Flexible LCDs fabricated with a slit coater: Not requiring an alignment film

A homogeneously aligned liquid crystal layer on a substrate film on which it is not necessary to form a liquid crystal alignment film can be assembled by a slit coater. Types of twisted nematic and in‐plane switching flexible liquid crystal displays were demonstrated. The production time can be considerably shortened because of the lack of need for an alignment film. The slit coater method is also applicable to the roll‐to‐roll process.     

基于BOE硅腐蚀现象的硅纳米线制作

介绍一种硅纳米线制作方法.在SOI顶层硅上制作硅纳米梁,通过离子注入形成pnp结构,利用新发现的没有特殊光照时BOE溶液腐蚀pn结n型区域现象,结合BOE溶液氧化硅腐蚀,实现硅纳米线制作.制作完全采用传统MEMS工艺,具有工艺简单,成本低,可控,可靠性好,可批量制作等优点.利用该方法制作出了厚50 nm,宽100 nm的单晶硅纳米线,制作的纳米线可用于一维纳米结构电学性能研究、谐振器研究等.     

Surface microfluidics fabricated by photopatternable superhydrophobic nanocomposite

Surface microfluidics can be of potential use in a variety of emerging applications, including biological and chemical analysis, cellular detection and manipulation, high-throughput pharmaceutical screening, and etc. In comparison with the conventional closed-channel microfluidic system, surface microfluidics shows the distinct advantages of simple construction, direct surface access, no cavitation or interphase obstruction, clear optical path, easy fluidic packaging, and device reusability. In this article, we first present surface microfluidic networks microfabricated by a single-step lithographic process using a novel superhydrophobic photosensitive nanocomposite formula. The photopatternable superhydrophobic nanocomposite (PSN) incorporates PTFE nanoparticles into a SU-8 matrix, in which superhydrophobicity (contact angle of above 160°) is primarily contributed by the extremely low chemical energy and nano-topology of PTFE nanoparticles, while the SU-8 polymer matrix offers photopatternability (lithographic resolution of 10 μm) and substrate adhesion. Moreover, an additive intermediate layer with hydrophilic sidewall considerably reduces flow resistance while improving the substrate adhesion, as a crucial improvement from the previous surface flow configuration. Furthermore, self-propelled microfluidic networks driven by surface tension-induced pressure gradient have been fabricated and characterized to demonstrate the applicability of the novel nanocomposite fabrication approach.     

Characterization of gear pumps fabricated by LIGA

 This paper presents the characterization of a positive displacement, magnetically-coupled, self-priming gear pump and a direct drive metal gear pump. In the magnetically coupled design (the in-line pump), the gears are indirectly driven by a electric motor coupled to a pair of magnets. The pump provides a flow rate of 350 μl/min at 5000 rpm, over 140 cm-H₂O (∼2 psi) of head pressure and 28.8 cm-H₂O vacuum on the suction side for a single stage pump. A two stage in-line pump generated 53 cm-H₂O vacuum at its inelt (21″H₂O). Very recently, we demonstrated a direct driven gear pump using a 3 mm smoovy^TM brushless DC motor. The direct driven pump provides a maximum flow rate of 2.5ml/min at 1200 Hz (72 krpm) and 3.6 psi dead head pressure. The direct drive pump provided 18 cm-H₂O vacuum at its inlet due to the large clearances in the first generation device. Received: 25 August 1997 / Accepted: 15 September 1997     

Tapered microvalves fabricated by off-axis X-ray exposures

 A method for creating angled structures for use in microvalve devices applicable to control of liquid flow is presented. This technique utilizes a modified LIGA process with successive angled and rotated exposures into free standing acrylic sheets to form a tapered valve seat structure. These valve seats are integrated with bulk micromachined silicon diaphragms and tapered PMMA valve bosses to complete the microvalve. The long term goal of this research effort is to develop a normally-closed, low power, microfabricated valve for use in an implantable drug delivery system. This paper reports on the design and fabrication of microvalves using off-axis LIGA exposures. Flow testing and fluid handling characterization results are also presented. Received: 25 August 1997 Accepted: 22 October 1997     

电视带通混合器

本文介绍共用天线电视系统前端装置中的电视带通混合器的用途工作原理，电原理图，并详细叙述了制作和调试方法。     

Two-dimensional metallic photonic band-gap crystals fabricated by LIGA

 Two-dimensional metallic photonic band-gap crystals, consisting of square and triangular lattices of nickel pillars, were fabricated by the LIGA process. In particular, PMMA slabs with a thickness of up to 800 μm were irradiated with synchrotron radiation and the holes produced were then filled with nickel via electroforming. The lattice constant, i.e., the center-to-center distance between the pillars, is either 60 μm or 40 μm for the square and triangular structures respectively. The metal filling ratio is 10% for the square and 20% for the triangular structures. Transmission and reflection measurements demonstrate that the metallic photonic band-gap crystals show a cutoff frequency in the far infrared regime between 2 and 5 THz. It is concluded that LIGA is a promising method for the fabrication of 2-D metallic photonic band-gap structures, which could be potentially used as passive filters in THz devices. Received: 10 August 2001/Accepted: 24 September 2001     

