the additional peak is linear with the liquid density in a given range.For a 5 MHz PQC with a reflection distance of 16 mm for longitudinal wave,the sensitivity to liquid density is 2.61×10^6 Hz g^-1 cm^3.The overlap between the primary resonant peak and the additional resonant peak causes a decrease in the intensity of the former and an increase in the intensity of the latter.In a combined impedance analysis method,the changes in surface mass loading,density and viscosity of the liquid were monitored simultaneously by a PQC sensor.

The influence of temperature on flow-induced forces on quartz-crystal-microbalance sensors in a Chinese liquor identification electronic-nose: three-dimensional computational fluid dynamics simulation and analysis

An electronic-nose is developed based on eight quartz-crystal-microbalance (QCM) gas sensors in a sensor box, and is used to detect Chinese liquors at room temperature. Each sensor is a highly-accurate and highly-sensitive oscillator that has experienced airflow disturbances under the condition of varying room temperatures due to unstable flow-induced forces on the sensors surfaces. The three-dimensional (3D) nature of the airflow inside the sensor box and the interactions of the airflow on the sensors surfaces at different temperatures are studied by computational fluid dynamics (CFD) tools. Higher simulation accuracy is achieved by optimizing meshes, meshing the computational domain using a fine unstructural tetrahedron mesh. An optimum temperature, 30 ℃, is obtained by analyzing the distributions of velocity streamlines and the static pressure, as well as the flow-induced forces over time, all of which may be used to improve the identification accuracy of the electronic-nose for achieving stable and repeatable signals by removing the influence of temperature.

Quartz Crystal Microbalance Sensor Deposited with LB Films of Functional Polymers for the Detection of Phenols in Vapour Phase

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Simultaneous Multimode Oscillation of Stress-Compensated Cut Quartz Resonator with Narrow-Band Wide Variable-Range Quartz Crystal Oscillator

A multimode-quartz-crystal oscillator was developed to excite stable dual-mode resonance at different frequencies: The oscillation of the 3rd harmonic resonance of the principle C-mode and an additional resonance B-mode of SC-cut crystal. Harmonic combinations of the 3rd and fundamental mode of B-mode with the 3rd harmonics of C-mode are demonstrated. The measurement of the temperature dependence of the oscillation frequency is demonstrated along with the stability determined by root Allan variance. Dependence on the open conductance of the active circuit and the dependence on the coupling capacitors are discussed.

Oscillation Conditions for An Electrode-separated Piezoelectric Sensor in Electrolyte Solution

Based on the needs of the oscillation equation and frequency stability, three oscillation conditions are proposed and have been experimentally verified for an electrode-separated piezoelectric sensor (ESPS ) in electrolyte solutions. The present paper covers the dependence of the minimum cell constant needed for the ESPS on solution conductivity. The oscillation conditions of the classical liquid piezoelectric sensor are discussed. The 'cease-to-oscillate' frequencies of the ESPS were measured.

An Oscillation Condition for an Electrode－separated Piezoelectric Sensor in Non－electrolyte Liquid

n oscillation condition was proposed and experimentally verified for an elec-troderaeparated piezoelectric sensor (ESPS) in non-electrolyte liquid, it was ex-pressed as , where C_s is the solution capaci-tance , R_q, C_o and w are the motional resistance , static capacitance and resonant an-gle frequency of the crystal , respectively. And Y-tgθ, where θ is the phase shift inthe oscillator. The relationships between the minimum cell constant needed for ES-PS to oscillate and each of the following parameters, permittivity, density and vis-cosity of the liquid as well as the oscillator phase shift were discussed. The″ cease-to-oscillate″ frequency of ESPS was measured. The oscillation ability of ESPS in-creases with increasing permittivity or decreasing density and viscosity of the liq-uid. An oscillator with a larger Y value is helpful to drive ESPS.

基于共价有机框架材料的QCM二氧化碳气体检测系统

为了实现人居环境下高精度二氧化碳气体检测,设计了一种基于共价有机框架材料COF-5的石英晶体微天平(QCM)二氧化碳气体传感器及检测系统。分析了QCM质量灵敏度分布原理并进行了有限元仿真分析,利用超声法合成敏感材料,采用滴涂法制备基于金电极的QCM二氧化碳气体传感器,并设计了一种基于FPGA的二氧化碳气体检测系统。实验测试结果表明:开发的二氧化碳气体传感器及检测系统在二氧化碳气体浓度为2000~5000 ppm下表现出良好的线性响应,拟合曲线相关系数为0.988,系统灵敏度为0.034 Hz/ppm,响应时间为32 s,恢复时间为20 s,表现出良好的动态响应性能,系统最大绝对误差小于±25 ppm,且系统具有较好的重复性及选择性。

