A micro electromagnetic low level vibration energy harvester based on MEMS technology

This paper presents a micro electromagnetic energy harvester which can convert low level vibration energy to electrical power. It mainly consists of an electroplated copper planar spring, a permanent magnet and a copper planar coil with high aspect ratio. Mechanical simulation shows that the natural frequency of the magnet-spring system is 94.5 Hz. The resonant vibration amplitude of the magnet is 259.1 μm when the input vibration amplitude is 14 μm and the magnet-spring system is at resonance. Electromagnetic simulation shows that the linewidth and the turns of the coil influence the induced voltage greatly. The optimized electromagnetic vibration energy harvester can generate 0.7 μW of maximal output power with peak–peak voltage of 42.6 mV in an input vibration frequency of 94.5 Hz and input acceleration of 4.94 m/s² (this vibration is a kind of low level ambient vibration). A prototype (not optimized) has been fabricated using MEMS micromachining technology. The testing results show that the prototype can generate induced voltage (peak–peak) of 18 mV and output power of 0.61 μW for 14.9 m/s² external acceleration at its resonant frequency of 55 Hz (this vibration is not in a low ambient vibration level).     

Design and experiment of an electromagnetic levitation system for a micro mirror

In this paper, the design and characterization of a contactless electromagnetic levitation and electrostatic driven microsystem is presented, which has applications for example for large scale angle rotation micro mirrors. The proposed design can levitate a fabricated aluminum micro rotor which can incorporate a mirror and control it to rotate around the vertical axis within the range of ± 180°, which enlarges the scanning angle dramatically compared with conventional torsion micro mirrors. The rotation angle of the micro rotor is detected by the change of capacitance and controlled by the electrostatic force produced by variable capacitors. The levitation of the micro rotor is realized by utilizing electromagnetic inductions. The rotation is achieved through electrostatic forces generated by a digital controller. The hybrid system design for a micro rotor, combining magnetic and electrostatic forces is introduced. The digital control strategy is based on a PID controller with bias voltage. The detection interface circuit, which is based on frequency multiplexing, is also presented in this paper. It has been experimentally shown that the proposed design can levitate a 1.65 mm radius and 8 µm thickness aluminum micro rotor to 100 µm height with 20 MHz frequency and 0.5A p-p input current. Square and slope wave input experiments were carried out. The experimental results show that the control principal is in good agreement with the simulation models and this applies as well to the time-response performance and stability.

     

A method to measure the micro-capacitance for MEMS comb actuators

A method is introduced to measure the micro-capacitance for MEMS comb actuators whose value is in pF even fF magnitude. This method uses so called peak detection measuring technology to realize this purpose. It is mainly composed of the signal generating circuits, C/V (Capacitance/Voltage) converting part, peak detector circuits and the digital solution element. In order to verify the correctness of the design, detailed theory analysis and simulation are made for every composed portion and corresponding mathematical model is built. It is concluded from the analyzed result that precision of the system can reach 237 aF for 0.98–2 pF measuring range. When corresponding measuring electric circuits is fabricated and debugged, high precision calibration device named Agilent E4980A is used to calibrate it. It is concluded from the calibrated result that the output voltage of the measurement circuit and the micro capacitance have good linear relationship, which verifies the correctness of the pertinent theory. Finally, in order to verify the correctness of the design, dynamic characters of a resonant MEMS gyroscope, which is fabricated with bulk technology and bonding process, is tested with this device. It is concluded from the measured result that relative error of the resonant frequency between the ideal value and the measured result is just 0.02%. Quality factor of this sensor is 312.5. Experimental results indicate this scheme is feasible to measure the static and dynamic characters of micro capacitors.     