Micro gas bearings fabricated by deep X-ray lithography

Micro bearing systems for Micro Electromechanical Systems (MEMS) have drawn attention for several decades as critical components for micro rotating machinery. Ideally, frictionless bearings are needed, and in practice, micro gas bearings approach the ideal. Typically, bearings function as a separate component, assembled onto sliding counterparts. However, in micro scale devices, assembly procedures are known to be very tedious and time consuming. This leads to the pursuit of single material monolithic structures. Critical issues arising from these approaches include: limitation of materials, friction, and reliability, among others. In this paper, new approaches have been pursued. Micro gas bearings were fabricated as a single component through X-ray lithography. A stainless steel gauge pin, machined to ultra precision, was used as a journal shaft. Simple and very easy assembly processes using self-aligning concepts were developed as an alternative method to conventional assembly. This article presents the design, fabrication, assembly, and testing of micro gas bearings.This project was funded from National Science Foundation (DMI-0115527) and Atoz CompuNet Ltd. The authors also acknowledge partial support from Center for Nano and Molecular Science and Technology and Welch foundation in The University of Texas at Austin.     

Hydrodynamic dispersion by electroosmotic flow of viscoelastic fluids within a slit microchannel

The biofluids being manipulated in lab-on-a-chip devices usually contain elastic macromolecules. Accordingly, for an accurate modeling of the relevant flow physics one should invoke viscoelastic constitutive equations. In this paper, attention is paid toward the hydrodynamic dispersion by the fully developed electroosmotic flow of PTT viscoelastic fluids in slit microchannels of low zeta potential. Adopting the Taylor–Aris approach, analytical solutions are derived for late-time solute concentration and effective dispersion coefficient. Finite element-based numerical simulations are also conducted to monitor the broadening of an analyte band from the moment of injection. Both approaches are found to be in a good agreement with an average error of below 8% in the calculated dispersion coefficients. It is observed that, for given zeta potential and electrolyte type, the hydrodynamic dispersion is severely pronounced by increasing the level of elasticity in the fluid. The variations are reversed and less pronounced when the analysis is made for a fixed mean flow rate. Moreover, the effective dispersivity grows by thickening the EDL when it is sufficiently thin, whereas the opposite is true for thick EDLs. Finally, an inspection of the average concentration reveals the formation of tails for thick EDLs that may reduce the resolution in sensing applications.     

搅拌机图像控制界面

介绍了滚筒式沥青混凝土搅拌机中常用的振动筛、提升机、泵类和皮带机部件运动的特点，归纳为水平、生趣和旋转运动的动画设计方法，采用Ｖｉｓｕａｌ Ｂａｓｉｃ语言编程实现动画要求，给出了中文Ｖｉｓｕａｌ Ｂａｓｉｃ５．０的程序。     

A micro cycloid-gear system fabricated by multi-exposure LIGA technique

 In this paper, a prototype of 2 mm-diameter micro-cycloid gear system fabricated by the multi-exposure LIGA technique is presented. The gear system is composed of a casing and three vertically stacked disks and gears. Each part consists of three different levels. The first level, 40 μm high, was fabricated by UV-lithography, and the second as well as the third level, 195 μm and 250 μm high respectively, were processed by aligned deep X-ray lithography (DXL). The alignment error between two DXL-processed layers has been measured to be within ±5 μm range. As a result of the height control process, the deviation of structural height has been maintained within ±3 μm range for the UV-lithography-processed structures, and ±10 μm for the DXL-processed structures. Preliminary tests of gear assembly have been implemented with 125 μm-diameter commercially available glass fiber, and the further efforts are being carried out.     

Biodegradable submicrometric sieves in PLLA fabricated by soft lithography

Sieves are membranes with a regular array of uniform pores that present low flow resistance. Because of such characteristics they are promising devices for filtration, separation of particles by size and drug delivery control systems. In this paper, we propose and demonstrated the use of a soft lithography process for fabrication of biodegradable sieves in PLLA (poly-l-lactide) with pores in the scale of hundred of nanometers. The fabrication process is suitable for mass production and submicrometric pore diameters can be fabricated with homogeneity of about 15%. The PLLA self sustained sieve can be integrated to PLLA capsules, compounding a drug delivery systems or implants.     

