A micromachined reaction force actuator (RFA) for a nanomanipulator preparation

A reaction force actuator (RFA) was fabricated to translate a microstage with nanostep movement, and its performance was experimentally evaluated using an optical fiber based built-in microinterferometer. The proposed RFA consists of a shuttle mass, movable electrode, fixed electrode, springs, and spring anchor, all of which reside on the movable substrate. The RFA placed on the platform is free to move when the driving force is larger than the static friction. The fixed electrodes are gold-wired to the external electrodes on the platform covered with a dielectric layer for electrical isolation. When external voltage is applied to the electrodes, the springs experience deflections, and the electrostatic force and restoring force react on the movable substrate through the spring anchor and the fixed electrode, respectively. If the driving voltage is large enough that the resultant force overcomes the friction from the platform, the RFA including the movable substrate can make a displacement with no physical collision between the movable and fixed electrodes. In order to suppress the drift motion due to external noise, electrostatic pressure was applied between the movable substrate and the platform on which a 100-/spl mu/m-thick dielectric thin film is positioned. The nanomotion of the fabricated actuator was evaluated with various voltages using an optical fiber interferometer. The minimum step movement 1.21/spl plusmn/0.24 nm was experimentally obtained at the driving voltage of 18 V, and the estimated total displacement was 450 nm at the highest affordable driving voltage of 85 V.     

A piezoelectric inertia rotary actuator based on asymmetric clamping mechanism

A newly piezoelectric inertia rotary actuator is presented by using asymmetric mechanical structure to produce asymmetric inertia impact force when the symmetric electrical signal is applied to the piezoelectric bimorph Mechanical analysis was derived and simulation model of asymmetric clamping mechanism was established to determine the influence of structural parameters to the output performance. A prototype was developed and a series of experiments were conducted to evaluate the performance in terms of angular displacement, speed, and load characteristic. The experimental results show that the angular displacement of the actuator is approximately proportional to the amplitude of driving voltage, and an angular displacement resolution of 12 µrad is obtained with a square wave of 15 V_p?p at a frequency of 4 Hz. The maximum torque can reach 3.96 N mm at 70 V_p?p applied voltage and 2 Hz driving frequency. The rotary actuator characterized with an asymmetric clamping mechanism will provide new references for the further research on piezoelectric inertia drive mechanism.     

A novel self-aligned electrostatic vertical actuator using plastic deformation technology

A novel method is presented to fabricate a self-aligned electrostatic vertical actuator using plastic deformation technology. The model of the vertical actuator is proposed and simulated using finite element analysis method. The fixed combs and movable combs, and spring beams are patterned using one mask and fabricated by DRIE technology simultaneously. The fixed combs and movable combs have staggered distance of 21.8 μm in the vertical direction on the condition of self-alignment using plastic deformation technology. The electrostatic vertical actuator has achieved large vertical drive displacement at low voltage. The measurement results show that the maximum drive displacement runs up to 17 μm at 17 V voltage between the fixed combs and movable combs. Experimental results verify the usefulness of the guidelines obtained from simulation and calculation.     

A micromachined impact microactuator driven by electrostatic force

This paper presents a novel micromachined actuator which is developed to produce precise and unlimited displacement. The actuator is driven by impact force between a silicon micro-mass and a stopper. The suspended silicon micro-mass is encapsulated between two glass plates and driven by electrostatic force. When the mass hits the stopper which is fixed on glass plates, impact force is generated to drive the whole actuator in a nano size step (/spl sim/10 nm). The overall dimension of the device is 3 mm /spl times/3 mm. The driving voltage is 100 V and average speed is 2.7 /spl mu/m/s. The total thickness is 600 /spl mu/m.     

Development of copper based miniature electrostatic actuator using WEDM with low actuation voltage

Fabricating electrostatic micro actuator, such as comb-drive actuator, is one of the demanding areas of the MEMS technology because of the promising applications in modern engineering, such as, micro-switches, attenuators, filters, micro-lenses, optical waveguide couplers, modulation, interferometer, dynamic focus mirror, and chopper. For the fabrication, most of the cases silicon monocrystalline wafers are used through complex process. To etch the silicon substrates, researchers often use deep reactive-ion etching or anisotropic wet etching procedure which are time consuming and unsuitable for batch fabrication process. Again, resent research shows that comb-drive actuators need comparatively high voltage for actuation. In solving these problems, the study presents a copper based electrostatic micro actuator with low actuation voltage. Using wire electrical discharge machine (WEDM), the actuator is fabricated where a light weight flexible spring model is introduced. Capacitor design model is applied to present a voltage controlling electronic circuit using Arduino micro controller unit. The experimental result shows that the actuator is able to produce 1.38 mN force for 15 V DC. The experiment also proves that coper based actuator design using WEDM technology is much easier for batch processing and could provide the advantages in rapid prototyping.     