SolidWorks在扑翼微型飞行器设计制造中的应用

扑翼微型飞行器是一种模仿鸟类或昆虫飞行的新概念飞行器。介绍SolidWorks设计软件在驱动机构运动仿真、翅翼频率分析和参数化设计中的应用。结果表明,SolidWorks应用于扑翼微型飞行器设计制造可以简化设计流程,提高设计效率。     

Integrated micro Pirani gauge based hermetical package monitoring for uncooled VO x bolometer FPAs

This paper presents the design and fabrication of a micro Pirani gauge using VO _x as the sensitive material for monitoring the pressure inside a hermetical package for micro bolometer focal plane arrays (FPAs). The designed Pirani gauge working in heat dissipating mode was intentionally fabricated using standard MEMS processing which is highly compatible with the FPAs fabrication. The functional layer of the micro Pirani gauge is a VO _x thin film designed as a 100 × 200 μm pixel, suspended 2 μm above the substrate. By modeling of rarefied gas heat conduction using the Extended Fourier’s law, finite element analysis is used to investigate the sensitivity of the pressure gauge. Also the thermal interactions between the micro Pirani gauge and bolometer FPAs are verified. From the fabricated prototype, the measured device TCR is about −0.8% K⁻¹ and the sensitivity about 1.84 × 10⁻³ W K⁻¹ mbar⁻¹.     

Micro robot system with moving micro-car driven by electrostatic comb-drive actuators

This paper describes a silicon micro robot system (MRS) that is capable of driving micro-cars in different directions based on a ratchet mechanism and electrostatic comb-drive actuators. Lateral movement of the ratchet racks makes the micro-car move in the perpendicular direction with different velocities. Based on MEMS technology, the MRS described in this article was fabricated from a silicon on insulator wafer by using only one photo mask. In our experiments, various driving frequencies ranging from 1 to 20 Hz were used to accelerate the micro-car up to 200 μm/s. It was observed that the velocity of the micro-car was proportional to the driving frequency used in the experiments. This relation was also confirmed with our theoretical calculation. When combined with microscopes, this MRS can be applied in bio-medical analysis for transportation and classification of small samples.     

一种MEMS微结构谐振频率的测试技术

MEMS技术的发展离不开相应的测试技术与装置,建立了一种简单的MEMS微结构动态特性的测试装置,以压电陶瓷为核心的基座激励装置实现对微结构的冲击,以微器件自身的输出作为被测信号.结合MEMS工艺中批量制作的特点,在同一测试装置的同一次测试中安装两种不同尺寸的被测微压电悬臂梁试件,采集两个梁的冲击响应信号及它们的联合输出信号,通过FFT频谱分析,比较三种情况下的频谱分析结果并提取出梁的固有频率,采用对比测试的方法获得压电微悬臂梁的谐振频率.试验结果与理论分析一致,该方法具有测试装置简单、实用性强等特点.     

A low voltage vertical comb RF MEMS switch

Design and simulations of a novel RF MEMS switch is reported as a solution to many RF wireless applications. A new comb structure for RF MEMS switch is proposed for low voltage and high frequency operations. Isolation degree and actuation voltage, both improved by the new structure. The mechanical and electromagnetic simulation results show better performance for this new switch compared to parallel plate switch. The simulation is done by the intellisuit and HFSS softwares. The Simulation results show that the actuation voltage is decreased by 13% and the linearity of the switch displacement with respect to the actuation voltage is improved by 22% compared to the parallel plate structure. The HFSS simulation results indicate an insertion loss better than 0.33 dB at 50 GHz and isolation greater than 13.4 dB at 50 GHz.     

Development and performance analysis of a low-cost MEMS microphone-based hearing aid with three different audio amplifiers

