一种基于MEMS技术的压电微泵的研究

介绍了一种基于MEMS技术的压电微泵。该微泵利用聚二甲基硅氧烷(PDMS)作为泵膜,使用了一个主动阀和一个被动阀,并利用压电双晶片作为驱动部件。压电双晶片和PDMS泵膜的组合可以产生较大的泵腔体积改变和压缩比,显著降低了加工成本,并提高了成品率。对压电微泵的输出流量进行了测试,结果显示:电压、频率以及背压对流量均有显著影响。在100 V,25Hz的方波驱动下,该压电微泵的最大输出流量为458μL/m in,最大输出压力为6 kPa。     

热膨胀驱动型微阀的设计与制备

利用IntelliSuite软件对热膨胀驱动微阀进行结构分析设计,讨论了微加热器结构等因素对于微阀的影响。利用SU—8胶成型工艺制备了聚二甲基硅氧烷(PDMS)微阀所需要的模具。热膨胀驱动微阀的制备过程分为:薄膜微加热器的金属淀积、阀腔的制备、弹性薄膜的制备和流体通道的制备四部分,详细阐述了各部分的制备工艺流程和各层之间的改性键合工艺等。通过微加工工艺提高了微阀的性能。利用蠕动泵作为流体驱动源,对微阀的性能进行验证,当阀腔驱动电压达到9 V时,实现了微阀关闭。     

预应力压电泵的结构设计与实验研究

提出了一种由压电晶片驱动的新结构微泵,采用精密机械加工工艺制作而成。设计了预应力阀膜,组装压电微泵,对预应力阀的可靠性和压电微泵的液体输送特性做了研究。通过系统的实验研究证明：预应力压电泵具有很好的防倒吸能力,稳定性高,具有很好的工作性能,在250V,200Hz方波信号下,流速可达5．5027mL／min,且适于微型化,可为该类型泵的实际应用提供有意义的借鉴。     

MEMS密闭腔内微气流的挤压膜阻尼效应研究

针对MEMS密闭腔内微气流与压电驱动机构的耦合振动,综合采用空气挤压膜阻尼效应和能量法进行理论分析。根据等温雷诺方程求解气体压力分布,进而计算微气流挤压膜阻尼能,将其代入能量方程,与压电-硅膜的耦合动能、势能、压电电场能进行能量耦合,将由能量方程确定的压电-硅膜-微气流耦合作用下的位移振形待定系数λ′与无气流影响下的压电-硅膜耦合振动位移振形待定系数λ对比后,找到了增加的阻尼项,微气流对驱动结构振动位移的影响正是通过该阻尼项体现的。研究可为微流体的驱动及协调控制提供相关理论基础及控制策略。     

一种低成本压电无阀微泵的研制

提出了一种低成本的由压电材料驱动的平面扩张/收缩管无阀微泵的制作工艺.通过数值模拟确定了扩张/收缩管扩张角的最优值,在此基础上,采用光刻和湿法刻蚀工艺,刻蚀了300μm深的泵腔基片和100 μm深的盖片;使用等离子体清洗技术将其与PDMS薄膜键合,完成了可以实现单向泵送的压电无阀微泵样机制作.研究了该压电无阀微泵样机的...     

基于声表面波实现数字微流体的产生

数字微流体的产生是压电材料为基片的微流控芯片进行微流分析的前提,报道了在压电基片上应用声表面波技术产生数字微流体的方法.在128°旋转Y切割X传播方向的LiNbO3基片上集成PDMS微通道,在微通道出口一侧为经疏水处理的铝薄片,注射泵产生恒定流量的微流体经PDMS微通道到达铝薄片并聚集,当聚集的微流体体积足够大时,微流体克服表面张力作用下滑到达压电基片,并在中心频率为27.7 MHz叉指换能器激发的声表面波作用下输运,实现微流体的数字化.同时,理论分析了微流体在铝薄片表面上受力状况,并以水为实验对象,进行微流体数字化实验.结果表明,声表面波作用下能精确产生微升量级数字微流体,为压电微流控芯片提供了一种新的微流体引入方法.     

聚二甲基硅氧烷微流体芯片的制作技术

基于MEMS技术的微流体芯片在分析化学和生物医学领域显示了巨大的应用潜力。作为构建微流体芯片的基底材料———聚二甲基硅氧烷(PDMS)已经表现出了许多的优点:良好的电绝缘性、较高的热稳定性、优良的光学特性以及简单的加工工艺等。采用浇注法制作了PDMS电泳微芯片,对PDMS微流体芯片的加工工艺、封装方法和结构特征进行了探讨,并提出了相应的解决方案。     

