非本征光纤F-P干涉声传感器的研究

为研究不同材料对法布里-珀罗(F-P)干涉声传感器性能的影响。采用几种不同金属材料,设计制作了基于光纤端面—膜片非本征型F-P干涉声传感器,利用有限元方法对圆形振动膜片进行模态分析,得到了一阶固有频率。实验结果表明:由金、锌合金材料制作的传感器可探测较低声压,且传感器灵敏度较高、对外界声波信号响应成良好的线性关系。     

基于极大倾角光纤光栅的龙门架低频振动传感系统的性能研究

提出了一种光强解调型极大倾角光纤光栅(Excessively Tilted Fiber Grating,ExTFG)的龙门架低频振动传感器。首先分析Ex-TFG振动传感的基本原理和传感特性,实验分析Ex-TFG的偏振相关谐振峰的损耗强度与横向压力的关系;然后通过弹性膜片将PZT的振动信号转换为对传感器的横向压力;再通过光电探测模块把光信号转化为电信号;并且对输出信号进行FFT变换分析。实验结果表明,所设计的传感系统对正弦信号频率响应时间为0.045s,检测范围为1~10Hz,平均误差为0.085Hz,最大误差率为1.4%,幅度响应的线性度为96.46%,传感性能良好,其FFT变换主频分量占80%以上,对低频振动信号的传感与检测具有一定的指导意义。     

SENSIM: A simulation program for solid-state pressure sensors

A simulation program is described which is capable of calculating the output response of silicon piezoresistive or capacitive pressure sensors as a function of both pressure and temperature. A thermoelastic plane-stress formulation is used in calculating the stress and deflection of the transducer diaphragm. Both analytical and finite-difference solution methods are available, depending on the sensor structure. Diaphragm thickness taper, oxide and package stress, and rim effects are simulated. For capacitive structures, the program accurately predicts the diaphragm deflection and pressure sensitivity as a function of pressure and temperature. Stepped diaphragm structures are shown to be capable of improving pressure sensitivity by as much as 50 percent. The package-induced thermal drift for electrostatically sealed glass-silicon devices is typically less than 0.05 mmHg/°C.     

Performance analysis of valveless micropump with disposable chamber actuated through Amplified Piezo Actuator (APA) for biomedical application

The precise manipulation of fluid through pumping systems has been the technological challenge in microfluidic applications. The biomedical applications call for precise and accurate delivery of fluid through miniaturized pumping systems. This paper presents a novel valveless micropump for biomedical applications operated by the Amplified Piezo Actuator. Integrating the disposable chamber and reusable actuator with the proposed micropump allows the actuator to be reused and eliminates the possibility of infection or contagion. The micropump was fabricated using low-cost polymeric materials like Polymethylmethacrylate (PMMA), Silicone rubber through CNC milling, Laser Cutting, conventional moulding operation. The micropump chamber, nozzle/diffusers, and a bossed diaphragm constituted disposable part and Amplified Piezo Actuator with structural support formed the reusable part of the micropump. The bossed diaphragm of the pump chamber consists of a central cylindrical protrusion to reduce the force of adhesion on the diaphragm and transmit force required for micropump actuation. A theoretical analysis was performed to assess the effect of diaphragm thickness and the bossed region on the effective stiffness of the diaphragm, which in turn influences the deflection achieved. Besides, an analytical approach has been presented to address the effect of adhesive force on the diaphragm surface due to the residual fluid and chamber depth. The experimental characterization of the micropump was carried out to determine the optimal performance parameters with water, fluids mimicking blood plasma, and whole blood. Based on the experimental results, the pumping rate and head developed by the micropump have been significantly affected by factors such as bossed ratio, diaphragm thickness, depth of the micropump chamber, and viscosity of the fluid. The optimum configuration of the micropump cosidered silicone rubber diaphragm with thickness of 0.20 mm having a bossed ratio of 0.33 and a chamber depth of 1.25 mm. With the optimal operating parameters of 150 V sinusoidal input of frequency 5 Hz, the proposed micropump was capable of delivering 7.192 ml/min, 6.108 ml/min, and 5.013 ml/min of water and blood plasma, whole blood mimicking fluid with the maximum backpressure of 294.00 Pa, 226.243 Pa, and 204.048 Pa respectively. The corresponding resolution, i.e., pumping volume/stroke of the micropump was about 23.972 µl, 20.358 µl, and 16.708 µl, respectively.     

