An Optical MEMS Sensor for Dynamic Wall Shear Stress Measurement in Complex Flow

This work presents an optical MEMS wall shear stress sensor specifically designed for dynamic measurements in complex flow. The sensor features a floating structure integrated with a differential optical readout scheme, enabling non-contact detection of micro-scale displacements with a high temporal resolution. This configuration offers strong immunity to electromagnetic interference. Structural parameters are optimized through a multi-objective genetic algorithm, resulting in a theoretical first-order resonance frequency of 10.4 kHz while preserving sufficient mechanical sensitivity. The performance of the fabricated sensor prototypes is comprehensively validated through a series of experiments, including static calibration in a laminar flow channel, transient response characterization in a shock tube, and unsteady wall shear stress measurements in various wind tunnel environments. The experimental results confirm that the sensor reliably captures abrupt variations in wall shear stress and exhibits consistent dynamic responses. A repeatability error of only 1.36% demonstrates the sensor's reliability and applicability in high-speed, unsteady flow measurements.