Experimental study on generation of non-Newtonian droplets in dripping mode in a flow focusing microchannel

Droplet microfluidic is an important branch of the microfluidic field and the biological fluids involved in it often have non-Newtonian properties. In order to understand the influence of non-Newtonian properties on droplet formation, four kinds of fluids with different rheological properties were configured to systematically study the non-Newtonian droplet formation in the dripping mode in a flow focusing microchannel. The results show that compared with Newtonian droplet formation, non-Newtonian droplet formation shows a more significant “beads-on-a-string” phenomenon. Different non-Newtonian properties have different effects on droplet formation. Shear thinning effect and elastic effect have opposite effects on the droplet size and formation frequency. The results of liquid column necking dynamics show that the process of liquid column necking is similar to that of Newtonian fluid due to a single shear thinning effect. The single elastic effect makes the capillary drive stage which appears of liquid column necking different from that of Newtonian fluid. The combined effect of the elastic effect and shear thinning effect leads to more significant capillary drive stage in the process of column necking and more significant “beads-on-a-string” after column necking.