In this paper, MEMS-based capacitive microphone and low-cost amplifier are designed for low-cost power-efficient hearing aid application. The developed microphone along with the associated circuitry is mounted on a common board in the form of pocket-type (body-worn) device. The designed microphone consists of a flexible circular silicon nitrite (Si₃N₄) diaphragm and a polysilicon-perforated back plate with air as dielectric between them. The incident acoustic waves on the sensor cause deflection of the diaphragm to alter the air gap between the perforated back plate (fixed electrode) and the diaphragm (moving plate) which causes a change in capacitance. The acoustic pressure applied to the microphone is from 0 to 100 Pa for an operating range of 100 Hz–10 kHz which corresponds to the audible frequency range in case of human beings. The main purpose of this work is to increase the longevity of battery used in conventional hearing aids. The designed MEMS microphone with Si₃N₄ diaphragm is capable of identifying acoustic frequencies (100 Hz to 10 kHz) which correspond to a specific change in absolute pressure from 0 to 100 Pa for 2-micron-thick diaphragm with a sensitivity of about 0.08676 mV/Pa. The design of the sensor and the characteristics analysis are performed in FEM-based simulation software, which are later validated in real time. The prototype is designed using MEMS microphone and low-cost amplifier ICs with biasing components in the form of pocket-type (body-worn) hearing aid. In order to study the performance of proposed device, three different market-available amplifiers with controllable gain are used. Finally, the performance of the hearing aid is studied through audio spectrogram analysis to choose the best-suited amplifier among the three.

     

MEMS 器件IP 库及系统应

针对目前MEMS设计方法中系统分析不完善的现状,提出了将IP库单元应用于系统分析的方法.本文描述了已建立的MEMS微传感器件IP库单元的原型及库单元的结构和关键参数.以梳状微机械谐振器为例,使用SPICE语言调用已建立的IP库单元进行模拟分析,实现了MEMS器件和电路的系统模拟.     

Broadband radio frequency MEMS series contact switch with low insertion loss

A new radio frequency (RF) micro-electro-mechanical-system (MEMS) single cantilever series contact switch is designed as a low-insertion-loss and low-power electronic component that is intended to provide integrated control of the opening and closing signals of other MEMS devices operating over a wide frequency range (DC–60 GHz). The MEMS switching element consists of an A-type top electrode that is fixed onto coplanar waveguide lines through anchor points to reduce the insertion loss in the on-state of the device. The air gap between the top electrode and the actuation electrode of the designed MEMS switch is optimized to improve the isolation characteristics of the switch. In addition, the switching voltage required is approximately 24 V. The simulation results presented here show that the insertion loss of the switch in the on-state is less than 0.71 dB, while the minimum isolation is 20.69 dB in the off-state at 60 GHz. The proposed RF MEMS switch will be useful for communication devices and test instruments used in broadband applications.

     

Electromechanical characterization of a new micro programmable blazed grating by laser Doppler vibrometry

The prototype of a new micro programmable blazed grating driven electrostatically was fabricated using a two-layer polysilicon surface micromachining process. And initially, to characterize its electromechanical performances, such as the driving voltage versus displacement relationship, frequency response and step response, the laser Doppler vibrometry was employed. The measured results reveal the pull-in voltage of 110–115 V, resonant frequency of 78 KHz, quality factor of 2.89, adjusting time of 12 μs, and damping ratio of ~0.68 for the achieved grating sample. As a result, the grating functions well electromechanically. As for its optical performances, a number of optical experiments are in progress.     

电磁振动式微扑翼飞行器动态特性研究

电磁驱动具有驱动电压低、作用力大等优点, 是微机械领域一种重要驱动方式。本文设计了一种电磁振动式微扑翼飞行器，在此基础上，建立了电磁振动式微扑翼飞行器非线性动力学模型，研究了不同电磁力激励下系统动态特性，获得了系统固有频率，并得出方波和正弦半波电磁力驱动能够产生较大扑动幅度的结论。最后，研究了电磁振动式微扑翼飞行器机-磁耦合非线性系统动态特性，研究结果表明电磁振动式微扑翼飞行器适合采用正弦半波电压激励，而且通过结构改进措施，提高了扑动的对称性和稳定性。     

微型磁通门的优化分析与性能测试

对铁芯结构的改进有利于满足微型磁通门传感器降低功耗的要求,但不同的拓扑结构所取得的效果不同,为此对铁芯结构进行了优化分析,并采用MEMS工艺制备了不同铁芯结构的微型磁通门进行性能测试与对比验证.测试结果表明,优化后的多孔铁芯结构能更好的降低微型磁通门传感器的功耗与噪声,提高灵敏度,改善器件的整体性能.     

