Development of X-beam electrothermal actuators

A new electrothermal actuator with X-shaped single crystal silicon beam structure is proposed and characterized. This new actuator is made by using SOI-DRIE processes. X-beam actuator of 2000 m projection length and 0.5° tilted angle can generate 90 m static displacement. This new design shows a better static displacement and stability in long travel range than the other actuators. From these experimental data, we conclude the feasibility of our new X-beam actuators. Any movable structure connected with one side of this X-beam can be pushed toward the other side. Therefore, it can be a basic actuation element in association with various structures for different applications.     

Improved design of polymeric composite electrothermal micro-actuator for high track density hard disk drives

Recently, we have developed a polymeric composite electrothermal micro-actuator for dual-stage applications in hard disk drives (HDDs). The polymer composite was demonstrated with a larger thermal expansion as compared to silicon. Yet, the previous design of polymeric composite thermal actuator was stiff, having a high mechanical resonant frequency at 33 kHz and a moderate static displacement stroke of 50 nm at 4 V. An even larger stroke above 100 nm is generally required to meet the need of HDD dual-stage systems. To meet the requirement for a large stroke, we presented an improved design of polymeric composite electrothermal micro-actuator by increasing flexibility of the composite thermal benders. As compared to the previous design, the new design doubled the displacement stroke up to 106 nm at 4 V while it maintained a high mechanical resonant frequency of 31 kHz, slightly below that of the previous design. In addition, a finite element analysis showed that electrothermal activation of the micro-actuator is rather localized and it causes only a small temperature rise of the neighbouring parts of head gimbal assembly. These good performances suggested that this improved design of thermal micro-actuator is promising for high bandwidth dual-stage positioning systems in future high track density HDDs.     

The monolithic integration system of bulk-Si sensors and actuators based on the Au–Au bonding technology

The monolithic integration of bulk-Si MEMS sensors and actuators using the Au–Au bonding technology is presented in this work. With this technology, the substrate isolation and electrical interconnection between the CMOS circuits and bulk-Si CMOS MEMS sensors are achieved perfectly. In order to demonstrate this technology, a pressure sensor and an electrothermal actuator have been monolithically designed and fabricated. In addition, by sputtering aluminium on the bulk silicon electrothermal actuator, the electrothermal actuator is modified and the sensitivity of the actuator is obviously improved. The measurement results show that the sensitivity of the pressure sensor is 0.29fF/hPa. And the sensitivities of the modified and non-modified electrothermal actuators are 20.23 μm/V and 3.34 μm/V, respectively. Compared with the non-modified electrothermal actuators, the sensitivity of the modified electrothermal actuators is improved by 6 times.     

Variable optical attenuator using planar light attenuation scheme based on rotational and translational misalignment

In the last decade, extensive developments of microelectromechanical systems based thermal actuator and/or electrothermal actuators have been dedicated to the applications, such as data storage devices, relays and optical switches, etc. In this paper, we demonstrated a novel planar micromechanism comprising a tilted mirror driven by a V-beam electrothermal actuator via a link beam. This electrothermally driven tilted mirror can have static displacement with a motion trace including rotational and translational movement. The rotational and translational misalignment of reflected light spot toward the core of output port fiber will lead to light attenuation. In other words, the attenuation is controlled in terms of the position of tilted mirror depending on driving dc voltage. This new micromechanism has granted us a more efficient way to perform the light attenuation regarding to the other kinds of planar variable optical attenuators. These devices were fabricated by the deep reactive ion etching process and can reach 30-dB attenuation at 7.5 V driving voltage. The polarization dependant loss is less than 0.1 dB within the 30-dB attenuation region. The static and transient characteristics of devices operated at ambient room temperature environment show good repeatability and stability.     

