Mechanism of the motion of spherical microparticle induced by a collapsed microbubble

Abstract

Collapse of a confined bubble is the core problem of bubble dynamics. The recent study has shown that the collapse of macroscopic bubble may drive the motion of suspended particle with the similar size, but, there has still been a lack of the relevant study on a microscale. In the experiment about the bubble driven micro-motor, the locomotion of motor pushed by microjetting has been noticed. However, due to the limitation of experimental conditions, it is difficult to reveal the details of propulsion mechanism. In this paper, the volume of fluid based numerical method is adopted to simulate the interaction process between a collapsing microbubble and the suspended particle nearby. The spatial distribution and the time evolution of flow field are obtained, and the velocity that the micromotor could be achieved is deduced by integrating the impulsive force. The results show that when the bubble size is fixed, the interaction force is inversely proportional to the size of microparticle and the gap between microparticle and bubble. The Kelvin impulse theorem is used to clarify the difference between the interaction on a macroscopic scale and that on a microscopic scale. This study not only extends the scope of cavitation dynamics, which reveals the characteristics of interaction between bubble and particle on a microscale, but also is significant for improving the efficiency of self-propelled micro-motor.