Characteristic studies of the piezoelectrically actuated micropump with check valve

This study presents the design and fabrication of a novel piezoelectric actuator for a micropump with check valve having the advantages of miniature size, light weight and low power consumption. The micropump is designed to have five major components, namely a piezoelectric actuator, a stainless steel chamber layer with membrane, two stainless steel channel layers with two valve seats, and a nickel check valve layer with two bridge-type check valves. A prototype of the micropump, with a size of 10 × 10 × 1.0 mm, is fabricated by precise manufacturing. The check valve layer was fabricated by nickel electroforming process on a stainless steel substrate. The chamber and the channel layer were made of the stainless steel manufactured using the lithography and etching process based on MEMS fabrication technology. The experimental results demonstrate that the flow rate of micropump accurately controlled by regulating the operating frequency and voltage. The flow rate of 1.82 ml/min and back pressure of 32 kPa are obtained when the micropump is driven with alternating sine-wave voltage of 120 Vpp at 160 Hz. The micropump proposed in this study provides a valuable contribution to the ongoing development of microfluidic systems.     

Integratable magnetic shape memory micropump for high-pressure,precision microfluidic applications

Precisely controlling the flow of fluids on a microscopic scale has been a technological challenge in the field of microfluidics. Active microfluidics, where a defined manipulation of the working fluid is necessary, requires active components such as micropumps or microvalves. We report on an optimized design of an integratable, wireless micropump made from the magnetic shape memory (MSM) alloy Ni–Mn–Ga. An external magnetic field generates a shape change in the MSM material, which drives the fluid in a similar fashion as a peristaltic pump. Thus, the pump does not need electrical contacts and avoids the mechanical parts found in traditional pumping technologies, decreasing the complexity of the micropump. With a discrete pumping resolution of 50–150 nL per pumping cycle, which is further scalable, and a pumping pressure well exceeding 2 bar, the MSM micropump is capable of accurately delivering the fluids needed for microfluidic devices. The MSM micropump is self-priming, pumping both liquid and gas, and demonstrates repeatable performance across a range of pumping frequencies. Furthermore, it operates simultaneously as both a valve and reversible micropump, offering superior possibilities compared to existing technologies within the flow rate range of 0–2000 µL/min. Due to its simplicity, this technology can be scaled down easily, which lends itself for future integration into lab-on-a-chips and microreactors for life science and chemistry applications.     

A low cost,high performance insulin delivery system based on PZT actuation

A low driving voltage, low cost, high performance insulin delivery system based on PZT actuation is presented in this paper, which consists of two functional units, namely, micropump unit and electronic control unit. The PZT micropump is the core of micropump unit and is the key base to ultimately realize insulin precision delivery of the whole system. The electronic control unit is the important auxiliary unit for the realization of the whole system function. To obtain a higher working performance under low voltage, a serial structure with two chambers and three check valves is adopted in the design of PZT micropump. In place of silicon and glass, main parts of micro-pump unit are manufactured using the polymers which have good biocompatibility, stability and low cost. Through the systematic experimental test for the prototype of PZT insulin delivery system in lab, the maximum backpressure of 14.64 kPa is recorded at applied voltage of 36 V and working frequency of 160 Hz, the maximum flow rate of 5.74 ml/min is obtained in the condition of 36 V and 300 Hz. Under the voltage of 36 V and working frequency of 200 Hz, the micro-dosage pumped by PZT micro-pump displays a good linear characteristic with the number of driving impulses. The minimum resolution of insulin delivery can obtain 3 × 10^?4 ml (0.03 U insulin at the concentration of 100 U).     

Characterization of a high-resolution solid-state micropump that can be integrated into microfluidic systems

Ni–Mn–Ga is a magnetic shape memory (MSM) alloy that can strain up to 6 % when a magnetic field is applied to it. By applying a localized magnetic field to the MSM element, the strain can be precisely controlled and manipulated. By using Ni–Mn–Ga and a local magnetic field, an MSM micropump that is capable of controlling the flow within a microfluidic system has been developed. A computational fluid dynamics analysis illustrates the flow of the liquid at the outlet of the micropump and will be used to optimize future models of the pump. The performance of the MSM micropump, such as its flow rate and pumping pressure, is measured and presented in this study. Beyond its performance, there are also several advantages intrinsic to the MSM micropump. It is controlled by a magnetic field and is therefore contact-free. Depending upon the magnetic field, the MSM micropump can act as either a valve or a reversible pump. It is self-priming and capable of pumping gases as well as viscous liquids, and it has a simple design which consists primarily of the MSM alloy itself. Coupled with its scalability, it is clear that the MSM micropump is a strong candidate for an integratable flow control solution.     

