A study on the MHD (magnetohydrodynamic) micropump with side-walled electrodes

This paper presents the continuous flow MHD(magnetohydrodynamic) micropump with side walled electrodes using Lorentz force, which is perpendicular to both magnetic and electric fields, for the application of microfluidic systems. A theoretically simplified MHD flow model includes the theory of fluid dynamics and electromagnetics and it is based upon the steady state, incompressible and fully developed laminar flow theory. A numerical analysis with the finite difference method is employed for solving the velocity profile of the working fluid across the microchannel under various operation currents and magnetic flux densities. In addition, the commercial CFD code called CFD-ACE has been utilized for simulating the MHD micropump. When the program was run(CFD-ACE), the applied current and magnetic flux density were set to be the variables that affected the performance of the MHD micropump. The MHD micropump was fabricated by using MEMS technology. The performance of the MHD micropump was obtained by measuring the flow rate as the applied DC current was changed from 0 to 1mA at 4900 and 3300 Gauss for the electrodes with the lengths of 5000, 7500 and 10000 μm, respectively. The experimental results were compared with the analytical and the numerical results. In addition, with the theoretical analysis and the preliminary experiments, we propose a final model for a simple and new MHD micropump, which could be applicable to microfluidic systems. This paper was recommended for publication in revised form by Associate Editor Seungbae Lee Bumkyoo Choi received a B.S. degree in mechanical engineering, M.S. in mechanical design engineering from Seoul National University, Seoul, Korea in 1981 and 1983 respectively, and PhD in engineering mechanics from the University of Wisconsin, Madison in 1992. From 1992 to 1994, he was a technical staff member of CXrL (Center of X-ray Lithography) in the University of Wisconsin where he developed a computer code for thermal modeling of X-ray mask membrane during synchrotron radiation. He is currently a professor in the Dept. of Mechanical Engineering of Sogang Univ., Seoul, Korea. His research interest includes microelec-tromechanical system (MEMS), micromatching and microfabrication technologies, and modeling issues. Sangsoo Lim received a B.S. degree in mechanical engineering from Sogang University, Seoul, Korea in 2005. He currently works at Hyundai Motors.     

微流控分析芯片的加工技术

综述了微流控分析芯片和加工技术和材质性能,光刻和蚀刻技术常用于加工硅,玻璃和石英芯片。有机聚合物由于品种多,易加工,是代替玻璃和石英的芯片材料。本文总结和讨论了各种芯片材料和它们的加工方法,如光刻,湿法刻蚀,干法刻蚀,模塑法,软刻蚀,热压法,激光切蚀法,LIGA技术和键合技术,引用文献36篇。     

Microchip technology in mass spectrometry

Microfabrication of analytical devices is currently of growing interest and many microfabricated instruments have also entered the field of mass spectrometry (MS). Various (atmospheric pressure) ion sources as well as mass analyzers have been developed exploiting microfabrication techniques. The most common approach thus far has been the miniaturization of the electrospray ion source and its integration with various separation and sampling units. Other ionization techniques, mainly atmospheric pressure chemical ionization and photoionization, have also been subject to miniaturization, though they have not attracted as much attention. Likewise, all common types of mass analyzers have been realized by microfabrication and, in most cases, successfully applied to MS analysis in conjunction with on‐chip ionization. This review summarizes the latest achievements in the field of microfabricated ion sources and mass analyzers. Representative applications are reviewed focusing on the development of fully microfabricated systems where ion sources or analyzers are integrated with microfluidic separation devices or microfabricated pums and detectors, respectively. Also the main microfabrication methods, with their possibilities and constraints, are briefly discussed together with the most commonly used materials. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:351‐391, 2010     

Development of in-process visualization system for laser-assisted three-dimensional microfabrication using photocatalyst nanoparticles