PZT-based concave diaphragm transducer with compliant supporting layer for releasing residual stress

This paper presents an innovative fabrication process to produce the PZT-based concave diaphragm transducer. The novel micromachining process builds a concave diaphragm with designed stiffness, curvature, and diameter as the supporting layer of the device. A parylene and heat resistant sealant (RTV) composite is utilized to construct the curved diaphragm with a flexible property. The large stress distribution induced by PZT sol-gel deposition on the compliant diaphragm can be released through the diaphragm curvature change without the PZT film cracking.Based on theoretical evaluation, the residual stresses ranging from 52.5 to 123 MPa induced by sol-gel PZT film preparation for different transducer designs in this study are released. The dielectric constant and loss tangent of the deposited film are also investigated. The frequency response of the 5 mm diameter transducer that has a radius of curvature of 5 mm fabricated with the developed process is further examined. According to laser vibrometer measurement, the device displays the displacement is more than 1.3 μm in air environment and 0.95 μm with 20 μL water loading when driven with sinusoidal waves within a frequency range of 200 kHz-1 MHz and 40 V_pp.     

Design and characterization of a high temperature fiber-optic pressure transducer

We have measured the pressure response of a high temperature pressure transducer fabricated from a super alloy. This transducer contains a microbend fiber-optic sensor to measure diaphragm deflection and a reference fiber to help reduce light source fluctuations caused by perturbations in the fiber leads. The transducer was characterized at pressures up to 22.8 MPa and temperatures to 430°C. The experimental data taken at constant temperature shows a 0.58 percent (of full scale pressure) minimum deviation between the fiber-optic pressure transducer output and output of a calibrated gage pressure transducer. Over the entire temperature range of20-430degC, the fiber-optic pressure transducer output exhibits a 1.2-percent (of full scale pressure) maximum deviation from calibrated pressure.     

一种微型光纤光栅压力传感器

设计并实现了一种新型光纤光栅压力传感器。该传感器以光纤布拉格光栅(FBG)为敏感元件,通过菱形钢结构,将压力转换为膜片横向应变,通过将光纤光栅粘于工形膜片中心轴线上,可将压力转换为光纤光栅轴向应变,通过解调光栅的中心波长漂移即可得到压力大小。传感器外壳采用圆柱体刚性封装,外高为13mm,直径为33mm。对设计的传感器进行了压力标定测试,得出传感器的线性拟合度为0.993 5,量程为0~0.234MPa,灵敏度为3.341nm/MPa。     

涡街提频振荡水柱驱动压电发电理论分析

海洋波浪能频率低(0.3～1 Hz),海浪进入振荡水柱气室压缩空气形成高速气流。在高速气流通道内放置绕流圆柱钝体,采用卡门涡街效应提高波浪能振荡水柱采集气室气压激振频率,实现高频驱动压电发电,提高海洋能量转换效率。推导波浪进入气室形成振荡的水气动力转换理论,计算了气室初级压强和流速。分析了低频高压气流经钝体形成卡门涡街高频涡流激振提频过程,计算出气压作用于钹型压电发电结构输出的电量。研究气体流速、钝体等系统参数与输出能量的关系。计算结果表明,周期为0.65～1.1 s的海浪进入气室经提频作用于钹型压电发电结构,稳定输出电能可达70～80 mW,为新型波浪能采集技术提供了理论基础。     

Finite element simulation of package stress in transfer molded MEMS pressure sensors

The goal of this paper is to investigate the effect of residual packaging stress resulting from transfer molding of a micro electro mechanical system pressure sensor. A model of a silicon diaphragm micro electro mechanical system pressure sensor geometry was used to simulate the stresses developed during the molding process. The analyses were carried out with an assumption that the epoxy molding compound was a temperature dependent elastic material. Finite element analysis was used to calculate the residual packaging stress. The stress values were used to obtain the electrical output signal and sensitivity of the packaged sensor. In this way, a direct link was established between package stress and device performance.The calculated output signal and sensitivity were compared with experimental data to verify the simulated stress and hence determine the effect of the packaging process on the pressure sensor. Four different service temperatures were considered to examine the temperature effects on the output signal and the sensitivity for the packaged sensor.     

