Dynamics of Fiber Optic Airgun Bubbles for Micropropulsion

While extensive research on pressure wave emissions from meter-scale airgun bubbles, the dynamics at the microscale, particularly regarding fiber laser-induced bubble generation, remains less explored. In this Letter, we investigate the dynamic properties of a fiber optic airgun that fires bubbles to propel polystyrene particles in a two-dimensional plane. A linear dependence of particle propulsion on energy distribution with respect to length is observed. The temporal ejection behavior of the particles is attributed to the abrupt jerk response caused by the expansion diminishes of the bubble. We identify two hydrodynamic regimes governing the liquid-solid interaction, i.e., the axial bubble pressure along the fiber is determined by the bubble-particle length, yielding a boundary coefficient of 0.65. We find the dimensionless maximum axial displacement of the particle approximately follows fourth-power scaling laws and aligns with the experimental results in their respective regimes. Such a study offers potential avenues for micromechanical configurations to manipulate interactions among disparate microsystems, especially in the field of microbubble-driven mechanical actuators.