Piezoelectrically Actuated Microvalve for Liquid Effluents - Tech Briefs

NASA’s Jet Propulsion Laboratory

Modifications have been proposed to effect further improvement of the device described in “Improved Piezo- electrically Actuated Microvalve” (NPO-30158), NASA Tech Briefs, Vol. 26, No. 1 (January 2002), page 29. To recapitulate: What is being developed is a prototype of valves for microfluidic systems and other microelectromechanical systems (MEMS). The version of the valve reported in the cited previous article included a base (which contained a seat, an inlet, and an outlet), a diaphragm, and a linear actuator. With the exception of the actuator, the parts were micromachined from silicon. The linear actuator consisted of a stack of piezoelectric disks in a rigid housing. To make the diaphragm apply a large sealing force on the inlet and outlet, the piezoelectric stack was compressed into a slightly contracted condition during assembly of the valve. Application of a voltage across the stack caused the stack to contract into an even more compressed condition, lifting the diaphragm away from the seat, thereby creating a narrow channel between the inlet and outlet. The positions of the inlet and outlet, relative to the diaphragm and seat, were such that the inlet flow and pressure contributed to sealing and thus to a desired normallyclosed mode of operation.

Like the prior valve, the proposed improved valve (see figure) would include a base that would contain a seat, an inlet, and an outlet. The piezoelectric stack would be connected to a valve boss at one end and to a rigid valve cap at its other end. In the absence of an applied potential, the valve boss would be pressed against the valve seat, so that flow would be blocked. The application of a potential of 60 V across the stack would cause the stack to shrink, pulling the valve boss away from the seat and thereby opening a flow channel between the inlet and the outlet.

In order to increase the spring bias of the valve toward the closed position and thereby help to minimize leakage in the absence of an applied potential, the boss plate would be slightly stretched. The force generated by the piezoelectric actuator would be about 100 N — enough to overcome both the tension in the boss plate and the pressure-aided valve-closing force at an upstream-to-downstream differential pressure as large as 300 psi (≈2 MPa).

This work was done by Eui-Hyeok Yang of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to

Refer to NPO-30562, volume and number of this NASA Tech Briefs issue, and the page number.

(reference NPO-30562) is currently available for download from the TSP library.

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This article first appeared in the December, 2003 issue of Motion Control Tech Briefs Magazine (Vol. 27 No. 12).

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The document presents an improved design for a micro valve actuated by a miniaturized piezoelectric stack, developed by Eui-Hyeok Yang at NASA's Jet Propulsion Laboratory (JPL). This innovation addresses the need for high-pressure liquid handling capabilities in microfluidic systems, particularly for space applications. The valve design features a compact structure, measuring only 0.9 mm x 0.9 mm x 10 mm, and operates using a piezoelectric stack actuator in d31 mode, which allows for longitudinal contraction.

The valve's operation is based on a simple mechanism: in the absence of an applied potential, the valve boss is pressed against the valve seat, blocking fluid flow. When a potential of 60 V is applied, the piezoelectric stack shrinks, pulling the valve boss away from the seat and allowing fluid to flow between the inlet and outlet. This design incorporates a spring bias to minimize leakage when the valve is closed, enhancing its reliability.

The document highlights the advantages of this valve over existing technologies. While other commercially available miniature valves, such as those developed by Hewlett Packard and IC Sensors, utilize thermopneumatic actuation, they are not suitable for high-pressure applications or space environments. The JPL valve, on the other hand, is designed to handle pressures up to 300 psi (approximately 2 MPa) and is capable of managing both liquid and gas, making it versatile for various applications.

The document also discusses the potential applications of this micro valve, including its use in miniature chemical labs for in-situ analysis, inflatable reflectors for pico-satellites, micro coolers for space instruments, and micro propulsion systems. The integration of this valve with other MEMS components could lead to significant advancements in miniaturized propulsion systems and fluidic MEMS technologies.

In summary, the improved micro valve design represents a significant step forward in the field of microfluidics, offering enhanced performance, reduced size, and increased applicability for high-pressure liquid handling in space and other demanding environments. The document serves as a technical disclosure of this innovative technology, inviting inquiries for commercial use.