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.     

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.     

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     

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.     

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。     

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.     

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.     

Quantitative amplitude and phase contrast imaging in a scanning transmission X-ray microscope

Phase contrast in X-ray imaging provides lower radiation dose, and dramatically higher contrast at multi-keV photon energies when compared with absorption contrast. We describe here the use of a segmented detector in a scanning transmission X-ray microscope to collect partially coherent bright field images. We have adapted a Fourier filter reconstruction technique developed by McCallum, Landauer and Rodenburg to retrieve separate, quantitative maps of specimen phase shift and absorption. This is demonstrated in the imaging of a germanium test pattern using 525eV soft X-rays.     

Design,fabrication and experimental investigation of a planar pump using electro-conjugate fluid

This paper presents the design, fabrication, and experimental investigation of a novel planar pump using electro-conjugate fluid. The electro-conjugate fluid (ECF) is a kind of dielectric functional fluid which generates a powerful jet flow (ECF-jet) when a static electric field is applied via a pair of rod-like electrodes. This phenomenon that ECF can generate jet flows from the positive electrode to the ground electrode in an applied electric field is called the ECF effect, and converts electric energy directly into kinetic energy of the fluid. The ECF-jet acts directly on the working fluids; therefore, the proposed planar ECF pump requires no moving parts and produces no vibration or noise. The fabricated planar ECF pump consists of three parts: a pump base, a top cover, and an electrode substrate with dimensions of 280 mm × 190 mm × 1 mm. In this paper, five different electrode patterns and three different flow channel heights were investigated for the realization of a high-performance planar ECF pump. Each array of electrodes was patterned on the glass epoxy substrates using a wet-etching process, and the flow channel heights were either 200 μm, 300 μm, or 500 μm. The pumping experiments used FF-1_EHA2 as the working fluid. Experimentation showed that a no-load flow rate of 5.5 cm³/s, maximum output pressure of 7.2 kPa, and maximum output power of 11.6 mW were achieved at an applied voltage of 2.0 kV.     

Stable, mode-matched, medium-finesse optical cavity incorporating a microcantilever mirror: optical characterization and laser cooling

A stable optical resonator has been built using a 30-microm-wide, metal-coated microcantilever as one mirror. The second mirror was a 12.7-mm-diameter concave dielectric mirror. By positioning the two mirrors 75 mm apart in a near-hemispherical configuration, a Fabry-Perot cavity with a finesse equal to 55 was achieved. The finesse was limited by the optical loss in the cantilever's metal coating; diffraction losses from the small mirror were negligible. The cavity achieved passive laser cooling of the cantilever's Brownian motion.     

Design of a rotary fast tool servo for ophthalmic lens fabrication

We have developed a novel fast tool servo and associated prototype diamond- turning machine for the production of plastic spectacle lenses. Our fast tool servo carries the cutting tool on a rotary arm and, thus, on a circular path, as opposed to straight line paths in conventional designs. The actuator, sensors, and bearings are standard elements that together allow experimentally demonstrated 500 m/s² instantaneous accelerations at the tool tip over a 3-cm range of cutting depth. We also describe in this paper new approaches we have developed for toolpath generation and calibration. The paper also presents associated control algorithms, because the controller must supply very high dynamic stiffness to the tool servo axis at multiples of the spindle frequency. This stiffness is achieved by means of repetitive control techniques. The new fast tool servo is shown to have great promise for machining asymmetric surfaces with large amplitude asymmetries.     

Direct STEM fabrication and characterization of self-supporting carbon structures for nanoelectronics

A quantitative model is proposed to interpret the experimental results concerning the observed anomalous behavior of the thickness of growing self-supporting carbon-containing rods: a decrease in the thickness with increasing beam current. The model is based on the surface diffusion of hydrocarbon molecules and takes into account their ionization and desorption from the positively charged end of the growing rod. Possible causes of self-maintained oscillation instability of the rod growth are discussed. Procedures are recommended to optimize the fabrication of self-supporting carbon-containing structures of complicated configurations and to reduce the negative effect of the incident beam electrons during their testing.     

Design and simulation for a hydraulic actuated quadruped robot

This paper describes the mechanical configuration of a quadruped robot firstly. Each of the four legs consists of three rotary joints. All joints of the robot are actuated by linear hydraulic servo cylinders. Then it deduces the forward and inverse kinematic equations for four legs with D-H transformation matrices. Furthermore, it gives a composite foot trajectory composed of cubic curve and straight line, which greatly reduces the velocity and acceleration fluctuations of the torso along forward and vertical directions. Finally, dynamics cosimulation is given with MSC.ADAMS and MATLAB. The results of co-simulation provide important guidance to mechanism design and parameters preference for the linear hydraulic servo cylinders.     

Measurement and control of residual amplitude modulation in optical phase modulation

Residual amplitude modulation is one of the major sources of instability in ultra-sensitive optical detections based on frequency modulation. Using a MgO·LiNbO(3) electro-optic crystal, we systematically measure the temperature and polarization dependence of residual amplitude modulation and our experimental results are in good agreement with a previous theoretical analysis. After optical phase modulation, two independent arms including optical detection and frequency demodulation are employed to closely examine the instability of the residual amplitude modulation. Residual amplitude modulation below 25 ppm is obtained with an active cancellation scheme in which the crystal temperature is varied so as to zero the baseline drifts with different origins. Possible improvements for better suppression and stability are discussed.