Low-voltage small-size double-arm MEMS actuator

The fabrication and characterisation of a double-arm cantilever-type metallic DC-contact MEMS actuator with low pull-down voltage are reported. Bi-layer TiW cantilevers with an internal stress gradient were fabricated using a microwave-compatible fabrication process. Owing to its small size, cantilever length (L = 5-50 mum) and width (W = 2-40 mum), i.e. ~10-100 times smaller in lateral dimensions than a standard MEMS actuator, this actuator showed actuation voltages lower than 10 V. RP measurements of the 10 mum-wide actuators yielded an average insertion loss less than 1 dB and isolation higher than 40 dB up to 25 GHz. The developed actuator is well suited for integration in reconfigurable microwave circuits and systems such as reconfigurable antennas and arrays.     

基于光学聚焦方法的热驱动微执行器位移测量

随着微机电系统（MEMS）设计日趋成熟,度量问题越来越成为微系统技术中的热点。使用改进的拉普拉斯求和方法（SML）和深度估计法来测量热度驱动微夹持器末端的弯曲程度。实验中,使用了10幅在42℃时微夹持器的水下工作图像来验证这种光学聚焦方法,结果证明使用光学聚焦方法可以测量出作为驱动器反馈输入的末端弯曲大小,实现对驱动器运动的精确控制。     

Control of ionic polymer metal composites

Robotic devices are traditionally actuated by hydraulic systems or electric motors. However, with the desire to make robotic systems more compact and versatile, new actuator technologies are required. In this paper, the control of ionic polymer metal composite actuators is investigated from a practical perspective. The actuator characteristics are examined through the unblocked maximum displacement and blocked force output. An open-loop position control and closed-loop position proportional-integral-derivative (PID) control are then applied to a strip of actuators. Finally, the performance of the polymer is investigated when implementing an impedance controller (force/position control).     

Design of a bidirectional MEMS actuator with high displacement resolution, large driving force and power-free latching

This paper describes the design and ANSYS modeling of a bidirectional thermal inchworm MEMS actuator featuring high actuation resolution (0.1 μm) combined with large driving force (100 mN) and power-free latching. A promising application of this device is for precision in-package positioning of optical fibers, but the actuator also has potential for wider use. The inchworm mechanism includes two E-shaped metallic actuators facing each other and a pusher between them that couples to a moveable object such as an optical fiber. Nickel is chosen as the material of the actuators due to its desirable electrical, thermal, and mechanical properties, and availability in fabrication facilities. Electrothermal actuation is used to move the pusher as well as the optical fiber in the desired direction by inputting electric currents in a particular sequence. A transient thermal-mechanical analysis shows the feasibility of the input sequence that drives the inchworm actuation.     

Carbon‐Based Photothermal Actuators

Actuators that can convert environmental stimuli into mechanical work are widely used in intelligent systems, robots, and micromechanics. To produce robust and sensitive actuators of different scales, efforts are devoted to developing effective actuating schemes and functional materials for actuator design. Carbon‐based nanomaterials have emerged as preferred candidates for different actuating systems because of their low cost, ease of processing, mechanical strength, and excellent physical/chemical properties. Especially, due to their excellent photothermal activity, which includes both optical absorption and thermal conductivities, carbon‐based materials have shown great potential for use in photothermal actuators. Herein, the recent advances in photothermal actuators based on various carbon allotropes, including graphite, carbon nanotubes, amorphous carbon, graphene and its derivatives, are reviewed. Different photothermal actuating schemes, including photothermal effect–induced expansion, desorption, phase change, surface tension gradient creation, and actuation under magnetic levitation, are summarized, and the light‐to‐heat and heat‐to‐work conversion mechanisms are discussed. Carbon‐based photothermal actuators that feature high light‐to‐work conversion efficiency, mechanical robustness, and noncontact manipulation hold great promise for future autonomous systems.     

