Research On Passive Micromixer With Free Motion Obstacles

The micromixer is an important part of microfluidic chip,which can quickly realize efficient mixing between different samples.It is classified into the active micromixer and the passive micromixer through working characteristics.The active micromixer relies on electric drive,piezoelectric drive,and acoustic wave drive to achieve mixing between different samples,which makes it difficult to integrate with other microdevices;The passive micromixer relies on changing the microchannel structure to quickly complete the efficient mixing between different samples,and it is convenient to integrate without external energy drive.The manufacturing method of the passive micromixer is divided into micro-channel fabrication and micro-channel packaging,which requires complex processing technology and high-precision processing equipment.In this paper,a method of integrated microfluidic chip forming is proposed,and a passive micromixer with free moving obstacles is fabricated,and the influence of different obstacles on the mixing performance of the micromixer is studied.The main research contents and innovations are as follows:(1)A microfluidic chip manufacture method combining 3D printing technology and polymer dissolution technology is proposed.3D printing technology was utilized to make dissolvable microchannel molds,and polymer dissolution technology was utilized to dissolve microchannel molds in PDMS substrates,the dissolvable microchannel mold materials including PVA and HIPS.PVA is a water-soluble high molecular polymer,and its dissolution process is divided into two stages: infiltration-swelling,dissolution-dispersion,and dissolution time shortens with the increase of water temperature,and the best water temperature is 85?;HIPS is a high molecular polymer soluble in limonene solution,and the main parameter affecting its dissolution rate is the concentration of limonene solution,and the optimum concentration is0.5mol/L.(2)The integrated fabrication method of the microfluidic chip was optimized.Microfluidic chips with Y-channel and T-channel were prepared utilizing two materials,respectively,and the fluidity of the microchannel was verified through mixing experiments;The dimensions of the microchannels prepared from the two materials were measured through inverted fluorescence microscopy;The actual width of the microchannel made of PVA material is 12%-25% larger than the designed width,and the actual height is 8%-12% higher than the design;the error between the designed width and the actual width of the microchannel made of HIPS material is0.5%-1%,the error between the design height and the actual height is 1%-2%.(3)A passive micromixer with obstacles of free motion is manufactured.There are several obstacles of free motion in the mixing chamber of the micromixer to enhance the chaotic convection effect of the fluid.The influence of the shape,volume and number of obstacles on the mixing efficiency of the micro-mixer was studied.When the obstacle shape is a cube,the number is 2,and the size is 0.55×0.55×0.55 mm,the mixing efficiency of the micromixer reaches0.95,which shows that when the obstacles are 2 cubes,the mixing performance of the micromixer maximum increase,which is consistent with the numerical simulation results;The effect of the initial injection flow rate on the mixing efficiency of the micromixer was discussed,When the initial injection flow was gradually increased from 0.2ml/min to 1.2ml/min,the mixing efficiency of the micromixer increased from 0.72 to 0.91,and the mixing efficiency of the micromixer increased with the increase of the initial injection flow rate.