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Showing papers on "Microfluidics published in 2000"


Journal ArticleDOI
TL;DR: This paper presents an overview of existing polymer microfabrication technologies for microfluidic applications, namely replication methods such as hot embossing, injection molding and casting, and the technologies necessary to fabricate the molding masters.
Abstract: A growing number of microsystem technology (MST) applications, particularly in the field of microfluidics with its applications in the life sciences, have a need for novel fabrication methods which account for substrates other than silicon or glass. We present in this paper an overview of existing polymer microfabrication technologies for microfluidic applications, namely replication methods such as hot embossing, injection molding and casting, and the technologies necessary to fabricate the molding masters. In addition, techniques such as laser ablation and layering techniques are examined. Methods for bonding and dicing of polymer materials, which are necessary for complete systems, are evaluated.

853 citations


Journal ArticleDOI
TL;DR: In this article, a liquid-metal droplet can be driven in an electrolyte-filled capillary by locally modifying the surface tension with electric potential, and a liquid micromotor is demonstrated at a speed of /spl sim/40 mm/s (or 420 r/min along a 2-mm loop).
Abstract: This paper describes the first microelectromechanical systems (MEMS) demonstration device that adopts surface tension as the driving force. A liquid-metal droplet can be driven in an electrolyte-filled capillary by locally modifying the surface tension with electric potential. We explore this so-called continuous electrowetting phenomenon for MEMS and present crucial design and fabrication technology that reduce the surface-tension-driving principle, inherently powerful in microscale, into practice. The key issues that are identified and investigated include the problem of material compatibility, electrode polarization, and electrolysis, as well as the micromachining process. Based on the results from the initial test devices and the design concept for a long-range movement of the liquid-metal droplet, we demonstrate a liquid micromotor, an electrolyte and liquid-metal droplets rotating along a microchannel loop. Smooth and wear-free rotation of the liquid system is shown at a speed of /spl sim/40 mm/s (or 420 r/min along a 2-mm loop) with a driving voltage of only 2.8 V and little power consumption (10-100 /spl mu/W).

395 citations


Journal ArticleDOI
TL;DR: Electrokinetic forces are emerging as a powerful means to drive microfluidic systems with flow channel cross-sectional dimensions in the tens of micrometers and flow rates in the nanoliter per second range.
Abstract: Electrokinetic forces are emerging as a powerful means to drive microfluidic systems with flow channel cross-sectional dimensions in the tens of micrometers and flow rates in the nanoliter per second range. These systems provide many advantages such as improved analysis speed, improved reproducibility, greatly reduced reagent consumption, and the ability to perform multiple operations in an integrated fashion. Planar microfabrication methods are used to make these analysis chips in materials such as glass or polymers. Many applications of this technology have been demonstrated, such as DNA separations, enzyme assays, immunoassays, and PCR amplification integrated with microfluidic assays. Further development of this technology is expected to yield higher levels of functionality of sample throughput on a single microfluidic analysis chip.

264 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe a small-scale, ultrasonic piezoelectric transducers that exert a directed body force on the fluid via acoustic attenuation, which is a type of acoustic streaming termed quartz wind in microfluidics applications.
Abstract: Miniature acousto-fluidic devices are described that operate as pumps without valves in channel widths of millimeters and below These devices can also be configured to produce mixing in low-Reynolds-number flows The prototypes are based on radio-frequency, ultrasonic piezoelectric transducers that exert a directed body force on the fluid via acoustic attenuation The process is a type of acoustic streaming termed quartz wind In microfluidics applications, this mechanism has the advantages of insensitivity to the chemical state of the fluid or walls and greatly reduced crosstalk in a multichannel system The observed pump flow velocities are on the order of 1 mm/s in 16×16 mm 2 channels and with a calculated maximum backpressure that can be pumped against of 013 Pa Due to the low backpressure, quartz wind devices are not competitive pumps for open-loop and high-impedance microfluidics systems but could find application in pumping in low-impedance planar and closed-loop systems and for mixing in reservoirs and channels

