Design, fabrication, and characterization of diffraction gratings for neutron phase contrast imaging

We have developed a neutron phase contrast imaging method based on a grating interferometer setup. The principal constituents are two absorption gratings made of gadolinium and a phase modulating grating made of silicon. The design parameters of the setup, such as periodicity, structure heights of the gratings, and the distances between the gratings, are calculated. The fabrication of each grating is described in detail. The produced diffraction gratings were finally characterized within the setup, by locally evaluating the produced contrast (visibility) in each detector pixel, resulting in a visibility map over the whole grating size. An averaged value of 23% is achieved.     

空间用碳化硅反射镜的设计制造与测试

碳化硅由于其优异的机械性能和热物理性能而成为颇具吸引力的反射镜材料。采用反应烧结碳化硅(RB-SiC)材料制备了空间用反射镜体,用化学气相沉积(CVD)工艺在镜体镜面沉积一层致密的碳化硅薄膜,反射镜采用蜂窝状背面开放式轻量化结构。对直径为250 mm反射镜的组织、性能做了一系列研究测试。结果表明:反射镜体为Si/SiC两相组织,薄膜为单相SiC,反射镜的机械、热性能优异,薄膜与基体结合强度为345.5 MPa,研磨后镜面表面粗糙度达到1.487 nm rms。采用本文工艺方法有能力制备米级直径的空间用碳化硅反射镜。     

近红外消偏振反射镜的设计与制备

设计并制备了一种在45°斜入射条件下使用的金属Ag消偏振反射镜,这种反射镜可以实现对目标波长810nm和850nm光线的反射,并保持线偏光的偏振方向和偏振消光比。为了消除s和p两偏振分量的分离,在金属Ag膜层上方添加了介质多层膜结构,并利用软件对膜系的结构进行了优化,设计结果的能量和相位特性满足目标需求。介质多层膜选用TiO2和SiO2分别作为高、低折射率材料,薄膜的制备采用了离子束辅助沉积工艺,并利用石英晶体振荡监控膜层厚度。得到了消光比达到10000∶1以上的样品,实现了光学薄膜器件对能量和相位的控制,满足了偏振编码空间光通信试验的需求。     

微型柔性热敏传感器阵列应用研究

边界层分离点检测是实现分离流主动控制的前提和基础，也是气动控制灵巧蒙皮系统研究的重点和难点。以流体边界层分离点检测技术为研究对象，以流体边界层分离点判定的风洞实验为验证目标，设计制作微型热敏传感器与聚酰亚胺柔性衬底，并首次利用微装配技术集成分立敏感元件与柔性衬底形成热敏传感器阵列。首先，采用分立元件通过表面贴装工艺来实现柔性微型热膜传感器阵列的集成，并研究该传感器阵列中敏感元件、柔性衬底的设计及传感器的排布。然后，在低速风洞实验中对传感器阵列的性能和传感器阵列输出信号采用统计量算法的方式进行处理判断，判定圆柱翼型的流体分离点位置。最后，对实验的结果所作的分析表明，该微型柔性热敏传感器阵列满足流体分离检测系统实时性、动态性的要求。     

Design and fabrication of a micro PZT cantilever array actuator for applications in fluidic systems

In this article, a micro cantilever array actuated byPZT films is designed and fabricated for micro fluidic systems. The design features for maximizing tip deflections and minimizing fluid leakage are described. The governing equation of the composite PZT cantilever is derived and the actuating behavior predicted. The calculated value of the tip deflection was 15 μm at 5 V. The fabrication process from SIMOX (Separation by oxygen ion implantation) wafer is presented in detail with the PZT film deposition process. The PZT films are characterized by investigating the ferroelectric properties, dielectric constant, and dielectric loss. Tip deflections of 12 μm at 5 V are measured, which agreed well with the predicted value. The 18 μ1/s leakage rate of air was observed at a pressure difference of 1000 Pa. Micro cooler is introduced, and its possible application to micro compressor is discussed.     

