A self-retracting fully compliant bistable micromechanism

A new class of fully compliant bistable mechanisms with the added benefit of integrated self-retraction has been developed (hereafter identified as Self-Retracting Fully compliant Bistable Mechanism or SRFBM). A technique using tensural pivots to manage compressive loading in compliant mechanisms is introduced and implemented in the SRFBM. The elimination of traditional kinematic joints and their associated clearance allows a total displacement between stable positions of 8.5 /spl mu/m, and the mechanism size is less than 300 /spl mu/m square when using 2.0 /spl mu/m minimum line widths. Maximum actuation force is approximately 500 /spl mu/N. The SRFBM's small linear displacement and reasonable actuation force facilitate integration with efficient thermal actuators. Furthermore, fully compliant mechanisms allow greater freedom in fabrication as only one mechanical layer is needed. Systems with on-chip actuation have been fabricated and tested, demonstrating bistability and on-chip actuation, which requires approximately 150 mW. A single fatigue test has been completed, during which the SRFBM endured approximately 2 million duty cycles without failure.     

Dynamical switching of an electromagnetically driven compliant bistable mechanism

Dynamical switching behaviors of a compliant bistable mechanism driven by electromagnetic force are investigated. The bistability of the mechanism originates from combined tension and bending of the beam structures. Finite element analyses are used to characterize the bistability of the mechanism under static loading. An analytical model is developed to analyze the dynamic behaviors of the mechanism. The main advantage of this dynamic actuation method is the absence of on-chip driving mechanisms. The dynamical switching characteristics of the bistable mechanism are examined. Microscale prototypes are fabricated and tested. Using the driving technique, we demonstrate dynamical switching in the fabricated device and verify that the performance predicted by theory is attained.     

Optical actuation of a bistable MEMS

This paper presents an optical actuation scheme for MEMS devices based on the well-established fact that light possesses momentum, and hence, imparts a force equal to 2 W/c when reflected by a surface. Here, W is the total power of the reflected light, and c is the speed of light. Radiation pressure, as it is known, is nearly insignificant for most macroscale applications, but it can be quite significant for MEMS devices. In addition, light actuation offers a new paradigm. First, intersecting light beams do not interfere, in contrast to electrical conductors, which short when they come into contact. Second, light can operate in high temperature and high radiation environments far outside the capability of solid state electronic components. This actuation method is demonstrated, both in air and in vacuum, by switching the state of a bistable MEMS device. The associated heat transfer model is also presented.     

柔顺双稳态机构的研究现状与进展

由于柔顺机构和双稳态机构分别所具有的独特优势,已使柔顺双稳态机构成为目前国内外研究的新热点.综合论述了基于MEMS技术的柔顺双稳态机构的最新研究成果,根据柔顺双稳态机构的驱动机制,系统介绍了机械锁定型、电热锁定型、磁致锁定型、多耦合场锁定型等柔顺双稳态机构,针对其原理、性能及应用等各个方面进行了综合比较.最后展望了柔顺双稳态机构的研究前景和可能遇到的问题与挑战.     

Fully compliant tensural bistable micromechanisms (FTBM)

A new class of bistable mechanisms, the fully compliant tensural bistable micromechanism (FTBM) class, is introduced. The class consists of linear bistable micromechanisms that undergo tension loads, in addition to the bending loads present, through their range of motion. Proof-of-concept designs fabricated in two different microelectromechanical systems (MEMS) surface micromachining processes were demonstrated. Three sets of refined designs within the FTBM class were designed using optimization methods linked with nonlinear finite element analysis (FEA), then fabricated and tested. Measured force and displacement performance are compared to values obtained by FEA. On-chip actuation of the bistable mechanisms was achieved using thermomechanical in-plane microactuators (TIMs). The FTBM class of bistable mechanisms explores a relatively new design space for fully compliant micromechanisms, and mechanisms from this class have promise in such applications as micro shutter positioning, microvalves, and electrical microrelays. [1448].     

Enumeration of optimal pin-jointed bistable compliant mechanisms with non-crossing members

An optimization approach is presented for enumerating pin-jointed bistable compliant mechanisms. In the first stage, the statically determinate trusses with non-crossing members containing a given set of nodes and some pre-defined members are regarded as minimally rigid framework or a Laman framework, and are enumerated without repetitions by the graph enumeration algorithm. In the second stage, the nodal locations and the cross-sectional areas are optimized under mechanical constraints, where the snapthrough behavior is extensively utilized to produce a pin-jointed bistable compliant mechanism. In the numerical examples, many bistable compliant mechanisms are generated to show the effectiveness of the proposed method.     

