Cascaded contraction-expansion channels for bacteria separation from RBCs using viscoelastic microfluidics

Implementation of viscoelasticity-based particle migration techniques has attracted significant interest thanks to its simplicity to achieve particle separation and enrichment at high sensitivity and accuracy for the last decade. Many methods have previously been developed for particle focusing and separation, but they all require long fluidic channels to enable the desired elastic force on particles. Here, a cascade contraction-expansion microfluidic system with a much shorter channel length is presented. Experimental results show that this system achieved continuous, sheathless particle separation in a viscoelastic fluid, and Enterococcus faecalis was successfully separated from red blood cells (RBCs). Thanks to its small size, the system provides extra advantage for its integration into small chips.