基于硅桥的新型甲醛气体传感器的研究

提出了一种基于高分子薄膜溶胀效应的新型MEMS压阻式甲醛气体传感器,其结构由嵌入惠斯通电桥的硅桥和一层改性丙烯酸酯气敏薄膜构成,敏感薄膜因吸收甲醛气体发生溶胀使硅桥上的惠斯通电桥产生输出电压,从而实现对甲醛气体的检测.基于弹性力学薄板原理构建了该气体传感器中硅桥与改性丙烯酸酯薄膜相互作用的模型,并推导出传感器的输出公式.实验结果验证了理论分析模型,实验结果表明该传感器有很好的线性,选择性.实验测得该传感器灵敏度为0.975×106ecr,分辨率为10×10-6,响应时间和恢复时间分别为50s和65s.该传感器结构简单、无须加热,工艺成熟、成本低,应用MEMS 工艺技术可实现与信号处理电路的集成.     

Fabrication and characterization of a new MEMS fluxgate sensor with nanocrystalline magnetic core

This paper presents a new MEMS fluxgate sensor with a Fe-based nanocrystalline ribbon magnetic core and 3D micro-solenoid coils. The excitation coils were placed vertically to the sensing coil on the chip plane. Second harmonic operation principle was adopted in this fluxgate sensor. The total size of the fluxgate sensor was 6.25 mm × 4.85 mm × 120 μm. A simple testing system was established to characterize the fabricated devices. A band pass filter was used to pick up the second harmonic signals in the sensing coils. When excitation rms current of 120 mA and the operational frequency of 200 kHz were selected for the testing of the fabricated devices, the sensitivity of the developed fluxgate sensor was 1005 V/T in the linear range of −500 μT to +500 μT. Due to the combination of the 3D structure coils with the nanocrystalline core, relatively low sensor noise was achieved. The noise power density was 544 pT/Hz^0.5@1 Hz and the noise rms level was 9.68 nT in the frequency range of 25 mHz-10 Hz.     

Measurement of thermal conductivity of fluid using single and dual wire transient techniques

A modified measurement device to measure thermal conductivity of fluids using transient hot-wire technique has been designed, developed, tested and presented in this paper. The equipment is designed such that the thermal conductivity could be measured using both single wire sensor of different length and dual wire sensor. The sensor, which is also a heater, is a platinum micro-wire of 50 μm diameter. The influence of wire length on the measurement of thermal conductivity of fluids is tested using two single wires of length 50 mm and 100 mm. The thermal conductivity is also measured using a dual hot wire arrangement; which is achieved by placing the 100 mm and 50 mm wires in a Wheatstone bridge with the 100 mm wire as the sensor and 50 mm wire as a compensation wire. The apparatus requires a 100 ml of test fluid to perform the experiment. The testing temperature of the test fluid during the experimentation can be suitably varied by the choice of heat exchange fluid used in the apparatus. Water is chosen as testing fluids for primary standards. When compared to single wires, the thermal conductivity of the fluids measured is consistent with dual-wire method with an uncertainty of ±0.25%.     

A magnetic MEMS actuator using a permanent magnet and magnetic fluid enclosed in a cavity sandwiched by polymer diaphragms

A magnetic microelectromechanical systems (MEMS) actuator using a small permanent neodymium-magnet surrounded by magnetic fluid (MF) was developed and characterized. The magnet is enclosed in a cavity sandwiched by two identical thin PET-sheet diaphragms and is able to move smoothly due to the MF. The diaphragms deflect when an external magnetic force is applied to the magnet. This structure was adopted to prevent the diaphragms from being stiffened by attaching or fabricating a magnetic layer on the diaphragm surface and to secure the necessary volume of magnetic material. The magnets are 2–4 mm in diameter and the cavity is 5 mm in diameter and 1 mm in depth. The diaphragms are 20 μm in thickness. Experiments showed the displacement amplitude generated at the diaphragm center was in the range of 10–50 μm for attractive and repulsive magnetic force when magnetic flux density of 4–30 mT was applied. The response was within about 1 s. The deflection profile of the diaphragms can also be varied by changing the magnet position.     

