Abstract
In the field of controlled drug delivery system, there are still many problems on those reported micro-valves, such as the small opening height, unsatisfactory particle tolerance and high cost. To solve the above problems, a novel normally-closed piezoelectric micro-valve is presented in this paper. The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper. The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism. The experiment indicates that maximum hydraulic amplification ratio is up to 14, and the cut-off pressure of the micro-valve is 39kPa in the case of no working voltage. The presented micro valve has a large flow control range (ranging from 0 to 8.75mL/min).
Highlights
His team[18] presented that a solid hydraulically amplified piezoelectric micro-valve with an incompressible gelatin elastomer as hydraulic medium, because it was using semisolid medium, the amplification and working frequency got constraints
The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper
The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism
Summary
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. The micro-valve presented in this paper was driven by circular unimorph piezoelectric vibrator based on hydraulic amplification mechanism. The micro-valve is normally closed, which makes the flow channel cut-off with pressure difference below 39kPa when powering off. The normally-closed micro-valve will not consume energy when it does not work, this feature is very important to drug-delivery system. The micro-valve can convert the small axial displacement (22μm) of piezoelectric vibrator into a large stroke (308μm) at valve stopper, with amplification ratio up to 14×. Since the flexible valve stopper has large seal contact area with valve hole, the micro valve has a high tolerance of particles
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