Showing papers on "Micropump published in 1998"

Thin-film shape-memory alloy actuated micropumps

Abstract: Micropumps capable of precise handling of low-fluid volumes have the potential to revolutionize applications in fields such as drug delivery, fuel injection, and micrototal chemical analysis systems (/spl mu/TAS). Traditional microactuators used in micropumps suffer from low strokes and, as a result, are unsuitable for achieving large fluid displacement. They also suffer low-actuation work densities, which translate to low forces. We investigate the use of the shape-memory effect (SMA) in sputter-deposited thin-film shape-memory alloy (SMA) titanium nickel (TiNi) as an actuator for microelectromechanical systems (MEMS)-based microfluidic devices, as it is capable of both high force and high strains. The resistivity of the SMA thin film is suitable for Joule heating, which allows direct electrical control of the actuator. Two micropump designs were fabricated-one with a novel complementary actuator and the other with a polyimide-biased actuator-which provided thermal isolation between the heated microactuator and the fluid being pumped. A maximum water flow rate of 50 /spl mu/l/min was achieved.

A novel micromachined pump based on thick-film piezoelectric actuation

Abstract: A new silicon-based micropump is described in this paper. The key element of the device is a thick-film/silicon micromachined hybrid actuator. The actuation principle relies on the flexure of a screen printed piezoelectric lead zirconate titanate (PZT) layer on a silicon membrane (8 mm × 4 mm × 70 μm). An investigation into the deposition technology of the bottom electrode for the piezoelectric material showed that a gold resinate or Pt evaporated electrode on a 500 nm thick SiO 2 covered silicon wafer achieved best results for the membrane actuator. Inlet and outlet valves are of the cantilever type and use deep boron diffusion together with KOH etching. Pump rates of up to 120 μl min −1 have been achieved. A maximum backpressure of 2 kPa was measured when using a 600 V pp sinusoidal drive voltage at 200 Hz across a 100 μm thick PZT layer. The pump was compared with a conventional surface mounted piezoelectric driven micropump. The conventional pump achieves a performance which was a factor of 3–6 more efficient, but does not allow mass production.

Microdiffusers as dynamic passive valves for micropump applications

Abstract: A coherent empiro-theoretical approach to the flow behavior of micro diffuser channels is tried. Microdiffusers may be advantageously employed as dynamic passive valves in micropumps. The central number of merit is the rectification efficiency e which expresses the flow directing performance of a passive valve. It mainly depends on the aperture angle, relative channel length, throat rounding, flow velocity, and frequency. The highest ¦ e ¦ -value possible is around 0.25…0.4. The approach is mainly based on general investigations of energy conversion and experimental data from classical hydraulics. The derivations are compared with test results of different authors.

Robust design of gas and liquid micropumps

Abstract: Due to the small stroke of micro actuators, the compression ratio of micropumps is frequently small. This means that serious constraints exist for most micropump designs concerning self-priming capability and bubble tolerance. To access this problem in this study, criteria for the minimum compression ratio of a micropump are derived depending on the medium transported. It turns out that under real operation and handling conditions (outgassing, incomplete priming) design rules applicable for gas pumps also have to be used for liquid pumps. Next, if the liquid pump is to be able to prime itself, a critical pressure has to be achieved, which leads to a further increase of the necessary compression ratio. To determine this critical pressure, the surface and interfacial energies of the liquid have to be taken into account.

Micromachined magnetohydrodynamic actuators and sensors

Abstract: A magnetohydrodynamic (MHD) micropump and microsensor which utilizes micromachining to integrate the electrodes with microchannels and includes a magnet for producing magnetic fields perpendicular to both the electrical current direction and the fluid flow direction. The magnet can also be micromachined and integrated with the micropump using existing technology. The MHD micropump, for example, can generate continuous, reversible flow, with readily controllable flow rates. The flow can be reversed by either reversing the electrical current flow or reversing the magnetic field. By mismatching the electrodes, a swirling vortex flow can be generated for potential mixing applications. No moving parts are necessary and the dead volume is minimal. The micropumps can be placed at any position in a fluidic circuit and a combination of micropumps can generate fluidic plugs and valves.

