Dynamics of laser-induced microbubbles in an absorbing liquid

Abstract

Abstract. The generation and subsequent dynamics of a microbubble in a liquid are investigated, both experimentally and theoretically. When a laser beam is focused into an absorbing liquid comprising colloidal red dye particles in isopropanol alcohol inside a thick quartz cuvette, microbubbles can be generated at around the focus due to nucleation and thermal cavitation. It is experimentally shown that in some cases, the generated microbubble that initially moves away from the focus due to the longitudinal optical gradient force is later attracted to the focus due to the longitudinal thermocapillary force. In our previous work, the thermocapillary force acting on a microbubble is studied two dimensionally. The thermocapillary force acting on the microbubble is determined by directly solving the three-dimensional (3-D) heat equation by 3-D Fourier transform methods. When developing the complete force model in microbubble dynamics, the thermo-capillary force, optical force, buoyancy force, gravity, and the viscous force have been considered.