Micropump System Research Articles

A stand-alone peristaltic micropump based on piezoelectric actuation

Despite significant efforts to develop micropumps, cumbersome driving equipment means that the design of portable micropumps remains a challenge. This study presents a stand-alone micropump system, which includes a peristaltic micropump based on piezoelectric actuation and a driving circuit. This battery-based driving circuit comprises a 12 V battery, an ATmega 8535 microprocessor, a 12 V-to-180 V DC to DC converter using transformerless technology, three differential amplifiers, an IC 7805, a phase controller, an A/D converter, a keyboard and an LCD module. The system can produce step-function signals with voltages of up to 228 V(pp) and frequencies ranging from 10 Hz to 100 kHz, as the inputs for the pump. It is portable and programmable with the package size of 22 x 12.8 x 9 cm. Additionally, this proposed system is used to design the driving signals of the pump which are 3-, 4, and 6-phase actuation sequences. This work performs the circuit testing and fluid pumping, and demonstrates the effects of actuation sequences on pump performance in terms of the dynamic behavior of the diaphragm, flow rates, back pressure and power consumption of the system. The experimental results show that the pump excited by the 6-phase sequence results in better performance compared with the 3- and 4-phase sequences, and produces a maximum flow rate of 36.8 microl/min and a maximum back pressure of 520 Pa with deionized water at 100 V (pp) and 700 Hz.

Implementation of microfluidic devices at a transparency

We have developed a scanning laser manufacturing technique to produce microfluidic structures directly on photocopy transparency films. The reasons for the selection of transparency include (i) its insignificant water diffusion and vapor loss characteristics, (ii) its reduced viscoelastic behavior and (iii) its very low cost. The stiffness of the transparency membrane can be carefully tailored by adjusting laser ablation power. To show the feasibility of the approach, we have fabricated membrane valves on the transparency, and demonstrated a peristaltic micro-pumping system. Our investigation offers the potential for developing new types of very low-cost disposable devices including flexible microfluidic systems.

An integrated micropump and electrospray emitter system based on porous silica monoliths

The work presents the design of an integrated system consisting of a high-pressure electroosmotic (EO) micropump and a microporous monolithic emitter, which together generate a stable and robust electrospray. Both the micropump and electrospray emitter are fabricated using a sol-gel process. Upon application of an electric potential of sufficient amplitude (>2 kV), the pump delivers fluids with an electroosmotically induced high pressure (>1 atm). The same potential is also harnessed to electrostatically generate a stable electrospray at the porous emitter. Electrokinetic coupling between pump and spray produces spray features different from sprays pressurized by independent mechanical pumps. Four typical spray modes, each with different drop sizes and charge-to-mass ratios, are observed and have been characterized. Since the monolith is silica-based, this integrated device can be used for a variety of fluids, especially organic solvents, without the swelling and shrinking problems that are commonly encountered for polymer monoliths. The maximum pressure generated by a 100 microm id monolithic pump is 3 atm at an applied voltage of 5 kV. The flow rate can be adjusted in the range of 100 nL/min to 1 microL/min by changing the voltage. For a given applied voltage across the pump and emitter system, it is seen that there exists one unique flow rate for which flow balance is achieved between the delivery of liquid to the emitter by the pump and the liquid ejection from the emitter. Under such a condition, a stable Taylor cone is obtained. The principles that lead to these results are also discussed.

Compact micropumping system based on LIGA fabricated microparts

This report presents design, fabrication and testing of a magnetically actuated microgear pumps based on the LIGA technology. These micropumps exhibit flow rates between 0.5 and 8.5 ml/min and head pressures up to 100 cm-H 2O. Geometries are determined for an optimal magnetic coupling, resulting in a linear behavior of the flow rate versus rotation speed.

Performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator

Presented in this paper is the study of the performance evaluation of a valveless micropump driven by a ring-type piezoelectric actuator. The application of this micropump is to circulate fuel inside a miniaturized direct methanol fuel cell (DMFC) power system. A theoretical model based on the theory of plates and shells is established to estimate the deflection and the volume change of this micropump without liquid loading. Both finite-element method (FEM) and experimental method are applied to verify this model. Using this model, the optimal design parameters such as the dimensions and the mechanical properties of the micropump can be obtained. Furthermore, various system parameters that will affect the performance of the micropump system with liquid loading are identified and analyzed experimentally. It is expected that this study will provide some vital information for many micropump applications such as fuel delivery in fuel cells, ink jet printers, and biofluidics.

An actuated pump on-chip powered by cultured cardiomyocytes

Cellular functions are frequently exploited as processing components for integrated chemical systems such as biochemical reactors and bioassay systems. Here, we have created a new cell-based microsystem exploiting the intrinsic pulsatile mechanical functions of cardiomyocytes to build a cellular micropump on-chip using cardiomyocyte sheets as prototype bio-microactuators. We first demonstrate cell-based control of fluid motion in a model microchannel without check valves and evaluate the potential performance of the bio-actuation. For this purpose, a poly(dimethylsiloxane) (PDMS) microchip with a microchannel equipped with a diaphragm and a push-bar structure capable of harnessing collective cell fluid mechanical forces was coupled to a cultured pulsating cardiomyocyte sheet, activating cell-based fluid movement in the microchannel by actuating the diaphragm. Cell oscillation frequency and correlated fluid displacement in this system depended on temperature. When culture temperature was increased, collective cell contraction frequency remained cooperative and synchronous but increased, while displacement was slightly reduced. We then demonstrated directional fluid pumping within microchannels using cantilever-type micro-check valves made of polyimide. A directional flow rate of nL min(-1) was produced. This cell micropump system could be further developed as a self-actuated and efficient mechanochemical transducer requiring no external energy sources for various purposes in the future.

Photopolymerized check valve and its integration into a pneumatic pumping system for biocompatible sample delivery

In this paper, we present a simple check valve whose operation mimics that of venous valves. Our check valve has a mono-leaflet and is constructed via an in situ fabrication method inside the PDMS platform. For the smooth operation of the valve's leaflet, the elasticity and the shape of the leaflet and the lubrication between the leaflet and the channel surface are important. We used 4-hydroxybutyl acrylate (4-HBA) as an elastic and photopolymerizable leaflet material. We mixed the triton X-100 with the 4-HBA pre-polymer solution for the adequate lubrication of the leaflet. We constructed the micro-pumping system by combining two venous-like check valves with an oscillating polymeric diaphragm driven by pneumatic force, and measured the flow rate according to the change of pumping frequency. We also investigated the pump's feasibility as a delivery system of biocompatible materials by using mouse embryo fibroblast cells.

A Nonmechanical, Membrane-Based Liquid Pressurization System

Nonmechanical pumping of liquids is of key importance for applications ranging from biomedical lab-on-a-chip systems to morphing mechanical structures. In this paper, we report a new, reversible micropumping and pressurization system, with no moving parts, that uses only modest external power. This new “e-pump” operates via a type of electro-osmosis (EO) in which a charge imbalance is created electrochemically across a cation-selective membrane, cations migrate to balance the charge, and solvent is transported across the membrane, along with the mobile cation. No gas is produced in this electrokinetic pumping system, so only liquids are involved in pumping and pressurization. In this proof-of-concept study, an aprotic solvent (dimethylformamide) was chosen to select the specific cation that is migrating (tetrapropylammonium ion). To date, pressures up to 23 atm have been successfully demonstrated.