有场制备的磁流变弹性体压缩弹性模量测试分析

针对磁流变弹性体压缩弹性模量随磁场变化的问题,在磁场存在的环境下制备出其材料配比分别为羟基铁粉为108 g,硅橡胶为28 g,硅油为18 g的磁流变弹性体磁流变弹性体,在压缩应变ε=2.6%的情况下分别对磁场方向与磁流变弹性体颗粒链压缩方向平行和垂直的情况下建立了数学分析模型。对磁流变弹性体的压缩弹性模量进行了理论分析,并通过实验印证了理论分析的准确性。研究结果表明,加载磁场方向与磁流变弹性体内部颗粒链压缩方向平行的情况下,材料内部磁致压缩力随着磁感应强度的增强而非线性增大;加载磁场方向与磁流变弹性体内部颗粒链压缩方向垂直的情况下,材料内部磁致压缩力随着磁感应强度的增强而非线性减小。     

导磁型磁流变换向阀设计及性能分析

针对因比例电磁铁响应频率限制及弹簧疲劳失效等导致换向阀响应速度不足的问题,基于磁流体磁流变特性以及惠斯通电桥原理,设计了一种主动引导磁力线方向的磁流变换向阀,建立其数学模型。使用MATLAB/Simulink软件对导磁型磁流变换向阀进行动态分析,得到不同电流组合下阀芯位移-时间特性曲线,并测试了导磁型磁流变换向阀的动态响应性能。测试与分析结果表明,导磁型磁流变换向阀动态响应时间较同通径电磁换向阀有显著缩短。     

Characterization of MEMS piezoresistive pressure sensors using AFM

Atomic force microscope (AFM) is adapted to characterize an ultrasensitive piezoresistive pressure sensor based on microelectromechanical system (MEMS) technology. AFM is utilized in contact mode to exert force on several different micromachined diaphragm structures using a modified silicon cantilever with a particle attached to its end. The applied force is adjusted by changing the trigger voltage during each engage step of the probe-tip on the diaphragm surface. The contact force is determined from the force plots obtained for each trigger voltage in advanced force mode. Low force values in the range of 0.3–5 μN have been obtained with this method. This force induces strain on the bridge-arm of the diaphragm where the polysilicon resistor is located. The resultant change in the resistance produced due to varying force/pressure is measured using a delta mode current–voltage (I–V) measurement set-up. The contact mode AFM in conjunction with a nanovoltmeter enables the calibration of very sensitive force sensors down to 0.3 μN.     

基于微控制器的风速风向传感器系统设计

提出了一种基于惠斯通全桥电路的热式风速风向传感器系统设计方案.传感器芯片结构利用ANSYS软件进行了热学和电学的耦合仿真,并进行了结构优化.芯片采用剥离工艺在陶瓷衬底上加工而成,利用直接安装技术对传感器进行封装.系统采用恒温差工作原理进行控制,热温差工作原理测量风速和风向.系统中微控制器集成的电流型D/A对传感器恒温差控制模式的初始状态进行设定,同时补偿环境温度的变化造成的输出信号的漂移,使得系统的工作温度扩展到-40～60 ℃.热温差检测模式利用位于片上的8个温敏元件构成两路惠斯通全桥电路连接,这种设计在保证灵敏度的同时提高了其测量范围.本系统的微控制器集成了大量模拟和数字模块,减少片外元件使用量,大幅缩小系统体积,同时能够提高测量系统的测量精度及可靠性.通过风洞测试表明,该系统能够完成360o风向检测,精度达到3°,风速的检测范围达到35 m/s.     

A diaphragm-type fiber Bragg grating pressure sensor with temperature compensation

A diaphragm-type fiber Bragg grating (FBG) pressure sensor with two bare FBGs directly bonded on a circular diaphragm along the radial direction has been proposed and studied. Measurement principle and simulation analysis of the pressure sensor are introduced. Using the wavelength shift difference of the two FBGs which respectively measure the positive and negative strain as sensing signal, the pressure sensitivity is increased and the temperature cross-sensitivity is compensated. Experimental results indicate that the measurement sensitivity is 1.57 pm/kPa in a range from 0 to 1 MPa, the correlative coefficient reaches 99.996%, and the temperature compensation performance is distinct. This kind of pressure sensor could be used to measure and monitor the static/dynamic pressure of gas or liquid.     