Influence of ionic liquid concentration on the electromechanical performance of ionic electroactive polymer actuators

We have investigated influence of ionic liquid concentration on the electromechanical response of ionic electroactive polymer actuators. Actuators were fabricated from ionomeric membrane and doped with different concentrations of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid. Samples were investigated for their electromechanical and electrochemical characteristics; and it was observed that the maximum electromechanical strain of approximately 1.4% is achieved at 22 wt% ionic liquid content. Increasing ionic liquid concentration results in saturation of the electrode–ionomer interface and formation of ionic double/multi layers, which in turn result an inward accumulation of ions; hence, generate strain in an undesired direction that deteriorates the electromechanical response of the actuator.     

MEMS静电驱动器的场致电子发射效应研究

为研究MEMS静电驱动器的场电子发射效应,设计并加工了排斥驱动器和平行板驱动器两种不同结构的静电驱动器,实验测试了电极间漏电流随驱动电压的变化关系,验证了其满足场发射效应的FN理论公式,从而首次观察到静电排斥驱动器的场致电子发射效应.根据测试结果计算得到了所设计的两种MEMS静电驱动器的名义发射面积和场增强因子.由于器件自身的结构设计特征,平行板驱动器相对于排斥驱动器具有更大的名义发射面积和更小的场增强因子.     

Improving electroactive polymer actuator by tuning ionic liquid concentration

We have fabricated actuators from a blend of fluoropolymer (FP) with ionic liquid (IL). Here a combination of graphene, graphite, and silver nanoparticles is used to raise the electrode conductivity. As the electrode composition is fixed, we found that the actuator displacement increases with decreasing amount of ionic liquid in the polymer gel electrolyte. A maximum strain of 0.48% was observed from peak-to-peak displacement for an actuator with IL/FP = 0.3 in the polymer gel electrolyte. The simulation results indicate that lowering IL concentration leads to a more compact ion distribution in the electrode layers and hence explains the increased strain in the actuators.     

A thermally-actuated latching MEMS switch matrix and driver chip for an automated distribution frame

This paper presents a thermally-actuated latching MEMS switch matrix together with an integrated driver chip for controlling these switches. The novel thermal actuators are heated by making use of a polysilicon heater underneath the structure, which results in a more stable actuation and a facilitated driving. The designed driver can generate adjustable latching waveforms which are needed to latch the switch into a closed or open state. As the thermal actuators in the MEMS switch require voltages up to 24 V, the high-voltage 0.35 µm  I3T50 technology of ON Semiconductor was used to fabricate the device. The driver, measuring 2 × 2 mm², contains 32 output drivers and can control a 4 × 4 latching switch matrix. This driver chip together with the latching MEMS switches were combined to create a prototype 2 × 2 double-pole single-throw latching MEMS switch matrix. The proposed MEMS switch matrix could be used in the fixed-access telecommunication network in which it can implement a compact automated distribution frame for connecting twisted pairs.     

Wound Roll Dielectric Elastomer Actuators: Fabrication, Analysis, and Experiments

Wound roll electroactive polymer actuators fabricated with dielectric elastomer (DE) materials provide high bandwidth actuation for robots, minipumps, loudspeakers, valves, and prosthetic devices. In this paper, we develop a DE wound roll actuator fabrication process that produces high strain (12%), reliable (3480 cycles at maximum strain), and stiff (144 N/m) actuators. An axisymmetric Unite element model with electrostatic and radial bulk modulus nonlinearity predicts actuator displacement and stress. The maximum compressive radial stress occurs at the center of the innermost active layer. This layer also has the thinnest material, indicating the most likely failure point. The nonlinear model predicts actuator displacement in response to applied voltage and load, matching experiments to within 1 mm.     