Accurate Load Detection Based on a New Piezoelectric Drive Principle Employing Phase-Shift Measurement

This paper introduces a technique for measuring the torque applied to a piezoelectric motor while it is operating. The technique utilizes phase measurement rather than amplitude measurement and takes advantage of the kinematical principle of a piezoelectric actuator drive (PAD) later described in the paper. Piezoelectric actuators are bidirectional converters of electrical energy into mechanical energy and vice versa. Due to the special kinematical principle of the PAD, an applied external torque and internal torque lead to a phase-shift between the driving signals (a voltage applied to actuators) and the corresponding mechanical feedback (a modulated force). The actuator acts as a sensor to the feedback force converting it into a charge signal. The charge signal is measured and converted into a voltage by a simplified Sawyer-Tower-Circuit. The dc bias of both signals the driving actuator voltage, and measured charge signal is removed by a high-pass filter. The signals are then amplified and limited to form digital signals out of the sinusoidal input signals. The phase-shift between both signals is analyzed by a phase detector based on a zero-crossing time difference measurement. By employing the theory of electromechanic conversion of the piezoelectric actuators under the marginal conditions of the drive setup, the torque value is calculated, based on the measured phase-shift. The described technique offers highly accurate real-time torque measurement and additional information that can be used for an on-line diagnosis of the piezoelectric ring motor. The theory was validated in an experiment showing typical errors of 5% and 312 to 1248 measurements per 360 deg turn of the motor shaft. The piezomotor used during the experiment offered a maximum torque of 5 Nm     

Scratch drive actuator with mechanical links for self-assembly ofthree-dimensional MEMS

The self-assembling of three-dimensional (3-D) MEMS from polysilicon surface micromachined part is very attractive. To avoid risky external manipulation, the practical use of integrated actuator to perform the assembling task is required. To that goal, this paper presents detailed characteristics of the electrostatic surface micromachined scratch drive actuator (SDA). First, from numerous SDA tests, it is shown that this actuator is able to produce a threshold force of 30 μN, with a yield above 60%. With polysilicon devices consisting of SDA mechanically linked to buckling beam, a horizontal force of 63 mN has been demonstrated with ±112 V pulse, and up to 100 μN can be obtained with higher voltage. With buckling beams, displacements up to 150 μm have been obtained in the vertical direction. The generation of vertical force of 10 μN was confirmed with a 100 μm displacement producing 1 nJ work in the vertical direction. Finally, SDA overcomes the usual sticking of surface machined polysilicon by producing enough vertical force to completely release wide polysilicon plate (500 μm×50 μm) without external manipulation. The above characteristic, both in terms of structure releasing and vertical/horizontal forces and displacements provides the SDA with the capability of self-assembling complex 3-D polysilicon part, opening new integration capabilities and new application field of MEMS     

V型电热硅微致动器动态频率特性

提出了V型电热硅微致动器的弯曲振动力学模型。考虑到微米尺度上的硅梁难以简化为质量块、弹簧振动模型,采用了连续体建模,据此可进行其模态分析及动态频率特性的理论研究。利用自行设计制造的在线动态测试机构,测试了V型电热硅微致器在不同激励电压驱动下的响应输出,结果表明其位移输出也是随交变驱动电压的变化而非同步地发生变化。     

Modeling of single and multilayer polyvinylidene fluoride film for micro pump actuation

Micro pumps are essential components of micro devices such as drug delivery systems. Large numbers of pumps have been proposed based on different actuating principles. Piezoelectric actuation offers advantages such as reliability and energy efficiency. Lead zirconate titanate (PZT) based piezoelectric actuation for micro pumps is predominantly explored despite its disadvantages such as brittle nature, low straining and difficulties in processing. Polymer piezoelectric materials like polyvinylidene fluoride (PVDF) could be promising replacements for PZT owing to their availability in form of films and good strain coefficients. Very limited literature on micro pump with PVDF as an actuator is available. In this paper, finite element analysis (FEA) model of a micro pump actuator using single and multilayer PVDF for actuation is developed in ANSYS^?. The model takes into account the influence of driving voltage and actuator geometry. The central deflection of the pump diaphragm which is instrumental in defining the pump performance is studied for driving voltages of 100?C200?V. The deflection of the pump diaphragm for single layer and multilayer actuation are determined from the model. It could be inferred from the initial part of the study that pump performance depends on driving voltage and actuator film thickness. In order to reduce driving voltage requirement multilayer stacked actuator is tried with four different configurations of the layers. It is concluded that stacking configuration of parallel energized straight polarity PVDF layers yielded best central deflection. An attempt is made to compare the performance of multilayer actuator with an equivalent single thick layer actuator. It is noticed that the multilayer actuator performance was better by about 101% when number of layers is doubled.     

