A piezoelectric microvalve for compact high-frequency, high-differential pressure hydraulic micropumping systems

Abstract

Abstract-A piezoelectrically driven hydraulic amplification microvalve for use in compact high-performance hydraulic pumping systems was designed, fabricated, and experimentally characterized. High-frequency, high-force actuation capabilities were enabled through the incorporation of bulk piezoelectric material elements beneath a micromachined annular tethered-piston structure. Large valve stroke at the microscale was achieved with an hydraulic amplification mechanism that amplified (40 50 ) the limited stroke of the piezoelectric material into a significantly larger motion of a micromachined valve membrane with attached valve cap. These design features enabled the valve to meet simultaneously a set of high frequency ( 1 kHz), high pressure( 300 kPa), and large stroke (20-30 m) requirements not previously satisfied by other hydraulic flow regulation microvalves. This paper details the design, modeling, fabrication, assembly, and experimental characterization of this valve device. Fabrication challenges, such as deep-reactive ion etching of the piston and valve membrane structures, wafer-level silicon-to-silicon fusion bonding, wafer-level and die-level silicon-to-glass anodic bonding, preparation and integration of piezoelectric material elements within the micromachined tethered piston structure, and filling of degassed fluid within the hydraulic amplification chamber are detailed.[829]

A normally-closed piezoelectric micro-valve with flexible stopper

“…More important, all of the hydraulically amplified piezoelectric micro-valves in Ref. 14,15, and 18 are normally opened valve and driven by PZT stack, which have expensive cost and are not suitable for the occasion of the flow channel need to be cut-off when powering off. In some controlled drug system, the micro-valve should be closed for several months or even a few years, 19 so normally opened valve will consume much energy when it is not delivering drugs.…”

“…12 and 13 can not provide high cut-off pressure, when it was used as the actuator of micro-valve. In 2003 and 2004, D.C. Roberts et al 14 and H.Q. Li et al 15 reported a piezoelectric driven hydraulic amplification micro-valve which took PZT stack as the driving source, multilayer silicon and glass structure was selected, it turned out that the working frequency was higher than 1 kHz, but it required a complex fabrication process including 22 photolithography steps and particle tolerance is low as it utilize rigid plate as valve stopper.…”

Out-of-Plane Knife-Gate Microvalves for Controlling Large Gas Flows

“…The actuator size, and thus the consumed valve footprint area for these devices, must be large in comparison to the minimum flow cross-sectional area, which prohibits large component counts per batch. Microvalves with actuation principles that require manual assembly include electrostatic actuation [8], [9], electromagnetic actuation [10], shape-memory alloy actuation [11], thermopneumatic actuation [12], and piezoelectric actuation [13], [14]. These valves offer larger energy density and larger stroke than do other techniques, however, cost more to assemble.…”

Optimal Materials Selection for Bimaterial Piezoelectric Microactuators

“…Present generation miManuscript received February 26, 2007; revised October 26,2007 Despite their promising characteristics, applications of piezoelectrics in commercial microsystems are not widely prevalent but do include the important case of inkjet printer heads [4] and noncontact atomic force microscope probes [5]. However, a much wider range of research or prototype applications of piezoelectrics in MEMS include linear micromotors [6]- [8], high power transformers [9], micropumps [10], [11], and power generators [12].…”