Mechanisms of microparticle lateral manipulation using viscoelastic fluids in microchannels with triangle patterns array

Microfluidic manipulation is widely used in lab-scale medical, chemical and environmental research. Passive methods of microparticle manipulation utilise only hydraulic forces in the fluid domain to enable size sorting, separation and purification of microparticles. Our previous experimental study demonstrated that Viscoelastic Fluids in Microchannels with Triangle Patterns Array can realise microparticle lateral manipulation to approach concentration and purification. However, the mechanism of this phenomenon remains unclear. In this study, a two-dimensional computational fluid dynamics model combined with a microparticle-tracing module was established. The hydraulic forces including drag force, elastic force and lift force were numerically investigated respectively based on the microparticle trajectory. The results show that the drag force and elastic force are the dominant factors that affect the performance of lateral manipulation. The two major forces are determined by the physical characteristics of the viscoelastic fluid, which are extensibility and viscosity. The effects of such parameters were investigated quantitatively and validated by experimental results. Furthermore, the numerical model was used to simulate and discuss the potential application of nano-scale particle manipulation using such passive method.