基于MEMS的微泵研究进展

主要介绍了基于MEMS的微泵 10年来的研究成果和研究现状。微泵是微电子机械系统(MEMS)中重要的执行器件 ,在系统中占有很重要的地位。微泵可以分为有阀泵和无阀泵两大类 ,一般来说 ,有阀泵的制造工艺和应用技术比较成熟 ,但存在加工尺寸限制和使用寿命的问题 ;无阀泵的原理新颖 ,结构相对简单 ,更适合微型化发展 ,是目前研究的热点。     

基于微振动马达的无阀微泵的研究

研制了一种可在低电压下工作的新型无阀微泵,该微泵利用有机玻璃(PMMA)制作泵腔,采用了扩散口/喷口的结构,以PDMS作为振动膜,利用微振动马达作为驱动部件。采用ANSYS软件进行有限元分析得到微泵扩散口/喷口的最佳尺寸。对微泵的振动频率和输出流量进行了测试,结果显示:电压为1.0～1.8 V时,微泵的输出流量随着电压的升高而增加,当电压为1.8～3.3 V时,微泵输出的流量保持稳定,达到150μL/min。该无阀微泵结构简单,驱动电压低,具有良好的性能和低廉的成本。     

一种无阀微流体驱动器的研究

一种适用于微流体系统的无阀驱动器利用印刷电路板(PCB)制作腔体以及扩散口和喷口,利用聚二甲基硅氧烷(PDMS)作为振动膜,并利用压电双晶片作为驱动部件。该驱动器的制作工艺简单,使用寿命长,具有良好的液体驱动性能。对于使用15mm长的压电双晶片制作的驱动器,在100V、60Hz、占空比为1的方波驱动下,最大流速可达l50μL/min。     

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.     

Design and fabrication of an electrochemically actuated microvalve

A microfluidic valve based on electrochemical (ECM) actuation was designed, fabricated using UV-LIGA microfabrication technologies. The valve consists of an ECM actuator, polydimethylsiloxane (PDMS) membrane and a micro chamber. The flow channels and chamber are made of cured SU-8 polymer. The hydrogen gas bubbles were generated in the valve microchamber with Pt black electrodes (coated with platinum nanoparticles) and filled with 1 M of NaCl solution. The nano particles coated on the working electrode helps to boost the surface-to-volume ratio of the electrode for faster reversible electrolysis and faster valve operation. To test the functionality of the microvalve, a simple micropump based on ECM principle was also integrated in the system to deliver a microscopic volume of fluid through the valve. The experimental results have showed that an approximately 300 μm deflection of valve membrane was achieved by applying a bias voltage of ?1.5 V across the electrodes. The pressure in the valve chamber was estimated to be about 200 KPa. Experimental results proved that the valve can be easily operated by controlling the electrical signals supplied to the ECM actuators.     

Development of a low cost hybrid Si/PDMS multi-layered pneumatic microvalve

We report on the design and fabrication of a low cost active microvalve with a soft elastomer membrane driven by pneumatic actuation. The valve was made in two separate parts, a fluidic part in biocompatible and optically transparent material (PDMS) and a robust pneumatic interface in silicon, which were assembled together. The main issue of alignment and localized selective bonding of the PDMS parts to preserve the membrane mobility, hence the valving function, is described. In this work we also investigated two types of silicon moulds for PDMS casting, made by KOH anisotropic wet etching or DRIE.     

Improvement of dynamic characteristics of polydimethylsiloxane based microvalve

Microfluidics is an indispensable part of micro total analysis system (μ-TAS) and lab-on-a-chip analysis systems. While most of the work in this area has focused on MEMS based actuation with micropumps and microvalves, polymer based Paraffin actuator is an attractive alternative in terms of ease in fabrication and low cost. While we made previous attempts in fabricating polydimethylsiloxane (PDMS) based devices, it suffered a drawback of low flow rates in the microchannel due to adherence of PDMS to the channel substratum. In the current work, we focused on improvement of mechanical properties of the PDMS membrane by altering prepolymer to crosslinker ratio. We found that a ratio of 100:15 produced sufficient tensile strength to the membrane and also enhanced actuation characteristics of microvalve fabricated with it.     

A layered modular polymeric <Emphasis Type="Italic">μ</Emphasis>-valve suitable for lab-on-foil: design,fabrication, and characterization