198 citations


Journal ArticleDOI
TL;DR: The use of polyelectrolyte multilayers (PEMs) to alter the surface charge and control the direction of flow in polystyrene and acrylic microfluidic devices is reported.
Abstract: Electroosmotic flow (EOF) is commonly utilized in microfluidics. Because the direction of the EOF can be determined by the substrate surface charge, control of the surface chemical state offers the potential, in addition to voltage control, to direct the flow in microfluidic devices. We report the use of polyelectrolyte multilayers (PEMs) to alter the surface charge and control the direction of flow in polystyrene and acrylic microfluidic devices. Relatively complex flow patterns with simple arrangements of applied voltages are realized by derivatization of different arms of a single device with oppositely charged polyelectrolytes. In addition, flow in opposite directions in the same channel is possible. A positively derivatized plastic substrate with a negatively charged lid was used to achieve top-bottom opposite flows. Derivatization of the two sides of a plastic microchannel with oppositely charged polyelectrolytes was used to achieve side-by-side opposite flows. The flow is characterized using fluorescence imaging and particle velocimetry.

179 citations


01 Jan 2000
TL;DR: In this article, the suitability of valve-less micropumps in biochemistry is shown, and the results show that the micropump successfully pumps fluids within the viscosity range 0.001-0.9 Ns/m2.
Abstract: The suitability of valve-less micropumps in biochemistry is shown. Fluids encountered in various biochemical methods that are problematic for other micropumps have been pumped with good performance. The micropump is self-priming and insensitive to particles and bubbles present in the pumped media. The results show that the valve-less micropump successfully pumps fluids within the viscosity range 0.001–0.9 Ns/m2. The micropump is not sensitive to the density, ionic strength or pH of the pumped media. Effective pumping of solutions containing beads of different sizes was also demonstrated. Living cells were pumped without inducing cell damage and no cell adhesion within the pump chamber was found.

99 citations


Patent
13 Nov 2000
TL;DR: In this article, surface-micromachining-based microfluidic devices are disclosed which can be manufactured using surface micromachines and utilize an electroosmotic force or an electromagnetic field to generate a flow of a fluid in a microchannel that is lined with silicon nitride.
Abstract: Microfluidic devices are disclosed which can be manufactured using surface-micromachining. These devices utilize an electroosmotic force or an electromagnetic field to generate a flow of a fluid in a microchannel that is lined, at least in part, with silicon nitride. Additional electrodes can be provided within or about the microchannel for separating particular constituents in the fluid during the flow based on charge state or magnetic moment. The fluid can also be pressurized in the channel. The present invention has many different applications including electrokinetic pumping, chemical and biochemical analysis (e.g. based on electrophoresis or chromatography), conducting chemical reactions on a microscopic scale, and forming hydraulic actuators.

80 citations


Patent
07 Apr 2000
TL;DR: Delectrophoresis (DEP), a phenomenon whereby polarizable particles move in response to a gradient in electric field, can be used to manipulate and separate DNA in an automated fashion, considerably reducing the time and expense involved in DNA analyses as discussed by the authors.
Abstract: Manipulation of DNA molecules in solution has become an essential aspect of genetic analyses used for biomedical assays, the identification of hazardous bacterial agents, and in decoding the human genome Currently, most of the steps involved in preparing a DNA sample for analysis are performed manually and are time, labor, and equipment intensive These steps include extraction of the DNA from spores or cells, separation of the DNA from other particles and molecules in the solution (eg dust, smoke, cell/spore debris, and proteins), and separation of the DNA itself into strands of specific lengths Dielectrophoresis (DEP), a phenomenon whereby polarizable particles move in response to a gradient in electric field, can be used to manipulate and separate DNA in an automated fashion, considerably reducing the time and expense involved in DNA analyses, as well as allowing for the miniaturization of DNA analysis instruments These applications include direct transport of DNA, trapping of DNA to allow for its separation from other particles or molecules in the solution, and the separation of DNA into strands of varying lengths

78 citations


Patent
02 Feb 2000
TL;DR: In this article, barriers are introduced between different compartments of the device to prevent fluid flow between the two compartments, and different materials and methods are employed for the introduction and removal of the barriers, including reversible gel particle expansion, reversible gellation, in situ polymerization, magnetic beads, and the like.
Abstract: Microfluidic devices are provided where barriers are introduced between different compartments of the device to prevent fluid flow between the two compartments. Different materials and methods are employed for the introduction and removal of the barriers, including reversible gel particle expansion, reversible gellation, in situ polymerization, magnetic beads, and the like. In this way mixing of agents may be temporally controlled during the operation of the device, where the barriers may be used in a passive manner or as an active agent involved in the operation being performed in the device.

