微机械连续薄膜变形反射镜

建立了微机械连续薄膜变形反射镜的静电力驱动理论模型,推导出微机械连续薄膜变形反射镜的变形位移和驱动电压的关系表达式,利用该公式、静电力表达式和弹性支撑的回复力分析了变形镜的稳定工作驱动、不稳定工作驱动和最大变形位移,讨论了变形镜的结构参数对变形位移的影响.所得结果对于设计微机械连续薄膜变形反射镜具有重要意义.     

大位移、低电压驱动MEMS静电梳齿驱动器的设计与研究

分析了MEMS静电梳齿驱动工作原理,以梳齿结构和弹性梁结构为基础,综合考虑了动态特性、可靠性以及加工工艺可行性要求。提出了非等高结构、变形曲臂梁结构、位移放大驱动器、垂直Z向位移静电梳齿驱动器等四种大尺度、低电压驱动线性MEMS静电梳齿驱动器结构设计。利用CAD采用FEA法分别建模、仿真,进行了大位移、低电压驱动MEMS静电梳齿驱动器的动态与静态的研究,并获得20V直流偏置、位移80～130μm、驱动器面积小于2mm×2mm的结果。     

基于热模压和切削减薄工艺制备聚合物微静电驱动器

为了满足运输蛋白质、细胞等微纳米级物体的需求,有必要研制聚合物微静电梳齿驱动系统。与硅静电梳齿驱动器相比,聚甲基丙烯酸甲酯(PMMA)静电梳齿驱动器具有成本低、成品率高、驱动电压低和能耗少等优点。首先通过微细加工工艺,制备硅静电梳齿驱动器模具。基于硅模具,利用热模压工艺制备PMMA微驱动器,再通过机械切削工艺释放制备好的PMMA微驱动器结构,得到带基底的PMMA微静电梳齿驱动器,最后通过切削减薄工艺,释放静电梳齿微结构,得到可动的PMMA微静电梳齿驱动器。驱动结果表明,PMMA微静电梳齿驱动器制备工艺具有可行性。     

梳齿式静电微驱动器稳定性分析与结构优化北大核心

针对典型梳齿式静电微驱动器驱动稳定性差的问题,建立微驱动器驱动稳定性分析模型,系统分析微驱动器驱动稳定性随其各结构参数的变化关系,提出基于稳定性因子的微驱动器驱动稳定性评估方法。提出弹性支撑机构外置方案,建立弹性梁非线性特征模型,基于模型分析结果设计预弯弹性梁结构,建立基于梳齿结构参数的静电力模型,研究不同梳齿结构对驱动器驱动稳定性的影响。研究结果表明,弹性支撑机构外置、预弯弹性梁结构以及线性交叠梳齿结构能够有效提高梳齿微驱动器大位移输出的驱动稳定性。     

静电拉伸薄膜反射镜成形机理研究

静电拉伸薄膜反射镜是利用静电场库仑力作用使薄膜产生面形变化,生成所需的光学曲面.由于薄膜反射镜成形过程中力场与静电场的相互耦合作用非常复杂,使其到目前为止在面形控制的理论分析上仍未有定量的结果.首先以平板电容理论为基础,对薄膜成形静电力场进行了近似分析,然后根据半球模型求解了薄膜结构变形,最终得到了薄膜反射镜面形尺寸与静电压参数的函数关系.所得结论对静电拉伸薄膜的研究工作具有一定的指导意义.     

大位移低电压的静电MEMS驱动器

制作了一种低驱动电压、位移达100μm的梳齿驱动器.为了增加驱动器的驱动位移,对驱动器的侧向稳定性进行了分析.根据分析结论,提出了一种采用小梳齿间隙,高纵/横向弹性常数比预弯曲支撑梁,无初始交叠、梳齿长度线性递增的梳齿驱动器.根据稳定性以及驱动位移和驱动电压的设计要求设计了驱动器的具体参数,并进行了器件制作.测试表明,器件共振点在573Hz,Q因子为35.88,在100μm位移时驱动电压为71V,与理论计算值相差2.1%.     