Temperature gradient controlled crystal growth from TIPS pentacene-poly(α-methyl styrene) blends for improving performance of organic thin film transistors

6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) from simple drop casting typically forms crystals with random orientation and poor areal coverage, which leads to device-to-device performance variation of organic thin film transistors (OTFTs). Previously, a temperature gradient technique was developed to address these problems. However, this approach simultaneously introduced thermal cracks due to the thermally induced stress during crystallization. These thermal cracks accounted for a reduction of charge transport, thereby impacting the device performance of TIPS pentacene based OTFTs. In this work, an insulating polymer, poly(α-methyl styrene) (PαMS) was blended with TIPS pentacene to relieve the thermal stress and effectively prevent the generation of thermal cracks. The results demonstrate that the incorporation of PαMS polymer combined with the temperature gradient technique improves both the hole mobility and performance consistency of TIPS pentacene based OTFTs.     

MEMS薄膜横向断裂强度的在线测试——热驱动法

就MEMS薄膜断裂强度的测试提出了一种新的测试结构 ,该结构由待测梁 (悬臂梁 )和驱动源 (V形热执行器 )两部分组成。热执行器用来作为悬臂梁断裂的驱动源。用指针标尺读数系统测量悬臂梁弯曲挠度 ,从而根据文中给出的测试用的理论公式就可计算出梁弯曲所能承受的最大应力。悬臂梁和热执行器的制造工艺兼容 ,故整个测试能在芯片上完成     

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     

Bioinspired Graphene Actuators Prepared by Unilateral UV Irradiation of Graphene Oxide Papers

Inspired by natural autonomous systems that demonstrate controllable shape, appearance, and actuation under external stimuli, a facile preparation of moisture responsive graphene‐based smart actuators by unilateral UV irradiation of graphene oxide (GO) papers is reported. UV irradiation of GO is found to be an effective protocol to trigger the reduction of GO; however, due to the limited light transmittance and thermal relaxation, thick GO paper cannot be fully reduced. Consequently, by tuning the photoreduction gradient, anisotropic GO/reduced GO (RGO) bilayer structure can be easily prepared toward actuation application. To get better control over the responsive properties, GO/RGO bilayer paper with a certain curvature and RGO patterns are successfully prepared for actuator design. As representative examples, smart humidity‐driven graphene actuators that mimic the cilia of respiratory tract and tendril climber plant are successfully developed for controllable objects transport.     

A new type of fish-like underwater microrobot

This paper presents a new prototype model of an underwater fish-like microrobot utilizing ionic conducting polymer film (ICPF) actuator as the servo actuator to realize swimming motion with three degrees of freedom. A biomimetic fish-like microrobot using ICPF actuator as a propulsion tail fin and a buoyancy adjuster for the swimming structure in water or aqueous medium is developed. The overall size of the underwater prototype fish shaped microrobot is 45 mm in length, 10 mm in width, and 4 mm in thickness. It has two tails with a fin driven respectively, a body posture adjuster, and a buoyancy adjuster. The moving characteristic of the underwater microrobot is measured by changing the frequency of input voltage from 0.1-5 Hz in water and the amplitude of input voltage from 0.5-10 V. The experimental results indicate that changing the amplitude and frequency of input voltage can control the swimming speed of proposed underwater microrobot.     

Harnessing the Actuation Potential of Solid‐State Intercalation Compounds

High‐strain, high‐force mechanical actuation technologies are desirable for numerous applications ranging from microelectromechanical systems (MEMS) to large‐scale “smart structures” that are able to change shape to optimize performance. Here we show that electrochemical intercalation of inorganic compounds of high elastic modulus offers a low‐voltage mechanism (less than 5 V) with intrinsic energy density approaching that of hydraulics and more than a hundred times greater than that of existing field‐operated mechanisms, such as piezostriction and magnetostriction. Exploitation of the reversible crystallographic strains (several percent) of intercalation compounds while under high stress is key to realization of the available energy. Using a micromachined actuator design, we test the strain capability of oriented graphite due to electrochemical lithiation under stresses up to 200 MPa. We further demonstrate that simultaneous electrochemical expansion of the LiCoO₂/graphite cathode/anode couple can be exploited for actuation under stresses up to ～ 20 MPa in laminated macroscopic composite actuators of similar design to current lithium‐ion batteries. While the transport‐limited actuation mechanism of these devices results in intrinsically slower actuation compared to most ferroic materials, we demonstrate up to 6.7 mHz (150 s) cyclic actuation in a laminated actuator designed for a high charge/discharge rate. The potential for a new class of high‐strain, high‐force, moderate‐frequency actuators suitable for a broad range of applications is suggested.     