63 citations


Proceedings ArticleDOI
23 May 2000
TL;DR: In this paper, the authors used electrokinetic (EK) micropumps with no moving parts and can generate maximum pressures of more than 20 atm at 2 kV applied voltage.
Abstract: Electrokinetic (EK) micropumps have been fabricated and demonstrated in which electroosmotic flow is used to transport fluids. Deionized water and pure acetonitrile have been used as working fluids to achieve low current density pumping conditions. These EK pumps have no moving parts and can generate maximum pressures of more than 20 atm at 2 kV applied voltage. Minimizing and controlling electrolytic gas generation is a major concern. Gas generated at the downstream electrode surfaces appears to be forced to dissolve into surrounding fluid at high pressure (>7 atm) condition, and this permits a stable pump operation. Measurements of flow rate have been used to estimate pump structure parameters.

61 citations


Book ChapterDOI
01 Jan 2000
TL;DR: In this paper, the authors present microfluidics on a CD platform, where multiple samples can be analyzed simultaneously without any tubing connected to the chip, using a passive valving technique that allows liquids with low surface tension.
Abstract: In this work we present microfluidics on a CD platform. Using this approach multiple samples can be analysed simultaneously without any tubing connected to the chip. Valving techniques based on surface tension and surface energy is presented together with a passive valving technique that allow liquids with low surface tension. To better understand the motion of discrete liquid plugs in the nanolitre range in the chip, we have compared experimental results on the hysteresis influence on microfluidic resistance with those from theoretical calculations.

Patent
20 Sep 2000
TL;DR: In this article, a microanalytical system based on a microfluidics/electrochemical detection scheme is described, where individual modules, such as microfabricated piezoelectrically actuated pumps and a microelectron cell, are integrated onto portable platforms.
Abstract: Microanalytical systems based on a microfluidics/electrochemical detection scheme are described. Individual modules, such as microfabricated piezoelectrically actuated pumps and a microelectrochemical cell were integrated onto portable platforms. This allowed rapid change-out and repair of individual components by incorporating “plug and play” concepts now standard in PC's. Different integration schemes were used for construction of the microanalytical systems based on microfluidics/electrochemical detection. In one scheme, all individual modules were integrated in the surface of the standard microfluidic platform based on a plug-and-play design. Microelectrochemical flow cell which integrated three electrodes based on a wall-jet design was fabricated on polymer substrate. The microelectrochemical flow cell was then plugged directly into the microfluidic platform. Another integration scheme was based on a multilayer lamination method utilizing stacking modules with different functionality to achieve a compact microanalytical device. Application of the microanalytical system for detection of lead in, for example, river water and saliva samples using stripping voltammetry is described.

Book ChapterDOI
01 Jan 2000
TL;DR: Two applications of centrifugal microfluidics for µTAS are presented: multiple, parallel assays provide a model for high-throughput screening and a centrifugal system automates sample processing and DNA amplification.
Abstract: We present two applications of centrifugal microfluidics for µTAS. In the first application, multiple, parallel assays provide a model for high-throughput screening. In the second, a centrifugal system automates sample processing and DNA amplification.

Journal ArticleDOI
TL;DR: In this paper, a hot embossing of polymer materials is used to produce stable and reproducible polymer microstructures with structural and optical properties meeting other biocompatibility and detection requirements for a wide range of microfabrication applications.
Abstract: Polymer microfabrication methods are becoming increasingly important as low-cost alternatives to the silicon or glass-based MEMS technologies. Polymer hot embossing and injection molding are replication methods applicable to microreplication of a diversity of materials and microstructures.Equipment with high precision control of pressure and temperature for hot embossing of polymer materials is now available commercially. These systems have made possible the replication of chips containing microchannels for capillary electrophoresis (CE) and microfluidics devices, microoptical components and microreactors. Stable and reproducible polymer microstructures have been demonstrated in several types of materials with structural and optical properties meeting other biocompatibility and detection requirements. The process involves few variable parameters and results in high structural accuracy suited for a wide range of microfabrication applications.After demonstrating equivalent and, in cases, improved performanc...