Recently, microfabrication technology has been used to develop micro-electro-mechanical systems (MEMSs), micro-total analysis systems (μ-TASs), and photonic crystals. Various microfabrication techniques have been proposed; however, a technique that can be used to efficiently fabricate 3-D structures via a simple procedure has not been reported thus far. Because 3-D metal structures have not only mechanical functions but also electromagnetic functions, it is desirable to develop such a technique. Our research group is in the process of developing a new technique for 3-D microfabrication that involves the use of a lower power continuous wave laser. Our technique is characterized by the reduction of silver ions via the photocatalysis of titanium dioxide (TiO2) excited at the laser beam waist. For the analysis and development of our microfabrication technique, we developed a microscope system that enabled us to observe the microfabrication process along the fabrication beam optical axis and its radial direction. We successfully visualized the microfabrication process in 3-D. The visualization showed that when the beam waist was swept, the silver structure grew in 3-D following its path. The effect of the substrate on the deposition condition was examined.     

Parallel-kinematics XYZ MEMS part 1: Kinematics and design for fabrication

Micro- and nanopositioning systems are widely used in the field of nanotechnology for probing, imaging, and increasingly for processing. This two-part set of papers presents a MEMS-scale parallel-kinematics mechanism, designed to achieve pure spatial (X, Y and Z) translation. With three independent kinematic chains connecting the end-effector to the base, a fully functional mechanism with axis actuation and displacement sensing is realized in a double device layer (“oreo”) SOI wafer using only conventional, microfabrication processes. This paper, the first in a two paper set, presents the mechanism, specially designed for scalable microfabrication. It analyzes its kinematics and dynamics, and characterizes its workspace. Part II of this set of papers describes the detailed design, fabrication, characterization and control of the devices.     

基于玻璃湿法刻蚀的微流控器件加工工艺研究

介绍了以玻璃为基体材料的微加工工艺流程,重点研究了玻璃湿法刻蚀工艺,选择多种不同成分的刻蚀剂进行了对比性刻蚀试验,同时研究了刻蚀温度、搅拌方式和清洗间隔时间等多种刻蚀条件对刻蚀效果的影响,研究主要以高刻蚀速率的深度刻蚀以及高表面质量的毛细管道刻蚀两种典型应用为目标。对比与分析了多种试验结果并对其适用范围进行了适当的评价,为基于玻璃材质的微流控器件加工工艺提供了基本选择方案及实际经验曲线。     

Multi‐Functional Particle Detection with Embedded Optical Fibers in a Poly(dimethylsiloxane) Chip

Abstract

This paper describes a polydimethylsiloxane microfluidic chip with embedded optical fibers for particle detection. It consists of a microchannel for sample delivery, two pairs of fibers for multi‐functional particle detection, and electrodes for high voltage supply to generate electrokinetic particle motion. A small size semiconductor laser and a Si‐PIN detector are used for optical detection. The detection system allows easy switch between two‐fiber detection mode and one‐fiber detection mode, and is capable of counting particles, measuring particle velocity, and identifying particle sizes in a single polydimethylsiloxane chip. The technique described here is potentially applicable to a range of particulate diagnostic systems.     

微流体芯片技术在免疫分析中的应用

微流体芯片技术最初起源于分析化学领域,它采用网络式的通道结构为免疫分析研究提供一个新的平台。在微流体芯片通道中,人们利用它所提供的较高比表面积来完成免疫反应,这样可大大提高分析速度,改善分析效率并降低样品和试剂消耗。随着微电子及微机械制作技术的不断进步,近年来微流体芯片技术发展迅速,并开始在化学、生命科学及环境科学等领域发挥越来越重要的作用。本文对微流体芯片技术在均相免疫分析和非均相免疫分析中的应用进行综述,介绍用于免疫分析研究的多种微芯片系统并讨论在芯片上进行免疫反应的各种方法。     

Simultaneous multi-dimensional spatial frequency modulation imaging

Abstract

One of the primary challenges in advanced manufacturing (AM) is the lack of efficient optical metrics for ensuring quality control over the manufacturing process. Many current imaging techniques have excessive data requirements and require computationally intensive post-processing to effectively characterize various AM environments. Spatial frequency modulated imaging (SPIFI) addresses many of these issues with the following benefits: it is compatible with long working distance optics, provides a large field-of-view, features single element detection, and can provide enhanced resolution. Here, we demonstrate SPIFI with enhanced resolution in multiple dimensions for the first time. This is achieved by incorporating multiple linear extended excitation sources oriented with axes at arbitrary angles with respect to each other. The system utilizes a single modulation mask enabling facile implementation within existing imaging systems such as those found in laser AM systems.     

