Development of an Air Flow Microsensor and Its Application to a Flow Control System

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A new conceptual air flow sensor based on wind-receptor hairs of insects which can detect low-velocity air flow was developed. This sensor is composed of two parts. The one is a cross-shaped beam (3 mm in length, 230 μm in width, and 10 μm in thickness) with the strain gauges fabricated at its four edges. The other part is a thin long wire (30 μm in diameter and 1-3 mm in length) which was made of gold and attached to the center of the cross-shaped beam. If the air flow attacks the wire, the cross-shaped beam is deformed. Therefore, we can find the velocity of air flow because the resistance of the strain gauges changes depending on the beam deformation.The characteristics of the sensor were measured in a wind tunnel. We found that the output voltage of the sensor has a linear relationship with the air velocity, and that, moreover, the sensor can detect not only the velocity of the wind but also its two-dimensional direction. The characteristics depend on the mechanical properties of the thin long wire and cross-shaped beam and the sensitivity of the strain gauges. Therefore, we particularly tried to get the optimal fabrication process of the strain gauges, and succeeded in fabricating them with a good yield and high reproduction.Moreover, the several basic experiments were made in order to show that the sensor has the feasibility of the application to a flow control system which will be used to reduce a drag force of airplanes. The micro system composed of several micro-sized hot wire sensors and many small electromagnetic actuators reduced the drag force of the cylinder by 16% which was 9 cm in diameter and had them on its surface.