Polymeric Thermal Microactuator With Embedded Silicon Skeleton: Part I—Design and Analysis

This paper presents the modeling of a new design of a polymeric thermal microactuator with an embedded meander-shaped silicon skeleton. The design has a skeleton embedded in a polymer block. The embedded skeleton improves heat transfer to the polymer and reinforces it. In addition, the skeleton laterally constrains the polymer to direct the volumetric thermal expansion of the polymer in the actuation direction. The complex geometry and multiple-material composition of the actuator make its modeling very involved. In this paper, the main focus is on the development of approximate electrothermal and thermoelastic models to capture the essence of the actuator behavior. The approximate models are validated with a fully coupled multiphysics finite element model and with experimental testing. The approximate models can be useful as an inexpensive tool for subsequent design optimization. Evaluation, using the analytical and numerical models, shows that the polymer actuator with the embedded skeleton outperforms its counterpart without a skeleton, which is in terms of heat transfer and, thus, response time, actuation stress, and planarity.$hfill$ [2007-0193]      

A nodal analysis model for the out-of-plane beamshape electrothermal microactuator

This paper introduces a nodal analysis model for the out-of-plane beamshaped electrothermal microactuators. The electrothermal microactuator is traditionally simulated with finite element method (FEM) due to the complex coupling of the electrical, thermal and mechanical problem. This complex problem is classified into two parts in this paper: the coupling electrothermal problem and the coupling thermomechanical problem. By utilizing the characteristic of the temperature distribution, the nodal analysis model for the coupling electrothermal behavior of the electrothermal microactuator is built. The model scale is much smaller than the finite element model, which results in less computational consumption. Then the coupling thermomechanical behavior, such as the shift of the heat flow from the bottom of each part of the actuator to the substrate due to its out-of-plane movement, is modeled to make the model more reasonable. Many other effects which remarkably influence the behavior of the actuator are also taken into account. This model is verified by available experimental results, and achieves an agreement.     

Spatially resolved temperature mapping of electrothermal actuators by surface Raman scattering

In this paper, we report spatially resolved temperature profiles along the legs of working V-shaped electrothermal (ET) actuators using a surface Raman scattering technique. The Raman probe provides nonperturbing optical data with a spatial resolution of 1.2 /spl mu/m, which is required to observe the 3-/spl mu/m-wide actuator beams. A detailed uncertainty analysis reveals that our Raman thermometry of polycrystalline silicon is performed with fidelity of /spl plusmn/10 to 11 K when the peak location of the Stokes-shifted optical phonon signature is used as an indicator of temperature. This level of uncertainty is sufficient for temperature mapping of many working thermal MEMS devices which exhibit characteristic temperature differences of several hundred Kelvins. To our knowledge, these are the first quantitative and spatially resolved temperature data available for thermal actuator structures. This new temperature data set can be used for validation of actuator thermal design models and these new results are compared with finite-difference simulations of actuator thermal performance.     

Modelling of Chevron electrothermal actuator and its performance analysis

Microsystem Technologies - In this work, a Chevron electrothermal actuator is designed and its analytical model is developed. Chevron actuator works on the principle of Joules heating effect and...     

A single-layer PDMS-on-silicon hybrid microactuator with multi-axis out-of-plane motion capabilities-Part i: design and analysis

This paper proposes a new single-layer electrostatic microactuator design that generates three-axis motion resulting in vertical translation and out-of-plane tilting. The new actuator design combines a micrometer-scale three-dimensional (3-D) polydimethylsiloxime (PDMS) structure fabricated using soft lithography with comb drives processed using a single mask on a silicon-on-insulator (SOI) wafer. The multi-axis actuation capability of the proposed actuator is enabled by coupling the in-plane actuation motion of the comb drives with the elastic bending of PDMS flexural microjoints. To predict the static and dynamic performance of the actuator, this paper develops a four-bar-linkage model and applies Lagrangian dynamics theory. The developed analytical model is validated using finite element analysis (FEA) and allows us to perform parametric design of the actuator. The analysis indicates that the proposed PDMS-on-silicon hybrid actuator can yield the desired multi-axis actuation capability with a dynamic bandwidth as large as 5 kHz.     