Experimental characterization of piezoelectrically actuated micromachined silicon valveless micropump

In this paper, performance of piezoelectrically actuated pyramidal valveless micropumps is studied experimentally in detail. Valveless micropumps based on silicon and glass substrate are fabricated using MEMS technology. Two different sizes of micropumps having overall dimensions of 5 mm × 5 mm × 1 mm and 10 mm × 10 mm × 1 mm are fabricated and characterized. In the fabricated micropumps, the thickness of silicon diaphragm is <20 µm which gives the advantage of operating pump at low voltage with excellent stability and consistency. The performance of micropumps in terms of flowrate and backpressure is evaluated for a wide range of driving frequency and actuating voltages. The maximum flowrate of water in the 10-mm micropump is 355 µl/min and backpressure of 3.1 kPa at zero flowrate for an applied voltage of 80 V at frequency 1.05 kHz. The reported micropumps have low footprint, high flowrate and backpressure. Thus, these micropumps are especially suited for biological applications as these can withstand adequate amount of backpressure. Comparative study of the performance of these micropumps with those available in the literature brings out the efficacy of these micropumps.     

Optimization design of multi-material micropump using finite element method

This paper presents a micropump fabricated from low cost materials with specific goal of cost reduction. The micropump does not require any valve flap and comprises one plastic pump polyether–ether–ketone (PEEK) body, one metal diaphragm, and three piezoelectric ceramics to form piezoelectrically actuated diaphragm valves. The valve actuation simplifies micropump structural designs and assembly processes to make the pump attractive for low cost bio-medical drug delivery applications. A detailed optimization design of geometric parameters of the piezoelectrically actuated diaphragm is undertaken by use of 3D finite element method (FEM) to maximize piezoelectric actuation capability and ensure actuation reliability. An optimized geometric dimensional design: the ratio of thicknesses between the piezoelectric ceramics and the metal diaphragm, and the lateral dimension of the piezoelectric ceramic, is obtained through simulations. Based on the optimized design, a good agreement has been reached between simulated and measured strokes of the micropumps. The tested results show that the micropump has a high pump flow rate for air, up to 39 ml/min, and for water, up to 1.8 ml/min, and is capable of ensuring diaphragm’s maximum stress and strain is within material strength for reliable work.     

串联压电微泵特性研究

介绍了一种压电驱动的串联无阀微泵.基于收缩管/扩展管整流特性的分析,建立了微泵输出特性的表达公式.采用有限元仿真软件ANSYS对微泵内流体的流动过成进行了数值模拟,结果显示,在相同的驱动条件下,串联无阀微泵的工作性能优于单腔无阀微泵的工作性能.泵流量随着驱动电压的增加而增加.当固定的驱动电压下,存在最优的压电层厚度使得泵流量最大.研究结果为串联微泵的优化设计提供了依据.     

A high flow rate thermal bubble-driven micropump with induction heating

A thermal bubble-driven micropump with magnetic induction heating is successfully demonstrated in this paper. Energy is transferred from the planar coil outside the microchamber to the metal heating plate inside the microchamber through the electromagnetic field, and Joule heat is induced by the eddy current in the heating plate. Sequential photographs of bubble nucleation, growth and shrink in open environment were recorded by a CCD camera. One advantage of the micropump is that there is no physical contact between the heating plate and the external power supply circuit, which resulted in an easy fabrication process. What’s more, compared with other thermal bubble-driven micropump with resistive microheater, the flow rate and the pump stroke have been improved significantly due to its larger dimension of the heating plate and larger bubbles volume. The experiments show that the maximum flow rate of this micropump is about 102.05 μL/min, which can expand the potential applications, especially for microfluidic system that requires higher flow rate.     