Design of MEMS switch for RF applications

Components like passive electronically scanned (sub) arrays, T/R modules, reconfigurable antennas etc., in RF applications are in need of MEMS switches for its re-configurability and polarization. This paper presents the analysis, design and simulation of a MEMS switch. The switch proposed in this paper is intended to work in the frequency range of 4–8 GHz. The proposed switch fulfills the switching characteristics concerning the five requirements loss, linearity, high switching speed, small size/power consumption, low pull down voltage following a relatively simple design, which ensures reliability, robustness and high fabrication yield. The switch implemented in this paper is based on the integration mode of operation and widely used in RF applications.     

A flexible encapsulated MEMS pressure sensor system for biomechanical applications

 The use of pressure sensors made of conductive polymers is common in biomechanical applications. Unfortunately, hysteresis, nonlinearity, non-repeatability and creep have a significant effect on the pressure readings when such conductive polymers are used. The objective of this paper is to explore the potential of a new flexible encapsulated micro electromechanical system (MEMS) pressure sensor system as an alternative for human interface pressure measurement. A prototype has been designed, fabricated, and characterized. Testing has shown that the proposed packaging approach shows very little degradation in the performance characteristics of the original MEMS pressure sensor. The much-needed characteristics of repeatability, linearity, low hysteresis, temperature independency are preserved. Thus the flexible encapsulated MEMS pressure sensor system is very promising and shows superiority over the commercially available conductive polymer film sensors for pressure measurement in biomechanical applications. Received: 1 December 1999/Accepted: 17 August 2000     

Cubic centimeter robot based on inertial stick–slip driving

In order to achieve the nano-operation in a limited space, a precision motion platform with a cubic centimeter volume based on the principle of inertial stick–slip driving is proposed in this paper. The mechanical structure and the operating principle are discussed. Kinematic models are used to analyze the performance of the prototype. To investigate the working performance of the prototype, a series of experiments are carried out. Experimental results show that the displacement outputs is related to the parameters of the electrical signal. The maximum moving speed of the platform reaches 13.1 mm/s when the driving frequency is 3.1 kHz. The maximum single step displacement reaches 4.8 μm. Through proper driving voltage and frequency, the proposed prototype can produce a satisfactory velocity.

     

电容式MEMS器件模态频率的电学测试方法研究

针对电容式MEMS器件,提出了一种基于调制解调原理的模态频率测试方法,详细介绍了该测试方法的测试原理和测试系统的组成。利用Ansys对某插齿式微加速度计进行了模态仿真分析,分析得到的模态频率为3 941 Hz,利用该测试方法对该微加速度计进行模态频率测试,得到的测试结果为3 440Hz。仿真与测试得到的结果接近,验证了该测试方法的有效性,产生偏差的主要原因可能是制造过程中的加工误差。     

基于MSP430的微电阻测试仪的设计

传统测量微电阻的方法操作繁琐,且引线电阻和触点电阻对测量结果影响较大.本文设计的基于交流恒流源激励的微电阻测试仪由交流激励源、数字移相电路、信号调理电路以及A/D转换与显示电路等四部分组成.微电阻由交流激励源注入交流信号后通过高阻低噪声运算放大器AD620提取响应信号,再经过锁相放大电路测得其真实的响应电压,锁定后的信号克服了内部噪声和外部电磁干扰的影响,能够实现对微小电阻的准确测量.通过对样机的测试和比对标称值,该测试仪工作稳定,具有较高的测量准确度,方便携带和使用.     

基于圆片级阳极键合封装的高g_n值压阻式微加速度计

设计了一种适合于高gn值压阻式微加速度计圆片级封装的结构,解决了芯片制造工艺过程中电极通道建立、焊盘保护、精确划片等关键技术。采用玻璃—硅—玻璃三层阳极键合的方式进行圆片级封装,较好地解决了芯片密封性、小型化和批量化等生产难题。在4 in生产线上制作的高gn值压阻式微加速度计样品,尺寸仅为1 mm×1 mm×0.8 mm;对传感器进行的校准与抗冲击性能测试,结果表明:样品具备105gn的抗冲击能力、0.15μV/gn/V的灵敏度以及200 kHz的谐振频率。