Analysis Of The Preparation Process Of Non-newton Microdroplets In Different T-junction Microchannels

Microfluidic droplets prepared based on microfluidics have the characteristics of small size,excellent monodispersity and no diffusion between droplet samples,which have important applications in drug screening,virus detection,material synthesis and chemical engineering.Since non-Newtonian fluids such as blood,lymphatic fluid and polymer solutions are widely used in real life production,the study of microdroplet preparation of non-Newtonian fluid is of great significance.In order to study the process of non-Newtonian fluid microdroplet generation in T-junction microchannels and the effect of different working conditions,disperse phase physical parameters and T-junction microchannel structure parameters on the non-Newtonian microdroplet generation process,this paper uses the volume of fluid model to numerically simulate the process,and conduct high-speed microscopic experiments to verify the accuracy of the numerical simulation results,and derive the orthogonal T-junction microchannel,different disperse phase inlet angle and inlet The prediction equations for the size of non-Newtonian microdroplets in T-junction microchannels with different inlet angles and inlet necking widths were derived.Two mechanisms of squeezing and shearing for the formation of non-Newtonian fluid droplets in T-junction microchannels were explored.The inlet flow rate of discrete phase is constant,and with the increase of capillary number of continuous phase,the relative length of discrete droplets of polymer aqueous solution with different mass concentration tends to decrease.With the increase of polymer mass concentration from 0mg/L to 150mg/L,the relative length of droplets decreases gradually,when the mass concentration increases from 150mg/L to 300mg/L,the relative length of droplets increases gradually.The results can provide a reference for the development of the formation technology of non-Newtonian fluid droplets.T-junction microchannel with different discrete phase inlet angles was designed and the non-Newtonian microdroplet generation process in these microchannels was investigated.For a fixed discrete phase flow rate,the frequency of non-Newtonian microdroplet generation tends to increase and then decrease with increasing the discrete phase inlet angle,while the relative length tends to decrease and then increase as the continuous phase capillary number increases from 0.038 to 0.086.Compared with other discrete phase inlet angles,the T-junction microchannel structure with an inlet angle of 90 produced the shortest non-Newtonian microdroplet size and the largest droplet generation frequency.As the inlet angle increases,the degree of shift of the velocity direction of the discrete phase at the T-node also gradually increases.When the inlet angle is less than 90,the smaller the inlet angle is,the longer the contact line between the continuous phase and the discrete phase neck junction is,and when the inlet angle is larger than 90,the volume of the subcontinuous phase intruding into the discrete phase channel from the horizontal channel increases with the increase of the inlet angle.T-junction microchannel with different discrete phase inlet necking widths was designed and the non-Newtonian microdroplet generation process in these microchannels was investigated.For a fixed discrete phase flow rate and an increase in the continuous phase capillary number from 0.038 to 0.086,the frequency of non-Newtonian droplet generation increases as the inlet necking width of the discrete phase decreases,and the relative length decreases as the inlet necking width of the discrete phase decreases.As the inlet necking width decreases,the average pressure in the discrete phase channel,initial pressure into the continuous phase channel and the peak pressure at the moment of droplet breakage increase.