集成成像系统中高填充率微透镜阵列的设计与加工

针对目前微透镜设计与加工中存在的问题,本文提出了一种大尺寸、高填充率的微透镜阵列设计与加工方法,并成功应用于基于手机屏幕的三维集成成像显示系统。根据焦面模式下的集成成像原理,建立了透镜阵列参数与集成成像显示关键参数的关系,并设计了高填充率透镜阵列的孔径与焦距。采用超精密铣削方法加工出金属母板,通过纳米压印和图形转移复制的方法,在涂有UV固化胶的PET透明膜上得到了高填充率的微透镜阵列膜,并将其应用于基于手机显示屏的集成成像系统。测试结果表明,在5.7英寸全高清手机屏幕上,直接覆盖孔径为0.526mm、焦距为2mm、填充率为100%的透镜阵列,可以实现立体图像出屏距离达4cm、视场角为12.5°的集成成像显示效果。系统的设计与透镜阵列的制作完全满足集成成像要求,裸眼观看立体图像清晰、逼真,系统集成度高,使用方便。     

测绘相机光学镜筒设计、加工及装配

测绘相机光学镜筒是保障测绘相机完成高精度测绘任务的重要部件,它的性能好坏直接影响测绘相机成像质量。为得到高质量成像相机,本文从材料选取、结构形式的确定和性能分析等方面详细阐述了测绘相机光学镜筒的设计过程。通过分析比较,最终选取铸钛合金ZTC4作为镜筒的材料,采用单镜组加筋壳结构的组合形式,并通过PATRAN/NASTRAN软件对主镜筒装配体的静力学和动力学分析得到具有很好整体性能的光机结构;同时给出了形位公差要求、拟定了严格的薄壁壳体的加工方法,并论述了单镜组和主镜筒整体装配的过程。     

Design, fabrication, and testing of a MEMS microturbine

This paper describes the design, fabrication, and testing of a microturbine developed at Seoul National University Here, the term “microturbine” refers to a radial turbine with a diameter on the order of a centimeter Such devices can be used to transmit power for various systems The turbine is designed using a commercial CFD code, and it has a design flow coefficient of 0 238 and work coefficient of 0 542 It has 31 stator blades and 24 totor blades A hydrodynamic journal bearing and hydrostatic thrust bearings counteract radial and axial forces on the rotor The test turbine consists of a stack of five wafers and is fabricated by MEMS technology, using photolithography, DRIE, and bonding processes The first, second, fourth, and fifth layers contain plumbing, and hydrostatic axial thrust bearings for the turbine The third wafer contains the turbine’s stator, rotor, and hydrodynamic journal bearings Furthermore, a turbine test facility containing a flow control system and instrumentation has been designed and constructed In performance tests, a maximum rotation speed of 11,400 rpm and flow rate of 16,000 seem have been achieved     

阵列式近红外目标模拟器的设计与实现

为了能够实现逼真的红外仿真环境,设计了一套红外成像仿真系统。该系统通过对红外发光二极管的特性研究,利用脉动光提高其发射距离,借助适当的光学装置,实现小功率发光器件模拟红外目标的功能。该系统可用于红外目标仿真,对红外成像系统的性能做出整体评价;也可以对不同红外成像系统的性能进行比较分析。通过对某型导弹动态测试,表明了该系统方案的可行性、实用性。     

Design of an adjustable-stiffness spring: Mathematical modeling and simulation, fabrication and experimental validation

An adjustable-stiffness actuator composed of two antagonistic non-linear springs is proposed in this paper. The elastic device consists of two pairs of leaf springs working in bending conditions under large displacements. Owing to this geometric non-linearity, the global stiffness of the actuator can be adjusted by modifying the shape of the leaf springs. A mathematical model has been developed in order to predict the mechanical behavior of our proposal. The non-linear differential equation derived from the model is solved, obtaining large stiffness variations. A prototype of the actuator was fabricated and tested for different load cases. Experimental results were compared with numerical simulations for model verification, showing excellent agreement for a wide range of work.     

基于微透镜阵列生成特定矩形光斑的TIR组合透镜设计与仿真

LED功率的不断增大使其逐渐替代传统光源,并广泛用于各种照明光源。在某些室内照明以及道路照明设计中,通常需要借助LED透镜产生矩形光斑从而充分利用光能避免浪费。利用Light Tools软件设计了一种全内反射(total internal reflection,TIR)透镜与特定微型透镜阵列的组合透镜,设置TIR准直透镜透射曲面和全反射曲面为二次曲面,并对其进行准直优化。然后建立单个微型透镜,设置单个矩形微透镜长宽比分别为1∶1、3∶2和4∶3,并将其阵列化。通过改变微型透镜的尺寸以及球面曲率半径进行进一步优化,最后生成与微型透镜长宽比对应的均匀矩形光斑,从而满足不同矩形照明区域的照明需求。     

