Microfabrication had a major impact on electronics and is expected to have an equally pronounced effect on chemistry and life sciences. Exploitation of these scientific fields is becoming increasingly dependent on the availability of systems that can perform fast accurate analyses, using minute volumes of sample. By combining microfluidics with micromechanics, microoptics, and microelectronics, systems can be realized that perform complete analyses. The possibility of realize structures with sizes that are in the same range as biological cells makes microtechnology especially interesting for cell analysis. Cell analysis already forms an important, integral part of medical diagnostics and research. Microtechnology provides the opportunity to refine existing cell analysis tools but also allows fabrication of instruments that cannot be realized with conventional technologies. Examples of first steps along this path are provided.
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.
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.
Study of an aqueous-phase reaction in an enzyme- catalyzedpolydimethylsiloxane (PDMS) microreactor is underway. In the present work, urease - an enzyme that catalyzes urea to ammonia and carbon dioxide has been immobilized within open microchannels of 450 micrometers (micrometers ) in diameter or less. Microchannels are templated within PDMS. Preliminary results demonstrate the proof of concept for conversion biochemicals via a PDMS-based microreactor system.
Different types of modular micro components such as pumps, values, reactors, separators, residence structures, extractors have been developed. Silicon was used as basic material. Most external dimensions of all different modules are equal. The components contain deep micro structures like channels or groves produced in dry or in wet chemical etching procedures. Different types of bonding technologies were applied to cover the flow structures. Openings positioned at the surface allow the connection with external standard tubes. These openings are arranged on each module at the same position. Due to this basic design a highly flexible combination of the micro modules is possible. Specific process conditions of chemical reactions can be adapted very easily and cost effective by means of module combinations. Holders for the modules contain the fluidic/electric connectors and allow their flexible combination. They are made of PEEK or PTFE. Fixing and sealing of external tubes to the modules can be realised by simple screwing procedures of standard tubes into the holders. Due to this simple screwing procedure all modules can be exchanged on demand. Operating pressures up to the limitation values of the external tubes can be applied to the modules. Electrical contacts arranged inside the holders allow the electrical connection of the modules to an external power supply, as well as a read out of electrical signals delivered from possibly integrated specific sensors. Stand alone examinations of single modules as well as specific chemical reactions in modular combinations were carried out to verify the performance of the micro devices. Successful and hopeful results were found in all cases.
A living cell has numerous kinds of proteins while only thousands of that have been identified as of now. In order to discover and produce various proteins that are applicable to biotechnological, pharmaceutical and medical applications, cell-free protein synthesis is one of the most useful and promising techniques. In this study, we developed an inexpensive microreactor with temperature control capability for protein synthesis. The microreactor consists of a sandwich of glass-based chip and PDMS(polydimethylsiloxane) chip. The thermo control system, which is composed of a heater and a temperature sensor, is fabricated with an ITO (Indium Tin Oxide) resistive material on a glass substrate by ordinary microfabrication method based on photolithography and etching techniques. The reactor chamber and flow channels are fabricated by injection micromolding of PDMS. Since one can use thermo control system on a glass substrate repeatedly by replacing only the easily-fabricated and low-cost PDMS reactor chamber, this microreactor is quite cost effective. As a demonstration, a DNA template of a GFP (Green Fluorescent Protein) is transcribed and translated using cell-free extract prepared from Escherichia coli. As a result, GFP was successfully synthesized in the present microreactor.
In this work we present an injection molding tool fabricated using current micromachining techniques. The process was used to fabricate micro fluidic channels in a plastic substrate with depths of approximately 27 micrometers . The process can easily be altered to form channels of varying depths ranging from a few microns to approximately 100 micrometers . The tool was made using a photosensitive epoxy (SU-8) on silicon. Complex two-dimensional micro channel / chamber shapes and intersections are also achievable because the process for defining SU-8 is lithography. Two polymers were successfully used for injection molding the channels, clear rigid polycarbonate and opaque flexible polypropylene. Plastic replications of the inverse pattern of the SU-8 tool were made with the described process. Fabrication time of the tool was approximately 30 minutes and survived without failure, 22 shots for polypropylene and eight shots for polycarbonate (Lexan). Some deformities of the channels were observed and were more pronounced in the PP channels. Channel height was increased by 2-3 micrometers due to a ridge that was formed due to shear forces generated during the release stage of the process. The channel width shrunk approximately 7.9% maximum for polypropylene after release from the mold.
