Research On Formation Mechanism And Control Strategy Of Microscale Standing Air Bubbles

Micro-nano operation technology has developed rapidly in the past two decades.Various applications have been gradually derived from the initial theoretical basic research,such as electronic silicon chip manufacturing,micro/nano-scale sensors,biological microfluidic,etc.Micro-nano manipulation revolutionized the fields of mechanical manufacturing,optoelectronic technology,ultra-precision processing,biomedical and so on.Nowadays,Micro-nano manufacturing level has become one of the important indicators to measure a country’s scientific and technological level.This paper summarized the research status of micro-nano manipulation and microfluidic bubbles firstly.A novel strategy for the micro bubble generation and control is porposed,called micro standing air bubble.Based on this,a new flexible bubble-based actuator was studied.Here,this paper elucidates the mechanism of standing air bubble nucleation and variation.Considering microscale hydrodynamics and the mass transferring between the gas-solid-liquid dynamic interface,the surface properties and structural characteristics of the microchannel,the physical model of the bubble generation is established.We also discussed the correlation between the initial state of standing sir bubbles and key parameters,such as liquid properties,channel surface properties and geometry characteristics and other factors.A two-dimensional model for standing air bubble generation has established using COMSOL Multiphysics simulation software.To study the air bubble formation and growth,the numerical simulation of is also implemented,including the mass transferring process.The continuous gas-liquid reactor has designed with the standing air bubble as a basic unit to further verify the gas mass transfer process.The reactor can not only precisely regulate the mass transfer interface morphology between the two phases,but also obtain a wide gas-liquid reaction interface by replicating or arraying the crack structure.A continuous,fast,and efficient gas-liquid reaction is achieved through the combination of a suitable gas pressure and relatively high flow rate.In this dersatation,we develop several bubble-based microfluidic chips,verifing the bubble generation and volume control process through experiments.Then optimize the chip structure parameters and design experiments to verify the effect of different control pressures,different PDMS partition thickness,the effect of different PDMS partition thickness and different crack widths,different channel widths on the bubble volume change rate.In order to realize the automatic control of the bubble,the machine vision is introduced into the real-time volume detection of the μSABs.The visual recognition system for bubble formation is established in the Open CV-Python environment by detecting the ROI region,binarizing the image,and counting the amount of pixel value change to detect the volume change of the resident bubble under the microscope.And use this program to explore the parking bubble open loop control strategy,and prepare for the closed loop control.