Showing papers on "Micropump published in 2005"

Design and simulation of a novel electrostatic peristaltic micromachined pump for drug delivery applications

Abstract: A novel electrostatic micromachined pump for medical applications is designed and simulated. The proposed structure for the micropump consists of an input and an output port, three membranes, three active membrane valves, microchannels, and three electrostatic actuation systems. Pumping mechanism of the proposed micropump is based on the peristaltic motion that has some advantages, such as high controllability and precision, over the other mechanism that makes it suitable to be used for the medical applications. Electrostatic actuation has been employed for the deflection of the membranes because of its benefits, such as the smaller size of the device in comparison with the other types, especially piezoelectric counterpart and so on. Employing active membrane valves instead of passive check valves resolves some of the problems, such as valve clogging and leakage. The designed micropump satisfies all medical drug delivery requirements, such as drug compatibility, flow rate controllability, self-priming, small chip size, and low power consumption. The flow rate of the designed micropump is 9.1 μl/min which is quite suitable for drug delivery applications, such as chemotherapy. Total size of the designed micropump is 7 mm × 4 mm × 1 mm, which is smaller than the other peristaltic counterpart micropumps. Assuming zero residual stress, low actuation voltage, and small size are the main advantages of our design. The designed micropump is simulated by the finite element method, using the ANSYS 5.7 software.

Design and test of a high-performance piezoelectric micropump for drug delivery

Abstract: With a micropump, the release rate of drug delivery is able to be controlled easily to maintain the therapeutic efficacy. A high-performance piezoelectric cantilever-valve micropump was investigated for this purpose. The effect of valves on the output performance of the PZT micropump was analyzed at first. With taking into account the influence of liquid added mass and added damping on the natural frequency of the valves and actuator, the design method of the cantilever valve was presented. Two micropumps were designed and fabricated for comparing experiments. The micropump with cantilever valves 2.5 mm in length obtained higher output values (the maximum flow rate and backpressure is 3.5 ml/min and 27 kPa, respectively) and had two optimal frequencies (0.8 and 3 kHz). While the micropump with cantilever valves 4.5 mm in length had only one optimal frequency (0.2 kHz), at which the micropump achieved lower output values (the maximum flow rate and backpressure is 3.0 ml/min and 9 kPa, respectively). The study results suggest that the output values and optimal frequency of micropump can be improved by the design of the cantilever valves.

A PMMA valveless micropump using electromagnetic actuation

Abstract: We have fabricated and characterized a polymethylmethacrylate (PMMA) valveless micropump. The pump consists of two diffuser elements and a polydimethylsiloxane (PDMS) membrane with an integrated composite magnet made of NdFeB magnetic powder. A large-stroke membrane deflection (~200 μm) is obtained using external actuation by an electromagnet. We present a detailed analysis of the magnetic actuation force and the flow rate of the micropump. Water is pumped at flow rates of up to 400 µl/min and backpressures of up to 12 mbar. We study the frequency-dependent flow rate and determine a resonance frequency of 12 and 200 Hz for pumping of water and air, respectively. Our experiments show that the models for valveless micropumps of A. Olsson et al. (J Micromech Microeng 9:34, 1999) and L.S. Pan et al. (J Micromech Microeng 13:390, 2003) correctly predict the resonance frequency, although additional modeling of losses is necessary.