A self-priming and bubble-tolerant piezoelectric silicon micropump for liquids and gases

Abstract: In this paper a novel silicon micropump for liquids and gases is presented, which is tolerant towards gas-bubbles and which is able to prime itself. The micropump is based on a piezoelectrically driven diaphragm actuator, which is combined with a valve unit consisting of two cantilever valves. The self-priming and bubble-tolerant operation mode was achieved by maximizing the compression ratio, which was realized by minimizing the dead volume of the valve unit as well as of the actuator unit and by maximizing the stroke volume of the pump diaphragm. The optimization of the actuator is based on simulations and experimental investigations of the pump diaphragm displacement. These studies yield the optimal dimensions of the pump diaphragm and the piezoactuator. The piezoelectrically actuated micropump was characterized by investigating the pump rate in dependence of the actuation frequency and the pressure on the inlet and the outlet port of the micropump. As essential results a maximum pumprate of 1 mY/min and a maximum backpressure of about I bar were measured for water. For gases the pumprate ranges up to 3 ml/min.

The dynamic micropump driven with a screen printed PZT actuator

Abstract: A hybrid actuated silicon-based micropump with dynamic passive valves is described in this paper. The actuator is based on a combination of thick-film and silicon micromachining technology and relies on the flexure of a membrane structure of lead zirconate titanate on silicon. Inlet and outlet valves use the passive dynamic principle, where flow direction is realized with a diffuser and a nozzle shaped element. Pump rates of up to 155 and a maximum backpressure of 1 kPa were achieved at a driving voltage of 600 . Additionally the fluidic modelling of the dynamic passive valves is described, using a CFD simulator. The results of the model agree well with device measurements.

Fabrication and experiment of a planar micro ion drag pump

Abstract: A micro ion drag pump with planar electrodes on a glass substrate is fabricated and tested. The pump consists of a planar electrode pair array driven by DC voltage using unipolar conduction. Ethyl alcohol is pumped in both directions, and the flow rate and the pressure are measured in channels of depth 100 μm or 200 μm and width fixed at 3 mm. It is found that the pump can be fabricated easily and at a lower cost than the micro ion drag pumps previously investigated.

A self-filling low-cost membrane micropump

Abstract: We present a new membrane micropump fabricated by micro mold injection and laser based techniques. Due to an innovative pump design featuring an extremely small internal volume and a large compression ratio the pumps are the first micropumps to combine outstanding technical performance with a really easy handling. The pumps work equally well with gases and liquids and exhibit a very reliable self-filling behavior with liquids. Pumping water we have achieved maximum pump rates of 400 /spl mu/l/min and a maximum back pressure of 2100 hPa. Using air the pumps can build up pressures of up to 500 hPa and generate a maximum flow rate of 3.5 ml/min. The maximum vacuum the pumps can create amounts to 350 hPa. Due to the use of replication based fabrication techniques and optimized assembly methods, the pump design has the potential for production costs on the order of 5 DM. The new micropump is being manufactured in a small series production and is available for industrial evaluation.

Valve-less diffuser micropumps

Abstract: Today there is growing interest in research on microfluidicsystems, e.g., for chemical analysis systems and microdosagesystems. One of the basic components in microfluidic systems ismicropumps. During recent years several different micropumpshave been presented based on different pump principles andusing different actuation principles. In this thesis the firstmicromachined versions of pumps based on the new valve-lessdiffuser pump principle are presented.The key element in the diffuser pump is the diffuserelement. A diffuser is a gradually expanding flow channelintended to raise the static pressure. The largest pressurerise is achieved for small opening angles. The diffuser elementis a diffuser with a rounded inlet and a sharp outlet. It ischaracterized by a lower flow resistance in the diffuserdirection than in the opposite direction, the nozzledirection.In the valve-less diffuser pump diffuser elements are usedas flow directing elements. One diffuser element is directedfrom the inlet chamber to the pump chamber and the otherdiffuser element from the pump chamber to the outlet chamber. Amoving boundary of the pump chamber forces the fluid throughthe two diffuser elements. The result is a net transport offluid from the inlet side to the outlet side due to thedifference in the flow resistances in the diffuser and nozzledirections.Pumps of different sizes for both liquids and gases havebeen fabricated in different materials using both conventionalfabrication methods and micromachining technology. Extensivemeasurements have been made to investigate the performance ofthe diffuser pumps. These results have been used together withnumerical simulations and classical fluid mechanics in order tounderstand the working principle of the diffuser pump and tofurther improve the design. Based on the empirical results andsimulations using a lumped-mass model improved designs aresuggested.All the tested pumps show good performance. The pump withthe best test result is fabricated in silicon using deepreactive ion etching (DRIE) which allows any arbitrary planardesign of the pump. A glass wafer is bonded to the pump cavityside of the silicon wafer. The pump diaphragms are excitedusing piezoelectric discs. The diffuser "throat" cross-sectionis 80×80 µm and the pump chamber diameter is 6 mm.The entire pump chip has a size of 15×17×1 mm. Forwater a maximum pressure head of 74 kPa was reached and amaximum volume flow of 2.3 ml/min was obtained.Keywords:micropump, valve-less pump, diffuser pump,diffuser elements, fluid, liquid, gas, microfluid system,KOH-etching, isotropic etching, deep reactive ion etching,micromachining, anodic bonding, bulk micromachining,Computational Fluid Dynamics, CFD, lumped-mass model.