Electrothermal properties and modeling of polysilicon microthermal actuators

This work addresses a range of issues on modeling electrothermal microactuators, including the physics of temperature dependent material properties and Finite Element Analysis (FEA) modeling techniques. Electrical and thermal conductivity are a nonlinear function of temperature that can be explained with electron and phonon transport models, respectively. Parametric forms of these equations are developed for polysilicon and a technique to extract these parameters from experimental data is given. A modeling technique to capture the convective and conductive cooling effects on a thermal actuator in air is then presented. Using this modeling technique and the established polysilicon material properties, simulation results are compared with measured actuator responses. Both static and transient analyzes have been performed on two styles of actuators and the results compare well with measured data.     

Safe working condition and optimal dimension of the electrothermal V-shaped actuator

Microsystem Technologies - This study presents design, optimization of the electrothermal V-shaped actuator (EVA) and aims to obtain condition of mechanical stability, thermal safety and large...     

On sufficient conditions to keep differential flatness under the addition of new inputs

It is well known that a controllable nonlinear system will retain its controllabality when new actuator inputs are added to it. In this article, we ask the question if a system, linearisable by static or dynamic feedback, will retain this property when new actuator inputs are added to it. Alternatively, a system may be linearisable after removing one or more inputs from it. This question is important in the design of robotic systems from the perspective of trajectory planning and control, specially if they are under-actuated. The goals of this article are as follows: (i) using counter examples, we first show that feedback linearisability may not be preserved when new inputs are added to a robotic system, (ii) sufficient conditions are determined when a system will retain this property under the addition of new inputs. The theory is illustrated through some examples from the robotics field.     

Parallel-beams/lever electrothermal out-of-plane actuator

We report on the design, modeling, fabrication and testing of a powerful electrothermal actuator allowing for various modes of movement and exhibiting forces large enough to be usable in a micro-tribotester. The performance of the actuator has been simulated combining numerical and analytical calculations, and then the results were compared with experiments performed in ambient conditions and in vacuum. Theoretical results and measurements are consistent if the temperature dependence of the properties of the polycrystalline Si is taken into account. The temperature dependence of the electrical resistivity and the linear thermal expansion coefficient of the Boron doped polycrystalline Si have been derived from experimental results and self-consistent numerical calculations. We delimited the reversible and irreversible actuation regions of the electrothermal actuator, thus the so-called plastic deformation for actuation at high electrical power can be avoided.The authors would like to thank the financial support of the Dutch Technology Foundation (STW) and the technical support of the TST (Micmec) technicians.     

A multipurpose electrothermal microgripper for biological micro-manipulation

A novel electrothermal SU-8 microgripper with a large gripping scope and multipurpose jaws is designed and ANSYS software was used to check its performances. Then, the microgripper is fabricated by a simple UV-LIGA process followed by two performance tests. The static test results show that with only 195 mV, 111.1 mW and 53.7 °C temperature increase at the actuator, a 71.5 μm jaws gap change is obtained. The dynamic response test result shows that driven by different step-type voltages, the response time is about 0.23 s during both closing and opening jaws process. Finally, two micro-manipulation sequences are carried. The experimental results show that due to the large gripping scope and the multipurpose jaws, the microgripper can be used as a multipurpose manipulator for biological micro-manipulations including the manipulation of micro blood vessel and the operation of small size cell, such as cyanobacteria cell.     