Additive manufacturing and characterization of a load cell with embedded strain gauges

In this paper we present the exploitation of Fused Filament Fabrication (FFF) to manufacture a load cell using double extrusion of conductive and non-conductive commercial materials in a single-step printing cycle. A load cell with four embedded strain gauges, manufactured with tailored process parameters and strategies, was used to deposit the conductive filament to obtain near equal electrical resistance values among the four strain gauges, aiming to connect them in a full Wheatstone bridge configuration. Subsequently, several tests were performed, firstly to understand the behavior of each strain gauge and then to characterize the load cell. The tests showed that the strain gauges are sensible to compressive and tensile deformation and that the load cell's voltage, obtained by connecting the four strain gauges in a full Wheatstone bridge, decreases as the force applied increases. This work demonstrates the potential of FFF technology in the sensor manufacturing field and that it is possible to integrate sensitive elements into non-sensitive elements without an additional assembly process by using low-cost commercial filaments and 3D printers.     

磁致变刚度原理的气动软体致动器设计与试验

软体机器人友好的人机交互特性使其在柔性抓取、生物医疗等领域有着广泛的应用前景。针对软体机器人“柔有余而刚不足”的缺陷，提出了一种具有快速、可逆变刚度能力的磁气混合驱动软体致动器。基于磁流变效应，设计了以磁流变弹性体材料作为基体的单自由度纤维增强型磁气混合软体致动器，并给出了软体致动器的浇注制造工艺。构建了磁-力耦合模型，分析磁流变弹性体中的刚度影响关系。基于自主开发的刚度测试平台，试验结果表明：设计开发的软体致动器可以在气压和磁场作用下实现可变刚度混合驱动，通过增加磁场强度可以明显提升软体致动器的刚度，最高可提高约40%。软体致动器末端位置控制实验结果表明：通过磁场激励作用，可将软体致动器携带负载的位姿保持能力提高1.4倍，具有动载荷下的位置保持驱动能力，调节响应时间小于1.5 s。     

A bi-material microcantilever temperature sensor based on optical readout

As one of the simplest MEMS sensors, microcantilever can sense temperature faster and more sensitively than traditional thermometers as its small size and low thermal mass. In this paper, an Au/SiNx bi-material microcantilever temperature sensor based on optical readout is presented. The deflection of the cantilever varies with the change of temperature due to the differences in thermal expansion coefficients between gold and silicon nitride. Then, the temperature could be accurately measured by detecting the deflection of the cantilever with optical lever method. By experiments, the theoretical model is verified and the temperature characteristics of the sensor are also determined. With a commercial microcantilever, the temperature resolution of the sensor is tested to be 0.02 K when 25 mm length of optical arm set. By optimizing the microcantilever parameters, the temperature resolution of the sensor could be 0.1 mK. High sensitivity makes it suitable for some special precise temperature measurements.     

Calibration and examination of piezoresistive Wheatstone bridge cantilevers for scanning probe microscopy

This paper describes the method of determining the force constant and displacement sensitivity of piezoresistive Wheatstone bridge cantilevers applied in scanning probe microscopy (SPM). In the procedure presented here, the force constant for beams with various geometry is determined based on resonance frequency measurement. The displacement sensitivity is measured by the deflection of the cantilever with the calibrated piezoactuator stage. Preliminary results show that our method is capable of measuring the force constant of Wheatstone bridge cantilevers with an accuracy of better than 5% and this is used as feedback for improvement of sensor micromachining process.     

钴基非晶磁芯巨磁阻抗效应电流传感器

利用钴基非晶薄带环形磁芯的巨磁阻抗效应研制了新型非接触电流传感器。磁芯在2kA／m横向磁场作用下，用密度为25A／mm。短时矩形脉冲电流退火30s，通过CMOS多谐振荡电路产生的频率为900kHz窄脉冲电流激励，最大阻抗变化率为34％，磁场灵敏度约为45％Oe。分析了传感器工作原理，设计了传感器电路，通过参数的优化和电流负反馈设计提高了传感器的分辨率、线性度、灵敏度和测量范围。设定测量范围为-2．5～＋2．5A时，传感器测量精度为0．45％，灵敏度为0．67V/A     