A magnetically driven PDMS micropump with ball check-valves

Abstract: In this paper, we present a low-cost, PDMS-membrane micropump with two one-way ball check-valves for lab-on-a-chip and microfluidic applications. The micropump consists of two functional PDMS layers, one holding the ball check-valves and an actuating chamber, and the other covering the chamber and holding a miniature permanent magnet on top for actuation. An additional PDMS layer is used to cover the top magnet, and thereby encapsulate the entire device. A simple approach was used to assemble a high-performance ball check-valve using a micropipette and heat shrink tubing. The micropump can be driven by an external magnetic force provided by another permanent magnet or an integrated coil. In the first driving scheme, a small dc motor (6 mm in diameter and 15 mm in length) with a neodymium–iron–boron permanent magnet embedded in its shaft was used to actuate the membrane-mounted magnet. This driving method yielded a large pumping rate with very low power consumption. A maximum pumping rate of 774 µL min−1 for deionized water was achieved at the input power of 13 mW, the highest pumping rate reported in the literature for micropumps at such power consumptions. Alternatively, we actuated the micropump with a 10-turn planar coil fabricated on a PC board. This method resulted in a higher pumping rate of 1 mL min−1 for deionized water. Although more integratable and compact, the planar microcoil driving technique has a much higher power consumption.

Plastic micropump with ferrofluidic actuation

Abstract: We present the realization and characterization of a new type of plastic micropump based on the magnetic actuation of a magnetic liquid. The pump consists of two serial check-valves that convert the periodic motion of a ferrofluidic plug into a pulsed quasi-continuous flow. The ferrofluid is actuated by the mechanical motion of an external NdFeB permanent magnet. The water-based ferrofluid is synthesized in-house using a coprecipitation method and has a saturation magnetization of 32 mT. The micropump consists of various layers of polymethylmethacrylate (PMMA), which are microstructured by powder blasting or by standard mechanical micromachining techniques, and are assembled in a single plastic structure using a monomer gluing solution. Two soft silicone membranes are integrated in the microfluidic structure to form two check-valves. Water has been successfully pumped at flow rates of up to 30 /spl mu/L/min and pumping is achieved at backpressures of up to 25 mbar.

Fabrication of a peristaltic PDMS micropump

Abstract: This paper presents fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force. The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port. The micropump is fabricated by the spin-coating process, the two-step curing process, the molding process using negative photoresist, etc. The diameter and the thickness of the actuator diaphragm are 2.5 mm and 30 μm, respectively. The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micropump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about 0.36 μL/s at 2 Hz for the zero hydraulic pressure difference, when the three-phase input voltage is 20 V.

A high current density DC magnetohydrodynamic (MHD) micropump

Abstract: This paper describes the working principle of a DC magnetohydrodynamic (MHD) micropump that can be operated at high DC current densities (J) in 75-µm-deep microfluidic channels without introducing gas bubbles into the pumping channel. The main design feature for current generation is a micromachined frit-like structure that connects the pumping channel to side reservoirs, where platinum electrodes are located. Current densities up to 4000 A m–2 could be obtained without noticeable Joule heating in the system. The pump performance was studied as a function of current density and magnetic field intensity, as well as buffer ionic strength and pH. Bead velocities of up to 1 mm s–1(0.5 µL min–1) were observed in buffered solutions using a 0.4 T NdFeB permanent magnet, at an applied current density of 4000 A m–2. This pump is intended for transport of electrolyte solutions having a relatively high ionic strength (0.5–1 M) in a DC magnetic field environment. The application of this pump for the study of biological samples in a miniaturized total analysis system (µTAS) with integrated NMR detection is foreseen. In the 7 T NMR environment, a minimum 16-fold increase in volumetric flow rate for a given applied current density is expected.

A ball valve micropump in glass fabricated by powder blasting

Abstract: We present the microfabrication and characterization of a ball valve micropump in glass, which is magnetically actuated using the sinusoidal current of an external electromagnet. We employ the use of a simple powder blasting technology for microstructuring the glass substrates and fusion bonding for assembly of the multi-layered microfluidic chip. The use of a polymer membrane with embedded permanent magnet gives rise to a large actuation stroke, making the micropump bubble-tolerant and self-priming. The micropump exhibits a backpressure as high as 280 mbar and water flow rates up to 5 mL/min thanks to the large magnetic actuation force and the use of high-efficiency ball valves. The frequency-dependent characteristics are in excellent agreement with a hydrodynamic damped oscillator model.