Journal ArticleDOI
TL;DR: In this article, a micromachined flow sensor for an integrated microfluidic system, operated in a pulse-modality, has been designed, fabricated and characterized, which has several unique operational and physical characteristics.
Abstract: A micromachined flow sensor for an integrated microfluidic system, operated in a pulse-modality, has been designed, fabricated and characterized. As a part of the complex of components constituting a generic fully integrated microfluidic system for autonomous biochemical analysis, this micro flow sensor has several unique operational and physical characteristics. A novel pulsing scheme compensates against any occurring temperature drift, resulting in high repeatability. Companion elements include microvalves, micropumps, microreservoirs, microchannels, etc., whose liquid (or gaseous) fluid dynamics must be characterized by the flow sensor described.

Patent
21 Dec 2000
TL;DR: In this article, a micro-system platform for use with a micromanipulation device to manipulate the platform by rotation, thereby utilizing the centripetal force resulting from rotation of the platform to motivate fluid movement through microchannels embedded in the microplatform.
Abstract: This invention provides methods and apparatus for performing microanalytic and microsynthetic analyses and procedures Specifically, the invention provides a microsystem platform for use with a micromanipulation device to manipulate the platform by rotation, thereby utilizing the centripetal force resulting from rotation of the platform to motivate fluid movement through microchannels embedded in the microplatform The microsystem platforms of the invention are also provided having microfluidics components, resistive heating elements, temperature sensing elements, mixing structures, capillary and sacrificial valves, and methods for using these microsystems platforms for performing biological, enzymatic, immunological and chemical assays An electronic spindle designed rotor capable of transferring electrical signals to and from the microsystem platforms of the invention is also provided

Book ChapterDOI
01 Jan 2000
TL;DR: A number of microfluidic devices have been developed that do not require any external power source or means for fluid movement, such as particle separators, valves, detection channels, mixers, and diluters.
Abstract: A number of microfluidic devices have been developed that do not require any external power source or means for fluid movement. They include particle separators, valves, detection channels, mixers, and diluters. Current applications for these devices include standalone blood plasma separators, and a variety of qualitative and semi-quantitative assays. Experimental data as well as the results of fluid modeling are shown.

DissertationDOI
01 Jan 2000
TL;DR: A microfabricated flow-cell device was developed using 'soft lithography', offering a small, cheap, robust, and contamination-free alternative to the complicated glass-capillary structure used in a conventional flow cytometer, and a highly sensitive single-molecule DNA sizing system was demonstrated.
Abstract: Science makes new technology and technology pushes science forward. For biological studies and hospital diagnoses, knowledge and techniques accumulated from other fields, such as semiconductors, optics, electronics, and chemistry, are generating huge impacts in almost every aspect and for almost everyone involved. Among these, tools for DNA diagnostics play a very important role. They are also essential to many genetic studies, drug discovery, and even forensic identifications. Working with Professor Stephen Quake, Professor Axel Scherer, and my colleagues in Caltech, I have developed several building blocks for rapid DNA sizing, cell sorting, molecular fingerprinting, and hybridization assays, based on those newly available technologies. First, a microfabricated flow-cell device was developed using 'soft lithography'. It offers a small, cheap, robust, and contamination-free alternative to the complicated glass-capillary structure used in a conventional flow cytometer. Based on this device, a highly sensitive single-molecule DNA sizing system was demonstrated. It is 100 times faster and requires a million times less sample than pulsed-field gel electrophoresis. For DNA molecules of 1-200 kbp, it has comparable resolution, which improves with increasing DNA length. To serve as a real substitute for a conventional flow cytometry, DNA and cell sorting has also been demonstrated under this system. Simple enclosed actuation schemes are implemented and system downtime due to capillary cleaning is totally eliminated because the device costs only pennies to make and thus becomes disposable. Therefore, there is no cross-contamination issue for both DNA sizing and cell sorting applications. Using this system, prototype work for rapid DNA molecular fingerprinting was devised as an alternative to the widely used Southern blot fingerprinting protocol. Molecular evolution, VNTR fingerprinting of human forensic samples, disease diagnosis based on restriction fragment length polymorphism (RFLP), and simple DNA genomic mapping can all be accomplished with this system. Because of the great flexibility of microfabrication, more complicated functions can also be designed and incorporated into these flow-cell devices. Therefore, this single-molecule sizing system can become a key component in the family of lab-on-a-chip devices. In addition, a multilayer soft lithography technique was invented, allowing monolithic microvalves and micropumps to be built into these flow-channel devices. Active microfluidic systems containing on-off valves, switching valves and pumps were made, entirely out of elastomer. The softness of these materials allows the device area to be reduced by more than two orders of magnitude compared with silicon-based devices. An actuation volume as small as about one picoliter is demonstrated. The other advantages of soft lithography, such as rapid prototyping, ease of fabrication, and biocompatibility, are retained. Based on these active components, an integrated diagnostic chip was built. More than two orders of magnitude improvement in terms of binding speed and efficiency over passive devices was shown. Selective surface patterning of DNA molecules, biotin, and avidin within the chips by elastomeric flow channels was also shown. With active pumping, we are able to make a rotary motion in these microfluidic devices and show fast inline mixing which overcomes the limitation of laminar flow in this low-Reynolds number regime. Moreover, the problem of buffer depletion due to electrolysis in electroosmotic or electrophoretic flow control does not exist in these devices. All of these serve as fast, cheap, and robust alternatives to many conventional techniques used widely in biological studies and hospital pathogenic diagnosis. They are all very simple to fabricate and easy to use. If desired, more complicated flow patterns and functions can also be incorporated with much less effort than their silicon counterparts. We anticipate that more applications and devices based on these systems and techniques will be developed rapidly in the near future.