Dynamic simulation of an electrostatic micropump with pull-in and hysteresis phenomena

Abstract: After presenting the role of micropumps in medical applications and demonstrating that an electrostatic micropump would seem to be the most appropriate, the geometrical and electrical static characteristics of this pump are summarized. Classical dynamic simulations do not take into account the pull-in effect or the hysteresis phenomenon, both of which appear in electrostatic micropumps. The novel principle of dynamic simulation, which includes these two non-linear characteristics, is then outlined; changes in pressure, volume, flow and current are also calculated. The last section displays the advantages associated with this global simulation.

Electrofluidic full-system modelling of a flap valve micropump based on Kirchhoffian network theory

Abstract: We describe a comprehensive methodology for setting up physically based consistent full-system models for the effort-economizing and yet accurate numerical simulation of microsystems and we demonstrate its practicality with reference to an electrofluidic micropump macromodel. In this approach, the microsystem is partitioned into functional blocks (lumped elements), which interact with each other as constituent parts of a generalized Kirchhoffian network. For each of them, a compact model with only a few degrees of freedom is formulated. This is achieved by using a flux-conserving discretization of the system of balance equations which govern the flow of the relevant physical quantities. In the case of a micropump, these quantities are the flows of volume, charge and momentum caused by the respective driving forces which, in continuum theory, are the gradients of the spatial distributions of pressure, voltage and velocity. In this sense, generalized Kirchhoffian network theory is the discrete counterpart of continuum transport theory and relies on the same basic physical conservation laws as described by the principles of irreversible thermodynamics. An adequate formal representation of the system description is provided by an appropriate analog hardware description language such as VHDL-AMS, as it allows the models of the individual system components to be coded as well as the full system to be assembled by linking the constituent parts. Again, the general principles underlying our approach are exemplified by a full-system transient analysis of our benchmark problem, the electrostatically driven micropump.

Hybrid-assembled micro dosing system using silicon-based micropump/ valve and mass flow sensor

Abstract: This paper presents a hybrid-assembled bidirectional micro dosing system for a water flow range of −40 μl/min to 80 μl/min. The system consists of a silicon micropump/valve chip (9 mm × 9 mm), a silicon flow sensor (6 mm × 12 mm) and a piezoelectric as well as an electrostatic actuator. The technology of each component and the hybrid assembly of the whole system are described. Results of numerical simulation of the micropump/valve and the mass flow sensor are presented and compared with experimental results. The new pulse-width-modulated control method for the actuator makes controlling the system easier.

Hydro-Acoustics of Piezoelectrically Driven Ink-Jet Print Heads

Abstract: The hydrodynamical heart of an ink-jet printer is the print head, in which a large number of miniature valveless pumps are integrated. Each pump, when actuated electrically, delivers exactly one droplet of a specified flight direction, speed and size (drop-on-demand: DOD). In studies of the behaviour of miniature pumps only one pump is usually considered. The issue discussed in this paper is: do size and velocity of a droplet depend on the design of the print head? To answer this question we modelled the print head as a number of identical Helmholtz resonators, all connected to a main supply channel. The main supply channel was connected to the ink reservoir through a hose pillar and was also modelled as a Helmholtz resonator. The behaviour of such a manifold of Helmholtz resonators was analysed in both the frequency and the time domain. The paper concerns the hydro-acoustics and hydrodynamics of piezoelectrically activated ink-jet print heads.

Piezoelectric mechanical pump with nanoliter per minute pulse-free flow delivery for pressure pumping in micro-channels