FeGa膜/AT切石英晶片双面复合蝶形谐振磁场传感器

蝶形磁致伸缩膜由于磁汇聚,其中心区域的磁致伸缩应变增强,但是和矩形AT切石英晶片复合时,磁膜耦合至矩形晶片电极区的应变会向周围无磁膜区域扩散,降低应变对晶片厚度剪切振动的作用,降低磁场传感器灵敏度。提出AT切石英晶片和FeGa膜形状一样的蝶形谐振磁场传感器,蝶形晶片可以将蝶形磁膜增强的晶片应变汇聚至晶片电极区,以提高传感器灵敏度。仿真结果预测,在23.8~118.9 Oe的磁场范围内,蝶形结构的灵敏度为蝶形磁膜/矩形晶片结构的3.73倍。通过微机械加工,制作了蝶形器件,对实际器件测试的结果表明,在76.4~117 Oe的线性区间内,蝶形传感器的灵敏度可达-29.08 Hz/Oe。

一种基于石英晶体微天平倍频相移信号的呼吸频率监测系统

对人体呼吸频率实时连续的监测具有重要的医学诊断价值,本研究以基频10 MHz压电石英晶体为呼吸监测传感元件,采用直接数字频率合成器(DDS)合成频率源在5倍频下激励压电石英体,实时连续测定呼吸气流下的压电石英晶体相移变化信号。由于高倍频下压电石英体对表面水分子吸附聚集过程具有高灵敏的质量响应,因此石英体表面不需厚膜修饰,直接采用金属电极(银电极)的石英体,成功实现了对呼吸频率的连续监测。与传统的频移法相比,该方法信号采样速度快,可低至0.05 s/点,无论对慢呼吸还是急促呼吸都可以实现准确监测。石英晶体微天平相移呼吸检测系统不仅能够满足连续呼吸监测的要求,还可以为人体呼吸监测提供呼吸频率、呼吸强弱,呼吸紊乱度等呼吸特征信息。

功能化MIL-101(Cr)修饰QCM气相传感器的组装与甲酸识别

挥发性有机化合物(VOCs)是一类主要的大气污染物,对人体健康和环境均可造成危害,因此发展可快速、灵敏检测VOCs的技术具有重要意义.本文分别以乙二胺(ED)和乙醇胺(EA)修饰MIL-101(Cr),制得了MIL-101(Cr)-ED和MIL-101(Cr)-EA,采用滴涂法制备了3种负载MIL-101(Cr)材料的石英晶体微天平(QCM)气相传感器,研究了其对甲醇、乙醇、异丙醇、丙酮、环己烷、二乙胺、甲酸、甲醛、氨气和乙酸的传感性能.实验结果表明,与负载MIL-101(Cr)的传感器相比,负载MIL-101(Cr)-ED和MIL-101(Cr)-EA的QCM传感器对甲酸的吸附性能显著提高,在甲酸浓度为350 mg/L时,传感器的振荡频率分别下降至-375.6和-232.1 Hz.在甲酸浓度为5~350 mg/L时,负载MIL-101(Cr)-ED的QCM传感器对甲酸响应的灵敏度为0.95 Hz·L·mg^(-1),检测限为0.95mg/L,表现出线性良好、灵敏度高、检测限低和重复性好的特点.这表明此类QCM气相传感器在VOCs实时检测方面具有良好的应用前景.

基于石英晶体薄膜的压力传感器研究

基于石英晶体薄膜,进行了直接键合、Au-Au键合、共晶焊和玻璃浆料封接,包括石英晶体—石英晶体、石英晶体—609金属双层封接、石英晶体三层封接、石英晶体—609金属多层封接。封接漏率低于1×10^(-13)Pa·m^(3)/s,强度达到了10MPa,翘曲降到了3μm。采用石英晶体作为敏感元件,利用MEMS加工工艺制备出带有电极图形石英,通过转接的方式,将石英晶体薄膜封接到609金属上制成电容压力传感器,测试了不同封接工艺零位漂移,实现了0.001~0.1 mmHg低真空度的测量范围,测量范围内精度±0.6%。15天长期零位漂移为0.8μmHg,漂移水平为0.5%FS。通过在石英晶体上设计“弓”型应力释放结构,采用上述相同工艺制备了电容压力传感器,15天长期零位漂移水平降至0.06%FS。

QCM传感器在生物医学检测中的应用研究进展

现代医学在治疗技术和药物研发不断提升的同时,也越来越依赖于医学检测技术的进步。石英晶体微天平(quartz crystal microbalance,QCM)是基于石英晶体压电效应的一种新型高灵敏的纳克级质量型传感技术,具有实时监测、高灵敏度、免标记等优势,近年在生物医学检测领域中广泛应用。该文概述了近年来QCM传感器的构建及其在核酸、蛋白质、癌细胞和微生物检测中的应用研究进展,并对其未来的发展方向进行探讨。

