Three-way silicon microvalve for pneumatic applications with electrostatic actuation principle

We present a normally closed electrostatically driven 3-way microvalve which is able to meet the requirements of industrial applications like small form factor, high flow rate, low weight, low power consumption and a short response time. The microvalve consists of a 3 layer full-wafer bonded silicon chip stack mounted on a ceramics substrate and a plastic cap covering the valve. A driver electronics which converts the TTL level to the actuation voltage of 200 V is placed on top of the valve. The valve operates in a pressure range of up to 8 bar and offers a flow rate of approximately 500 sccm. Due to the electrostatic actuation principle the peak power consumption is below 10 mW and the response time is below 1 ms.     

An enhanced microfluidic control system for improving power density of a hydride-based micro fuel cell

Microfuel cells (MFCs) can potentially power emerging technologies that require power sources in the microliter size range. The recent development of a microfluidic mechanism for self-regulated generation of hydrogen has enabled fabrication of MFCs orders of magnitude smaller than previously possible. In this study, we report an order of magnitude enhancement in the power density of a microliter-scale fuel cell incorporating a new microfluidic design. The microfluidic mechanism is part of an on-board hydrogen generator that uses a reaction between a metal hydride, LiAlH₄, and water vapor to generate hydrogen. The hydrogen generated exits the hydride reactor through a porous silicon wall to reach a Nafion-based membrane electrode assembly (MEA). The microfluidic design increased the water vapor release rate to the hydride reactor by one order of magnitude over a previous design. A 9 μL device incorporating the enhanced microfluidic design delivered a power density of 92 W L⁻¹. Details of a parametric study conducted to improve the water vapor release rate of the microfluidic mechanism and performance analysis of the integrated device are presented in this paper.     

悬臂梁式微型阀

分析了悬臂梁微型阀的静态过流特性,得到了阀的静态压差－－流量曲线并与实验结果比较。采用悬臂梁的拓动微分方法分析了悬擘梁式型阀的动态过波特性。当阀片两介的压差随时间变化时,阀片的启闭与压差的变化之间的存在一定的相位差,有可能引漏甚至反向流动。对阀片的几何尺寸对动态过流特性的影响进行了分析。     

Study of Piezoelectrically Actuated Micropumps with Multiple Parallel Chambers

This study investigated the performance of the piezoelectrically actuated parallel micropumps. The displacement of the piezoelectric (PZT) actuator and the flow rate of the micropump were studied in terms of operating parameters. Using a nonlinear regression technique, empirical models of the micropumps were established based on the experimental data. The experimental results indicated that the displacement of the piezoelectric actuator increased with actuating voltage but decreased with frequency. The flow rate of the micropump was proportional to the applied voltage and demonstrated that the maximum flow rate occurred at an adequate frequency. When operated at a voltage of 140 V and a frequency of 20 Hz, the single micropump delivered a maximum flow rate of 91 µ 1/min. At the same input signal, the maximum flow rate of the double parallel micropump was 1.5 times that of the single micropump, and approximately twice that of the single micropump for triple parallel operation. Furthermore, the obtained non-linear regression formulae can be utilized to predict the flow rate of the micropump with multiparallel chambers.     

Normally-closed peristaltic micropump with re-usable actuator and disposable fluidic chip

We present a new peristaltic micropump offering three key features: (i) a disposable pump body and a re-useable actuator unit, (ii) an intrinsic normally-closed mechanism blocking unintended liquid flows up to a pressure of 100 kPa and (iii) a backpressure independent pump performance up to 40 kPa. The modular concept basing on a re-usable actuator unit and a low-cost disposable microfluidic chip enables an easy and cost-efficient exchange of all contaminated parts after use, which addresses especially the needs in the health care sector. The intrinsic normally-closed feature blocks liquid flow in both directions up to a pressure difference of 100 kPa when the electric power is off. The micropump is actuated in a peristaltic manner by three piezostack actuators. Up to a frequency of 15 Hz the pump rate increases linearly with operation frequency leading to a pump rate of 120 μL/min. This was proved for an operation voltage of 140 V by pumping water. In addition the pump rate is independent on backpressure up to 40 kPa and shows a linear decrease for higher pressure differences. The maximum achievable backpressure at zero flow rate was extrapolated to be 180 kPa. As for all peristaltic micropumps, the pump is bidirectional, e.g. the pump direction can be changed forward to reverse mode.     

微型泵和微型阀的进展

微型泵、阀及微量流体控制系统由于其广泛的应用前景，成为微型机械研究中一活跃的分支。本文着重介绍微型泵、阀的研究现状，论述微型泵、阀的结构设计，致动原理及其实现性能等。     

CMOS compatible bistable electromagnetic microvalve on a single wafer

This paper presents our work in the bistable electromagnetic actuated microvalve. The microvalve is entirely fabricated by surface micromachining on top of a single Si (silicon) substrate. The microvalve has an overall diameter of 1600 μm and the overall height of 600 μm, including the wafer thickness. The bistable mechanism is achieved by integrating an electroplated micro CoNiMnP magnet on the membrane. The microvalve was tested in the flow of deionized (DI) water at 0-50 μL/min. The latching/unlatching of the microvalve was performed to control the flow DI water at 30 μL/min, it required the operational current of 0.38 A and the power of 1.17 W. The latching/unlatching response time of the microvalve is 10 ms, with the leaking rate of 0.16-0.8 μL/min.     

新型光敏聚酰亚胺微型阀

微型阀是微流体测量系统的重要组成部分，本文提出了一种微型光敏聚酰亚胺被动阀，分析了该材料性能，叙述了微型阀的特点、结构设计和工艺流程，并讨论了加工过程中的一些关键技术。     

A piezoelectric microvalve with a flexure-hinged driving frame and microfabricated silicon sealing pair

This paper describes a piezoelectric microvalve for attitude control of micro-satellite with a mass in the range of 20–100 kg. The microvalve comprises of a driving mechanism with a flexure-hinged frame and a valve body with a silicon sealing pair. The silicon valve core with sealing rings can achieve a low leak rate with a small structural deformation. The driving mechanism using a flexure-hinged frame and piezoelectric actuators assures the microvalve normally closed and leads to a fast response of the microvalve. The response time of the driving mechanism is characterized to be as small as 0.6 ms. A maximum flow rate of 3100 mL/min is achieved at an inlet pressure of 0.6 MPa while applied with a maximum voltage of 200 V. The static power consumption is 48 mW with a driving voltage of 200 V, and the dynamic power consumption is approximately 0.9 W at 100 Hz.     

Nonlinear buckling of microfabricated thin annular plates

Annular plate structures are commonly used in MEMS devices, particularly in pumps and valves. In MEMS applications, large nonlinear deflections are routinely achieved. In this paper, the nonlinear buckling of a thin elastic annular plate under a compressive radial force acting in the plane of the plate is considered. Although the critical loads at which buckling starts can be determined by solving a linear eigenvalue problem, the large deflection behavior of a buckled plate beyond the critical loads can be described by the nonlinear theory proposed by von Kármán. The buckling loads of the annular plate for various boundary conditions are calculated and the post-buckling behaviors are examined. Interestingly, the buckling of an annular plate exhibits a supercritical pitchfork bifurcation. Thus, the post-buckling behavior is stable and will not collapse catastrophically. Several design implications for microfabricated structures, in particular microvalves, are also given.