Improvements in Fixed-Valve Micropump Performance Through Shape Optimization of Valves

Abstract: The fixed-geometry valve micropump is a seemingly simple device in which the interaction between mechanical, electrical, and fluidic components produces a maximum output near resonance. This type of pump offers advantages such as scalability, durability, and ease of fabrication in a variety of materials. Our past work focused on the development of a linear dynamic model for pump design based on maximizing resonance, while little has been done to improve valve shape. Here we present a method for optimizing valve shape using two-dimensional computational fluid dynamics in conjunction with an optimization procedure. A Tesla-type valve was optimized using a set of six independent, non-dimensional geometric design variables. The result was a 25% higher ratio of reverse to forward flow resistance (diodicity) averaged over the Reynolds number range 0

A membrane micropump electrostatically actuated across the working fluid

Abstract: A novel electrostatically actuated valveless micropump is presented whereby an actuation voltage is applied across a working fluid, which takes advantage of the higher relative electrical permittivity of water and many other fluids with respect to air. The device is fabricated in silicon and the diaphragm is made of electroplated nickel, while the assembly is carried out using flip–chip bonding. A reduced-order model is used to describe the micropump's performance in terms of electrical properties of the fluid, the residual stress in the diaphragm, geometrical features and the actuation voltage. The tested prototype featured a ~1 µl min−1 flow rate at 50 V actuation voltage. The model predictions show the possibility of achieving flow rates >1 µl min−1 with the actuation voltage <10 V for devices with 3 mm diaphragm size.

A disposable thermopneumatic-actuated micropump stacked with PDMS layers and ITO-coated glass

Abstract: A thermopneumatic-actuated polydimethylsiloxane (PDMS)-based micropump has been fabricated and its properties have been characterized. Diffusers are used as flow-rectifying elements instead of passive check valves. The advantages of the proposed micropump are the low cost fabrication process and the transparent properties of the PDMS and indium tin oxide (ITO)-coated glass. We present a PDMS micropump that is easily integrated with in-channel PDMS microvalves on the same substrate. The flow rate of the micropump increases linearly with increasing applied pulse voltage to the ITO heater with resistance of 6.54 kΩ. The peak flow rate of 78 nl/min is observed at the duty ratio of 10% for the applied pulse voltage of 55 V at 6 Hz.

Simulation of a piezoelectrically actuated valveless micropump

Abstract: This paper numerically studies the performance of a piezoelectrically actuated valveless micropump with consideration of the three-way electro–mechanical–fluid couplings. Simulation of the piezoelectrically actuated valveless micropump (PVAM) indicates that both the pumping rate and the membrane deflection amplitude increase with the increase of the actuating frequency in a low frequency range ( 7.5 kHz). At even higher frequencies (>50 kHz), the pumping rate decreases further because the deflection amplitude decreases. This agrees with reported experimental results. The changing membrane deflection shapes at various frequencies clearly play an important role in the performance of the pump.

Piezoelectrically actuated dome-shaped diaphragm micropump

Abstract: This paper describes a piezoelectric micropump built on a dome-shaped diaphragm with one-way parylene valves. The micropump uses piezoelectric ZnO film (less than 10 /spl mu/m thick) to actuate a parylene dome diaphragm, which is fabricated with an innovative, IC-compatible process on a silicon substrate. Piezoelectric ZnO film is sputter-deposited on a parylene dome diaphragm with its C-axis oriented perpendicular to the dome surface. Two one-way check valves (made of parylene) are integrated with a piezoelectrically actuated dome diaphragm to form a multi-chip micropump. The fabricated micropump (10/spl times/10/spl times/1.6 mm/sup 3/) consumes extremely low power (i.e., 3 mW to pump 3.2 /spl mu/L/min) and shows negligible leak up to 700 Pa static differential pressure.

