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Proceedings Paper

Liquid and gas-liquid phase behavior in thermopneumatically actuated microvalves
Author(s): Albert K. Henning
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Paper Abstract

Thermopneumatically actuated microvalves rely on the thermal expansion of a gas, liquid, or gas-liquid mixture, hermetically sealed within an actuation cavity. This cavity is, typically, mechanically rigid on all sides, except for the side containing a mechanically flexible membrane, which is responsible for controlling the flow of fluid in the microvalve. Taken as a system, this actuation technique requires simultaneous consideration of the mechanical behavior of the membrane, the mechanical behavior ofthe control fluid, and the coupled thermal behavior ofthe valve and control fluid. Previous work has discussed the details of the liquid and gas-liquid behavior of the hermetically-sealed control fluid'. Figures ofmerit were developed for membrane behavior as a function ofYoung's modulus, valve structural parameters, and some of the thermodynamic properties of the thermopneumatic control fluid. However, the effects of initial thermodynamic state of the control fluid, external temperature (including thermal gradient), external pressure, and the temperature boundary condition at the control fluid's heat source were not considered. In this work, these effects are considered quantitatively. A model for the steady-state valve behavior (membrane deflection versus input heater power) is developed. The utility ofthis model in designing microvalves for gas and liquid flow control is also demonstrated.

Paper Details

Date Published: 10 September 1998
PDF: 11 pages
Proc. SPIE 3515, Microfluidic Devices and Systems, (10 September 1998); doi: 10.1117/12.322096
Show Author Affiliations
Albert K. Henning, Redwood Microsystems, Inc. (United States)

Published in SPIE Proceedings Vol. 3515:
Microfluidic Devices and Systems
A. Bruno Frazier; Chong Hyuk Ahn, Editor(s)

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