Released Si microstructures fabricated by deep etching and shallowdiffusion

A novel etch-diffusion process is developed for fabricating high-aspect-ratio Si structures for microsensors. This is accomplished by first dry etching narrow gap Si microstructures using an electron cyclotron resonance (ECR) source, followed by a shallow B diffusion to fully convert the etched microstructures to p⁺⁺ layer. Microstructures up to 40 μm deep with 2-μm-wide gaps were etched with a Cl₂ plasma generated using the ECR source. Vertical profile and smooth morphology were obtained at low pressure. A shallow B diffusion at 1175°C for 5.5 h. was then carried out to convert the 40-μm-thick resonant elements to p⁺⁺ layer. A second dry etching step was used to remove the thin p⁺⁺ layer around the bottom of the resonant elements, followed by bonding to glass and selective wet etch. Released high-aspect-ratio Si microsensors with thicknesses of 35 μm have been demonstrated. At atmospheric pressure, only 5 V_dc driving voltage is needed for 2.5 μm vibration amplitude, which is less than the 10 V_dc required to drive 12-μm-thick resonators fabricated by conventional dissolved wafer process     

Micron-scale polymer-metal cantilever actuators fabricated by focused ion beam

Polymer-metal microcantilever actuators have been fabricated using an innovative approach based on focused ion beam micromachining technology. The fabrication involves depositing a thin metal film onto the surface of the polymer and machining using the ion beam. The microcantilever created is then extracted and transferred to a desirable support using a micromanipulator. This approach demonstrates the potential for maskless and resistless prototyping of cantilevers that can be evaluated for use as MEMS/NEMS actuators. Nanometer-scale displacement of the resulting polystyrene-platinum bimorph microactuator with respect to temperature change is demonstrated via visual monitoring in a scanning electron microscope with a heating stage. The performance of the bimorph cantilever microactuators is verified using both analytical and finite element modeling.     

Microplastic lens array fabricated by a hot intrusion process

A microplastic lens array has been successfully constructed on top of a 500-/spl mu/m-thick PC (Polycarbonate film) by using a micro hot intrusion process. A single-layer LIGA process is used to fabricate the high-aspect-ratio nickel mold insert that has circular hole patterns of 80 /spl mu/m in diameter and 200 /spl mu/m in depth. Under the hot intrusion process, plastic material can be intruded into these circular-shape holes and stopped at desired depth under elevated temperature and pressure to fabricate microlenses. By adjusting the embossing load, temperature and time, the curvature and height of the lens are controllable when the same mold insert is used. The optical properties of these microlenses have been characterized and the average radius of curvature is found as 41.4 /spl mu/m with a standard deviation of 1.05 /spl mu/m. Experimental characterization and theoretical model are conducted and developed for the micro-intrusion process in terms of the radius of curvature and height of the lenses and they correspond well with experimental data within 5% of variations. The focusing capability of the lenses is demonstrated by comparing the images of laser light with and without using the lenses. When the projection screen is placed 200 /spl mu/m away from the lens, the full-width at half-maximum (FWHM) for the lens is 110 /spl mu/m while the original FWHM of the optical fiber is 300 /spl mu/m.     

利用MEMS技术研制硅脉象传感器

利用MEMS技术在N型<100>晶向的单晶硅衬底上设计并制作了以纳米硅/单晶硅异质结为源极和漏极的P-MOSFETs脉象传感器.在方形硅膜上制作四个以纳米硅/单晶硅异质结为源极和漏极P-MOSFETs,并将P-MOSFETs的沟道电阻设计成惠斯通电桥结构,从而实现对微小脉象信号的准确检测.实验结果表明,该硅脉象传感器在恒压源-3.0 V供电条件下,灵敏度为1.623 mV/kPa,准确度为2.029%F·S.     

Buckling analysis of laminated plates by wavelets

This paper addresses, for the first time, the buckling analysis of isotropic and laminated plates that are subjected to partial inplane edge loads by a first-order shear deformation theory. The numerical approach is based on collocation with wavelets. It is shown that the present method produces highly accurate critical loads and modes.     

Analysis of plates by the initial-value method

The initial-value method, which is an approximate numerical method, is applied to the analysis of isotropic plates. The initial-value method consists of solving the governing differential equation of plates by an integration technique. The integration is carried in one direction, and the derivatives in the other direction are represented by finite-difference operators on the deflections. The results and efficiency of the method are compared to the results of classical, finite-difference and finite-element methods. A wide variety of plate problems is considered, which include plates with transverse loading, plates with in-plane loading and continuous plates. The initial-value method has the lowest magnitudes of errors for all the examples considered in this study. To obtain high precision for a plate problem, the initial-value method requires the solving of far fewer simultaneous equations than the finite-difference and the finite-element methods.     

Analysis of plates by finite strip method

New finite strips are developed for the analysis of plates. Based on Reissner's plate theory, the effect of shear deformation is included in the formulation. To eliminate artificial hardening, the shape functions for the strips are so chosen that there is no mismatched term along the interpolation functions for the interpolation parameters. Numerical examples are reported to demonstrate that the strips can work equally well in thick as well as thin plates.     

Optimization of stiffened plates by genetic search

This paper deals with the optimization of stiffeners on plates by varying their positions, while having well-defined dimensions. Considering the nonlinearity, the non-convexity and the discontinuity of this problem, we have chosen to use a stochastic method, that is the genetic algorithm (GA). This work is above all a study of feasibility. Some improvements in the GA have been used and their influence on the convergence of the GA, while varying a number of parameters is made obvious by application on numerical examples and mechanical ones. To our knowledge, the problem in question, that is the topology optimization of the stiffeners on a plate, has not been treated in depth up till now, a fact that gives this subject particular importance.