A very simple room-temperature procedure is presented herein for formation of true three-dimensionality of microplumbing in plastic (silicone elastomer in this case), by molding the plastic to simply encapsulate a pre-formed network of sacrificial wax threads or other connected wax configurations which are ultimately to become micro channels and cavities in the plastic motherboard. When these wax sacrificial areas are etched away with acetone, precise cavities, channels, and capillaries results with direct arbitrary three- dimensionality for the first time. This method leads also to a simple and effective external interconnect scheme where ordinary fused silica tubes may be press-fitted into the surface opening to withstand high pressure. This method may be extended for connection of multiple levels of silicone motherboards together using small sections of fused silica tubing, with no loss of stacking volume because of the lack of any connector lips or bosses. An array of micro channels having circular cross sections with diameters of 100, 150 and 200 microns were molded on silicone elastomer using wax thread. The wax thread was dissolved in acetone after the silicon elastometer became components (motherboards) while being able to control the channel lengths within the stacks as desired. Mixing chambers were also molded in a single silicone elastomer layer, because true three-dimensionality is trivially possible without the complexity of multi stacked lithography.
Buried optical channel waveguides integrated with a fluidic channel network on a planar microdevice are presented. The waveguides were fabricated using silica-on-silicon technology with the goal to replace bulk optical elements and facilitate various optical detection techniques for miniaturized total analysis systems or lab-on-a-chip systems. Waveguide structures with core layers doped with germanium were employed for fluorescence measurements, while waveguides with nitrogen- only doped core layers were used for absorbance measurements. By the elimination of germanium oxygen deficiency centers transmission of light down to 210nm was possible, allowing absorance measurements in the mid and far UV region (210 to 280nm), which is the region where a large number of different molecules absorb light. Robust, alignment-free microdevices, which can easily be hooked up to a number of light sources and detectors were used for fluorescence measurements of two dyes, fluorescein and Bodipy, and absorbance measurements of a stres-reducing drug, propranolol. The lowest detected concentrations were 250pM for fluorescein, 100nM for Bodipy and 12(mu) M for propranolol.
In addition to existing microfabrication technologies for the manufacturing of glass or silicon-based microfluidic devices, the increasing demand for polymer based systems requires the establishment of equivalent technologies for the microstructuring of polymers. These technologies can be divided into two fields, the structuring of the polymer itself and the subsequent back-end processes. This article describes a complete technology chain covering these two technology fields.
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.
An experimental system has been designed and constructed to conduct gas- solid heterogeneous catalytic reactions in microreactors. This apparatus is inteded to be used for any exothermic or endothermic reaction, including those with multiple feeds. It can be used to test the effectiveness of a microreactor design for a particular catalyst or to test the behavior of the catalyst itself. The system uses a test block that is plumbed for multiple feeds and vacuum to hold down a standard size microreactor chip. This chip has two exit vias, which includes one for the reactor effluent and one for the exit stream from a possible reactor membrane wall. The reactors are systems of channels with a smallest cross-dimension as small as 5 micrometers. The experimental system is equipped with temperature control and automatic data acquisition. The reactors can be stacked in order to scale up to higher throughput. A simulator has been developed that accounts for the unique physical aspects of reaction and flow in very small channels. Along with design, it assist in determining operating conditions and interpreting experimental results.
Microchip separations can achieve high resolution at speeds much faster than conventional capillary electrophoresis, due to the ability to inject a very small sample plug defined at the intersection of two channels. To achieve these benefits, separations must be carried in conditions where resolution is controlled by both sample plug size and by diffusion. Thus, to design an optimal microchip separation system, it is necessary to determine the diffusion coefficients of the species being separated. We propose a novel method to determine diffusion coefficients in separation systems. Since we have the ability to observe species at any point of the separation channel, we can measure the widening of a peak as a function of separation distance. This allows diffusion to be measured at a constant electric field, as opposed to varying the field to achieve different diffusion times at a fixed observation point. This distinction is important in cases such as DNA separations in polymeric sieving matrices, where the diffusion coefficient has been reported to be field-dependent. In this work, glass microchips with channels 10 micrometers deep and 30 micrometers wide were used for separations, at distances varying from 3 to 15 mm. Samples used were fluorescent molecules, single-stranded DNA oligos, and dsDNA. For the DNA samples, diffusion coefficients between 3.6 x 10- 7 and 4.2 x 10-8cm2/s were observed. For double-stranded DNA, we found that the diffusion coefficients increased strongly as the electric field was increased.