Combined optimization of bi-material structural layout and voltage distribution for in-plane piezoelectric actuation

This paper investigates the combined optimization of bi-material structural layout and actuation voltage distribution of structures with embedded in-plane piezoelectric actuators. The maximization of the nodal displacement at a selected output port is considered as the design objective. A two-phase material model with power-law penalization is employed in the topology optimization of the actuator elements and the coupled surrounding structure. In order to incorporate the actuation voltage directly into the design for achieving the best overall actuation performance, element-wise voltage design variables are also included in the optimization. For the purpose of easy implementation of the electric system, the allowable voltage levels at an individual element are confined to three discrete values, namely zero and two prescribed values with opposite signs. To this end, a special interpolation scheme between the tri-level voltage values and the design variables is used in the optimization model. Based on the design sensitivity analysis of the objective function, the combined optimization problem is solved with the MMA algorithm. Numerical examples are presented to demonstrate the applicability of the proposed optimization model and numerical techniques. The optimal solutions also confirmed that larger output displacement can be achieved by introducing voltage design variables into the design problem.     

On an open problem in bistable stabilization

We propose an equivalent representation of an open problem in bistable stabilization. Using this new formulation we derive two simple necessary condition tests for the solution of the problem. For certain special cases we also obtain the sufficient conditions.     

Sensitivity analysis of an in-plane MEMS vibratory gyroscope

Microsystem Technologies - This paper aims to put forward a detailed sensitivity analysis of an in-plane MEMS gyroscope with respect to various performance criteria that are very critical for use...     

A class of biaxial micro/meso-scale structures for isotropic in-plane inertial sensing and actuation: design,fabrication and experiments

Microsystem Technologies - A micro/meso-scale monolithic architecture was designed, fabricated and tested for in-plane inertial sensing and actuation with isotropic stiffness in the sensitive plane...     

Analysis of an in-plane micro-generator with various microcoil shapes

This study presents an analysis of an in-plane micro-generator with various microcoil shapes and multiple aspects of coupling, and reports the fabrication of a prototype micro-generator. It is important to establish analytical solutions for the micro-generator to predict the induced voltage. These analytical solutions can be used to estimate the micro-generator power to reduce the experimental time and the cost. Understanding the physical meanings of the variables can optimize the structure of the micro-electromagnetic generator. This model considers electromagnetism, kinematics, and geometry. The proposed in-plane rotary electromagnetic micro-generator was fabricated using low-temperature co-fired ceramic technology to co-fire the silver microcoils on the ceramic substrate with different shaped coils (e.g., square-shaped, circle-shaped and sector-shaped) both with the printing linewidth and 100 μm spacing of these microcoils. A planar permanent magnet with an outer diameter of 9 mm and a thickness of 700 μm was sintered by Nd/Fe/B. Its residual induction is 1.4 T. The experimental data in this study can be compared with analytical solutions. Analytical results show that the micro-generator with a sector-shaped microcoil generates a maximum effective value of 218.127 mV induced voltage at 1395.34 rad/s. Experimental measurements show a close agreement with these analytical solutions.     

水解聚马来酸酐的微观阻垢机理研究

利用分子模拟方法优化了水解聚马来酸酐的构型,模拟了水解程度不同时各聚合物与碳酸钙晶体之间的相互作用,并计算了其作用能量和原子键距的变化。计算结果显示:所有阻垢剂分子均逐渐接近方解石晶体,阻垢剂分子链中的活性羧酸基团与Ca2 螯合,某些基团与Ca2 离子的键距越来越趋近,占据晶体的晶格生长点或嵌入晶体内部,同时分子结构存在小幅度的变形;说明该聚合物的阻垢机理是抑制晶体成核即抑制碳酸钙的长大,同时使晶体晶格扭曲畸变使垢松软。作用后动能、势能和总能量均有不同程度的降低,趋于更稳定的构型,并随着水解度的增大,阻垢作用更加明显。     

The design of an in-plane compliance structure for microfluidical systems

Two compliance structures for the use in liquid-based microfluidic systems have been realized with the aid of silicon micromachining. The basic principle is that these structures contain air bubbles that dampen the flow and pressure variations that may arise from a micropump. The compliance structures were specifically designed to work with the no moving parts valve (NMPV) pump [Proc. ASME Fluids Eng. Division, 1995, in press]. The structures were modeled and simulated. From the results of these simulations and the model, design rules for the compliance are formulated.Measurements on the compliance structures could only be performed for the steady state. These measurements were in very good agreement with the model. Working with two sets of pumps showed that pumps without the compliance structure needed an external compliance in order to get them to work, whereas the pumps with the on-chip compliance pumped right away.     