Abstract: A novel computer-controlled mechanical syringe pump is described which uses a piezoelectric actuator and a pivoted lever for amplification of the linear displacement of the piezo-actuator to deliver solvents free from pump pulsations at volumetric flow rates approaching 1 nl min–1 even at high loading levels (high output pressures). The flow patterns can be programmed by controlling the voltage waveform to the piezo-actuator to produce a linear displacement of 72 µm. By using the pivoted lever, a ninefold amplification of the piezo-expansion was achieved producing a total linear displacement of 648 µm. When a gas-tight glass syringe of 1.0 mm diameter was interfaced to the piezo-pump, the total volume delivered in a single pump stroke was 511 nl. Whereas the pumping profile was governed by the expansion behavior of the piezoelectric actuator, the flow rate was also slightly affected by the loading pressure on the pump as well. The piezo-pump was found to deliver adequately a stable flow of solutions with loading pressures as high as 3.79 × 105 Pa (actual loading pressure at the piezo-actuator = 3.41 × 106 Pa). Monitoring the flow stability using fluorescence indicated that the volume flow was fairly noise free at pumping rates from 4 to 150 nl min–1. Below a volume flow rate of 4 nl min–1, the pump exhibited extensive noise characteristics due to the step resolution of the DAC driving the piezo-actuator. A diffuser–nozzle system was fabricated which allowed automatic refilling of the syringe pump and was micromachined into Plexiglas (PMMA) using X-ray lithography. The diffuser–nozzle system contained channels that were 50 µm in depth and tapered from 300 to 30 µm. The diffuser–nozzle system was interfaced to the syringe pump by connecting conventional capillary tubes to the PMMA-based diffuser–nozzle, the piezo-pump and the chemical analysis system.

AMANDA—low-cost production of microfluidic devices

Abstract: AMANDA is a process that allows the production of microfluidic devices by molding of the device housings, surface micromachining of a diaphragm, and transferring it to the molded parts. Various devices have been produced with AMANDA, and the reliability of the process was proven in a small-scale production line for the manufacture of micropumps showing a yield of 70%. Low-cost production is achieved by batch fabrication of polymer devices. A further reduction of expenditure appears to be feasible by miniaturizing the devices and enlarging the batches. Long-term investigations show that the diaphragms of pumps and valves may stand more than 300 million deflections. For example, one micropump pumped unfiltered room air for nearly half a year at 20 Hz. During all tests, no defect of a valve and no clogging of a pump occurred. In any case of failure, the pumps were damaged by a crack in the heater of the thermo-pneumatic actuator. Folds in the diaphragm appear to be responsible for these cracks.

Electrohydrodynamic Pumps for High-Density Microfluidic Arrays

Abstract: We have developed electrohydrodynamic (EHD) pumps for fluid delivery in high-density microfluidic arrays as part of a drug discovery collaboration with Orchid Biocomputer, Inc. and SmithKline Beecham Pharmaceuticals. The multi-layer array structures are fabricated in glass and silicon, and have no moving parts. Each pump is comprised of two planar-processed, conductive via electrodes that are in contact with fluid inside the array. Typical applied voltages (300–500 V) result in pressures on the order of inches of water. EHD pumping in microfluidic array chips has been demonstrated and characterized for flow direction and relative pumping efficiency with more than one hundred different organic solvents and solvent-reagent compounds. A basic theory for the phenomena is presented, and quantitative velocity measurements for some representative solvents are shown.

Micromotors, linear motors, micropumps, methods of using the same, microactuators, methods of controlling flow properties of fluids, and apparatuses for controlling flow properties of fluids

Abstract: The present invention provides a use of an electro-sensitive movable fluid, that is, a micromotor, a linear motor, a micropump and a method of using the micropump, a microactuator, and an apparatus which these devices are applied to, and a method and an apparatus of controlling flow properties of a fluid.

The study of single-chip integrated microfluidic system

Abstract: A novel single-chip integrated microfluidic system is presented. After 3D structures are formed with deep cavities and stiff mechanical membrane as sealing layer in single-chip, additional standard IC processes are applied to achieve single-chip integrated microfluidic systems, including micropumps, valves, channels, cavities and some different sensors. We have applied different principles, bimetallic and electrostatic driving, to the driving and control of the micropumps and microvalves. The final micropump driving membrane is 1 mm/spl times/1 mm/spl times/2 /spl mu/m and the valve membrane is 6 mm/spl times/0.6 mm/spl times/2 /spl mu/m. Preliminary experiments show that the on/off flow ratio of the integrated micropump is 180. The results of the sensitivity and the temperature coefficient of the sensors are also reported.

A Silicon Micropump with a High Bubble Tolerance and Self-Priming Capability

Abstract: In this paper we present a silicon micro diaphragm pump for liquids and gases with self-priming and bubble-tolerant operation characteristics. The micropump consists of two passive check valves at the inlet and outlet port and a piezoelectrically actuated pump diaphragm. The micro fluidic device is designed to yield a pumprate of about 1ml/min for water and 3.8 ml/min for gases. The self-priming and bubble-tolerant operation mode was achieved by enlarging the compression ratio of the micropump. These measures yield on an easy-to-use device for industrial and research applications. Furthermore a miniaturized driver electronic driver for the piezoelectrically actuated micropump will be presented. With dimensions of 30×l3,5×8 mm3 the electronic allows the use of the micropump for portable and/or miniaturized analysis systems or measurement systems and is distinguished by high flexibility.