This paper focuses on two main subjects encountered in the design process fo the ducts working in the micro yard. They are: the achievement of the Poiseuille number P0 and the achievement of an analytical formula for the velocity field in the hydrodynamically developed flow. These subjects are dictated by the new technologies that support building hexagonal ducts etched in <100$GTRsilicon, an usual component of the structures operating in the fluid environment. Concerning the first subject, we develop a procedure for obtaining the Poiseuille number P0 versus that aspect ratio of the hexagonal cross section. The validity of this procedure is proven using different shapes of cross sections. We underline the merit of this procedure, namely the rather straightforward use of a commercial software package. Another subject detailed herein is the building of an approximative analytical formula for the velocity field inside hexagonal ducts. We detail two approaches and we discuss their limitations in practical circumstances encountered during the design process of a structure for determination of fluid and flow characteristics. The simple applicability of the inferred formulas contrasts with the classical and huge time consuming numerical approaches, these formulas being suitable tools in the design process of the structure operating in the micro world. The results presented in this paper might be adapted for similar structures operating in the macro world as well as for many other situations where devices containing ducts having various non-circular cross sections are present.
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.
We observe dielectrophoretic effects in mixed electrokinetic and dielectrophoretic flows in uniform arrays of posts. Above a threshold applied electric field, flowing filaments of concentrated and rarefied particles appear in the flow. Above a higher-threshold applied field, zones of highly concentrated, immobilized particles appear. At the lower and higher thresholds, dielectrophoresis apparently begins to dominate diffusion and advection/electrokinesis, respectively. The patterns of filaments and trapped zones depend dramatically on the angle of the array with respect to the mean applied electric field and the shape of the posts in the array.
This paper reports on a research effort to design, microfabricate and test an AC-type magnetohydrodynamic (MHD) micropump using UV-LIGA microfabrication. The micropump is driven using the Lorentz force and can be used to deliver electrically conductive fluids. In the AC-type MHD micropump developed in our laboratory, a diffuser/nozzle is integrated with a MHD driving chamber. With a magnetic field supplied by an external permanent magnet, and an AC electrical current supplied across two copper side-walls, the distributed body force generated will produce a pressure difference on the fluid in the pumping chamber. The directional dependence of the flow resistance of the diffuser/nozzle allows for a net output flow in response to the oscillating pressure generated by the sinusoidal current. The major advantage of a MHD-based micropump is that it does not contain any moving parts. It may have potential applications in medicine delivery, and biological or biomedical studies. An AC-driven micropump may be used to improve on the performance obtained in tests of a DC-driven prototype micropump, that showed pumping performance was significantly degraded by bubble generation.
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.
Electroporation is a technique with which DNA molecules can be delivered into cells in a chamber using high electric field pulses. The limited amount of target cells and the potential risk from the high voltage are the two drawbacks in this technique. This study aimed to fabricate an electroporation chip to manage large amount of cells continuously with a lower applied voltage. The electroporation chip, consisting of a micro-channel with thin film electrodes made of gold or platinum wire electrodes on both sides, was fabricated on PMMA material using evaporation, photolithography, wet- etching, lift-off, and fusion-bonding methods. The suspension fluid of Huh-7 cell lines (1 x 106 cells/ml) mixed with 10 micrometers plasmids equipped with lacZ genes in a volume of 500 (mu) l flowed through the channel with a variety of flow rates under a series of square pulses. The transfection rate was evaluated with blue-staining cells under X-Gal stain 24 hours later. The dimensions of the channel were 5 mm wide, 0.2 mm high, and 25 mm long. Two types of electrodes, parallel-plate type and parallel-line type electrodes, were fabricated and tested in these experiments. The fabricated microchip can deliver genes into the flowing of cells. The electric pulse frequency that determines the shock number for each cell for a fixed flow rate can be optimized for better transfection and survival rates.
Microfluidic devices have applications in chemical analysis, biomedical devices and ink-jets1. An integrated microfluidic system incorporates electrical signals on-chip. Such electro-microfluidic devices require fluidic and electrical connection to larger packages. Therefore electrical and fluidic packaging of electro-microfluidic devices is the key to the development of integrated microfluidic systems. Packaging is more challenging for surface micromachined devices than for larger bulk micromachined devices. However, because surface micromachining allows incorporation of electrical traces during microfluidic channel fabrication, a monolithic device results. A new architecture for packaging surface micromachined electro- microfluidic devices is presented. This architecture relies on two scales of packaging to bring fluid to the device scale (picoliters) from the macroscale (microliters). The architecture emulates and utilizes electronics packaging technology. The larger package consists of a circuit board with embedded fluidic channels and standard fluidic connectors. The embedded channels connect to the smaller package, an Electro-Microfluidic Dual-Inline-Package (EMDIP) that takes fluid to the microfluidic integrated circuit (MIC). The fluidic connection is made to the back of the MIC through Bosch2 etched holes that take fluid to surface micromachined channels on the front of the MIC. Electrical connection is made to bond pads on the front of the MIC.
