Experimental Study On Micro-bubble Generation And Ultrasonic Manipulate

Micro-bubbles are micron scale bubbles,which have unique hydrodynamic characteristics and scale effect,making its widely used in more and more fields,especially biomedicine.Therefore,it has become a hot topic now to study the preparation of micro-bubbles,the control of its size and motion.In this paper,the formation of bubbles and the movement of micro-bubbles under ultrasound are studied by experiment and heoretical analysis.In this paper,micro-bubbles were generated by means of microfluidic elements.Designed the fluid focusing microchannel and made it by PDMS.Then built experimental platform,and the micro-bubbles were prepared by the experimental method.Changing the gas pressure and liquid flow can control the size of bubbles in50?m to 200?m.The experimental results show that the bubble size is inversely proportional to the liquid flow,and is proportional to the gas pressure.The changes of the gas liquid interface morphology during the formation of micro-bubbles were recorded by a high speed camera.The VOF software was used to simulate the formation of micro-bubbles in Fluent.The formation mechanism of micro-bubbles in the microchannel was studied based on the analysis of the pressure distribution and velocity field in the microchanne combined with experiment.The bubble formation extends from the two phase interface to the neck,the bubble head expands,pinch off and fall off.The pressure difference between the two phases in the microchannel,the axial direction and the radial direction of the fluid flow field,and the velocity difference control of the gas phase velocity control the formation of a bubble.Analysised the mechanism of micro-bubbles controlled by ultrasonic standing wave field,established standing wave equation and acoustic radiation force equation,analyzed the force of micro-bubbles in standing wave,established equations of motion of micro-bubbles in water.Designed the micro-bubbles experiment system to control the motion of micro-bubbles in water.When the frequency is 30 k Hz,themotion of micro-bubbles which size less than 100?m can be controled by moving standing wave node.The motion distance is proportional to the adjustment of the acoustic phase.