Performance of a Micro-Optical Wall Shear Stress Sensor Based on Whispering Gallery Mode Resonators

In this paper, we discuss the dynamic performance of a novel wall shear stress sensor concept based on whispering gallery mode (WGM) shifts of a dielectric microsphere resonator. In the shear stress sensor model, the wall shear stress acting on a sensing element, typically 125 m in diameter, is transmitted mechanically to the microsphere and the transmitted force leads to shifts in the WGMs of the microsphere. By monitoring these WGM shifts, the magnitude as well as the direction of the wall shear stress can be measured. The measurement principle was demonstrated in a previous paper which presented static shear stress results. The sensor used in the present study is a dielectric microsphere made of Polydimethylsyloxane (PDMS), and is tested for loading for dynamic measurements, An electronic circuit is developed to track the fast moving optical resonances (WGM) under dynamic loading