Research On Microbubble Formation Characteristics In Microfluidics

Microbubbles have many characteristics which differ from those of ordinary bubbles.Microbubble dispersions have been widespread applied in chemical engineering,environment,biological science and drug engineering.As an advanced technique for microbubble generation,microfluidic utilizes micro channel,flow focusing,electrical hydrodynamics and so on comprehensively in order to generate microbubbles whose size distribution is narrow with a microscale size.Common techniques for microbubble generation can't realize above goals.The development of microbubble techniques would be promoted substantially if the strong size controllability of microfluidics is utilized adequately,then the application of microbubble could be broaden to those wider and deeper field.The present study focused on the formation of microbubble in microfluidic devices.Microbubble formation surrounded by co-flowing liquid was investigated.Reasonable assumptions were adopted to simplify the mechanics condition of microbubble during its growth.Both spherical and non-spherical model were proposed to predict the formation process of target microbubble,then the simulation model based on the MATLAB/Simulink was built to complete the calculation of above-mentioned spherical model.The detachment volume,formation time and growth process were obtained on the basis of above theoretical works.A mechanically assembled microfluidic chip was designed and fabricated based on several capillary tubes which were pulled into micro scale.The experimental system for microbubble formation was built in order to figure out the effect of gas pressure and co-flowing liquid rate on the detachment volume,formation time,volume variation as time,center displacement and move velocity of target microbubble.Meanwhile,the analysis results of theoretical model on the microbubble formation under the action of co-flowing liquid were verified adequately.Microbubble formation affected by the vibration of capillary tube was investigated in the present study.According to the inverse piezoelectric effect,a low-frequency vibration platform was developed to figure out the effect of vibration on microbubble formation.For the tiny displacement which the piezoelectric actuator outputs,a mechanism based on flexible hinges was developed to amplify the displacement amplitude of the PZT actuator.Another experimental system was built to complete series of tests on the microbubble formation under the action of vibration.The influences of the frequency of sinusoidal signal and the voltage amplitude on the average size and formation frequency of microbubble were experimentally studied respectively.On the basis of flow focusing principle in microfluidics,a new microfluidic device utilizing 3D print technique and glass capillary tubes was developed innovatively.Tests on this new microfluidic device were conducted in order to investigate its ability on the production of microbubbles,meanwhile,the formation characteristics of microbubble in it were studied.Finally,for the goal of generating microbubbles whose size distribution was controllable and on the basis of different integration methods,the integrated microfluidic device was developed.