Abstract
This paper describes a microvalve which is actuated by electrostatic force for the flow control of fuel in portable direct methanol fuel cell systems. The microvalve is fabricated by using standard MEMS fabrication techniques including photolithography, wet etching, thin film deposition and anodic bonding. The microvalve is equipped with a novel pressure-balance mechanism for normally-closed operation against pressurized fuel. The pressure-balance mechanism is composed of a pressure-balance tank whose pressure is adjusted to the same pressure as inlet by a soft corrugated diaphragm. This balanced pressure pushes the boss, which is supported by a soft actuator diaphragm, to close the microvalve, enabling a low driving voltage operation. By applying 100 Vdc, the microvalve controlled the flow rate of methanol up to maximum flow rate of 100 μl/min at an inlet pressure of 40 kPa. The microvalve is expected to miniaturize the fuel delivery system, and eventually increase the practical energy density of portable fuel cell systems.
