Fabrication and characterization of thermally driven fast turn-on microvalve with adjustable backpressure design

This paper presents a newly developed thermally driven normally-closed microvalve with fast switch-on capability and a backpressure resistance that can be specified by the designer. Two key components are involved in this micromachined valve: (1) an upper elastic blockade with stiffness adjustability; (2) a lower 3-dimensional microheater with rapid heating rate. During actuation, volume expansion of paraffin wax inside the microheater forms micro-bulges that protrude through holes in the top wall of the paraffin’s encapsulation. The protruding micro-bulges lift the valve blockade, allowing fluid to pass. When power to the microheater is turned off, the paraffin cools and valve returns to its normally closed state. Based on a design capable of 25 kPa backpressure, the valve attains its fully open state within 0.125 s under either a 3 V or 6 V battery-powered supply. When heating power is turned off, the valve returns to its fully closed state within 3.5 s. Details of fabrication, characterization and a discussion are presented in the text.     

Design and quasi-static characteristics study on a planar piezoelectric nanopositioner with ultralow parasitic rotation

This paper presents a particular mechanism design which is inherently inclined to have no parasitic rotation. The flexure-based stage comprises symmetric flexure guiding mechanism and two piezoelectric stack actuators. The layout of the stage is evaluated by finite element analysis, and the results indicate that the proposed design exhibits ultralow parasitic rotation. A prototype of the stage is then fabricated, and its performance is tested. Experimental results show that the stage has a stroke of 500 μm × 500 μm and the crosstalk is less than 1%. The maximum parasitic rotation is ±1.2 arcsec at a stroke of 500 μm.     

A miniature generator using piezoelectric bender with elastic base

Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added.     

Modeling and control of a piezoelectric microactuator with proprioceptive sensing capabilities

In this paper, modeling and control strategies for a new observability-optimized piezoelectric microactuator are presented. The targeted applications mainly concern the design of microgripper for micromanipulation tasks. The device has been designed using a topological optimization method, which takes into account the optimal full integration of piezoelectric actuating and sensing elements within the device. It is achieved in link with modal controllability and observability considerations. The vibrational modes that govern the tip deflection of the monolithic compliant structure are proved to be fully observable by the integrated sensing area of the device. The proposed control strategy permits to simply reconstruct the deflection using electric charges measurement and modal state observer. Finally, the vibrations that are naturally induced by the flexible structure are successfully damped using robust and low order controller.     

Design and dynamics of a 3-DOF flexure-based parallel mechanism for micro/nano manipulation

This paper presents the mechanical design and dynamics of a 3-DOF (degree of freedom) flexure-based parallel mechanism. Flexure hinges are used as the revolute joints to provide smooth and high accurate motion with nanometer level resolution. Three piezoelectric actuators are utilized to drive active links of the flexure-based mechanism. The inverse dynamics of the proposed mechanism is established by simplifying flexure hinges into ideal revolute joints with constant torsional stiffnesses. Finite element analysis is used to validate the performance of the proposed 3-DOF flexure-based parallel mechanism. The interaction between the actuators and the flexure-based mechanism is extensively investigated based on the established model. Experiments are carried out to verify the dynamic performance of the 3-DOF flexure-based mechanism.     

The structural and piezoelectric properties of epitaxial AℓN on Aℓ2O3

The piezoelectric properties of epitaxial AℓN films grown by the method of chemical vapor deposition utilizing trimethylaluminum and ammonia as chemical reactants were investigated. Large variations of the measured electromechanical coupling coefficient, k², were found in different regions of the same sample and on different samples having approximately the same h/λ value. Electron microscope observations of replicated as-grown and etched surfaces of epitaxial AℓN were used to show a relationship between surface facet ordering and the magnitude of k². A plot of k² measured at various h/λ values shows k² as large as 0.6% for films grown at a rate of ˜0.2 μm/min and measured at ˜400 MHz. This work was supported in part by Contract No. F33615-72-C-1473, Air Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio     

A local approach for the LPV identification of an actuated beam using piezoelectric actuators and sensors

This paper considers the identification of structural dynamics by identifying its frequency response functions (FRFs) – a mathematical representation of the relationship between the vibration response at one location and excitation at the same or another location. The spatially-varying characteristics of the FRFs at various input and output locations are explored, and lead to a spatial linear parameter varying (LPV) representation. A local LPV identification technique for lumped systems is adapted here to spatially-interconnected systems. The identification of a spatial LPV model facilitates the experimental work, and also simplifies the controller synthesis. The proposed approach is applied to identify an actuated beam equipped with an array of collocated piezoelectric actuators and sensors for performance illustration.     