Angular vertical comb actuators assembled on-chip using in-plane electrothermal actuators and latching mechanisms

We have designed, fabricated and tested self-aligned angular vertical comb-drive (AVC) actuators by on-chip assembly using in-plane electrothermal actuators and latching mechanisms. The on-chip assembly process is carried out by engaging latching mechanism connected to the torsion bars through the off-centered thinned down silicon beams. When the latching mechanism is fully engaged, the assembled AVC actuator forms permanent initial tilt angle by the retraction force of electrothermal actuators. The AVC actuators and latching mechanisms are fabricated on a silicon-on-insulator (SOI) wafer using three photomasks and three times of deep etch steps. The maximum optical scan angle of 30.7° is achieved at 4.56 kHz under the sinusoidal driving voltage of 0–80 V applied to the AVC actuator. After the reliability test performed by operating the actuator for 1.6 × 10⁸ cycles at its resonance, the measured optical scan angle variation and resonant frequency change were within 1.1% and 8 Hz, respectively, and the robustness of the latched mechanism was ensured.     

Rotational micro actuator for microsurgery

In this paper an innovative hydrostatic micro actuator system for controlling the rotational degree of freedom of microsurgery instruments is presented. From the possible hydrostatic motor designs, an annular gear motor in orbit configuration has been chosen based on its suitability for micro manufacturing. The innovative actuator design includes a rotor-integrated control mechanism for connecting the actuator’s individual positive-displacement chambers. First a macro-model of the new actuator was fabricated and tested. The obtained test results already confirm the functionality and show the actuator’s exciting potential. The important design parameters were identified and a mathematical model was developed and is presented in this paper. Thereby optimized design parameters enable a further miniaturization and the use within minimal invasive surgery tools. A potential application of this novel device is discussed in the context of endovascular and interventional resection treatment. Combined with a shape memory alloy actuator a tool for the resection of calcified aortic valves was developed. Because of its small size it is possible to integrate it into a trocar channel.     

Robust H ∞ static output feedback stabilization of T-S fuzzy systems subject to actuator saturation

This paper proposes a method for designing robust H_?? static output feedback stabilization of Takagi-Sugeno (T-S) fuzzy systems under actuator saturation. In this paper, the input saturation is represented by a polytopic model and the modeling error is assumed a norm-bounded uncertainty. A set invariance condition for robust H_?? static output feedback system under actuator saturation is first established. Then, the estimation of the largest domain of attraction for the system is formulated and solved as a Linear Matrix Inequality (LMI) optimization problem. Two examples are used to demonstrate the effectiveness of the proposed design method.     

Analysis of the deflection of a circular plate with an annular piezoelectric actuator

A new analytical model for predicting the deflection of a circular plate with an annular piezoelectric actuator is presented. The plate and actuator are treated as a mechanically over-constrained system and a structural mechanics approach is applied to establish the relevant equations of geometrical compatibility and static equilibrium, assuming that the interaction forces between the actuator and plate are concentrated at the edges of the actuator annulus. These equations can be solved analytically or numerically to determine the interaction forces. Analytical expressions for plate deflection in terms of the interaction forces are then presented for three sets of plate boundary conditions. The analytical results are shown to be in good agreement with finite element simulations and provide an efficient alternative to finite element analysis for design and optimization studies.     

Pt/3C-SiC electrothermal cantilever for MEMS-based mixers

Microelectromechanical resonators are currently applied as MEMS-based mixers-filter for communication systems. Silicon carbide, as a material with high potentiality to replace silicon material, can be utilised in the design of MEMS-based mixers. A Pt/SiC electrothermal actuator, resonating at fundamental frequency of 117.1 kHz, was fabricated and designed to perform frequency mixing. Two signals were multiplied and the sum, as well as the difference, was used to drive the fabricated cantilever into resonance.     

电热驱动Bimorph微执行器对流系数估算方法研究

随着电热驱动MEMS器件尺寸进一步缩小,传统热对流系数的取值已无法满足微系统分析建模需求。针对电热型Bimorph结构的MEMS微镜驱动器,通过分析其温度分布,并以其平均温度为参考指标建立简单热阻和对流热阻分段模型,推算出微尺度下精确的对流系数,提高了微执行器设计模型的驱动性能。经理论计算和实验测试验证,对流系数值的误差在8.1%以内,满足实际设计需求,验证了该方法的合理性和可行性。