Development of a capacity analysis and planning simulation model for semiconductor fabrication

Micro-machining has gained increased application to produce miniaturized parts in various industries. However, the uncut chip thickness in micro-machining is comparable to cutting edge radius. The relationship between the cutting edge radius and uncut chip thickness has been a subject matter of increasing interest. The acoustic emission (AE) signal can reflect the stress wave caused by the sudden release of the energy of the deformed materials. To improve the precision of machining system, determination of the minimum uncut chip thickness was investigated in this paper. The AE signal generated during micro-cutting experiments was used to analyze the chip formation in micro-end milling of Inconel 718. The finite element method (FEM) simulation was used to analyze the results of the experiments. The results showed that the cutting tool geometry and material properties affected the minimum uncut chip thickness. The estimation of the minimum uncut chip thickness based on AE signals can produce quite satisfactory results. The research on the minimum uncut chip thickness can provide theoretical basis for analysis of surface quality and optimal choice of cutting parameters.     

基于MEMS的人工视网膜微电极阵列设计仿真

本文介绍的是一种基于微机电系统（MEMS）技术的表面型人工视网膜微电极阵列设计与仿真。电脉冲通过微电极刺激视网膜神经细胞,在大脑皮层视觉区域引起对应的特征电位反应,部分恢复患者的视觉。为研究表面型人工视网膜微电极阵列在人眼压力环境下的位移,特别设计了多种微电极阵列,进行了应力仿真。     

Design, fabrication and experiment of a MEMS piezoresistive high-g accelerometer

High-g accelerometers are widely used in explosion and shock measurement. This paper describes a MEMS piezoresistive high-g accelerometer whose range is more than 50000g. It is designed on the basis of silicon on insulator (SOI) solid piezoresistive chip. The chip has a structure where both ends of the beam are fixed. Through the stress analysis and mode analysis of the accelerometer, the detailed parameters of the structure are established. The experimental results obtained from the drop hammer shock machine test and live-fire test show good properties of the accelerometer such as good output characteristic, repeatability and fast response speed. Therefore, the accelerometer in this paper meets the requirement of explosion and shock measurement basically.     

The fabrication of a multi-spectral lens array and its application in assisting color blindness

This article presents a compact multi-spectral lens array and describes its application in assisting color-blindness. The lens array consists of 9 microlens, and each microlens is coated with a different color filter. Thus, it can capture different light bands, including red, orange, yellow, green, cyan, blue, violet, near-infrared, and the entire visible band. First, the fabrication process is described in detail. Second, an imaging system is setup and a color blindness testing card is selected as the sample. By the system, the vision results of normal people and color blindness can be captured simultaneously. Based on the imaging results, it is possible to be used for helping color-blindness to recover normal vision.     

Edge-lit sine-shape wedged light guides: Design,optical simulation,laser-remelting-based precision fabrication,and optical performance evaluation

Light guiding is an essential functionality of automotive lighting responsible for styling, safety, and artistic effects. The functional performance of optical lighting and illumination products and components depends on novel optical designs and advanced technologies for cost-effective fabrication of tooling with strict surface quality and form geometry accuracy. The present multi-objective study introduces a new design for an edge-lit wedge planar light guide (LG) with sine-shape riblets as well as an advanced microfabrication technology called surface structuring by laser remelting (SSLRM). In the proposed LG design, sine-shape riblets act as optical structures used to redirect - through total internal reflection - the incoming collimated light onto the illuminated surface. Numerical simulations showed that LGs with different amplitudes of sine-shape riblets (e.g., 25 μm, 40 μm, 55 μm) can reach an illumination efficiency of 97.7%. Furthermore, the applicability of SSLRM process for an efficient fabrication of edge-lit LG tooling inserts was demonstrated and several tooling inserts were fabricated with geometric parameters matching the proposed optical designs. Following this, the geometry and surface quality parameters of the fabricated inserts were presented. In addition, functional plastic prototypes of LGs were produced by means of a hot embossing technology that preserved the original form geometry and surface quality characteristics. Their actual optical performance was comparatively evaluated with respect to a LG with a flat-wedged surface and also to LGs with different amplitudes of sine-shape riblets. The maximum actual optical performance was achieved by LGs with a sine-shape amplitude of 55 μm that exhibited a total luminance of 0.1395 cd while the flat wedged LG without light redirecting structures exhibits 0.0006 cd only. It is also demonstrated that the sine-shape amplitude significantly contributes to the overall LG optical performance gaining 1811% improvement with respect to the LG with 25 μm amplitude delivering 0.0073 cd. The results obtained demonstrate the applicability and the high potential of the proposed edge-lit sine-shape wedged LGs as well as that of the SSLRM process used for their high precision microfabrication.     