Book ChapterDOI
01 Jan 2000
TL;DR: In this paper, the authors investigated the possibility of using ink jet printing techniques for the integration of hydrophobic areas, i.e. surface modifications, in microfluidic plastic chips.
Abstract: This work addresses a solution for making localised hydrophobic areas on a hydrophilic surface in order to produce a large number of hydrophobic valves in a microfluidic device. The study was made to investigate the possibility of using ink jet printing techniques for the integration of hydrophobic areas, i.e. surface modifications, in microfluidic plastic chips.

Proceedings ArticleDOI
TL;DR: In this paper, surface tension attenuates liquid movement so effectively in microscale, and surface tension can even be used as an attractive driving force for microactuation in microfluidics.
Abstract: This review summarizes our on-going effort to establish surface tension as a useful force for MEMS, especially microfluidics. Presented are several examples of using surface tension for microdevices. Droplet ejection mechanism using bubble check valve, pumping with sequential bubbles in microchannel, and electrostatic switching of liquid-metal droplet demonstrate how surface tension attenuates liquid movement so effectively in microscale. Liquid pumping using a bubble (or a droplet) under thermal gradient and electrically driving liquid-metal droplets in microchannel demonstrate that surface tension can even be used an an attractive driving force for microactuation.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
TL;DR: In this paper, an active microfluidic mixer for mixing of microparticles and liquid samples using electrohydrodynamic (EHD) convection for applications in micro-based biochemical analysis systems and biochips is presented.
Abstract: This paper presents a new active microfluidic mixer for mixing of microparticles and liquid samples using electrohydrodynamic (EHD) convection for applications in microfluidic-based biochemical analysis systems and biochips. To understand the EHD convection mixing, analytical analysis on the micro mixer have been performed for two different liquid samples with different electric conductivities. Through the analytical simulation, a new active micro mixer for both liquid/liquid mixing and liquid/microparticles mixing has been designed, fabricated, and demonstrated for application of a magnetic microbead- based analysis system. Magnetic beads that are dispersed in buffer solution have been fully mixed with the selected liquid sample while passing the mixing zone, which has voltage of between 7 to 25 V applied across it. Since the realized micro mixer has simple structure and no mechanically moving parts, it shows very reliable and repeatable mixing performance. The active micro mixing device studied in this work also shows feasible mixing capabilities of microparticles in naon- or pico-liter range of liquid volumes by applying a low voltage of 7 V across the microchannel. Furthermore reliable, robust mixing and manipulating of microparticles in liquid samples can be rapidly achieved.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
TL;DR: The T-Sensor as mentioned in this paper is based on the same laminar flow diffusion principle, but combines sample preparation with self-calibration and detection, and it can be used not only in stand-alone research and point-of-use testing applications, but they can also be integrated, as well as integrated, into the H-Filter.
Abstract: Microfluidic flow conditions allow the design of highly effective, yet simple devices for on-chip sample preparation and cleanup. Over the past few years, Micronics has developed a number of novel microfluidic structures that are compatible with complex samples such as whole blood or contaminated environmental fluids. The H-Filter is a technology based on the parallel laminar flow of two or more miscible streams in contact with each other. Such streams do not mix, but chemicals contained in these streams can diffuse from one stream into the other, with smaller molecules diffusing faster than larger ones. This principle can be used, for example, to remove salt from a solution containing DNA, or to extract smaller molecules from whole blood. The T-Sensor is based on the same laminar flow diffusion principle, but combines sample preparation with self-calibration and detection. These devices can be used not only in stand-alone research and point-of-use testing applications, but they can also be integrated, as...

