Phase transformation type micro pump

A new type micro pump which uses liquid-vapor phase transformation is developed. Along with liquid to vapor phase transformation, coefficient of kinematic viscosity increases. This means that viscous resistance for mass flow through a channel can be changed by phase transformation. Volume expansion and viscous resistance change by the controlled evaporation produce one directional mass flow. This pump consists of a micro channel and an array of heating elements. This structure is favorable for a micro pump because no mechanical moving parts such as valves are needed. A prototype pump was fabricated by the silicon micro machining technique. By scanning electric current that is supplied through the heaters with different phases cyclically, water in the channel was evaporated and pumped toward the scanning direction.