Modelling the steady state response of CuAlNi/polyimide bimorph actuator

Microsystem Technologies - Microactuators developed from shape memory alloy (SMA) thin films on flexible substrates find good applications in MEMS design. This article presents the models of the...     

Optofluidic device for ultra-sensitive detection of proteins using surface-enhanced Raman spectroscopy

An optofluidic device is reported in this paper that can highly improve the robustness of surface-enhanced Raman scattering (SERS) detection and provide fingerprint information of proteins with a concentration in the nanogram per liter range within minutes. Moreover, the conformational change of protein can also be obtained using this device. Fabricated by standard photolithography processes, the optofluidic device has a step microfluidic–nanofluidic structure, which provides robust SERS detection. The sensitivity of the device is investigated using insulin and albumin as target analytes at a concentration of 0.9 ng/L. The ability to detect conformational changes of proteins using this technology is also shown by probing these analytes before and after their denaturation.     

Numerical simulation of a polysilicon thermal flexure actuator

 An electrothermal equation of a polysilicon thermal flexure actuator is presented, which takes heat conduction, air convection and radiation into account. A numerical method is developed to solve the equation. The deflection model based on the matrix displacement method, i.e. finite element method (FEM) in structural mechanics, is given. It transforms deflection equations into a matrix and is easy to calculate numerically. Simulation results for the actuator with typical dimensions are presented. Discussions are finally given. Received: 28 April 2000/Accepted: 9 January 2001     

Continuously tunable terahertz metamaterial employing a thermal actuator

In order to increase the flexibility of the resonance frequency, a widely and continuously tunable terahertz metamaterial structure that employs a thermal actuator for tuning the resonance frequency of a two-cut split-ring resonator is proposed in this paper. The tunable metamaterial device model is designed and simulated based on the MetalMUMPs process. The use of V-shaped thermal actuators enables continuous tuning of the resonance frequency over a large range from 1.374 to 1.574 THz. The transmission curves have a sharp dip in every resonance frequency, which indicates an excellent performance of strong resonance. The geometrical parameters of the V-shaped thermal actuator are optimized by COMSOL Multiphysics 4.2 in order to obtain enough displacement under minimum driven current. The relationship between driven current and slabs’ displacement is also characterized. The reliability of the metamaterial structure array actuated by the thermal actuator is also calculated and discussed.     

Implementation of substrates for surface-enhanced Raman spectroscopy for continuous analysis in an optofluidic device

The fabrication of substrates for surface-enhanced Raman spectroscopy (SERS), which offer high enhancement factors as well as spatially homogeneous distribution of the enhancement, plays an important role for expanding the surface-enhanced Raman spectroscopy to a powerful quantitative and non-invasive measurement technique. In this paper, a method for the fabrication of capable SERS-active substrates by laser treatment of gold films supported on glass with single 351?nm UV-laser pulses is presented. Resulting nanometer scaled structures show enhancement factors of up to 10⁶ with very high spatial reproducibility for a monolayer of benzenethiol. A method for integration of these substrates into PDMS microchannels is shown. A technique for the generation of a simple mold master for PDMS replication is presented. Rhodamine 6G is used as model system to demonstrate continuous measurements on a solid SERS-active substrate in a microchannel. The label-free detection of the biological molecule albumin is improved by an order of magnitude.     

Analytical modeling and optimization for a laterally-driven polysilicon thermal actuator

 An electro-thermally and laterally driven microactuator is analytically examined which is based on the asymmetrical thermal expansion of the microstructure with different lengths of two beams. Deflection of the microactuator is modeled by the structural analysis. Analytical results are compared with the finite element model (FEM) results, and show a reasonable agreement. The magnitude of the deflection depends strongly on the geometry of the microactuator. The analytical model allows one to optimize efficiently the laterally driven thermal actuators.     