Manufacturing of Self-Priming Plastic Micropumps

Abstract: Micropumps will be key components in tomorrow’s miniaturized chemical analyzers and drug delivery systems as well as in consumer products In this paper a recently developed plastic micropump that was manufactured using conventional technologies, ie injection molding, is described By applying well known techniques and ‘off the shelf’ materials flexible and economic fabrication of micropumps for various applications is feasible even at low production volumes The resulting pumps were self-priming and pump liquid at flow rates up to 2 ml/min and gases at around 4 ml/min The maximum back-pressure reached is 125 hPa

Micropump for viscous liquids and muds

Abstract: This work was focused on the development of a micropump that allows the transport of fluids with high viscosities or fluids containing pigments in a large amount. This new pump should be produced by means of silicon micromachining technologies. Due to adhesion forces as well as sedimentation processes the transport of highly viscous and particle loaded fluids is a difficult problem. Dead volumes must be surely avoided in the pump because they are preferred regions of adhesion and sedimentation, respectively. The developed micropump is nearly free of dead volumes. It consists of silicon chips and a PTFE-membrane bonded together without real gluing procedures. The silicon chips contain deep etched structures manufactured by simple wet chemical etching procedures. Pressure on the liquid can be generated inside the structures by pushing the elastic membrane. A pneumatic drive was used to deflect the membranes. In a peristaltic mode it was possible to pump liquids like honey or mustard with a noticeable flow rat up to 0.6 ml/min without any back flow.

Impedances for Design of Microfluidic Systems

Abstract: System analysis is essential for accurate design of complex microfluidic systems. For instance, lumped-parameter system models of micropumps with no-moving-parts (NMP) valves need fluid elements that represent the separated, oscillating, laminar flow that occurs in these valves. No experimental or analytical method is currently available to determine the impedance of this type of flow. A numerical method for deriving NMP valve impedance has been developed, based on an extension of analytical methods for channels of non-varying cross-section. The resistance and inertance calculated are 20% lower than for a straight rectangular channel of equivalent length.

Transient measurement of surface deflection for beams and membranes in micromechanical devices

Abstract: This paper deals with the application of laser- interferometric vibration measurement for experimental characterization of beams and membranes in micromechanical devices. Such small structures are used in many sensor and actuator applications, where they represent the functional key elements. Due to the down-scaled geometrical size and to the fabrication process, the behavior is strongly influenced by many interactions and cross-coupling effects, which are extremely difficult to describe by theoretical models. For demonstration, two different examples are examined: a piezoelectric driven micropump and a 2D-scanning mirror device. The measured data can be compared to the simulated behavior of the structures, and contains important information for the optimum design of the devices. The two main conclusions are, that firstly certain effects of these devices can not be described by theoretical models alone, but have to be combined with experimental measurements, and secondly, that the deflection curvature of the structures must be determined by scanning rather than single-point measurements.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Computational fluid dynamics modeling of flexural plate wave pumps

Abstract: This paper presents design issues and a numerical model of a micromachined pump based on acoustic streaming in water. Influences of channel height, wave amplitude, and backpressure on the velocity profile and flow rate are investigated. Using these results, design rules for the acoustic micropump are derived. Thermal transport effects of the acoustic streaming are also discussed in order to integrate a thermal flow sensor into the pump or to apply the pump for cooling purposes.

A PZT-driven micropump

Abstract: The design, fabrication and characterization of a PZT-driven micropump is presented in this paper. It consists of a chamber, a membrane, two microvalves and a driving mechanism. The thickness of the micropump membrane is 11 /spl mu/m. The micropump chamber is round with diameter of 5 mm and depth of 0.4 mm. The microvalves made of single crystallite silicon are used on this micropump as flow direction control elements. The dimension of the valve cover is 1.5 mm/spl times/1.0 mm/spl times/7.4 /spl mu/m and dimension of the valve opening is 200 /spl mu/m/spl times/200 /spl mu/m. Its capability of flow is more than 10 ml/min at a pressure level of about 10 kPa. The open pressure in the obverse direction is less than 200 Pa while the leakage of reverse direction is almost zero. The features of the microvalve fit the requirement of the micropump well. When the micropump chamber chip and two valve chips are assembled together as a micropump, this micropump is mounted on a metal base and then the PZT bimorph cantilever is mounted above the micropump membrane. The maximum flow rate of the micropump is 365 /spl mu/l/min under 100 V, 20 Hz square wave power supply and zero pressure fall. The back pressure is 2.38 kPa and the flow control precision is better than 1 /spl mu/l.