Influence of fluid viscosity on particle separation in microchannel

Most microfluidic particle separation research are based on the liquid with low viscosity, such as DI water. The influence of the liquid viscosity on the particle separation has not been taken into account. Study on the particle separation in liquid with high viscosity is highly needed, such as the debris separation in lubricant oil for machine monitoring. In this paper, microchannel with symmetric sharp corners on two sides is used to study the influence of liquid viscosity on particle separation. The result shows when the liquid viscosity is low, big particles are mainly subjected to the momentum-change-induced inertial force, migrating towards the center of the microchannel; small ones are mainly subjected to the inertial lift force, moving towards the two symmetric equilibrium positions at two sides of the channel. The particle separation efficiency is ~100% in DI water. When the liquid viscosity becomes high, the drag effect of liquid on particles increases. As a result, the lateral migration of particles in microchannel becomes weak; particle separation efficiency reduces to ~71.5%. This research is of great help for microfluidic technologies in practical applications.