Modeling and characterization of a chemomechanical actuator using protein transporter

Plants and animal cells are naturally occurring actuators that exhibit force and motion driven by fluid transport through the cell membrane. The protein transporters embedded in the cell membrane serve as the selective gateway for ion and fluid transport. The actuator presented in this work generates force and motion from mass transport through an artificial membrane with protein transporters extracted from plant cell membranes. The artificial membrane is formed from purified 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-[Phospho-l-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero-3-Phosphoethanolamine (POPE) lipids and supported on a porous substrate. The protein transporter used in the actuator membrane is a proton–sucrose cotransporter, SUT4, extracted from yeast cells genetically modified to grow the cotransporter in their cell membranes. The SUT4 transporter conducts proton and sucrose from the side of the membrane with higher concentration and carries water molecules across the membrane. It is observed from transport characterization experiments that fluid flux through the membrane varies with the applied sucrose concentration and hence is chosen as the control stimulus in the actuator. A modified four-state facilitated diffusion model is applied to the transport characterization data to compute the two characteristic parameters for fluid transport, saturation concentration and translocation rate, through the membrane. The flux rate through the membrane is observed to increase with the concentration until a particular value and saturates at a higher concentration. The saturation concentration for the actuator is experimentally found to be 6±0.6 mM sucrose on the side with lower pH. The corresponding maximum translocation rate is found to be 8.5±1.2 nl/ g cm² min. The maximum steady state deformation measured on the actuator is 60 m for 30 mM sucrose that corresponds to a force of 0.89 mN.     

光学头多维力矩器的多学科设计

一、简介力矩器(Actuator)是目前光盘读写装置内的关键部件。当光盘处于高速旋转的工作状态时,由于各种误差的存在,盘片总是会产生一定的上下起伏、倾斜以及轨道偏移,从而导致信息轨道的读取产生一定超出光学容差范围的偏差。这种偏差将导致信号读出误码率的增加,甚至使光学头无法工作。为了提高光     

基于DeviceNet现场总线的电动执行器控制系统开发

介绍了具有DeviceNet现场总线通信接口的电动执行器的开发过程。保留了原有电动执行器现场控制功能,增加了DeviceNet远程控制和故障信号的采集。给出了软硬件实现方案和程序流程图,并详细讨论了DeviceNet对象模型的建立和在Keil C中对象化的实现方法。该电动执行器支持组态软件的接入并实现与其他DeviceNet现场总线产品的互连、互操作。     

RHA系列电动执行机构在钢铁厂的应用

简述了R H A系列电动电动执行机构安装、调试、应用等方面的使用经验及其优点。     

Fabrication and characterization of a monolithic piezoelectric actuator for fiber coupling

PZT thick-films are printed on an Al₂O₃-substrate, generating a cantilever monomorph. A task of positioning with two degrees of freedom is successfully fulfilled. It is realized by two parallel arranged cantilevers that are mechanically combined with a bar that has solid hinges. Different combinations of hinges are simulated and practically tested. In the presented work, a lens is successfully positioned in front of a laser diode. The loss of the coupling efficiency due to the shrinking of the adhesive joint can be scaled down. The paper presents the theoretical work including the report on analytic and FEM simulation of both deflection and stress. The practical validation is also presented. A simple sensor system is used to find an optimized position of the lens in front of the diode. This position is automatically held over a long period of time. With the fabrication of the actuator using thick-film printing and laser cutting a low cost device is built.     

Modeling of a three-layer piezoelectric bimorph beam withhysteresis

Piezoelectric actuators are usually stacked or bimorph in configuration. In this paper the mechanics of a three-layer piezoelectric bimorph is discussed and its dynamic model with hysteresis is presented. The results can be used to analyze piezoelectric actuators constructed with three-layer piezoelectric bimorphs. A piezoelectric bimorph actuator has been fabricated and experiments have been carried out to verify the model. The calculated results of this model closely matched the tested results. This model can also be used with other types of piezoelectric actuators with a slight modification     

Head-positioning control system using thermal actuator in hard disk drives

In this paper, we propose a head-positioning control system with a thermal actuator in hard disk drives (HDDs). The frequency response of the thermal actuator showed that the thermal actuator system has no mechanical resonant mode. Therefore, this head-positioning system with a thermal actuator can control the head-position beyond the major mechanical resonances caused by a voice coil motor (VCM) or suspensions. In this study, the system was a dual-stage actuator system; the first actuator was a VCM, and the second was a thermal actuator. Simulation results for a track-following control in an HDD demonstrated the validity of the proposed method.     

