The application of thermopneumatic actuators to microvalves and microfluidic processing systems continues to attract research and development interest. Yet, as with most microvalve and microfluidic work, little information has been reported with respect to the reliability of microfluidic and microflow systems. In this work, therefore, we extend our earlier discussions of factors affecting silicon membrane reliability, to encompass particular effects of thermopneumatic actuators on such membranes. Specifically, we report experiments demonstrating the effect of cavitation in thermopneumatic actuators on silicon membranes. These experiments show that the nature of cavitation, in a hermetic, thermopneumatic actuator cavity which includes a silicon membrane, is to initiate fast transient pressure pulses in the cavity. The membrane moves mechanically in response to these pressure pulses. If the magnitude of these pressure pulses causes the membrane stress to exceed the silicon yield strength, then fracture of the membrane can occur. The work concludes with a conceptual approach to the design of thermopneumatic actuators, to ensure this failure mode does not occur.
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