Study Of Microbubble Generation And Motion Characteristics Based On Microfluidics

Ionic liquids are widely explored as reactants or separation media in multiphase systems.Combined with the recent trend of miniaturized chemical processes,the flow and dispersion dynamics of gas-ionic liquid systems at the microscale becomes increasingly important for enhancing the efficiency of chemical processes/reactions.The current research on the detailed descriptions of the formation and dispersion kinetics of microbubbles in different ionic liquids within microfluidics are lacking.At the same time,chemical reactions usually are gas-liquidsolid three-phase flow,where catalytic particles are heavily employed.To achieve efficient transport in practical miniaturized chemical synthesis,understanding gas-liquid-solid threephase flow at microscale is urgently demanded.In this work,flow-focused glass capillary microfluidics are designed to systematically study gas-ionic liquid two-phase flow and gasionic liquid-solid particle three-phase flow.The effects of different influencing factors on the generation and motion of microbubbles in the microfluidics are analyzed.Firstly,a microscope with a high-speed camera was used to observe and record the twophase gas-ionic liquid flow processes in microfluidics with different geometries.The effects of microfluidics geometry,gas phase flow rate,liquid phase flow rate,and different liquid phases on the flow pattern distribution were analyzed.The following conclusions were obtained: at higher gas phase flow rates and lower liquid phase flow rates,it was easier to form slug flow.Bubble flow was more likely to form in microfluidics with smaller gas outlet diameters and smaller flow channel diameters at constant phase flow rates.In higher viscosity ionic liquids,shear forces are stronger,resulting in smaller regions of slug flow and larger regions of the bubble flow.Then,the formation and dispersion kinetics of microbubbles in different ionic liquids in flow-focused glass capillary microfluidics were investigated based on the flow range of the bubble flow.The following conclusions were obtained: at the constant phase flow rate,the bubble size decreased significantly with decreasing gas outlet diameter and decreasing flow channel diameter,and the bubble generation frequency and bubble velocity increased accordingly.For a constant liquid phase flow rate,the bubble size,deformation,and velocity increase with increasing gas phase flow rate,while the curvature of the head and tail of the bubble and the frequency of bubble generation decrease.With a constant gas phase flow rate,as the liquid phase flow rate increases,the bubble size decreases,the curvature of the head and tail increases,the degree of deformation remains almost constant,and the frequency and velocity of bubble increase significantly.Establish mathematical relationships for predicting the bubble size in different ionic liquids in flow-focused glass capillary microfluidics with different geometries,and good prediction results were achieved.Finally,different concentrations of solid particles were added to the liquid phase and their effects on bubble size,deformation,generation frequency,and velocity were investigated.The following conclusions were obtained: with increasing concentration of solid particles,bubble size,generation frequency,and velocity decreased,the deformation was almost constant.The mathematical equation established for predicting bubble size in ionic liquids in the gas-liquid two-phase system still provides good predictions for bubble size in slurries in the gas-liquidsolid three-phase system.The slurry bubble flow has the characteristics of standard bubble flow with uniform size,stable flow,and controllable generation frequency,but also circumvents the problems of cumbersome replacement operation of deactivated catalysts and channel blockage due to catalyst particle deposition,and has promising applications in the efficient transport of microchemical reaction processes.