Valveless piezoelectric micropump for fuel delivery in direct methanol fuel cell (DMFC) devices

Fuel cells are being considered as an important technology that can be used for various power applications. For portable electronic devices such as laptops, digital cameras, cell phone, etc., the direct methanol fuel cell (DMFC) is a very promising candidate as a power source. Compared with conventional batteries, DMFC can provide a higher power density with a long-lasting life and recharging which is almost instant. However, many issues related to the design, fabrication and operation of miniaturized DMFC power systems still remain unsolved. Fuel delivery is one of the key issues that will determine the performance of the DMFC. To maintain a desired performance, an efficient fuel delivery system is required to provide an adequate amount of fuel for consumption and remove carbon dioxide generated from fuel cell devices at the same time. In this paper, a novel fuel delivery system combined with a miniaturized DMFC is presented. The core component of this system is a piezoelectric valveless micropump that can convert the reciprocating movement of a diaphragm activated by a piezoelectric actuator into a pumping effect. Nozzle/diffuser elements are used to direct the flow from inlet to outlet. As for DMFC devices, the micropump system needs to meet some specific requirements: low energy consumption but a sufficient fuel flow rate. Based on theoretical analysis, the effect of piezoelectric materials properties, driving voltage, driving frequency, nozzle/diffuser dimension, and other factors on the performance of the whole fuel cell system will be discussed. As a result, a viable design of a micropump system for fuel delivery can be achieved and some simulation results will be presented as well.

進行波を用いた薄膜バルブレスマイクロポンプの開発(J22-3 センサ・アクチュエータシステムとその知能化(3),J22 センサ・アクチュエータシステムとその知能化-実環境で活躍するメカトロニクスを目指して)

Micropumps play a significant role in fluid transportation system of μ-TAS. We propose a peristaltic micropump system composed of a microchannel made of silicon rubber. Bottom surface of the microchannel is deformed by the electrostatic attraction between upper and lower electrodes made of copper thin films. Since the pump has simple structure using the electrostatic thin film actuators without valves, the fabrication process is also as simple as just stacking organic films or layer on PMMA substrate. The micropump is suitable for low-cost disposable applications. We could observe clear deflection of the channel wall which is proportional to the a square of the applied voltage. In addition, we confirmed active motion of microbeads in the fluid by the peristaltic actuation of electrostatic force.

中耳しん出液排出用電動式マイクロポンプの開発

For the treatment of otitis media with effusion, aspiration of fluid through a suction tube is conventionally performed after puncture or myringotomy. However, hypertrophy scars and sclerosis of the tympanic membrane can occur when the radial fiber bundles are cut by myringotomy. It is also very difficult to aspirate the hyperviscous fluid. We thus developed a micropump for use with a small caliber needle to avoid unnecessary injuries to the tympanic membrane. It is also equipped to mechanically transport viscous fluid.The micropump is composed of a motor and needle to puncture the tympanic membrane. Two spiral helical wires inside the needle which are connected to the airspindle (first model) or electric (second model) rotation machine rotate to remove even highly viscous fluid. We used standard viscosity oil to test the relationship between the viscosity of fluid and removal speed. We found that the faster the rotation, the quicker the removal of fluid, independent of viscosity. We confirmed the clinical usefulness of the new micropump and needle system for otitis media with effusion because the puncture needle is fine enough to perform a minimally invasive puncture of the tympanic membrane.We treated 16 patients (19 ears) with otitis media with effusion using this electric micropump between October 2000 and April 2001. In 15 ears, effusion was removed successfully, in 2 ears, we almost totally removed the effusion with very little residual fluid, and in 2 ears we could not remove the effusion due to the extremely high viscosity.

ARBITRARY LAGRANGIAN EULERIAN ANALYSIS OF A BIDIRECTIONAL MICRO-PUMP USING SPECTRAL ELEMENTS

Performance analysis of a reversible micro-pump system is obtained by numerical simulations. The unsteady incompressible Navier–Stokes equations are solved in a moving micro-pump system using a spectral h/p element algorithm, employing an arbitrary Lagrangian Eulerian (ALE) formulation on structured/unstructured meshes. The performance of the micro-pump is evaluated as a function of the Reynolds number and the geometric parameters. The volumetric flowrate is shown to increase as a function of the Reynolds number. The unsteady traction forces on the pump membrane and the vorticity dynamics within the pump cavity are presented.