基于快速成形的MEMS微制造技术

评述了当前主要的MEMS微制造技术方法及特点，综述了基于快速成形的MEMS微制造系统的基本原理和基本结构，目前所能达到的精度与应用典型实例，微型制造技术的优越性与局限性，对最新发展的每一层面一次曝光的高速快速成形MEMS微制造系统原理与研究示例进行了介绍。     

Temperature measurement of microfluids with high temporal resolution by laser-induced fluorescence

Temperature of microfluidic system is greatly sensitive because of fast heat conduction and small heat capacity due to the scale effect. The purpose of this study is the development of a measurement system for the temperature field of liquids in a microfluidic device with high spatial- and temporal-resolution. Measurement method employed in this study is laser-induced fluorescence using fluorescein with the temperature dependence of fluorescent intensity. In order to measure the transient temperature field, an image-intensified high-speed camera was utilized. The signal-to-noise ratio can be improved by the time- or phase-averaging scheme. Applying the synchronization mechanism, phase-averaged temperature data with the time resolution of 500 μs can be obtained. Spatial resolution estimated from the Rayleigh limit was approximately 530 nm. The validity of the developed measurement system was confirmed by the experiments for the transient behavior of the liquid temperature undergoing the laser heating in the microfluidic device. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Masahiro Motosuke received his B. S. degree from Department of System Design Engineering at Keio University, Japan, in 2001. He received his M. S. and Ph. D degrees from Keio University in 2003 and 2006. He is now an Assistant Professor at Department of Mechanical Engineering in Tokyo University of Science, Japan. His research interests are in the development of advanced sensing and control for the fluid or particle motion and properties in a microfluidic system based on optical or electrokinetic approach. Dai Akutsu received his B. S. degree in Mechanical Engineering from Tokyo University of Science, Japan, in 2008. He is currently in the master course of the graduate school of Mechanical Engineering in Tokyo University of Science. His research interests include the temperature measurement of the highly tiny region in a microfluidic device using micro-LIF and the development of micro- mixer/ sorter by means of electrokinetics. Shinji Honami received his B. S. in Mechanical Engineering from Keio University, Japan, in 1967. He received his M. S. and Ph. D degrees from Keio University in 1969 and 1974, respectively. He is a Professor at School of Engineering, Department of Mechanical Engineering, Tokyo University of Science, Japan. His research interests include turbulent and laminar flow control and microfluidics.     

PCR生物芯片微加工技术的研究

聚合酶链式反应（PCR）在生命科学研究及诸多相关领域已经得到了广泛应用。PCR生物芯片是利用微加工技术制作的能够实现PCR扩增反应的微装置。文中给出了基于MEMS技术的PCR生物芯片的微加工技术及加工方法，特别对集成在芯片上的加热器及温度传感器的微加工方法进行了重点介绍，并对它们的特性进行了分析比较。最后预测了PCR生物芯片微加工技术的发展方向及要克服的主要难题。     

Microfluidic methods used in exosome isolation

Exosomes are important biomarkers for clinical diagnosis. It is critical to isolate secreted exosomes from bodily fluids such as blood, saliva, breast milk, and urine for liquid biopsy applications. The field of microfluidics provides numerous benefits for biosample processing, diagnostics, and prognostics. Several microfluidics-based methods have been employed for the isolation and purification of exosomes in the last ten years. These microfluidic methods can be grouped into two categories based on passive and active isolation mechanisms. In the first group, inertial and hydrodynamic forces are employed to separate exosomes based on their size differences. In the second group, external forcefields are integrated into microfluidic platforms to actively isolate exosomes from other bioparticles. In this paper, the application of microfluidic methods in exosome isolation is discussed, and future perspectives on this field are highlighted.     