Design, Modeling, and Demonstration of a MEMS Repulsive-Force Out-of-Plane Electrostatic Micro Actuator

An analytical model is developed for a two-layer repulsive-force out-of-plane micro electrostatic actuator by using conformal mapping techniques. The model provides the means to establish the performance characteristics in terms of stroke and generated force of the actuator and is used to develop design and optimization rules for the actuator. Numerical simulations were conducted in order to verify the analytical model. A simple physical model is also presented that explains the mechanism for generating the repulsive force. A Multi-User-MEMS-Processes repulsive-force out-of-plane rotation micromirror is developed to experimentally verify the analytical model and to demonstrate the repulsive-force actuator's capability of driving large-size rotation plates by using surface micromachining technology. Experimental measurements show that the repulsive-force rotation micromirror with a size of 312 mum times 312 mum achieved a mechanical rotation of 0deg-2.1deg at a dc driving voltage of 0-200 V. The micromirror achieved an open-loop settling time of 2.9 ms for a mechanical rotation of 2.3deg and an open-loop bandwidth of 150 Hz (-3 dB).     

Hybrid micro electrostatic actuator

A hybrid micro-electrostatic actuator is presented. The actuator integrates a vertical comb driving (VCD) unit and a parallel-plate driving (PPD) unit. The hybrid actuator is fabricated using a one structural layer microfabrication process, i.e., MetalMUMPs instead of a two-layer microfabrication process needed for traditional vertical comb-drive actuators by taking advantage of the residual stress gradient in the MetalMUMPs nickel layer, which raises the moving parts of the actuator above the substrate after release. The hybrid actuator significantly simplifies the fabrication process for vertical comb-drive actuators, i.e., turning a process requiring two structural layers into a process requiring only one structural layer and thus avoids any misalignment between the two layers. The hybrid actuator can generate larger force and then a larger displacement than the actuator having only the VCD with the same area since no extra space is needed for the PPD unit which uses the moving electrode existing in the VCD unit and a fixed electrode under the VCD unit. The VCD and PPD units in the hybrid actuator are subject to the same driving voltage and work together to pull the moving parts of the actuator downward. A model is established for the hybrid actuator to analyze its displacement. The analytical results show that displacement of the moving part of the hybrid actuator is about half of the gap between the electrodes of the PPD unit. Prototypes are fabricated and tested. With a driving voltage of 150 V, the hybrid actuator achieved a measured displacement of 6.48 µm.     

The effect of series elasticity on actuator power and work output: Implications for robotic and prosthetic joint design

Evidence from biomechanics research suggests that tendon series elasticity allows muscle to act in an optimal range of its force–length and force–velocity curves to achieve work and power amplification. In this investigation we put forth a simple model to quantify the capacity of series elasticity to increase work and power output from an actuator. We show that an appropriate spring constant increases the energy that an actuator can deliver to a mass by a factor of 4. The series elasticity changes the actuator operating point along its force–velocity curve and therefore affects the actuator work output over a fixed stroke length. In addition, the model predicts that a series spring can store energy and deliver peak powers greater than the power limit of the source by a factor of 1.4. Preliminary experiments are performed to test model predictions. We find qualitative agreement between the model and experimental data, highlighting the importance of series elasticity for actuator work and power amplification across a fixed stroke length. We present several non-dimensional relations that can aid designers in the fabrication of robotic and prosthetic limbs optimized for work and power delivery.     

Design of a new triple electro-magnetic optical image stabilization actuator to compensate for hand trembling

Recently, the demand for a new two-axis driving actuator for optical image stabilization (OIS) system has increased in mobile devices such as digital cameras and digital camcorders. In this paper, we proposed a novel OIS actuator with triple electro-magnetic (TEM) circuits and a three-ball supporting mechanism for a digital camcorder and considered the driving force, magnetic spring, and moment equilibrium of the TEM circuits. To design the TEM circuits with the high sensitivity and adequate magnetic spring, the electro-magnetic circuit was improved. At first, a sensitivity analysis was performed using the design of experiment procedure. Based on these results, effective design parameters were selected and an objective function was defined and gradient-based optimization was carried out. Finally, the improved TEM OIS actuator was fabricated for a digital camcorder and the feasibility of the OIS actuator with the TEM circuits and three-ball supporting mechanism was verified and the performance was investigated experimentally. The experimental results indicated that the proposed OIS actuator exhibits sufficient performance with respect to sensitivity.     