Design and control of a piezoelectric driven reticle assist device for prevention of reticle slip in lithography systems

This paper presents a device for managing the inertial loads on photoreticles of lithography scanners. At high scan accelerations, the reticle inertial load can approach the clamp force limit. As a result, nanometer-level presliding slip can occur. Reticle slip is one limitation on increasing the throughput of the lithography scanners. In this paper, we present a reticle assist device which can eliminate reticle slip by compensating better than 95% of the inertial loads when tested in a bench-top tester. The reticle assist device consists of a coarse approach mechanism, for accommodating reticle load/unload, and a piezoelectric stack for fine actuation. The device utilizes a sensorless control system design. The control system uses a self-sensing contact detection method, which is inspired by self-sensing scanning probe microscopy, to find the reticle edge. It also uses a charge amplifier with a novel hybrid hysteresis compensation technique to linearly control the piezoelectric actuator extension, without the need for closed-loop position control. When tested with a replicated force profile with 60 N peak force and 6400 N/s force rate, the assist device compensated better than 95% of the inertial load.     

A non-redundant piezoelectric center-rotation platform with a single-layer structure and a large working range

This paper reports the design, modeling, and testing of a new single-layer center-rotation platform driven by a single piezoelectric actuator. The platform avoids actuator redundancy and exhibits a large rotation angle, high-precision resolution, and high resonant frequency. The pure center- rotation motion is realized by combining the improved Scott-Russell (SR) mechanism and lever- guided structure. The auxiliary stiffness mechanism at the input end of the SR mechanism also improves the stability of the rotation platform. An analytical model is established based on the finite element method, and the key parameters affecting the structural performance are investigated. A prototype is finally manufactured, and several experiments are conducted to test the proposed platform. The experimental results show that the rotation angle is 16.8 mrad, the resonant frequency is 527.3 Hz, and the resolution is 0.29 μrad. Thus, the platform is capable of precision center rotation.     

A technique to compensate an influence of mobility degradation by combining a source coupled pair with a transconductor

A transconductor is a basic building for integrated analogue circuits. High linearity of the transfer characteristic is necessary to a transconductor. However, along with miniaturisation of a device, linearity of the transconductor has deteriorated because of the mobility degradation from an effect of a vertical electric field. This paper proposes a new technique to reduce the influence of mobility degradation and to improve linearity of a transconductor. In order to improve the linearity, a source-coupled pair is combined with the transconductor. It is confirmed that the proposed technique reduces the transconductance error by about 1/5. For a sinusoidal input voltage of 1 V_p-p and 1 MHz, the total harmonic distortion is 3% or less.     

基于旋转折变型长周期光纤光栅对的高分辨率扭曲传感器

报道了一种基于光纤环形激光器和旋转折变型长周期光纤光栅(R-LPFG)对的高分辨率扭曲传感器。激光器的环形腔中包含由一对相同R-LPFG)形成的Mach-Zehnder干涉仪(MZI)。R-LPFG是利用CO2激光器在扭曲单模光纤(SMF)上写入的,通过激光器输出波长的漂移量及漂移方向可以实现对施加在MZI上的扭曲量和扭曲方向的同时测量。由于激光器的输出具有线宽窄和对比度高的优点,因此本文的扭曲传感器比普通的无源扭曲传感器测量更加精确。该扭曲传感器在±100rad/m范围内的灵敏度为0.084nm/(rad/m);当光谱仪(OSA)的分辨率为10pm时,传感器的扭曲分辨率可达0.12rad/m。     

A new type of high-efficiency bifacial silicon solar cell with external busbars and a current-collecting wire grid

Results regarding bifacial silicon solar cells with external busbars are presented. The cells consist of [n⁺p(n)p⁺] Cz-Si structures with a current-collecting system of new design: a laminated grid of wire external busbars (LGWEB). A LGWEB consists of a transparent conducting oxide film deposited onto a Si structure, busbars adjacent to the Si structure, and a contact wire grid attached simultaneously to the oxide and busbars using the low-temperature lamination method. Bifacial LGWEB solar cells demonstrate record high efficiency for similar devices: 17.7%(n-Si)/17.3%(p-Si) with 74–82% bifaciality for the smooth back surface and 16.3%(n-Si)/16.4%(p-Si) with 89% bifaciality for the textured back surface. It is shown that the LGWEB technology can provide an efficiency exceeding 21%.     

Creation of a new high voltage device with capable of enhancing driving current and breakdown voltage

This work reports a novel SOI MESFET including silicon N-type and P-type wells inside the drift and buried oxide regions. The drift-diffusion equations along with the main physical models such as impact ionization, Shockley-Read-Hall and self-heating effect are carefully solved inside the structures. Modification of the potential profile occurs in the channel region and results in decrease in peak electric field. Output power density is successfully boosted owing to improved driving current and breakdown voltage, simultaneously. In addition, self-heating effect is alleviated in the proposed structure due to decreased effective thermal resistance of the channel region. Comprehensive DC and AC performance comparisons show that the proposed device promises a more reliable candidate than the conventional SOI structure for high voltage applications.     

