High temperature gradient micro-sensor for wall shear stress and flow direction measurements

International audienceWe present an efficient and high-sensitive thermal micro-sensor for near wall flow parametersmeasurements. By combining substrate-free wire structure and mechanical support using siliconoxide micro-bridges, the sensor achieves a high temperature gradient, with wires reaching 1 mmlong for only 3 µm wide over a 20 µm deep cavity. Elaborated to reach a compromise solutionbetween conventional hot-films and hot-wire sensors, the sensor presents a high sensitivity to thewall shear stress and to the flow direction. The sensor can be mounted flush to the wall for research studies such as turbulence and near wall shear flow analysis, and for technical applications, such as flow control and separation detection. The fabrication process is CMOS-compatible and allows on-chip integration. The present letter describes the sensor elaboration, design, and micro-fabrication, then the electrical and thermal characterizations, and finally the calibration experiments in a turbulent boundary layer wind tunnel