基于二维模型的静电梳状结构平稳性分析

微静电驱动器作为MEMS中一个重要的功能实现器，是当前MEMS中研究的热点。文章基于二维模型结合垂直平移刚度及转动刚度两方面综合考虑，对静电微驱动结构单元的面不平稳性及最大静态位移进行了研究分析。其最大静态位移与叉指间距，初始重叠长度以及弹性系数比有关，分析了理论结果并通过FEM进行验证。     

应用于流动控制的MEMS传感器和执行器

出现于20世纪80年代后期的微机械技术可以制作出微米尺度的传感器和执行器。这些微器件与信号调节和处理电路集成后,组成了可执行分布式实时控制的微电子机械系统(MEMS)。这种性能为流动控制研究开辟了一个崭新的研究领域。利用MEMS技术设计和制作了一种传感器和一种执行器。实验证明,采用体硅腐蚀的工艺制作微流体器件是可行的,同时可以避免牺牲层腐蚀和释放的复杂工艺。     

System integration of high voltage electrostatic MEMS actuators

A system integration for High Voltage (HV) electrostatic MicroElectroMechanical Systems (MEMS) actuators is introduced on a micro-Printed Circuit Board. The system includes a programmable microcontroller, a programmable DC/DC converter, a multi output HV interface and electrostatic MEMS actuators. The system produces high output voltages (10–300 V) and can control a large variety of MEMS capacitive loads (1 to 50 pF) by combining diverse semiconductor technologies. This system proves that technologies, such as low voltage CMOS of different processes, high voltage DMOS and MEMS, can interact, communicate and even be integrated as a System In Package (SIP), providing significant size and cost reductions. The system was programmed to control electrostatic MEMS actuator. The DC/DC converter was made from components of different technologies and two addressable high voltage CMOS interfaces were fabricated with DALSA's 0.8 μm High Voltage process. A prototype of the global system has been built and tested.     

Biomimetic 4D-Printed Breathing Hydrogel Actuators by Nanothylakoid and Thermoresponsive Polymer Networks

Shape-morphing actuators, which can breathe with the accompany of morphology changes to mimic botanical events, are challenging to fabricate with soft hydrogel materials. Herein, 4D printed-smart hydrogel actuators are reported that can not only dynamically deform but also generate oxygen (O₂) upon external stimulations. The printed breathing actuators featured with spinach leaf-derived thylakoid membrane (nanothylakoid) for photothermal conversion and catalytical O₂ evolution, a poly(N-isopropylacrylamide) (PNIPA) thermoresponsive polymer network for generating deformation forces by swelling/shrinkage (rehydration/dehydration), and an asymmetric bilayer poly(N-isopropylacrylamide)/polyacrylamide (PNIPA/PAA) structure to amplify the mechanical motions. Upon thermal stimulation or laser irradiation, the actuator can reversibly bend/unbend because of the photothermal conversion of nanothylakoid and the printed thermoresponsive asymmetric bilayer structure. Additionally, the catalase-like property of nanothylakoid imparts the actuator with O₂ evolution capability to breathe for further mimicking botanical systems. Notably, 4D printing can greatly facilitate and simplify the actuator fabrication process, including adjusting the size and layer compositions. This artificial breathing actuator with photothermal and catalytical properties provides a strategy in designing intelligent hydrogel systems and proves to be a highly promising material candidates in the fields of 3D/4D printing, automated robotics, and smart biomedical devices.