The tissue response to epimysial electrodes for diaphragm pacing indogs

Epimysial electrodes stapled to the abdominal surface of the diaphragm produced a chronic inflammatory response that appeared to be mediated by mechanical stresses placed on the encapsulation tissue by periodic diaphragm contraction. The tissue response surrounding 34 epimysial electrodes implanted in 11 dogs was studied three months post implant. The tissue response was characterized by a capsule having a mean thickness of 1.24 mm between the electrode and the muscle, while having only a very thin capsule on the back, or abdominal side of the electrode. The tissue response between the electrode and the muscle was comprised of two tissue layers: a layer of granulation tissue and a layer of collagen. The granulation tissue layer contained evidence of acute inflammatory processes including the presence of polymorphonuclear leukocytes in 68% of the samples. Granulation layer thickness was inversely correlated with back encapsulation indicating a reduction in granulation tissue for mechanically stabilized electrodes. In addition, encapsulation tissue surrounding the granulation layer was comprised of collagen fibers with an oblique orientation and an extraperitoneal locale suggesting mechanical load transfers between the electrode and the surrounding tissue. As a result, the histological response to epimysial electrodes implanted on the diaphragm suggests that mechanical loading, induced by movement associated with the contraction of adjacent muscle, must be a consideration for devices that employ epimysial electrodes     

Diaphragm design guidelines and an optical pressure sensor based on MEMS technique

The design guidelines for micro diaphragm-type pressure sensors have been established by characterization of the relationships among diaphragm thickness, side length, sensitivity, and resonant frequency. According to the study, the thickness need to be thin and the side length need to be small in order to get the sensitive diaphragm with high resonant frequency. A Fabry-Perot based pressure sensor has been designed based on the guidelines, fabricated and characterized. In principle, the sensor is made according to Fabry-Perot interference, which is placed on a micro-machined rectangular silicon membrane as a pressure-sensitive element. A fiber-optic readout scheme has been used to monitor sensor membrane deflection. The experimental results show that the sensor has a very high sensitivity of 28.6 mV/Pa, resolution of 2.8 Pa, and up to 91 kHz dynamic response.     

基于Sedona平台的智能供水系统

介绍了一种建立在Sedona平台上的全自动恒压变频供水系统。设计是由Sedona控制器30P、变频器、压力传感器、 I/O 设备、触摸屏显示器等主要设备构成。本系统采用一种新的自动控制技术,通过变频器控制水泵转速,根据给水量、用水量来调节出水压力达到恒压。系统出现故障时仍能自动运行,保证不间断供水。实验测试表明,系统运行稳定,能快速、准确地的达到目标压力。     

基于进口膜片的光纤光栅压力传感器的研究

分析了光纤布喇格光栅(FBG)的压力传感特性,给出了FBG的中心波长与压力的关系以及压力灵敏度系数的表达式,并将FBG纵向粘贴在富士公司生产型号为FBC 20WB2的膜片上进行了压力实验。实验结果表明粘贴在FBC 20WB2型膜片上的FBG压力传感器的灵敏度系数为0.376 nm/MPa左右,其测量精度在满量程范围内为1%,而理论的压力灵敏度系数为0.385 nm/MPa。同时发现粘贴在该膜片上的FBG压力传感器的中心波长与压力变化有着良好的线性关系和很高的相关系数并且迟滞现象较小,说明基于该膜片的FBG压力传感器非常适合于压力测量。     

Effect of thermal stresses on stability and frequency response of a capacitive microphone

This article deals with effects of thermal stresses on stability and frequency response of a fully clamped circular microplate, which acts as the diaphragm of a capacitive MEMS microphone. Static and dynamic pull-in phenomena limit the stable regions of a capacitive MEMS microphone. The results show that the non-dimensional static pull-in voltage of the studied case is about 5.23 (38.6 V). On the other hand, according to the results, the non-dimensional dynamic pull-in of the diaphragm is about 4.74 (34.98 V), which is as low as 90.63% of the static pull-in threshold. Because of the thermal expansion coefficient, diaphragm temperature increment leads to compressive thermal stresses and conversely, decrement of the diaphragm temperature creates tensile thermal stresses. The effect of temperature on the pull-in parameters is given by a design-correcting factor.As results demonstrate, the deflection of the diaphragm subjected to a given electrostatic force can be controlled by means of the temperature changes. In the absence of electrostatic force, as the results show, although temperature changes do not create any deflection, but for a critical temperature increment the diaphragm stiffness vanishes and the buckling phenomenon takes place. Effects of the electrostatic force and the temperature variation on the frequency response of the microphone subjected to a sound pressure wave are investigated. As the results illustrate, increment of the electrostatic force or increment of the diaphragm temperature increases the output level and sensitivity of the microphone and decreases the fundamental frequency of the microphone, limiting the upper band of its bandwidth. It is obvious that decrement of the diaphragm temperature acts conversely. In addition, the results show that in the presence of the electrostatic force sensitivity of the output level of the diaphragm to the temperature change increases.     