Experimental study and modeling of polydimethylsiloxane peristaltic micropumps

Abstract: We present here an experimental study of three-valve peristaltic micropumps fabricated using polydimethylsiloxane multilayer soft lithography, along with a simple model representing their behavior. Variations of the generated flow rate with peristaltic cycle frequencies, design parameters, actuation pressures, and fluid viscosities are analyzed experimentally for a set of ten micropumps. The largest flow rates are obtained for particular “optimal” basic parameters (actuation pressures and cycle frequencies) that depend on design features. A single-valve model, based on nonlinear equivalent electrical circuits, is numerically and analytically solved in relevant cases, leading to qualitative and quantitative agreements with experiments. From this theoretical study, useful predictive rules are deduced for pump design. The maximum flow rate we could achieve is 7.5μL∕min, one order-of-magnitude improvement compared to the highest level reported for this particular type of micropump. The design of the actuation...

Development of an electrohydrodynamic injection micropump and its potential application in pumping fluids in cryogenic cooling systems

Abstract: Cryogenic cooling has become a widely adopted technique to improve the performance of electronics and sensors. A potential application of an electrohydrodynamic (EHD) pumping system is its use in pumping fluids in cryogenic cooling systems. In this paper, we present the results of a theoretical/experimental investigation to study the feasibility of using an EHD injection micropump for pumping liquid nitrogen. First, the mechanisms of charge transport and ionization phenomenon in cryogenic liquids are discussed. Next, the design and fabrication of an EHD injection micropump that employs an array of interdigitated saw-tooth/plane electrodes are described. Finally, experimental results and observations are presented. An asymmetric saw-tooth/plane geometry was designed to achieve a strong inhomogeneous electric field. Each emitter electrode had a base width of 10 /spl mu/m. Each tooth on the emitter electrode had a base length of 10 /spl mu/m with a tip angle of 60/spl deg/. The collector electrode consisted of a planar strip with a width of 10 /spl mu/m. The gap between emitter and collector electrodes was 20 /spl mu/m. The distance between each neighboring stage (a pair of emitter and collector electrodes) was 40 /spl mu/m. The patterned area was 10 mm by 20 mm allowing approximately 200 stages to be fabricated along the length of the micropump. The maximum pressure head achieved by this micropump in the absence of a net flow was 550 and 205 Pa for 3M's HFE-7100 thermal fluid and liquid nitrogen, respectively. Also, the maximum mass flow rate was 3.9 g/min at the generated pressure of 180 Pa during a closed loop test with HFE-7100.

Fabrication and test of a micro electromagnetic actuator

Abstract: This paper presents the fabrication, test results and the finite element analysis of an electromagnetic micro actuator with three diaphragms that can be driven individually. The actuator consists of parylene diaphragms, spiral copper coils and permanent magnets. Parylene is waterproof and its Young’s modulus is small compared with metals, silicon and silicon compounds. So, it is adequate for the actuator diaphragm of a micropump. The static and dynamic characteristic tests are performed. The static deflections of the flat diaphragm and the corrugated one are 15 and 30 μm at 1 Hz, respectively, when the input current amplitude is 100 mA and the duty ratio is 50%.

A generic analytical model for micro-diaphragm pumps with active valves

Abstract: We present a fully analytical model for micro-diaphragm pumps with active valves, based on the peristaltic working principle Our model is suited for very fast as well as for very slow actuation mechanisms Therefore it can be applied to a variety of actuation principles, eg piezoelectric, pneumatic, thermo-pneumatic or pre-stressed shape memory actuation We show that the dynamics of this kind of micropump can be fully described by a lumped element approach taking only the mechanical behaviour of the diaphragms and the viscous losses at the valves into account The full flow versus frequency and backpressure characteristic is derived Our model is capable of predicting the maximum achievable flow rate and the maximum sustainable backpressure of micro-diaphragm pumps with active valves Different modes of operation, which are distinguished by the speed of the actuation mechanism, the pressure history inside the pump and the applied driving scheme, are identified We show that micro-diaphragm pumps with active valves generally suffer from a linear dependence of the flow rate on the applied backpressure This fact, which is already known from micropumps with passive valves, is remarkable, because it is in contradiction to the characteristics of macroscopic peristaltic pumps A set of design rules for the dimensioning of the valves in dependence on the actuation force and the desired hydrodynamic characteristics (maximum flow rate and maximum sustainable backpressure) are derived Our theoretical results are proven by experimental results of our piezoelectrically actuated micropump A maximum flow rate of 14 ml min−1 and a maximum sustainable backpressure of 40 kPa were achieved

