A Proportionally Controlled Microvalve using a Piezoelectric Unimorph Microactuator
A. Gunda (TU Delft - Mechanical Engineering)
Murali K. Ghatkesar – Mentor (TU Delft - Micro and Nano Engineering)
Marcel Tichem – Graduation committee member (TU Delft - Micro and Nano Engineering)
JFL Goosen – Graduation committee member (TU Delft - Computational Design and Mechanics)
J.C. Lötters – Graduation committee member (University of Twente)
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Abstract
Microvalves are important flow-control devices in many standalone and integrated microfluidic applications. PDMS-based (Polydimethylsiloxane) pneumatic microvalves are the most commonly used type for research purposes, but they require large peripheral connections and cannot be used for controlling gases due to the high gas permeability of PDMS. There are many alternatives found in the literature that use Si-based microvalves, but variants that can throttle even moderate pressures (1 bar) tend to be bulky (cm-range), have a complex fabrication process, or consume high power. This thesis details the development of a low-power, normally-open piezoelectric microvalve to control flows with a maximum driving pressure of 1 bar, but also retain a small effective form-factor of 5mm x 5mm x 1.8mm. A novel combination of rapid-prototyping methods like stereolithography and laser-cutting was used to realize this device. The maximum displacement of the fabricated microactuator was measured to be 8.5 μm at 150V. The fabricated microvalve has a flow-range of 0 - 90 μL/min - water at 1 bar inlet pressure. When fully closed, a leakage of 0.8% open-flow was observed with a power-consumption of 37.5 μW. A flow resolution of 0.2 μL/min was measured at 0.5 bar pressure.