Computational Study on the Effect of Paddle Number of Optical Micro-Rotors on the Mixing Performance

Abstract

The mixing performance of optical micro-rotors, which were invented as an active micromixer, is studied by the aid of CFD simulations. Our focus in this paper is on the effects of paddle number (3,4 and 5) of the rotors. Fluid torque acting on the rotors is obtained by solving the 3-dimensional Navier-Stokes equations. Also optical torque produced on the rotors by a laser beam is calculated by considering changes in momentum of the laser beam at the times of refraction and reflection. To quantify the mixing effect of the rotor, the mixing rate is calculated. By balancing the fluid torque and the optical torque at various rotation speeds of the rotors and inlet speeds of the liquid reagents, the mixing performance is analyzed. It was found that the 5-paddle rotor has the best mixing performance in a large space but the 3-paddle rotor is the best in a Y-shaped channel. Further, similarity is observed between the mixing rate, rotation speed and inlet velocity.