A microfluidic ‘blinking bubble’ pump

Abstract: The paper reports data obtained on a simple micropump, suitable for electrolytes, based on the periodic growth and collapse of a single vapor bubble in a microchannel. With a channel diameter of the order of 100 µm, pumping rates of several tens of µl/min and pressure differences of several kPa are readily achieved by the system. The pump is notable for its effectiveness, simplicity, absence of mechanical moving parts, robustness and low cost. In the absence of a complete theory for the device, the data are interpreted and rationalized on the basis of simple physical arguments. It is also shown how the pump can induce strong mixing in two channels coming together at a Y-junction.

A polymeric paraffin actuated high-pressure micropump

Abstract: Abstract We present the potentially strongest mechanical micropump in sub-cm3 size yet for microfluidics, using simple processes and materials such as epoxy, paraffin and polyimide. Utilizing the large volume expansion associated with the melting of paraffin for actuation, a pump consisting of two active valves and one pumping chamber operated by three identical paraffin actuators has been realized with a rapid prototyping process. The main construction material is UV curable epoxy, which encloses the paraffin, forms the channel structure and joins the glass cover, actuator membrane and resistive heaters for melting the paraffin. With water as a pumping fluid and a low voltage waveform, a flow rate of 74 nl/min was obtained. The valves were subjected to pressures up to about 1 MPa without showing any leakage.

A novel electro-osmotic pump design for nonconducting liquids: theoretical analysis of flow rate-pressure characteristics and stability

Abstract: We present the design and theoretical analysis of a novel electro-osmotic (EO) pump for pumping nonconducting liquids. Such liquids cannot be pumped by conventional EO pumps. The novel type of pump, which we term the two-liquid viscous EO pump, is designed to use a thin layer of conducting pumping liquid driven by electro-osmosis to drag a nonconducting working liquid by viscous forces. Based on computational fluid dynamics, our analysis predicts a characteristic flow rate of the order nL/s/V and a pressure capability of the pump in the hPa/V range depending on, of course, achievable geometries and surface chemistry. The stability of the pump is analyzed in terms of the three instability mechanisms that result from shear-flow effects, electrohydrodynamic interactions and capillary effects. Our linear stability analysis shows that the interface is stabilized by the applied electric field and by the small dimensions of the micropump.

Single-disk and double-disk viscous micropumps

Abstract: The development and testing of two versions of a novel micropump are described: (i) the single-disk viscous pump and (ii) the double-disk viscous pump. The rotational movement of the disk(s) induces viscous stresses on the fluid that forces the fluid from an inlet channel, and then, through the pumping volume above the single disk, or between the two disks. A wiper acts to “wipe” the fluid from the disk(s) toward the outlet channel. The fluid flow through the double-disk pump is visualized using a red Rhodamine dye that is injected into the fluid passage upstream of the pumping volume. These visualizations provide information on the relative importance of viscous forces, centrifugal forces, and static pressure variations. The maximum flow rates and pressure rises are 1.0 ml/min, 643 Pa, and 2.1 ml/min 1.19 kPa for the single-disk and double-disk pumps, respectively, for a rotational speed of 5000 rpm, a disk diameter of 2.38 mm, and a gap height of 103 μm, and supplied power to the motor of 7 W. The disk pumps are fabricated using precision machining techniques employed on a lathe and milling machine. Advantages of the viscous disk pumps include: simplicity of design, planar structure, continuous flow, well controlled flow rate, and, if desired, the ability to augment mixing in the fluid.