Design and modeling of electromagnetic actuator in mems-based valveless impedance pump

This study models and optimizes the electromagnetic actuator in an MEMS-based valveless impedance pump. The actuator comprises an electroplated permanent magnet mounted on a flexible PDMS diaphragm and electroplated Cu coils located on a glass substrate. In optimizing the design of the actuator, the objective is to maximize the output flow rate of the micropump while maintaining the mechanical integrity of its constituent parts. The study commences by developing optimized theoretical models for each of the components within the actuator, namely the diaphragm, the magnet, and the micro-coils. The theoretical models are then verified numerically using FEA software. The magnitude of the magnetic force acting on the flexible diaphragm is calculated using Ansoft/Maxwell3D FEA software. The simulation results obtained by ANSYS FEA software for the diaphragm deflection are found to be in good agreement with the theoretical predictions. In general, the results show that the desired diaphragm deflection of 15 μm can be obtained by passing a current of 0.6–0.7 A through the micro-coil to produce a compression force of 11 μN. The valveless micro impedance pump proposed in this study is easily fabricated and is readily integrated with existing biomedical chips due to its plane structure. The results of this study provide a valuable contribution to the ongoing development of Lab-on-a Chip systems.     

Development of peristaltic antithrombogenic micropumps for in vitro and ex vivo blood transportation tests

This study involves the design, fabrication and characterization of a biocompatible silicon micropump. Three experiments were conducted to study the performance of this pump in clinical environments. They were a blood compatibility test, and in vitro and ex vivo studies. Whole blood is an intrinsically complex material and difficult to manipulate using a microsystem device. In the blood compatibility experiments, two materials N-(triethosilylpropyl)-O-polyethylene oxide urethane (PEOU) and polyethylene glycol (PEG) were employed to form a self-assembled monolayer (SAM) on a chip surface. According to the platelet remaining test and a 30-min blood transportation test, PEOU protected the micropump from thrombus. In the second experiment, the micropump handled several liquids, including DI water and whole blood. When the pump was operated at a voltage of 140 V_pp, the flow rates of the DI water and whole blood were 121.6 μl/min at 500 Hz and 50.2 μl/min at 450 Hz, respectively. The maximum back pressure of the water and the blood in the micropump were 3.2 and 1.8 kPa, respectively. Finally, the micropump injected phosphated buffered saline (PBS) and whole blood into the veins of rats. The pump was characterized ex vivo and discussed. The third experiment reveals that the micropump fulfilled the dosing condition for clinical medicine and did not affect the physiological function of the rats. This pump is highly promising for biomedical applications, such as in drug delivery for patients, or in clinical care. Moreover, the pump has potentials to control precisely medication to improve conventional clinical treatments.     

Fully coupled modeling and design of a piezoelectric actuation based valveless micropump for drug delivery application

The precise control over the drug delivery involved in several vital applications including healthcare is required for achieving a therapeutic effect. For such precise control/manipulation of the drugs, micropumps are used. These micropumps are basically of two types viz. check valve-based and valveless micropumps. The valveless micropumps are preferable due to the congestion-free operation of diffuser/nozzle valves. In this paper, design optimization of a valveless piezo-electric actuation based micropump is carried out using COMSOL Multiphysics 5.0 by coupling two Multiphysics interface modules namely fluid–structure interaction and piezoelectric physics modules. Using simulation studies, the influence of pump design parameters including diffuser angle, diffuser length, neck width, chamber depth, chamber diameter and diaphragm thickness on net flow rate is studied. An optimal set of design parameters for the proposed micropump is identified. Further, the influence of actuation frequency on the flow rate is analysed. It is found that the proposed micropump is capable to deliver a net flow rate of 20 µl/min and a maximum back pressure attainable is 200 Pa.

     

磁能驱动微型泵的性能实验研究

在电磁场驱动原理的基础上,设计并研制了一种磁能驱动的微型泵。微型泵包括进／出液管、扩散管／喷管、驱动薄膜、腔体、电磁线圈和永磁体。微型泵的整体尺寸约为Ф11mm×4mm,腔室半径为5mm,深2mm。利用正交实验方法,对微型泵的性能进行了测试。在电压为4V、驱动薄膜厚度为6μm、频率为5Hz方波脉冲的最佳实验条件下,微型泵的最大泵送流速约为0．21mL／min。     

Analysis of double-chamber parallel valveless micropumps

The characteristics of a double-chamber valveless parallel micropump are analysed using a one-dimensional non-linear model. The relationships between the mean volume flux, pressure difference and (measurable) characteristics of the pump are derived in a closed-form expression which are validated against the numerical solutions. These results show that when pump chambers are driven exactly out of phase, the volume flux is maximum and the variation of the pump chamber pressure is (significantly) reduced. The model predictions were tested against the experimental results of Olsson et al. (Sens Actuators A Phys 47:549–556, 1995) for both in and out of phase pumps. The mean volume flux decreases linearly with pressure rise. For both cases, the agreement is good and is an improvement over previous analytical models. The implications of these results for optimal pump design are discussed.     

