Piezoelectric micropump having actuation electrodes and stopper

Details Piezoelectric micropump having actuation electrodes and stopper Piezoelectric micropump having actuation electrodes and stopper

1996-06-05

1998-06-02

McAndrews, Roland

Pumps

Motor driven

Magnetostrictive chamber

4174132, 4174133, 92 132, F04B 1700

Patent

active

057590150

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention is concerned with a micropump including at least one base plate, at least one upper plate and one intermediate plate sandwiched between the two other plates and made of a material which can be machined so as to define a pumping chamber, at least one control member for the inflow of the fluid to connect the pumping chamber with at least one inlet to the micropump and at least one control member for the outflow of the fluid to connect the pumping chamber with at least one outlet of the micropump, the pumping chamber including a movable wall which is machined in the intermediate plate and which can be displaced in two opposite directions during the suction of a fluid from the inlet to the pumping chamber or during the expelling of this fluid from the pumping chamber to the outlet, actuating means being provided to move said movable wall to cause a periodic variation of the volume of the pumping chamber.
Such pumps can be used in particular for the in situ administration of medicinal drugs, the miniaturization of the pump allowing a patient to carry the same on his body, or even to have the pump implanted directly in the body. Furthermore, such pumps allow the administration by injection of small metered amounts of fluid.
In an article entitled "A piezoelectric micropump based on micro-machining of silicon"published in "Sensors and"Actuators" N15 (1988), pages 153 to 167, H. Van Lintel et al. give the description of two embodiments of a micropump, including each a superposition of three plates, namely of a machined silicon plate placed between two glass plates.
The silicon plate is etched to form a cavity, which, with one of the glass plates, defines the pumping chamber, an inflow or suction valve and at least one outflow or expelling valve, allowing the pumping chamber to communicate respectively with an inflow channel and an outflow channel. The part of the plate forming a wall of the pumping chamber can be deformed by a control member provided for example as a piezoelectric chip or crystal. The same is equipped with two electrodes which, when they are connected to a source of voltage, cause the deformation of the chip and, consequently, the deformation of the plate, which causes a variation of the volume of the pumping chamber. This movable or deformable wall of the pumping chamber can thus be moved between two positions.
The functioning of the micropump is as follows. When no voltage is applied to the piezoelectric chip, the inlet and outlet valves are in their closed position. When a voltage is applied, an increase of the pressure inside the pumping chamber occurs, which causes the opening of the outlet valve. The fluid contained in the pumping chamber is then expelled through the outflow channel by the displacement of the deformable wall from a first position towards a second position. During this phase, the inlet valve is maintained closed by the pressure prevailing in the pumping chamber.
Conversely, when the voltage is decreased, the pressure in the pumping chamber decreases. This causes the closing of the outlet valve and the opening of the inlet valve. The fluid is then sucked into the pumping chamber through the inflow channel, owing to the displacement of the deformable wall from the second position to the first position.
As already mentioned, these micropumps are used in particular for the administration of medicinal drugs. It is therefore important that the flow rate of the micropump be well defined, so that the medicinal drug injected be metered very precisely. However, known micropumps suffer in this respect, from certain imperfections.
In actual fact, the flow rate of the micropump depends on the variation of the volume of the pumping chamber between the two positions of the deformable wall. This variation of the volume depends on several parameters, among which the voltage applied to the piezoelectric chip and the physical characteristics of the piezoelectric chip (thickness, diameter, dielectric constant) and of the deformable wall (materia

REFERENCES:
patent: 417035 (1889-12-01), Hyatt
patent: 1183486 (1916-05-01), Pardue
patent: 5085562 (1992-02-01), Van Lintel
patent: 5171132 (1992-12-01), Miyazaki et al.
patent: 5271724 (1993-12-01), Van Lintel
H.T.G. Van Lintel, "A Piezoelectric Micropump Based on Micromachining of Silicon", Sensors and Actuators, 1988, vol. 15, pp. 153-167, Elsevier Sequoia/Printed in the Netherlands.

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