Laser-assisted active microfluidic mixer

Many analytical microsystems use molecular diffusion to mix small quantities of different liquids. However, this passive mixing process requires a relatively long microchannel which may impose design restrictions on the physical dimensions of the fluidic network. To shorten the length of the mixing channels, an active micromixer driven by a focused laser beam is described in this paper. The proposed solution improves the mixing rate by using low power laser radiation to heat the disparate fluids being transported through the channels. The operating principle is ba sed on the observation that the rate of molecular diffusion for non-reactive fluids increases with elevated temperatures. Preliminary experiments on a Y-channel micromixer were conducted using a 1mW, 670nm laser. The laser beam was focused on the microchannel using a 100mm focal length objective lens. The laser-assisted mixing of the test fluids showed a 36.4% increase in the average diffusion coefficient value with 1 to 10μL/min flow rates. The maximum percentage difference of diffusion distances had increased by approximately 7.85% over the non-laser-assisted conditions.