Proceedings ArticleDOI
TL;DR: An artifical separation device with an array of entropic traps that could be used to analyze proteins or other biopolymers, and the ability to modify and control the device precisely for the optimization of a separation process.
Abstract: Fluidic devices with sub-micrometer dimensions provide new opportunities in manipulation and analysis of various biomolecules, such as deoxyribonucleic acid (DNA). As an example of such devices, a microchannel with an array of entropic traps is introduced. The existence of sub-100nm constriction causes long double-stranded DNA molecules to be entropically trapped, and the length-dependent escape of DNA from the trap enables a band separation of DNA. Entropic traps are also used to manipulate and collect many DNA molecules into a narrow, well-defined initial band for electrophoresis launching. In addition to its speed and compactness, another important advantage of this artifical separation device over conventional gel electrophoresis is the ability to modify and control the device precisely for the optimization of a separation process. The similar device could be used to analyze proteins or other biopolymers.

Proceedings ArticleDOI
TL;DR: In this article, a micro-capillary electrophoresis ((mu) -CE) device for DNA separation and detection has been demonstrated on polymethylmethacrylate (PMMA) substrate.
Abstract: Design and fabrication of microfluidic devices on polymethylmethacrylate (PMMA) substrates using novel microfabrication methods are described. The image of microfluidic devices is transferred from quartz master templates possessing inverse image of the devices to plastic plates by using hot embossing method. The micro channels on master templates are formed by the combination of metal etch mask and wet chemical etching. The micromachined quartz templates can be used repeatedly to fabricate cheap and disposable plastic devices. The reproducibility of the hot embossing method is evaluated after using 10 channels on different plastics. The relative standard deviation of the plastic channel profile from ones on quartz templates is less than 1%. In this study, the PMMA chips have been demonstrated as a micro capillary electrophoresis ((mu) -CE) device for DNA separation and detection. The capability of the fabricated chip for electrophoretic injection and separation is characterized via the analysis of DNA fragments (phi) X174. Results indicate that all of the 11 DNA fragments of the size marker could be identified in less than 3 minutes with relative standard deviations less than 0.4% and 8% for migration time and peak area, respectively. Moreover, with the use of near IR dye, fluorescence signals of the higher molecular weight fragments ($GTR 603 bp in length) could be detected at total DNA concentrations as low as 0.1 (mu) g/mL. In addition to DNA fragments (phi) X174, DNA sizing of hepatitis C viral (HCV) amplicon is also achieved using microchip electrophoresis fabricated on PMMA substrate.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Proceedings ArticleDOI
TL;DR: In this article, the conductivity changes occur when liquid flow causes movement of the boundary between two solutions of differing conductivities, and the current monitoring method, used in capillary electrophoresis, is employed to determine conductance-time waveforms during electroosmotic pumping.
Abstract: This paper investigates methods of flow rate quantification in micro- fluidic devices, using electrodes to measure the conductivity of solution. Conductivity changes occur when liquid flow causes movement of the boundary between two solutions of differing conductivity. The fabrication technology for the micromachined silicon structures is based on anisotropic etching and anodic bonding to glass. The silicon processing is simplified by using a single-mask process, whereby 9 - 15 mm long, 50 - 100 micrometers wide capillaries and access through-holes are created with a single etch step. Thin film gold electrodes patterned on the glass provide contact with the liquid in the capillary. The current monitoring method, used in capillary electrophoresis, is employed to determine conductance-time waveforms during electroosmotic pumping. The waveforms for silicon based devices are distorted due to oxide capacitance and the profiles of the ends of the channel. The transitions are much more linear for reference devices formed using standard glass capillary tubing. Electrical models are developed for the devices and these are used to determine flow velocities and hence volume flow rates of liquid.