Cost-effective fabrication of microfluidic networks require that all components have to be manufactured with up-scalable processes such as reel-to-reel fabrication of foil-based devices. A microvalve design must take into account functional requirements together with manufacturing feasibilities. Here we present the development of a modular polymeric laser structured microvalve. The complete valve structure is designed to be used in a bendable lab-in-foil system. The modular microvalve design consists of three layers: an actuator layer, an interfacing membrane, and a passive microchannel layer to be separately fabricated and then stacked. Different actuator layer concepts are compared out of which a thermal actuation scheme generating sufficient stroke using phase changing paraffin is chosen. The passive layer is designed with a shallow and sufficiently smooth spherical cavity that acts as the valve seat from which paraffin material can reliably retract during solidification. The shape and dimensions of the shallow cavity are derived from the natural membrane deflection and from the channel cross section. It is not essential that all the paraffin within the actuator cavity to be molten for valve closure allowing a high degree of assembly tolerance and inherent sealing of actuator cavity. All the module layers in the current prototype are structured using 3D laser fabrication processes but mass-fabrication methods like reel-to-reel hot-embossing are foreseen as well. A prototype microvalve stack was assembled with a thickness of 1.1 mm which could be further reduced to meet the requirements of extremely flexible lab-on-foil systems. The closed valve is tested up to a pressure of 3 kPa without any measurable leakage. The dynamics of valve closure is evaluated by a new optical characterization method based on image processing of color micrograph sequences taken from the transparent valve.     

Electromagetically driven microvalve

We discuss photolithographic fabrication techniques and experimental results for a prototype electromagnetically driven microvalve. The valve is constructed on a silicon substrate, using a magnetic suspension spring with a valve cap, a valve plate with a 30 μm diameter bore, and an external coil for driving the valve cap. The external electromagnetic drive approach was chosen for its ease of use and practicality in controlling the valve actuator. The valve cap, made of soft magnetic material (NiFe) and supported by the spring, moves vertically as a result of the magnetic field applied by the external coil. To precisely adjust both the valve cap and the valve plate bore and to minimize fluid leakage, a new self-alignment process was developed. The valve is controlled by a 0.1–100 Hz rectangular magnetic field applied by the external coil. The resulting minimum gas flow rate can be controlled to within the neighborhood of 3 × 10⁻⁵ torr·l/s.     

Hybrid replication development for construction of polymeric devices

The combination of poly(dimethyl)siloxane (PDMS) replica molding, hot-embossing of poly(methyl)methacrylate (PPMA) and PDMS membrane transfer has been explored for the construction of a pneumatically-actuated, multi-levelled polymeric microvalve. The critical part of the process, bonding of the three polymeric levels, has been demonstrated. It involves bonding of PDMS to PDMS using two different methods, one with oxygen plasma treatment and heat treatment, and the other one with PDMS as glue, whereas PDMS was bonded to PMMA using a commercial primer. A method for replicating PDMS parts in large number was also described.Nicolas Alamagny and Sylvain Lefèbvre are thanked for their help in the microvalve fabrication and hot embossing respectively. The cleanroom staff is also greatly acknowledged for their help throughout this work. Michel de Labachelerie and Michel Froelicher are also thanked for helpful discussions on the microfluidic aspect of the project and the hot embossing respectively.     

A pneumatic micropump incorporated with a normally closed valve capable of generating a high pumping rate and a high back pressure

This study reports on a new pneumatic micropump integrated with a normally closed valve that is capable of generating a high pumping rate and a high back pressure. The micropump consists of a sample flow microchannel, three underlying pneumatic air chambers, resilient polydimethylsiloxane (PDMS) membrane structures and a normally closed valve. The normally closed valve of the micropump is a PDMS-based floating block structure located inside the sample flow microchannel, which is activated by hydraulic pressure created by the peristaltic motion of the PDMS membranes. The valve is used to effectively increase pumping rates and back pressures since it is utilized to prevent backflow. Experimental results indicate that a pumping rate as high as 900 μL/min at a driving frequency of 90 Hz and at an applied pressure of 20 psi (1.378 × 10⁵ Nt/m²) can be obtained. The back pressure on the micropump can be as high as 85 cm-H₂O (8,610.5 Nt/m²) at the same operation conditions. The micropump is fabricated by soft lithography processes and can be easily integrated with other microfluidic devices. To demonstrate its capability to prevent cross contamination during chemical analysis applications, two micropumps and a V-shape channel are integrated to perform a titration of two chemical solutions, specifically sodium hydroxide (NaOH) and benzoic acid (C₆H₅COOH). Experimental data show that mixing with a pH value ranging from 2.8 to 12.3 can be successfully titrated. The development of this micropump can be a promising approach for further biomedical and chemical analysis applications.     

Development of a Latchable Microvalve Employing a Low-Melting-Temperature Metal Alloy

We present the design, fabrication, and characterization of a latchable microvalve. The valve can be held in the on- or off-state without consuming power. A low-melting-temperature metal alloy provides structural support to hold the valve in place when latched. The metal alloy piece liquefies when it is heated above 62degC, allowing a pneumatic actuator to change the valve state. When the metal cools and solidifies, the valve is once again latched. This type of valve may be useful for portable lab-on-a-chip devices that require low-power operation and long-term fluid storage. A thin-film metal heater has been integrated into the polydimethylsiloxane device to provide localized heating for individual valve elements. Valve closing and opening response times have been simulated and verified by experiment. The burst pressure has been experimentally characterized and parameters influencing this burst pressure have been modeled.