大位移低电压的静电MEMS驱动器

制作了一种低驱动电压、位移达100μm的梳齿驱动器. 为了增加驱动器的驱动位移,对驱动器的侧向稳定性进行了分析. 根据分析结论,提出了一种采用小梳齿间隙,高纵/横向弹性常数比预弯曲支撑梁,无初始交叠、梳齿长度线性递增的梳齿驱动器. 根据稳定性以及驱动位移和驱动电压的设计要求设计了驱动器的具体参数,并进行了器件制作. 测试表明,器件共振点在573Hz, Q因子为35.88,在100μm位移时驱动电压为71V,与理论计算值相差2.1%.     

边界位移调节量对薄膜反射镜成形的影响

圆形薄膜周边夹持预应力调节对静电薄膜反射镜面形的成形质量具有重要的调节作用.分析了φ180 mm口径的静电薄膜反射镜边界位移的调节范围,计算出了相应调节极限,并结合静电拉伸薄膜实验进行了四种边界位移调节工况的验证.预应力施加过大会造成电极施加电压增高,严重时造成薄膜击穿,但预应力施加过小会造成面形质量不佳.最大边界位移调解量影响薄膜反射镜结构参数和所施加电压,同时薄膜反射镜结构参数和所施加电压也限制着最大位移边界调解量的取值.合理选取并精密控制圆薄膜的边界位移量对于大口径静电薄膜反射镜的精确成形来说至关重要.     

MOEMS静电旋转结构的Pull-in现象分析

对MOEMS静电旋转结构的Pull鄄in(吸合)现象进行了理论分析,重点研究了平板电极旋转结构和摆动梳齿旋转结构。摆动梳齿旋转结构不出现Pull鄄in现象的原因是电容变化率为恒值;平板电极旋转结构在电极旋转过程中电容变化率持续增大是Pull鄄in现象出现的根本原因,设计平板电极旋转驱动器时,如果需要得到较大的稳态旋转角度,可以通过合适的结构参数减小电容变化率的变化速率。     

新型磁驱动增大检测电容的高精度MEMS惯性传感器研究

增大传感器振子的质量和静态测试电容可以减小电容式MEMS惯性传感系统的噪声,而深度粒子反应刻蚀工艺由于复杂的工艺原因,当深宽比较大时,不能刻蚀出大质量和大初始电容的传感器.据此,本文研究了一种磁驱动增大检测电容的MEMS惯性传感器,通过电磁驱动器,传感器的静态测试电容可以大幅增加,在梳齿电容上刻蚀阻尼槽后,其机械噪声达到0.61μg每根号赫兹,仿真其共振频率为598Hz,静态位移灵敏度为0.7μm每重力加速度,基于硅 玻璃键合工艺,制作了栅形条电容式惯性传感器,并用电磁驱动的方式测试其品质因子达到715,从而验证了制作工艺的可行性和电磁驱动器改变传感器初始静态测试电容的可行性.     

Electrostatic linear actuator with a long stroke rolling spring guide

In contrast with diverse design concepts of actuators, we have developed an electrostatic linear actuator integrated with a long stroke rolling spring guide. The rolling spring guide realizes guiding function through rolling movements of two parallel preloaded belt-shaped springs. The electrostatic actuating force is generated by applying electrical fields to the structure of spring guide. Besides the driving voltage, the geometric size and the preloaded span of the spring guide are the main influential parameters of electrostatic actuating force and actuating displacement. With adequate adjustment of the preloaded span, this electrostatic actuator can generate not only a large actuating displacement in /spl mu/m range, but also a fine positioning displacement in /spl mu/m range. The finite element analysis (FEA) and the geometric analysis are applied to analyze spring stress and to derive the shape equation of the spring guide. Furthermore, a theoretical model for our electrostatic actuating principle is deduced on the basis of the shape equation. In addition to the theoretical analyses, the performance of the electrostatic actuator is experimentally tested and studied.     