Study of an innovative one-sided actuating piezoelectric valveless micropump with a secondary chamber

Previous studies have indicated that a one-sided actuating piezoelectric micropump (OAPMP) combined with two valves may enhance the liquid flow rate to 4.1 ml/s and make it possible to reach the maximum pump head of 9807 Pa in a limited space. In this study, an innovative one-sided actuating piezoelectric valveless micropump (OAPMP-valveless) has been developed to actuate fluid at a higher flow rate in one direction by adding a secondary chamber. The secondary chamber plays a key role in the application of the valveless micropump: the flow rate of the pump can reach 0.989 ml/s by adding a secondary chamber. The maximum pump head is 1522.5 Pa when using the 0.3 mm-thick secondary diaphragm and the 0.5 mm-thick primary diaphragm. In addition, if a nozzle/diffuser element is applied to the OAPMP-valveless with a secondary chamber, the flow rate can be further improved to 1.183 ml/s at a frequency of 150 Hz. A three-dimensional numerical model of the valveless micropump has been built to compare the measured results with the simulated results.     

Performance improvement of an AC electroosmotic micropump by hydrophobic surface modification

This paper describes the improvement of bi-directional micropump velocity by deposition of a hydrophobic nanocomposite monolayer. A polymer base nanocomposite coating consisting of a homogeneous mixture of silicon nanoparticles in polydimethylsiloxane (PDMS) is used to improve the hydrophobicity of the micropump surfaces. For hydrophobic nature of PDMS and the monolayer coating with nanoscale surface roughness, the hydrophilic surface of a biased AC electroosmotic micropump will transform to a hydrophobic surface. In our previous research the applied AC voltage, frequency, channel dimension, and electrode width were optimized (Islam and Reyna, Electrophoresis 33(7), 2012). Based on the prior results obtained for the biased AC electroosmotic micropump, the pumping velocity was 300 micron/s in 100-μm channel thickness for applied voltage of 4.4 V at 1 kHz frequency. Here in this work, improvement of the micropump velocity is investigated through a surface modification process. The highest velocity of 450 micron/s is observed by modifying the surface characteristics. This paper will also discuss the synthesis process and characteristics of the polymer base nanocomposite monolayer. In addition to hydrophobicity improvement, adding a thin nanocomposite monolayer will physically separate the electrodes from the pumping liquid, thus eliminating their reaction, which is usually observed due to the application of voltage. As a result, higher voltages can be applied to the electrodes and higher pumping rates are achievable.     

Microfabricated centrifugal pump driven by an integrated synchronous micromotor

This paper presents the development of a new design of the microfabricated centrifugal force pump. The pumping concept is based on running an impeller (a rotor including permanent magnets carrying straight and backward blades) within an integrated synchronous motor, which can be operated at different rotational speeds to pump water. The impeller is 5.5 mm in diameter, and is 1.5 mm in height. This micropump with 7-straight-blade impeller can operate smoothly up to a rotational speed of 9000 rpm. It can deliver a non-pulsating maximum flow rate of up to 12 ml/min and allows water to be pumped up to a 24 cm water head. Additionally, the micropump with the backward-blade-impeller pump delivered a flow rate of up to 14.3 ml/min. at a rotational speed of 11,400 rpm with no back pressure. The micropump was patterned using a series of microfabrication processes including sputtering, photolithography and electroplating within a clean room. Such a pump can be integrated into a system of a compact size and can provide a wide range of flow rates. It could also be a promising device for use within biological and micro biomedical fields. To our knowledge, this is the smallest centrifugal pump in the world with an integrated electromagnetic synchronous motor that offers such high flow rates.