带弹性放大器的双稳态压电振动能量采集器

针对带弹性放大器的双稳态压电振动能量采集器,利用Hamilton原理和Raleigh-Ritz方法建立了压电振动能量采集器的机电耦合分布参数模型.重点分析了激励频率Ω≥1时系统质量比、刚度比、磁铁对间距等参数对系统输出性能的影响.研制了压电振动能量采集器原理样机,搭建了实验测试平台,实验测试了压电振动能量采集器的输出性能.研究结果表明带弹性放大器的压电振动能量采集器是一个非线性双自由度系统,具有两个双稳态运动区域;在激励频率Ω≥1时压电振动能量采集器需要较大的激励能量才能进入大幅值周期振动状态.     

Design of distributed compliant micromechanisms with an implicit free boundary representation

In this paper, a parameterization approach is presented for structural shape and topology optimization of compliant mechanisms using a moving boundary representation. A level set model is developed to implicitly describe the structural boundary by embedding into a scalar function of higher dimension as zero level set. The compactly supported radial basis function of favorable smoothness and accuracy is used to interpolate the level set function. Thus, the temporal and spatial initial value problem is now converted into a time-separable parameterization problem. Accordingly, the more difficult shape and topology optimization of the Hamilton–Jacobi equation is then transferred into a relatively easy size optimization with the expansion coefficients as design variables. The design boundary is therefore advanced by applying the optimality criteria method to iteratively evaluate the size optimization so as to update the level set function in accordance with expansion coefficients of the interpolation. The optimization problem of the compliant mechanism is established by including both the mechanical efficiency as the objective function and the prescribed material usage as the constraint. The design sensitivity analysis is performed by utilizing the shape derivative. It is noted that the present method is not only capable of simultaneously addressing shape fidelity and topology changes with a smooth structural boundary but also able to avoid some of the unfavorable numerical issues such as the Courant–Friedrich–Levy condition, the velocity extension algorithm, and the reinitialization procedure in the conventional level set method. In particular, the present method can generate new holes inside the material domain, which makes the final design less insensitive to the initial guess. The compliant inverter is applied to demonstrate the availability of the present method in the framework of the implicit free boundary representation.     

Study of an eletrostatically actuated torsional micromirror with compliant planar springs

This paper presents modelling, fabrication and testing of a torsional micromirror suspended by two compliant ortho-planar springs attached at the sides. The proposed cantilevered serpentine spring is a single-chain frame, composed of nine beam segments to form a serpentine together with an initial segment and a final segment. Castigliano theory is used to formulate the spring constants under certain loads. Two equivalent spring constants for the micromirror are obtained according to structure analysis. The 2-DOF model for torsion and bending of the micromirror is presented. Finite element analysis (FEA) of the coupled domain of the structure is performed to verify the analytical results. Further validation of the prediction is carried out through static testing of a fabricated micromirror using a PSD (position sensing detector) sensor based experimental set-up. Due to relative compliancy of the dominant torsion mode, the fabricated micromirror is actuated to some angle at a lower voltage. The comparison between FEA and analytical results shows good agreement, demonstrating the accuracy prediction by the derived model. Small deviation from experiments is expected due to the nonlinear nature of electrostatic field.     

Correction to: A class of biaxial micro/meso-scale structures for isotropic in-plane inertial sensing and actuation: design,fabrication and experiments

Microsystem Technologies - In the original publication, footnote marks 4, 5 and their respective notes were incorrectly added to the text. The correct footnote marks and the notes are given here.     

Design and manufacturing of micromechanism elements of 2-DOF micromanipulator

Studies on optical switches have been researched and developed for optical information networks for a highly developed information technology society. In reality, however, a manipulator cannot apply for multi input and output due to a rather small output displacement at the mirror parts inside the manipulator. Therefore, in order to develop optical switches capable of switching to multi input and output, we suggested an electrostatic driving-type 2-DOF micro-manipulator that was composed of one mirror with four screw type beams, four screw type electrodes on a substrate and one mirror support pyramid situated under the mirror. One mirror with four screw type beams for support of the mirror and four screw electrodes on the substrate with a one mirror support pyramid were made separately. In the final step of the manufacturing process, these two parts were combined. The four beams are able to move by the electrostatic forces between the screw beams and the four screw electrodes on the substrate. We call this four beam type actuator an electrostatic suction actuator. In the results, the micro mirror is capable of a large angular output displacement about plus or minus 30° in theory. The manufactured mirror and beams and the manufactured screw electrodes and mirror support pyramid, respectively are manufactured. In this research, after having studied the shapes and dimensions of micro-manipulators capable of a large angular displacement based on theoretical analysis, we also discovered that the suggested micro-manipulator can have a large angular displacement though the use of the suction phenomena. Moreover, our study suggested a manufacturing process using a semiconductor manufacturing process and then discussed the concerns of the dimension of the manufactured mirror and beams, and the manufactured screw electrodes, and mirror support pyramid for the optical switch.