Force balanced micromachined pressure sensors

This paper discusses the fabrication and testing of two low-voltage force-balanced pressure sensors. In these devices the force acting on a diaphragm under external pressure and its corresponding deflection are counterbalanced with the force and deflection generated in a parallel plate electrostatic actuator mechanically coupled to the diaphragm. The low balancing voltage is attained using a force multiplication scheme. The first device is implemented using an open gap actuator constructed on top of a vacuum sealed sense diaphragm. The open gap design is exposed to the measurement environment hence susceptible to contamination. The second device eliminates this problem by enclosing the actuator in an hermetically-sealed cavity. Both devices have a full scale pressure range of 1 atmosphere (1.013 bar). The open actuator device has a nominal capacitance of 0.34 pF and a full scale range of 70 fF. The sealed actuator device a nominal capacitance of 2.12 pF and a full scale range of 100 fF. The pressure is balanced by voltages in the range of 12-25 V demonstrating the feasibility of force balanced pressure sensor compatible with low-voltage electronics     

Technologies for Cofabricating MEMS and Electronics

Microfabrication technologies initially developed for integrated electronics have been successfully applied to batch-fabricate a wide variety of micromechanical structures for sensing, actuating, or signal-processing functions such as filters. By appropriately combining the deposition, etching, and lithography steps for microelectromechanical devices with those needed for microelectronic devices, it is possible to fabricate an integrated microsystem in a single process sequence. This paper reviews the strategies for cofabrication, with an emphasis on modular approaches that do not mix the two process sequences. The integrated processes are discussed using examples of physical sensors (infrared imagers and inertial sensors), chemical and biochemical sensors, electrostatic and thermal actuators for displays and optical switching, and nonvolatile memories. By adding new functionality to integrated electronics, the use of microelectromechanical systems is opening new applications in sensing and actuating, as well as enhancing the performance of analog and digital integrated circuits.     

Laser‐Induced Rapid Carbon Nanotube Micro‐Actuators

Laser‐induced rapid actuating microstructures made of aligned carbon nanotube (CNT) arrays are achieved. Desirable operational features of the CNT micro‐actuators include low laser power activation, rapid response, elastic and reversible motion, and robust durability. Experimental evidence suggests a laser‐induced electrostatic interaction mechanism as the primary cause of the optomechanical phenomenon. Oscillating CNT micro‐actuators up to 40 kHz are achieved by driving them with a modulated laser beam. The micro‐actuators are utilized in exerting a sub‐micro‐Newton force to bend nanowires. Electrical coupling of the micro‐actuator and feasibilities of multi‐actuator systems made entirely out of CNTs are also demonstrated.     

A Large-Stroke MEMS Deformable Mirror Fabricated by Low-Stress Fluoropolymer Membrane

This letter presents a deformable mirror (DM) which consists of a 25-mm square flexible membrane and an array of 67 hexagonal electrodes that can pull down a membrane by electrostatic force. The membrane is a 2.15-mum-thick fluoropolymer film and is bonded to an electrode substrate with an 80-mum-thick adhesive acrylic spacer. The fabrication process is completed by a microelectromechanical systems batch process. The surface roughness of polymer membrane is approximately 41 nm. The device demonstrated maximum 38-mum center deflection by applying 250 V because of small residual stress (2.2 MPa) and low Young's modulus (15 GPa) of fluoropolymer film. The response time of the DM is experimentally demonstrated around 10 ms in atmosphere. The proposed device is suitable for large stroke and low sampling rate applications.     

