Thermal and Coriolis type micro flow sensors based on surface channel technology

Recently, we proposed a fabrication technology to realize fluidic channels at the surface of a silicon wafer [1]. The channels have semi-circular cross section and a flat top so that low hydraulic resistance is combined with easy integration of actuation and readout structures. In this paper we present a number of flow sensors that have successfully been realized using this technology. Thermal flow sensors were realized in which heating resistors and thermopile sensors were integrated on top of freely suspended channels. With these sensors, a resolution in the order of nl/min can be achieved. Furthermore, Coriolis type flow sensors have been realized in which a freely suspended channel is brought into vibration so that the moving fluid experiences Coriolis forces. The Coriolis forces excite another vibration mode which can be detected optically or capacitively.