Flow-sensing mechanism of harbor seal whisker to hydrodynamic perturbation

The harbor seal can accurately perceive minute hydrodynamic perturbations only by its beaded whiskers when vision or hearing is eliminated. The perception ability of whiskers is mainly affected by the whisker structure, the oscillating fluid (perturbation), and the fluid–structure interaction between them. However, the content has not been systematically studied. This paper first establishes a biomechanical theoretical model based on fluid–structure interaction between the oscillating fluid and the harbor seal whisker. Then, the effects of the whisker structure and the oscillating fluid on the hydrodynamic perturbation perception sensitivity are systematically investigated. For the whisker structure, reducing the whisker aspect ratio and density can improve the whisker sensitivity. Increasing the whisker height and the density can improve whisker tuning ability, that is, enhancing the sensing ability of whiskers to hydrodynamic perturbations. For the oscillating fluid, the fluid force, fluid density, and fluid oscillation direction can affect the force exerted on the whisker and then affect the sensing sensitivity of the whisker. We find that considering the additional drag and increasing fluid density can enhance the whisker tuning ability. When the oscillation direction of the fluid is perpendicular to the whisker's dorsal side, the bending stiffness of the dorsal side is less than the bending stiffness of the ventral side, resulting in a larger frequency response and sensing sensitivity and a stronger tuning ability. These findings provide new insights into the flow-sensing mechanisms of harbor seal whiskers and offer valuable inspiration for developing bioinspired flow-sensing technologies.