Hydrodynamics of light levitated droplet evolution

Light levitation of droplets over a locally heated gas–liquid interface by an infrared focus laser has been recently reported, but the hydrodynamics of light levitated droplet evolution remains unclear. Herein, we report that the condensed droplet experiences a periodic damped vortex motion process before evolving to a stably levitated droplet. In the later stage of the periodic damped vortex motion, the velocity decay rate is linearly proportional to the growth of condensed droplets. The linear scaling factor approximates the dynamic viscosity of the ambient fluid, which is analogous to the shear stress–shear relationship in the Newtonian friction law. This study deepens the understanding of the underlying mechanism of light levitated droplet evolution.