基于多孔氧化铝的高品质因数QCM湿度传感器的研究

石英晶体微天平(QCM)传感器以频率形式输出信号,具有成本低、响应快、灵敏度高等优点,因而使用多孔α-Al_(2)O_(3)作为湿敏材料来提高QCM传感器对湿度的检测灵敏度。基于QCM传感原理,通过COMSOL软件研究不同结构尺寸对传感器谐振频率、品质因数、导纳的影响,优化传感器的几何参数。探究传感器在一定湿度范围内的灵敏度和动态特性,实验结果表明,该传感器具有显著的湿度辨别能力,最大频率响应可达到13 kHz,灵敏度为155 Hz/(%RH),响应、恢复时间分别为20 s和8 s。因此,使用多孔α-Al_(2)O_(3)作为湿敏材料的QCM传感器在湿度检测方面具有一定的可靠性和准确性。

分子印迹纳米膜的制备及其在检测神经性毒剂沙林中的应用

采用电化学聚合法首次合成了对有机磷毒剂沙林有快速响应和高灵敏度的分子印迹纳米膜。用压电晶体频移法测出其膜厚约为 35nm ,对影响电聚合反应的因素 (如模板分子浓度、单体浓度、扫描电位和扫描次数 )进行了筛选 ,进而在石英晶体微天平 (QCM)上制成了纳米分子印迹传感器。这种新型传感器响应速度快 (最初响应时间 2s) ,抗干扰能力强 ,检测范围宽 (0 .7～ 5 0 μL L) ,灵敏度高 (1nL L)。

压电石英晶体传感器检测血浆凝血酶原时间及其初步应用

目的 建立一种压电石英晶体传感器检测血浆凝血酶原时间 (PT)的方法。方法 采用AT切向、基频 1 0MHz的银膜石英晶体作为压电元件 ;观察血浆凝集过程中晶体振荡频率的变化 ,确定血浆凝集反应的起点和终点。结果 ①血浆标本加入反应体系后 ,晶体振荡频率呈阶梯状快速下降 ,接着频率瞬时上升 ,然后再缓慢降低达到平稳 ,频率阶梯下降的起点为血浆凝集反应的起点 ,频率从快速上升变为下降的转折点为血浆凝集的终点 ,计算两点之间的时间即为血浆凝血酶原时间。②该方法的检测结果与STAGO磁珠检测法的相关性好 (γ =0 .97) ,批内CV =0 .78% ,批间CV =2 .3 8%。结论 压电石英晶体传感器检测血浆凝血酶原时间 ,血浆凝集反应起点和终点确定方便、可靠。且操作简单、快速、成本低廉 ,检测结果准确 ,是一种敏感性高、重复性好的血浆凝血酶原时间检测新方法 。

压电石英晶体活化部分凝血酶时间检测传感器的构建及初步应用

目的 建立一种检测血浆活化部分凝血酶时间 (APTT)的压电石英晶体传感器。方法 采用AT切向、基频 1 0MHz的银膜石英晶体作为压电元件 ;观察血浆凝集过程中晶体振荡频率的变化 ,确定血浆凝集反应的起点和终点。结果 (1 )血浆标本加入反应体系后 ,晶体振荡频率呈阶梯状快速下降 ,接着频率瞬时上升 ,然后再缓慢降低达到平稳 ,频率阶梯下降的起点为血浆凝集反应的起点 ,频率从快速上升变为下降的转折点为血浆凝集的终点 ,计算两点之间的时间即为血浆活化部分凝血酶时间。(2 )该方法检测结果与STAGO磁珠检测法的相关性好 (γ =0 .972 ) ,批内CV =2 .5 4 % ,批间CV =7.1 4 %。结论 压电石英晶体传感器检测血浆活化部分凝血酶时间 ,血浆凝集反应起点和终点确定方便、可靠。且操作简单、快速、成本低廉 ,检测结果准确 ,是一种敏感性高、重复性好的血浆活化部分凝血酶时间检测新方法 ,可用于临床常规检测。

压电石英晶体传感器液相检测的影响因素

目的 探讨压电石英晶体传感器液相检测的影响因素。方法 采用AT切向镀金膜的石英晶体制成 2× 5型石英晶体微阵列 ,观察晶体振荡频率在不同粘度和密度的甘油PBS( 0 .15mol LpH 7.0 )溶液、不同浓度的NaCl溶液、不同pH的PB溶液( 0 .0 6 7mol L)及不同体积的PBS溶液 ( 0 .15mol LpH 7.0 )中的变化规律以及机械冲击和重新加样对晶体振荡频率的影响。结果 石英晶体振荡频率随溶液粘度和密度、离子浓度、pH的增大而降低。溶液体积、机械冲击和重新加样对晶体频率基本无影响。结论 石英晶体传感器所处溶液体系的性状如粘度、密度、离子浓度、pH等因素对其振荡频率有较大的影响 。