用200 kV高分辨电子显微镜辨认3C-SiC中的硅和碳原子

用200 kV六硼化镧灯丝的高分辨电子显微镜拍摄了外延生长在硅衬底的3C-SiC薄膜的[110]显微像.经过解卷处理和衍射振幅校正,把实验像转换为直接反映晶体投影结构的结构像,近邻Si、C原子柱显现为黑(灰)的像点对,即所谓的哑铃.测量了结构像中不同厚度区域哑铃的灰度变化,分析了哑铃中二个端点的相对灰度值随厚度的变化关系,结合赝弱相位物体近似像衬理论进行分析,辨认出Si与C原子柱.     

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.     

A polymer based miniature loop heat pipe with silicon substrate and temperature sensors for high brightness light-emitting diodes

Solid State Lighting (SSL) systems, powered by light-emitting diodes (LEDs), are revolutionizing the lighting industry with energy saving and enhanced performance compared to traditional light sources. However, around 70%–80% of the electric power will still be transferred to heat. As the elevated temperature negatively affects the maximum luminous output, efficiency, light quality, reliability and the lifetime of the SSL systems, thermal management is a key design aspect for LED products. In this work, an innovative thermal management with a package, a silicon substrate with temperature sensors and a polymer based loop heat pipe (LHP) was designed, manufactured and assembled. It can supply a low and relatively stable temperature to maintain higher optical power, more luminous flux and less color shift. In a word, the novel design can provide LEDs with the efficient thermal management and temperature monitoring with reduced weight, easy fabrication, less energy consumption and better light quality.     

Progress on large area n‐type silicon solar cells with front laser doping and a rear emitter

We report on the progress of imec's n‐type passivated emitter, rear totally diffused rear junction silicon solar cells. Selective laser doping has been introduced in the flow, allowing the implementation of a shallow diffused front surface field and a reduction of the recombination current in the contact area. Simplifications have been implemented towards a more industrial annealing sequence, by replacing expensive forming gas annealing steps with a belt furnace annealing. By applying these improvements, together with an advanced texturing process and emitter passivation by atomic layer deposition of Al₂O₃, 22.5% efficient cells (three busbars) have been realized on commercial 156 · 156 mm² Czochralski‐Si. This result has been independently confirmed by ISE CalLab. Copyright © 2016 John Wiley & Sons, Ltd.     

采用新颖自对准法制备高精度硅衍射微透镜阵列及其与红外焦平面阵列集成

硅衍射微透镜阵列通常被用来与红外焦平面集成而提高器件性能。在常规套刻法用于制备硅衍射微透镜阵列时光刻误差是很难避免的。这对器件性能及后续应用产生严重的影响。针对此问题,本文提出一种高精度硅衍射微透镜阵列制备的新颖自对准方法。该方法中硅衍射微透镜阵列的制备精度只由第一次掩膜光刻的精度决定。在后续的刻蚀中,采用掩膜层和牺牲层或保护层将已刻蚀区域进行保护,对未保护区域进行刻蚀,有效地阻挡非刻蚀区域,精确刻蚀所需刻蚀区域。采用新颖自对准法可以制备出高精度硅衍射微透镜阵列,其衍射效率可达到92.6%。与红外焦平面探测器集成后,平均黑体响应率提高了8.3%,平均黑体探测率提高了10.3%。这表明硅微透镜阵列可以通过会聚作用提高焦平面阵列占空因子,同时降低串扰,进而提高焦平面阵列性能。该研究结果对通过优化微纳器件制作水平提升其性能具有重要参考意义。     

A Numerically Controlled Oscillator with a Fine Phase Tuner and a Rounding Processor

We propose a fine phase tuner and a rounding processor for a numerically controlled oscillator (NCO), yielding a reduced phase error in generating a digital sine waveform. By using the fine phase tuner presented in this paper, when the ratio of the desired sine wave frequency to the clock frequency is expressed as a fraction, an accurate adjustment in representing the fractional value can be achieved with simple hardware. In addition, the proposed rounding processor reduces the effects of phase truncation on the output spectrum. Logic simulation results of the NCO using these techniques show that the noise spectrum and mean square error (MSE) for eight output bits of a 3.125 MHz sine waveform are reduced by 8.68 dB and 5.5 dB, respectively, compared to those of the truncation method, and 2.38 dB and 0.83 dB, respectively, compared to those of Paul's scheme.     

A 10 bit Current-Mode CMOS A/D Converter with a Current Predictor and a Modular Current Reference

This paper describes a 10 bit CMOS current-mode A/D converter with a current predictor and a modular current reference circuit. A current predictor and a modular current reference circuit are employed to reduce the number of comparator and reference current mirrors and consequently to decrease a power dissipation. The 10 bit current-mode A/D converter is fabricated by the 0.6 m n-well double poly/triple metal CMOS technology. The measurement results show the input current range of 16–528 A, DNL and INL of ±0.5 LSB and ±1.0 LSB, conversion rate of 10 M samples, and power dissipation of 94.4 mW with a power supply of 5 V. The effective chip area excluding the pads is 1.8 mm×2.4 mm.