耐高温压阻式压力传感器研究与进展

传统的硅扩散压阻式压力传感器用重掺杂4个P型硅应变电阻构成惠斯顿电桥的力敏检测模式，采用PN结隔离，高温压阻式压力传感器取消了PlN结隔离，与半导体集成电路平面工艺兼容，符合传感器的发展方向。根据力敏材料的分类，分别介绍了多晶硅中高温压力传感器、SiC高温压力传感器和单晶硅SOI（silicon on insulator）高温压力传感器的基本工作原理和国内外的发展现状，重点论述了BESOI（bonding and etch-backSOI）、SMARTCUT和SIMOX（separation by implanted oxygen）技术的SOI晶片加工工艺。以及由此晶片微机械加工成的芯片封装的高温微型压力传感器部分特性，对此领域的发展作了展望。     

Analysis and comparison of the performance of MEMS fluxgate sensors with permalloy magnetic cores of different structures

This paper presents four MEMS fluxgate sensors which were fabricated with same processes but with magnetic cores of different structures. Thick photoresist-based UV lithography and electroplating were adopted in the fabrication of the fluxgate sensors. Solenoid coils used as excitation and sensing elements were made of copper, whereas the magnetic core material was permalloy. Polyimide was used to support the structures of the sensors. An electronic testing system based on the second harmonic principle was established to characterize the fabricated devices. Each sensor was tested with the excitation coils being excited by a sine waveform current whose frequency was 100 kHz. From these experiments we can obtain some information about how the magnetic core structures affecting the magnetic field measuring performance of the fluxgate sensors, which might make some contribution to the performance improvement and miniaturization of fluxgate sensors.     

Miniature low-power IR monitor for methane detection

A portable methane gas monitor based on an infrared spectrum absorption principle has been developed using a dual-channel and dual-wavelength pyroelectric infrared detector, active filters around the overtone absorption lines of methane at 3.31 μm, reference filters around the non-absorption lines of methane at 3.93 μm, mid-IR LEDs, a miniature gold-filled cell structure, temperature sensors for gas concentration calibration and compensation, an electrical modulation source, and a highly integrated intelligent controller. A detailed investigation has been carried out to design a low-cost portable IR optical sensor for methane detection that can operate in harsh environments with temperature variations between −10 °C and 40 °C. The infrared detection optics principle used in developing this system is mainly analyzed. A prototype based on this design showed an accuracy of ±0.05%, which meets the technology requirements of lower-power consumption, reduced volume, and wide measurement range.     

磁致伸缩压力传感器设计及其输出特性

研究了铁镓合金(Galfenol)的磁致伸缩特性,提出一种基于Galfenol的新型磁致伸缩压力传感器,以实现机器人的触觉力精确感知。该传感器利用磁致伸缩逆效应将压力转换为电压信号,从而完成对压力的精确测量。设计、制作了磁致伸缩压力传感器,采用双永磁体回形磁路优化了压力传感器的磁场。对传感器进行了理论分析与实验研究,讨论了偏置条件、外压力等因素对输出电压峰值的影响。实验结果表明,在偏置磁场为4.8kA/m、施加的压力为2.5Hz、6N时,传感器的输出电压峰值达16mV,且输出电压峰值与压力呈较好的线性关系。研制的传感器具有结构简单、线性度好、反应速度快等特点,可以满足机器人触觉感知的需求,也可应用于其他领域的压力测量。     

适用于恶劣环境的MEMS压阻式压力传感器

为了消除潮湿、酸碱、静电颗粒等恶劣环境对压力传感器压敏电阻的影响,提出了一种新型结构的压阻式压力传感器.该传感器将压敏电阻置于应力薄膜的下表面并通过阳极键合技术密封在真空压力腔中,从而减少了外界环境对压敏电阻的影响.介绍了此种压力传感器的工作原理,使用ANSYS软件并结合有限元方法模拟了压敏薄膜在压力作用下的应力分布情况.最后,利用微机电系统(MEMS)技术成功制作出了尺寸为1.5 mm×1.5 mm×500 μm的压阻式压力传感器.用压力检测平台对该压力传感器进行了测试,结果表明,在25～125℃,其线性度小于2.73％,灵敏度约为20mV/V-MPa,满足现代工业使用要求.