Fast algorithms for frequency, amplitude and phase evaluation of nonsinusoidal signals with noises

A fast and accurate algorithm for frequency, amplitude and phase estimation of the signals with white Gaussian noises is proposed in this paper. The proposed algorithm need two sample and computation process, one of which is used for frequency estimation in half cycle of the signal and another of which is used for amplitude and phase estimation in another half cycle. The proposed algorithm spends at most 1 cycle. Frequency estimation is based on numerical differentiation, and amplitude and phase estimation is based on fast Fourier Transform. With an initial sample frequency of 512 × 50 Hz, the signal is sampled and the frequency of the signal with white Gaussian noises is estimated at an error of 0.001% over a range of 1 Hz–1000 kHz. With another sample frequency based on the estimated frequency, the signal is once again sampled and the amplitude of the signal is estimated an error of 0.001% over a range of 1 V–320 V and the phase angle of the signal is estimated an accuracy of 0.001% over a range of 0–360. Using Matlab software, the simulation results of the test example are satisfactory.     

Magnetic microposts for mechanical stimulation of biological cells: fabrication, characterization, and analysis

Cells use force as a mechanical signal to sense and respond to their microenvironment. Understanding how mechanical forces affect living cells requires the development of tool sets that can apply nanoscale forces and also measure cellular traction forces. However, there has been a lack of techniques that integrate actuation and sensing components to study force as a mechanical signal. Here, we describe a system that uses an array of elastomeric microposts to apply external forces to cells through cobalt nanowires embedded inside the microposts. We first biochemically treat the posts' surfaces to restrict cell adhesion to the posts' tips. Then by applying a uniform magnetic field (B<0.3 T), we induce magnetic torque on the nanowires that is transmitted to a cell's adhesion site as an external force. We have achieved external forces of up to 45 nN, which is in the upper range of current nanoscale force-probing techniques. Nonmagnetic microposts, similarly prepared but without nanowires, surround the magnetic microposts and are used to measure the traction forces and changes in cell mechanics. We record the magnitude and direction of the external force and the traction forces by optically measuring the deflection of the microposts, which linearly deflect as cantilever springs. With this approach, we can measure traction forces before and after force stimulation in order to monitor cellular response to forces. We present the fabrication methods, magnetic force characterization, and image analysis techniques used to achieve the measurements.     

Design,fabrication, and testing of a 3-DOF piezo fast tool servo for microstructure machining

Fast tool servo (FTS) cutting has the superiority of high efficiency and high precision, which has attracted great attention from the field of microstructure machining. 3-degree-of-freedom (DOF) FTS device driven by piezoelectric (PZT) actuator, with high frequency, high precision, and low crosstalk property, are quite appealing for realizing complex microstructure machining. Therefore, a novel 3-DOF piezo-actuated FTS mechanism with high natural frequency and decoupling property is proposed in this paper. First, the static and dynamic models of the mechanism are established by using the compliance matrix and Lagrange equation methods, respectively. Then, the structural parameters of the mechanism are optimized by the genetic algorithm (GA) based Pareto multi-objective optimization algorithm. With the purpose of verifying the property of the above approach, the finite element analysis (FEA) acting on the designed mechanism has been carried out. Moreover, the modeling tasks in terms of cutting principle and trajectory planning are demonstrated in detail. Besides, a series of tests are carried out to verify the performance of the developed 3-DOF FTS. The testing results indicate that the working stroke of the mechanism is up to 40 μm, the natural frequency is above 873 Hz, and the mechanism has excellent motion decoupling performance (within 2%). The error of the trajectory tracking in all three directions are kept within ±0.7 μm. Finally, compared with the desired surface, the error of the machined microstructural surface is kept within ±1.5 μm, which further verifies its satisfactory performance towards ultra-precision FTS machining of microstructure.