新型FBG渗压传感器在隧道涌水模型中的应用

结合波纹膜片的压力敏感特性和光纤Bragg光栅(FBG)的应变传感特性,设计了一种新型的FBG渗压传感器。传感器通过拉杆式结构将波纹膜片在应力下的挠度变形转化为FBG的轴向应变,通过恒温条件下的压强标定试验,得出传感器的压强灵敏度约为20 nm/MPa,和普通光栅相比,其压强灵敏度提高了6 000多倍。对传感器探头内部的光栅进行了温度特性标定试验,通过温度补偿光栅消除外界温度对渗压测量结果的影响。将该传感器用于隧道涌水模型的开挖试验,测得模型注水过程中测点的渗压值不断增大并趋于稳定,隧道开挖过程中渗压值轻微波动,提升水位时渗压值急剧增大。     

Optically excited resonant diaphragm pressure sensor

Silicon diaphragms fabricated by anisotropic etching are coated with a thin layer of aluminium. An intensitymodulated laser beam focused on the diphragm generates transverse vibrations which are detected interferometrically. Differential pressure is applied to the diaphragm and the pressure-induced change in the fundamental resonant frequency is reported.     

Differential Pressure/Pressure Transmitters Applied with Semiconductor Sensors

The optimum design for silicon diaphragm-type pressure sensors and that for a sensing body of the transmitters have been considered. Three types of sensors, which have different section shapes, have been developed for measuring wide-range pressure with high sensitivity and good linearity. The transmitters of the range from 0-100 Pa up to 0-50 MPa with an accuracy of 0.2 percent have been developed. For a differential pressure transmitter a three-metal diaphragm structure has been devised to protect the sensor from an overpressure. The characteristics of the transmitters are high accuracy, high reliability, and long-term stability.     

Atmospheric pressure ionization mass spectroscopy for the study ofpermeation in polymeric tubing

An atmospheric pressure ionization mass spectrometer (APIMS) is used to determine the permeation coefficients for two widely used kinds of polymeric tubing, PF and Kel-F (PCTFE), at 25°C and 75°C. In the experiments, an ultra-high-purity N₂ gas flow was maintained through the test tubing. The net impurity uptake by nitrogen due to the permeation of O₂, CO₂, H₂O, and CH₄ from surrounding air into the polymeric tubing was measured by APIMS with sub-ppb sensitivities. CH₄ had the highest and O₂ had the lowest permeation coefficients. Results show that Kel-F was a superior barrier material for all impurities studied. The permeation coefficients for these polymers increased with temperature but did not change significantly with the permeant partial pressure. The permeability of PFA showed a stronger temperature dependence than that of Kel-F     

磁力弹簧式气体隔膜泵的研究

提出了利用磁力弹簧构造气体隔膜泵,并对气体隔膜泵的具体结构与工作原理进行阐述。对气体隔膜泵的核心部件压电振子、被动截止阀等进行选择和设计;对磁力弹簧结构进行分析,通过理论计算确定磁力弹簧的轴向力与轴向间隙的关系;通过实验方法,对不同阀口直径气体隔膜泵的输出流量与压力进行验证。结果表明,磁力弹簧构造气体隔膜泵能大幅提高泵体容积变化率,磁力弹簧能提供很好的刚度,输出流量、压力与同类气体泵相比大幅提高。     

Equivalent Circuit Analysis of High-Frequency Ventilators Including a New High-Impedance Flow-Interrupting Ventilator

The small tidal volumes (VT) delivered to the lungs by highfrequency ventilators can be very sensitive to changes in the patient's respiratory mechanics. Analysis of a Thevenin equivalent circuit, consisting of a ventilator internal oscillatory pressure source in series with a ventilator internal impedance and a patient's respiratory impedance, reveals the need of a high-internal-impedance ventilator to minimize this VT sensitivity problem. We present a general methodology to estimate the internal impedance of any type of ventilator. The internal impedance, at a given frequency and flow setting, is calculated from the slope of the relationship between the generated peak-to-peak pressure and the VT delivered into a calibrated rigid tank through a varying constriction. We tested a typical high-frequency jet (HFJ) ventilator and a new high-impedance flow-interrupting (HIFI) ventilator consisting of a flow source, a rotary valve, a high-impedance expiratory tube, and a servocontrolled mean proximal airway pressure (MPAP) regulator. We found that the VT delivered by the HIFI ventilator was independent of MPAP and decreased by 12 percent after a fivefold increase in the constriction-tank system impedance. In contrast, the VT delivered by the HFJ ventilator decreased by 80 percent after a similar change in load. We therefore conclude that the VT delivered by the HIFI ventilator should be significantly less sensitive to changes in patient's respiratory impedance than the VT delivered by an HFJ ventilator.