Design and characterization of a multi-stable magnetic shape memory alloy hybrid actuator

This paper describes the design and the characterization of a multi-stable hybrid actuator composed of a single magnetic shape memory alloy element and an electromagnetic actuator. The series arrangement of the active material and the electromagnetic actuator allows a new shape of hysteresis curve and a precise positioning can be obtained. The design of the different magnetic circuits has been done by analytic and numeric simulations in MatLab and FEMM 4.2. This study gives results of the elongation, the blocking force, and the holding force that can be obtained with such an actuator. Strokes up to 0.35 mm and a blocking force of 2.6 N have been measured for the hybrid actuator using a magnetic shape memory alloy with a cross section of 2.5 mm². Such an actuator can find application in precise positioning and medium frequency actuation systems. Nevertheless, there is much design space for improvements in terms of energy consumption, heat transfer, and overall cost of the device.     

Theoretical performance of a coiled coil piezoelectric bimorph

The electromechanical coupling behaviour of a novel, highly coiled piezoelectric strip structure is developed in full, in order to expound its performance and efficiency. The strip is doubly coiled for compactness and, compared to a standard straight actuator of the same cross-section, it is shown that the actuator here offers better generative forces and energy conversion, and substantial actuated displacements, however, at the expense of a much lower stiffness. The device is therefore proposed for high-displacement, quasi-static applications.     

An experimental characterization of a tunable separation device

By the use of an experimental setup for microfluidic flows, we have characterized the separation and concentration characteristics of the so-called Trilobite^? separation unit. Our separation unit consists of microfluidic channels and an elliptical separation geometry with a solid and a permeable wall region. We show that it is possible to adjust the thickness of different flow layers by changing the flow rates and pressure drop over the permeable wall. For high pressure drops, the separator shows promising concentration characteristics. For low pressure drops, an increase in flow rate results in a thinning of the flow layers. For sufficiently high flow rates, it should therefore be possible to create flow layers sufficiently thin that the particle separation is entirely dominated by hydrodynamic forces. This, in turn, will enable clog-free particle separation.     

Fabrication and characterization of a thermal switch

The development of a thermal switch based on arrays of liquid–metal micro-droplets is presented. Prototype thermal switches are assembled from a silicon substrate on which is deposited an array of 1600 30-μm liquid–metal micro-droplets. The liquid–metal micro-droplet array makes and breaks contact with a second bare silicon substrate. A gap between the two silicon substrates is filled with either air at 760 Torr, air at of 0.5 Torr or xenon at 760 Torr. Heat transfer and thermal resistance across the thermal switches are measured for “on” (make contact) and “off” (break contact) conditions using guard-heated calorimetry. The figure of merit for a thermal switch, the ratio of “off” state thermal resistance over “on” state thermal resistance, R_off/R_on, is 129 ± 43 for a xenon-filled thermal switch that opens 100 μm and 60 ± 17 for an 0.5 Torr air-filled thermal switch that opens 25 μm. These thermal resistance ratios are shown to be markedly higher than values of R_off/R_on for a thermal switch based on contact between polished silicon surfaces. Transient temperature measurements for the liquid–metal micro-droplet switches indicate thermal switching times of less than 100 ms. Switch lifetimes are found to exceed one-million cycles.     

Development of a compact displacement accumulation actuator device for both large force and large displacement

The design, fabrication, and testing of a compact displacement accumulation device is presented in this paper. The piezoelectric device provides both large displacement (mm) and large force (100 N). The device is based on conventional inchworm motor design that produces large displacement. The device integrates piezoelectric stacks for large force output and high-speed operation with MEMS ridges as a new clamping system. The device should be able to push and pull 450 N at 11 mm/s in a relatively compact size. FEM analysis is used for the design, EDM is used for the fabrication of a prototype, and conventional test techniques are used to evaluate performance. Stress and modal analysis are used to confirm that the device has an infinite fatigue life and a first modal frequency at 1309 Hz. Experimental data for clamping strength of the ridges and blocking force of the device validate that the device transfers the required load of 450 N. The device is successfully tested over a wide range of operating conditions at speeds up to 11 mm/s using open loop control. The stall load of the device is measured to be exceeding 2250 N. For the dynamic loading test, the device pushes test weights up to 50 N with the open loop control approach.