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.
A micromachined fluidic sensor array for the rapid characterization of multiple analytes in solution has been developed. A simple micromachined fluidic structure for this biological and chemical agent detection system has been designed and fabricated, and the system has been tested. Sensing occurs via optical changes to indicator molecules that are attached to polymeric microspheres (beads). A separate charged-coupled- device (CCD) is used for the simultaneous acquisition of the optical data from the selectively arranged beads in micromachined etch cavities. The micromachined bead support structure has been designed to be compatible wit this hybrid optical detection system. The structure consists of four layers: cover glass, micromachined silicon, dry film photoresist, and glass substrate. The bottom three layers are fabricated first, and the beads are selectively placed into micromachined etch cavities. Finally, the cover glass is applied to confine the beads. This structure utilizes a hydrophilic surface of the cover glass to draw a liquid sample into the sensor array without moving components, producing a compact, reliable, and potentially low-cost device. We have initially characterized fluid flow through a complete chip, showing complete filling of the sample chamber in approximately 2 seconds. The test results show that this system may be useful in micro total analysis systems ((mu) - TAS), especially in single-use biomedical applications.
Over the past decade, there has been tremendous interest in developing miniaturized chemical analysis systems using microfabrication techniques. Microfluidic components such as pumps and valves form an integral part of such microsystems. Emerging biological assays like single molecule studies of DNA and cell adhesion analyses demand a robust pumping system that can deliver non-pulsatile flows at extremely low velocities. Several types of valved and valve-less pumps have been constructed on both silicon and glass substrates. However, most of the valved pumps involve moving parts and deliver pulsatile flow, while the valveless pumps employ high electric fields. In this paper, we describe the design, construction and operation of a microfabricated valveless micropump, for continuous pumping of reagents at controlled, ultra low flow velocities in the range of 50 micrometers /s. This novel pumping concept is based on pinning a liquid meniscus inside a microchannel by selective hydrophobic patterning and controlling the evaporation rate of the liquid at the meniscus. The resulting pumping action delivers non- pulsatile, low velocity flows that can find applications in a variety of biological assays involving single molecules.
Analytical and numerical methods are employed to investigate species transport by electrophoretic or electroosmotic motion in the curved geometry of a two-dimensional turn. Closed-form analytical solutions describing the turn-induced diffusive and dispersive spreading of a species band are presented for both the low and high Peclet number limits. We find that the spreading due to dispersion is proportional to the product of the turn included angle and the Peclet number at low Peclet numbers. It is proportional to the square of the included angle and independent of the Peclet number when the Peclet number is large. A composite solution applicable to all Peclet numbers is constructed from these limiting behaviors. Numerical solutions for species transport in a turn are also presented over a wide range of the included angle and the mean turn radius. Based on comparisons between the analytical and numerical results, we find that the analytical solutions provide very good estimates of both dispersive and diffusive spreading provided that the mean turn radius exceeds the channel width. These new solutions also agree well with data from a previous study.
The miniaturised Biofactory-on-a-Chip devices described here are integrated systems capable of the rapid analysis of small volume particulate samples and have applications in areas such as medical and biological cell diagnostics, chemical detection and water quality control. The devices use the A.C. electrokinetic phenomena of dielectrophoresis, travelling wave dielectrophoresis and electrorotation to manipulate, separate and characterise particle systems by exploiting their dielectric properties. Biofactory fabrication makes use of conventional photolithographic processes along with precision excimer laser ablation based micromachining. Using this combination of technologies, a wide range of manufacturing issues have been addressed and are discussed here. For instance, reliable interconnection of multilayer electrodes has been achieved using laser machining of via- holes between lithographically produced electrodues. Also, accurate fluidic microchannel systems with varying curved cross-sections that allow the smooth transport of a sample through the device whilst eliminating problems of particle trapping have been developed using excimer laser machining. Although the biofactory devices presented here have been applied to the fractionation of micro-organisms such as E. coli from red blood cells, the flexibility of design allows these devices to perform a wide range of complex bioprocessing function in a single, low-cost and miniaturised package.