Proceedings ArticleDOI
TL;DR: In this article, a bi-functional micro system for DNA affinity assay is presented, which consists of optical fiber coupling with planar waveguide for illuminating the labeled DNA samples, and micro lens arrays for collecting the induced fluorescence light.
Abstract: Based on laser induced fluorescence detection a miniaturized and sensitive optical system is developed for micro total analysis systems (u-TAS) application. A micro optical system integrated with a micro fluid device is a convenient way to realized biochemical reaction and detection on one chip. Such a bi-functional micro system for DNA affinity assay is presented in this paper. The optical system composed of optical fiber coupling with planar waveguide for illuminating the labeled DNA samples, and micro lens arrays for collecting the induced fluorescence light. High signal-to-noise ratio can be achieved because of evanescent field excitation mode. A specially designed micro chamber, with chemical process, including small pipes for guiding sample agent is included in the system in order to enable DNA affinity reaction, and to wash the chamber afer reaction. These components will be integrated within the encapsulation of a photoelectric array detector, so the size of this system can be greatly reduced. This bi-functional micro system has merits of integration of reaction and detection together, more compactness, multi-channel detection, high sensitivity and good compatibility with biological samples. This system is a promising candidate to be integrated into a micro total analysis system, such as a portable DNA diagnostics device.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Book ChapterDOI
01 Jan 2000
TL;DR: Multi-disciplinary computational tool, CFD-ACE+MEMS, for simulation and design of microfluidic bioMEMS is presented and demonstrated on 3D high-fidelity simulations in microfluidity channels and on a complex DNA filtration chip.
Abstract: In the last few years there has been tremendous interest in developing a complete biomedical/biochemical intelligent microsystem for extraction, concentration, amplification, analysis and processing of DNA. This paper presents multi-disciplinary computational tool, CFD-ACE+MEMS, for simulation and design of microfluidic bioMEMS. It is demonstrated on 3D high-fidelity simulations in microfluidic channels and on a complex DNA filtration chip.


Proceedings ArticleDOI
12 Oct 2000
TL;DR: In this paper, a reusable microfluidic flow cell for real-time DNA detection is proposed, which is realized by a microstructured Silicon-Polymer-Hybrid that is pressed onto a sensing element consisting of thin metallic interdigitated electrodes with immobilized capture DNA.
Abstract: Describes the design of a reusable microfluidic flow cell for real time DNA detection. This Microfluidic-Device-Stamp-System (MDSS) is realized by a microstructured Silicon-Polymer-Hybrid that is pressed onto a sensing element consists of thin metallic interdigitated electrodes with immobilized capture DNA for hybridization detection. The hybridization temperature is controlled by integrated heating and sensing elements manufactured with standard microsystem technologies. Two-dimensional FEM flow analyses using ANSYS 5.5/FLOTRAN were done to optimize the homogeneities of fluid flow and DNA mass transport in the sensing region.

Book ChapterDOI
01 Jan 2000
TL;DR: In this article, the authors present a fabrication method for microfluidic devices and in the development of new tools for fluorescence based experiments, which is fully compatible with current processing techniques of the semiconductor industry.
Abstract: We present fabrication and testing of a microfluidics/integrated optics device. We present a fabrication method for microfluidic devices and in the development of new tools for fluorescence based experiments. The fabrication technique, relying on the use of sacrificial layers to form microfluidic circuitry is fully compatible with current processing techniques of the semiconductor industry. This bonding-free method opens the door to the integration of conventional CMOS electronics with microfluidics systems.