Design, fabrication, and operation of submicron gap comb-drivemicroactuators

Making submicron interelectrode gaps is the key to reducing the driving voltage of a micro comb-drive electrostatic actuator. Two new fabrication technologies, oxidation machining and a post-release positioning method, are proposed to realize submicron gaps. Two types of actuator (a resonant type and a nonresonant type) with submicron gaps were successfully fabricated and their operational characteristics were tested experimentally. The drive voltage was found to be lower than that of existing actuators. The stability of comb-drive actuators is discussed     

Optimization of Comb-Driven Devices for Mechanical Testing of Polymeric Nanofibers Subjected to Large Deformations

Comb-driven electrostatic actuators applied to mechanical testing of nanostructures are usually designed by a ldquobrute-forcerdquo approach for maximum electrostatic-force output, which results in limited actuation range. This issue is more prevalent when testing soft nanofibers with large ductility. In this paper, the design considerations for a comb-driven platform for nanoscale mechanical testing of ductile nanofibers subjected to 50%, or larger, inelastic extensions are presented. The optimization carried out aimed at increasing the net-force output by comb drives with clamped-clamped tethers, which also improves on the accuracy in the calculation of the force that is applied onto the nanofiber specimens. At large actuator motions, tethers of low bending stiffness increased the net force applied to a nanofiber and provided better accuracy in the calculation of the applied force. On the contrary, at small actuator motions, the maximum net-force output by the comb drives increased with the axial tether stiffness due to the associated increase in the pull-in-instability voltage. The fabricated surface-micromachined devices enabled experiments with individual electrospun polyacrylonitrile nanofibers at a maximum force of 30 muN and extensions up to 60%. The force output calculated from the voltage input to the electrostatic devices was compared to direct measurements by an independent optical method. [2008-0252]     

新型动磁式直线振荡执行器的动子位移自传感

针对一种新型无内定子动磁式直线振荡执行器,在建立其机电系统数学模型的基础上,提出一种基于全维状态观测器的动子位移自传感算法。通过对执行器输入电压和输出电流信号的处理和计算来估算动子位移。仿真和实验结果均表明:在变压变频控制方式下,该算法能实现不同电气驱动频率下的动子位移自传感;采用该算法进行行程估算的绝对误差最大值为0.32 mm,相对误差最大值为2.6%。此算法可以满足直线压缩机和直线泵类负载的变行程控制要求。     

A single-layer PDMS-on-silicon hybrid microactuator with multi-axis out-of-plane motion capabilities-part II: fabrication and characterization

This paper reports on fabrication and characterization of a new electrostatic microactuator that achieves out-of-plane multi-axis motion with a single silicon device layer. The multi-axis motion with the simple actuator design is possible by incorporating a three-dimensional (3-D) polydimethylsiloxane (PDMS) microstructure. This paper develops a new device processing method named "Soft-Lithographic Lift-Off and Grafting (SLLOG)" to fabricate the previously designed PDMS-on-silicon hybrid actuator structure. SLLOG is a low-temperature (less than 150/spl deg/C) process that allows replica molded PDMS microstructures to be integrated in silicon micromachined device patterns. The fabricated actuator is characterized using laser vibrometry. The experimental results demonstrate actuation motions achieved in three independent axes with fast dynamic response reaching a bandwidth of about 5 kHz. The fabricated PDMS-on-silicon actuator yields a vertical displacement up to 5 /spl mu/m and rotational motions with a 0.6-/spl deg/ tilting angle at a 40-V peak-to-peak ac actuation voltage.     

微电热驱动器中偏置层的分析

设计了一种电热微驱动器,根据几何关系、泰勒公式和材料力学求得偏置层结构末端的位移公式,并验证了采用镍作为偏置层材料的合理性.通过Coventorware软件中的有限元模块进行仿真分析,得出施加驱动电压为5 V,响应时间为5 ms,驱动器的初始温度为300 K时,得出偏置层宽度W1与驱动器位移d的曲线关系.通过验证驱动器的最大应力为235 MPa,小于镍的许用应力,确定驱动器在W1=20μm可以进行可靠的工作.分析偏置层厚度和宽度的加工误差对驱动器末端位移的影响,可得在对偏置层进行加工时要严格控制偏置层厚度H1的加工误差.     

Fabrication of distributed electrostatic micro actuator (DEMA)

A distributed electrostatic micro actuator (DEMA) has been proposed. The actuator has many small driving units which consist of two wave-like insulated electrodes. Both ends of insulated electrodes are connected to each other, and the driving unit has narrow gap for deformation caused by electrostatic forces. The driving units have large area of electrodes and are distributed in series and in parallel. So, a strong electrostatic force can be obtained, and the deformation and the generated force of the actuator would be large. Macro model of the DEMA was fabricated with polyimide films, and the deformation of the actuator was measured. When the applied voltage was 200 V, the deformation ratio was 36%. A micro actuator was fabricated by use of photolithography and electroplating. The displacement of 28 μm was observed when applied voltage was 160 V. Experimental results of the micro actuator were compared with the results simulated by finite element method (FEM) analysis