Endovascular treatment of cerebral aneurysms: An in vitro study with detachable platinum coils and tricellulose acetate polymer.

The purpose of our experimental study was to determine the effectiveness of filling the cavity of in vitro aneurysms with detachable platinum coils and the combination of detachable platinum coils and liquid embolic agent. Silicone aneurysm models were connected to a circulatory system to simulate arterial flow. A microcatheter was used to introduce detachable coils into the aneurysm cavities. First, platinum coils were introduced until the point of minimal dense packing, indicated by aneurysmal circulatory exclusion. Packing was continued up to maximal dense packing, indicated by protrusion of the coil into the parent artery. Volumetric ratios (coil volume-aneurysm volume) were calculated for minimal and maximal dense packing. Then, after purposeful undercoiling of aneurysm models, a micropump system was used to fill the aneurysm by stepwise injection of tricellulose acetate polymer through the coil mesh until angiographic aneurysm exclusion was completed. The volumetric ratios of maximal packing with coils and tricellulose acetate polymer in relation to the aneurysm volume were calculated. Maximal dense packing ratios with coils (mean, 32.5%; standard deviation [SD], 3%) were slightly higher than those with the minimal dense packing (mean, 28. 2%; SD, 3%) but were always less than 37%. The ratios of packing with the combined use of coils and tricellulose acetate polymer were greater than 100% (mean, 124.4%; SD, 15%). Knowledge of the volumetric ratio of maximal dense packing was useful for effective filling with coils and tricellulose acetate polymer. The combined use of coils and liquid polymer appeared more effective than the use of coils alone for the complete occlusion of the aneurysm lumen.

Simulation and Analysis of a Magnetoelastically Driven Micro-Pump

The operation of a micro-pump system driven by a magnetoelastic polymeric membrane developed at Texas A&M University is analyzed by numerical simulations. Unsteady, incompressible Navier-Stokes equations in a moving boundary system are solved by a spectral element methodology, employing an Arbitrary Lagrangian Eulerian (ALE) formulation on unstructured meshes. The performance of the micro-pump is evaluated as a function of the Reynolds number and the geometric parameters. The volumetric flowrate is shown to increase as a function of the Reynolds number. The system is simulated by assuming the deformation of the membrane. The required voltage and current are then calculated by a lumped parameter analysis.

Preoperative Assessment of the Implantable Middle Ear Pump System Using CT Scans and Conventional X-rays of the Temporal Bone

A completely implantable micropump system for drug delivery has recently been developed. After implantation in the temporal bone, this microdosage system enables application of drugs into the middle ear and round window area. Successful application of this new technology depends upon a suitable fit of the micropump within the patient's temporal bone. To obtain information about the fit before surgery, we analyzed 50 cadaver temporal bone specimens before total mastoidectomy, using conventional X-ray and spiral CT scans for water volume determination. Spiral CT is a feasible method for preoperative planning of the surgical implantation of the implantable middle ear micropump system (TI-DDS). The best parameter for a preoperative judgment is the volume of the mastoid cavity, as determined by CT. Implantation may be recommended when the mastoid volume, as measured by CT, is greater than 6.6 ml. To be certain that the implantable drug delivery system will be implantable, a cut-off value of 9.3 ml seems to be advisable. Spiral CT imaging is of great value as a tool for testing implantation preoperatively. The imaging is accomplished in approximately 30 seconds. Our preliminary results with cadaveric temporal bones are encouraging. Further studies are needed in order to transfer the results to a clinical implantation situation.

The behavior of liquid jets escaping microchannels

A mathematical model is presented which describes the behavior of fluid jets escaping microchannels. Channels with non-circular cross-sections serve as basis for the model. The application of the model to defined geometrical shapes or orifices leads to a deflection of the liquid jets from the axis of the channel. Experimental testings on a micropumping system confirm the results. At orifices with triangular cross-section areas of about 1750 mu m deflections of up to 85 degrees were observed, these being dependent on the streaming velocity.