Previously, we have reported the science and technology of micromachiend valves and orifices, and their integration to form high-performance mass-flow controllers (MFCs), and vacuum leak rate shut-off devices (SOVs). In this work, we expand the science and technology base of these devices, to include not only performance, but more practical aspects of their behavior. Specifically, for MFCs we have studied long-term drift, mean time tofail, particle generation, dry down after moisture contamination, gas replacement, effects of gravitational orientation, and sensitivity to inlet pressure and ambient temperature. For SOVs, we have studied mean time to fail, particle generation, dry down after moisture contamination, vacuum leak rate, and sensitivity to inlet pressure and ambient temperature.
This paper presents a high performance micropump based on the printed circuit board technology. This pump was our first effort to lower the packaging cost by combining functional elements (diffuser/nozzle) with packaging materials (PCB, inlet/outlet tubes). The paper presents in details the numerical simulation, the fabrication and the experimental characterization of the pump. Experimental results have shown a high pump performance. A flow rate of 3 ml/min can be achieved with a drive voltage of 120V. Pumps with different distances between inlet and outlet were tested. Characterization results agreed well with simulation results. Pumps with a short distance between inlet and outlet have a better performance.
Previous research has indicated that micropolar fluid theory may provide a better model of fluid flow in microfluidic devices than classical Navier-Stokes theory. Micropolar theory augments classical Navier-Stokes theory with additional equations that account for conservation of micro- inertia moments. In our work, a two-dimensional numerical model based on micropolar fluid theory is used to examine flow behavior in micro orifices. This particular flow geometry has many application within microfluidic systems and devices such as flow sensors and micro valves. The numerical model is validated by comparison to experimental data and an analytical solution determined for fully developed flow conditions in microchannels. The numerical model was used to examine the effect of orifice geometry on pressure drop and the size of the recirculation region. Simulations were performed for orifice contraction ratios of 0.2, 0.44, and 0.6. The numerical results indicate an increase in the pressure drop when compared to traditional macroscale theory predictions and a decrease in the size of the recirculation zones after the orifice. The results provide further evidence that micropolar fluid theory may provide a better approximation for the observed increases in friction that have been reported in the literature for experiments on microchannel flows.
This paper reports the design, fabrication and testing of silicon based micropump for liquid and gases. This piezoelectrically driven membrane pump is designed to be tolerant to gas-bubbles and to be suitable for self-priming. Reducing the dead volume within the pump, and thus increasing the compression ration, achieves the gas pumping. The main advantage of the pump described in the paper is the self-aligning of the membrane unit to the valve unit and the possibility of using screen printed PZT as actuator, which enables mass production and thus very low-cost micropumps. Dynamic passive valves are used, as those valves are very reliable having no moving parts and being not sensitive to smaller particles. Furthermore they can follow high frequencies, hence allowing the pump to run at resonance frequency enabling the maximum deflection of the diaphragm. First tests carried out on the micropump have produced promising results.
Silicon micromechanics in an emerging field which is beginning to impact almost every area of science and technology. In areas as diverse as the chemical, automotive, aeronautical, cellular and optical communication industries, Silicon micromachines are becoming the solution of choice for many problems. In this paper we will describe what they are, how they are built, and show how they have the potential to revolutionize lightwave systems. Devices such as optical switches, variable attenuators, active equalizers, add/drop multiplexers, optical crossconnects, gain tilt equalizers, data transmitters and many others are beginning to find ubiquitous application in advanced lightwave systems. We will show examples of these devices and describe some of the challenges in attacking the billions of dollars in addressable markets for this technology.
Silicon bulk micromachining which is based on a silicon etching and a glass-silicon anodic bonding plays important roles to make micro sensors and micro actuators. Three dimensional microfabrication of other functional materials as piezoelectric materials are also important to develop high performance microactuators, micro energy source and so on. Vacuum sealing is required to prevent a viscous dumping for packages micromechanical sensors. Extremely small structures as microprobe are required for high resolution, high sensitivity and quick response. As sophisticated microsystems which are made of many sensors, circuits and actuators are required for example for maintenance tools used in a narrow space. Developments for those required will be described.
The continuous progress in micro- and nano-system technologies has allowed the successful development of many innovative products in process control, environmental monitoring, healthcare, automotive and aerospace as well as information processing systems. In this paper on overview will be given of current progress in micro- and nanofabrication process technologies, such as deep reactive ion etching, micro-electro discharge machining, thick photoresistant processing and plating. The availibility of these micro- and nanofabrication processes will be illustrated with examples of new generations of silicon-based sensors, actuators and Microsystems with a particular emphasis on real applications of these components and systems.