Development, characterization, and theoretical evaluation of electroactive polymer-based micropump diaphragm

Abstract: A micropump diaphragm, based on the high energy electron irradiated poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)), an electroactive polymer (EAP), has been developed for air dynamic flow control. Its displacement stroke, profiles, and volume stroke rate (the volume change rate) have been characterized as a function of the electric field and the driving frequency. The displacement at the center of the diaphragm can reach 21 μm at 106 V/μm with the driving frequency of 10 Hz. The dispersion of the displacement is less than 30% for more than four frequency decades (0.1–1000 Hz). The characteristics of the electroactive polymer micropump diaphragm (EAPMPD) have also been theoretically evaluated. The volume rate of the EAPMPD can be 550 μL/min at 80 V/μm with the frequency of 1000 Hz. This study demonstrates that the volume rate of the diaphragm is high, and either the amplitude or the frequency of the applied electric field can tune it. In addition, when the performance of the diaphragm is modeled, the agreement between the theoretical results and the experimental data validates that the modeling provides an effective tool to guide EAPMPD design for an optimized performance. The results demonstrate that the diaphragm can be a candidate for aerospace applications to replace the traditional complex mechanical systems, increase the control capability, and reduce the weight for future air dynamic control systems.

A novel valveless micropump with electrohydrodynamic enhancement for high heat flux cooling

Abstract: Integrated microchannel cooling systems, with micropumps integrated into microchannels, are an attractive alternative to stand-alone micropumps for liquid-cooled microchannel heat sinks. A new micropump design capable of integration into microchannels and especially suited for electronics cooling is presented. It combines induction electrohydrodynamics (EHD) with a valveless nozzle-diffuser micropump actuated using a vibrating diaphragm. A comprehensive numerical model of the micropump has been developed to study the combined effect of EHD and valveless micropumping. The numerical model has been validated using theoretical and experimental results from the literature. The flow rate achievable from the new micropump is presented and the effect of several key parameters on the micropump performance investigated.

'Blinking bubble' micropump with microfabricated heaters

Abstract: A micropump based on the periodic growth and collapse of a single vapor bubble in a microchannel is described The bubble is generated by a vacuum-deposited platinum heater on a quartz chip The pump is formed by bonding to the chip an acrylic cover with input and output ports in which a 125 µm channel is machined Pumping rates on the order of 10 µl min−1 were obtained In the absence of a complete theory for the device, the data are interpreted and rationalized on the basis of simple physical arguments In particular, optimal performance conditions are derived The micropump described here is simple in concept and realization and robust, as it does not have mechanical moving parts A bi-directional pump can easily be built by providing two heaters

Pumping of mammalian cells with a nozzle-diffuser micropump

Abstract: We discuss the successful transport of jurkat cells and 5D10 hybridoma cells using a reciprocating micropump with nozzle-diffuser elements. The effect of the pumping action on cell viability and proliferation, as well as on the damaging of cellular membranes is quantified using four types of well-established biological tests: a trypan blue solution, the tetrazolium salt WST-1 reagent, the LDH cytotoxicity assay and the calcium imaging ATP test. The high viability levels obtained after pumping, even for the most sensitive cells (5D10), indicate that a micropump with nozzle-diffuser elements can be very appropriate for handling living cells in cell-on-a-chip applications.

A high performance bidirectional micropump for a novel artificial sphincter system

Abstract: We present the design, fabrication and testing of a novel medical implant based on a high performance silicon micropump. An analytical model was exploited for further optimization of our micropump design. The experimental data obtained are in a good accordance with theory. Two sphincter prostheses of different sizes were developed and tested. Their general medical capability as a prosthesis has been proven.