A Novel Sapphire-Based MEMS Wall Shear Stress Sensor with Remarkable Thermal Endurance up to 800 °c

Wall shear stress is one of the key parameters in near-wall turbulent flow, with profound implications for aerodynamic optimization and drag reduction in aerospace systems. This work presents a novel floating optical MEMS sensor for wall shear stress measurement in harsh flow, featuring a sapphire-based sensing microstructure, remarkably enhancing its thermal endurance. By leveraging integrated femtosecond laser ablation and micro-welding with precision polishing of concave cavities, inherent sapphire machinability and bonding challenges are resolved, enabling prototype fabrication. Calibration via a two-dimensional Poiseuille channel demonstrates a static sensitivity of 0.51 mV/Pa and full-scale nonlinearity ≤ 1.2%. The sensor resolves transient shear stress fluctuations during laminar-turbulent transitions with high dynamic response. Crucially, after 15 minute 800° C exposure, functional integrity is maintained with sensitivity drift limited to 3.9%. This technology enables reliable flow diagnostics in high-Mach propulsion and combustion chambers, advancing energy-efficient flow control strategies.