多晶硅微机械零件的制作及测试

探讨利用硅表面微细加工工艺制造微型机械的方法，制作了微涡轮，微传动齿轮，微螺旋弹簧和微凸轮传动机构等微机械结构，实现了齿轮的啮合传动，微弹簧扭转及微凸轮传动机构的运动。对多晶硅材料的机械物理性能，微机械系统动力学特性进行了测试分析。     

Modular Component Optics System for use in Laser Analytical Systems

ABSTRACT

The use of lasers as irradiation sources for molecular fluorescence and spectroscopy has increased the sensitivity and selectivity of these analytical techniques. A new design approach has been taken to satisfy both the safety requirements of laser bean containment and the utilization of components for various analytical techniques. This approach is in the form of a modular component optical system.     

Time-Correlated Single Photon Counting With Microchannel Plate Detectors

ABSTRACT

We describe the experimental techniques and methods of analysis used in our laboratory in the study of a wide range of chemical and biological systems. In addition to standard single exponential decay time measurements we discuss the resolution of multiexponential decays and the analysis of fluorescence anisotropy experiments.     

A switchable cantilver for a chemically sensitive scanning force microscope

We describe a cantilever device for a novel ’Time-Of-Flight Scanning Force Microscope (TOF-SFM)’ concept that has the capability of chemical analysis. The cantilever device consists of a switchable cantilever (SC), a microfabricated extraction electrode, and a LEGO-type microstage, which combines two different systems. It allows quasi-simultaneous topographical and chemical imaging of a sample surface to be performed in the same way as with conventional scanning probe techniques. This is achieved by the micromachined SC with a bimorph actuator that provides a reasonable switching speed in comparison with mechanically operated switches. Secondly, a short tip-electrode distance to minimize the ions extraction voltage can be realized by LEGO-type microfabrication. The measured SC tip deflection is -100 μm at 35 mW, corresponding to an estimated heater temperature of -250°C. The maximum switching speed between the two modes is -10 msec, and the sensitivity ΔR/R of an integrated piezoresistive deflection sensor is -6.7× 10^-7/nm. The tip-electrode distance is only 10 μm. The TOF-SFM is currently integrated in an ultra-high-vacuum system to perform several measurements.     

Meetings & Symposia

SUMMARY

Linear potential sweep voltammetry at stationary or quasi-stationary electrodes has become a widely accepted analytical technique. In contrast with the well-known dc polarographic current-voltage curve which reaches a limiting current (i¹) at potentials sufficiently removed from the half-wave potential (E^1/2), the voltammetric curve at a stationary electrode in unstirred solution reaches a maximum value (i^p) after which the current decreases rather slowly as the potential is increased further. This “tail” is a matter of concern in the analysis of multicomponent systems if two or more species react during a single sweep of the electrode potential. This communication presents the results of calculations made to determine the separation of half-wave potentials required to permit the quantitative determination of each species in multicomponent systems. Regular, first-, and second-derivative techniques are considered.     

Autoranging in High Speed Data Acquisition Systems

ABSTRAC

This paper is a presentation of various types of autoranging amplifiers and methods of incorporating them into fast digital data acquisition systems. The advantages and drawbacks of each type of autoranging method are examined. An example of fast autoranging using rapid scan square wave polarography is presented in which trace amounts of materials are detected in the presence of large amounts of other electroactive species.     

HOT EMBOSSING METHODS FOR PLASTIC MICROCHANNEL FABRICATION

Fabrication of microchannels on polymethylmethacrylate (PMMA) substrates using novel microfabrication methods is demonstrated. The image of microchannels is transferred from a silicon master possessing the inverse image of the microchannel to a PMMA plate by using hot embossing methods. The silicon master is electrostatically bonded to a Pyrex 7740 glass wafer, which improves the device yield from about 20 devices to hundreds of devices per master. Effects of embossing temperature, pressure and time on the accuracy of replication are systematically studied using the orthogonal factorial design. According to the suggested experimental model, the time for the whole embossing procedure is shorten from about 20 min to 6 min, and the accuracy of replication is 99.3%. The reproducibility of the hot embossing method is evaluated using 10 channels on different microfluidic devices, with variations of 1.4 % in depth and 1.8% in width.