     

Design and modeling of a novel microsensor to detect magnetic fields in two orthogonal directions

In this paper, we present the design and modeling of the electrical–mechanical behavior of a novel microsensor to detect magnetic fields in two orthogonal directions (2D). This microsensor uses a simple silicon resonant structure and a Wheatstone bridge with small p-type piezoresistors (10 × 4 × 1 μm) to improve the microsensor resolution. The resonant structure has two double-clamped silicon beams (1000 × 28 × 5 μm) and an aluminum loop (1 μm thickness). The microsensor design allows important advantages such as small size, compact structure, easy operation and signal processing, and high resolution. In addition, the microsensor design is suitable to fabricate using silicon on insulator (SOI) wafers in a standard bulk micromachining process. An analytical model is developed to predict the first bending resonant frequency of the microsensor structure using Macaulay and Rayleigh methods, as well as the Euler–Bernoulli beam theory. Air and intrinsic damping sources of the microsensor structure are considered for its electrical–mechanical response. The mechanical behavior of the microsensor is studied using finite element models (FEMs). For 10 mA of root mean square (RMS) excitation current and 10 Pa air pressure, this microsensor has a linear electrical response, a fundamental bending resonant frequency of 52,163 Hz, and a high theoretical resolution of 160 pT.     

Study on a piezoelectric micropump for the controlled drug delivery system

We present the design of a new controlled drug delivery system potential for in vitro injection of diabetics. The system incorporates some integrated circuit units and microelectromechanical system devices, such as micropump, microneedle array and microsensor. Its goal is to achieve safer and more effective drug delivery. Moreover, a valveless micropump excited by the piezoelectric actuator is designed for the drug delivery system, and a simple fabrication process is proposed. A dynamic model is developed for the valveless micropump based upon the mass conservation. To characterize the micropump, a complete electro-solid-fluid coupling model, including the diffuser/nozzle element and the piezoelectric actuator, is built using the ANSYS software. The simulation results show that the performance of micropump is in direct proportion to the stroke volume of the pump membrane and there is an optimal thickness of the piezoelectric membrane under the 500 V/mm electric field. Based on this simulation model, the effects of several important parameters such as excitation voltage, excitation frequency, pump membrane dimension, piezoelectric membrane dimension and mechanical properties on the characteristics of valveless micropump have been investigated.     

Design of swing arm type actuators considering thermal and dynamic characteristics

The present state of the design of swing arm actuators for optical disc drives is to obtain the highly efficient dynamic characteristics within a very compact volume. As a necessary consequence, the need of the small form factor (SFF) storage device has arisen as a major interest in the information storage technology. Due to the size constraint, the thermal stability of the optical pick-up head is important: therefore, the actuator is designed to emit the heat, which is generated by the optical pick-up, along the structural body easily. In this paper, we suggest the miniaturized swing arm type actuator that has effective heat emission quality as well as satisfies the dynamic requirements for the SFF optical disk drive (ODD). The actuator is targeted to be installed in CF-II card size drive to be competitive with flash memory or mini hard disk drive used in mobile electric devices; therefore the dimension of the actuator is required as 11.0 mm × 2.5 mm × 25.0 mm (width × height × length). Because of its small size, the dynamic requirements are severe to ensure the enough gain-margin for the system control together with satisfying the DC/AC sensitivity conditions. Moreover, due to the small size, the maximum pick-up temperature is critical in design because the system has high possibility to reach the shut-down temperature. For the operating mechanism, it uses a tracking electromagnetic (EM) circuit for the focusing motion together and the initial model is designed and promoted by the design of experiments (DOE) only considering the dynamic characteristics. New concept design is suggested based on the topology optimization method considering the thermal conductivity. Furthermore, the new design is modified by DOE to maintain the high sensitivity and to have wide control bandwidth and decreasing mass and inertia. The final design of a swing arm type actuator for SFF ODD is suggested and its dynamic characteristics are verified.     

新型压电微泵的结构设计与理论分析

微泵在微流控化学分析芯片中有很大的应用前景,日益成为人们研究的热点。从结构设计、理论分析和工艺加工3个方面研究了微阀与微泵,设计出用压电驱动和聚二甲基硅氧烷(PDMS)作为泵膜的集成微阀与微泵,其特点是原理新颖、结构简单、易于加工、操作方便。结构主要是由PDMS泵膜、硅片和压电驱动器组成,其中,PDMS既是泵膜和缓冲单元,也是主动阀片。在直流电压的驱动下,其工作状态是微阀,阻止流体的单向流通,在方波信号的驱动下,其工作状态是微泵,实现流体的吸入与泵出。给出各种几何参数、工作原理和工艺流程。