Capillary force actuators: Modeling,dynamics, and equilibria

Capillary force actuators provide forces via the alteration of the capillary pressure within a conducting liquid bridge through the application of electrical potential. A dynamic model of a capillary force actuator is developed. Separate models of the fluid/flexured platen and electrodynamics are constructed and linked together via the Young–Lippmann relation. Since the bridge height is small in comparison to the diameter, the liquid slug is shown to have a parabolic velocity profile. The radial pressure variation is then readily determined. Integration of the pressure and summation of the contact line tension term yields the actuation force. Combining this model with the electrodynamics and mechanical components yields a nonlinear model relating applied voltage to platen movement. The equilibria of this equation are determined as a function of voltage and their stability are analyzed. We show that the equilibrium will be stable for displacements exceeding one-third of the nominal bridge height, a greater range than that obtained with parallel plate electrostatic actuators. Depending on actuator design this range may be as large as 7/9th of the nominal bridge height but no larger.     

Tailoring unconventional actuators using compliant transmissions:design methods and applications

Matching a drive system to the force-displacement characteristics of the load is the cardinal principle in electromechanical systems design. Unconventional actuation schemes; such as piezoelectric, electrostatic, and shape-memory alloys (SMAs), seem to exhibit certain limitations in terms of power density, stroke length, bandwidth, etc., when one attempts to employ them directly to an application. Integrating them with mechanical transmission elements so that the integrated actuator-transmission system matches the load characteristics of the application can enhance the utility of such unconventional actuators. Conventional mechanical devices are sometimes difficult to integrate with unconventional actuating schemes. For instance, the two-dimensional nature of microelectromechanical systems (MEMS) and no-assembly constraints arising from their batch fabrication make it difficult to fabricate, assemble, and integrate a conventional micromechanism with an electrostatic actuator. However, a monolithic “solid-state” mechanical transmission device enables easy integration. The paper presents a systematic method of designing such unconventional mechanisms. The paper presents a generalized methodology for designing compliant mechanisms. Our systematic synthesis formulations provide a mathematical basis for designing compliant mechanisms for: (1) topology generation and (2) size and shape optimization. Design examples illustrate integration with electrostatic, piezoelectric, and SMA actuators for MEMS and smart-structures applications     

Pulse drive and capacitance measurement circuit for MEMS electrostatic actuators

In this paper we present an electronic circuit for position or capacitance estimation of MEMS electrostatic actuators based on a switched capacitor technique. The circuit uses a capacitive divider configuration composed by a fixed capacitor and the variable capacitance of the electrostatic actuator for generating an output signal that is a function of the input voltage and capacitive ratio. The proposed circuit can be used to simultaneously actuate and sense position of an electrostatic MEMS actuator without extra sensing elements. This approach is compatible with the requirements of most analog feedback systems and the circuit topology of pulsed digital oscillators.     

基于MEMS技术的一种新型可变形反射镜

给出基于硅微加工技术的一种新型可变形反射镜的设计和加工方法,并且通过工艺流片制造出有效反射面积为30 m m×30 mm,拥有4 9个静电驱动单元的可变形反射镜.测试得到的镜面变形-电压数据显示其与模拟结果具有很好的一致性.     

Large-Stroke Microelectrostatic Actuators for Vertical Translation of Micromirrors Used in Adaptive Optics

Two microelectrostatic actuators able to produce a repulsive force in the out-of-plane direction are presented in this paper. The electrostatic actuators use an asymmetric electric field surrounding the top and bottom surfaces of the moving fingers to produce a repulsive force. The displacement of translation micromirrors driven by these actuators is not limited by the “pull-in” effect and, therefore, can achieve a large stroke. In addition, the usage of a repulsive force leads to the elimination of the stiction problem. An analytical model relating the displacement of the first actuator to voltage applied is presented. The analytical model and numerical simulations show that a translation micromirror driven by the first actuator can achieve a stroke as large as 6$muhboxm$at a driving voltage of 50 V. The second actuator, suitable for fabrication using Multi-User-MEMS-Processes (MUMPs), is developed. A prototype translation micromirror driven by the second actuator achieved a vertical stroke of 2$muhboxm$, which is more than three times the stroke of conventional MUMPs translation micromirrors.