Simulation and experiment of capillary-driven planar baffle micromixers

Different capillary-driven planar baffle micromixers with a trigger valve which were fabricated on polymethylmethacrylate sheets using CO₂ laser ablation and thermal bonding are investigated. Two main modified staggered and meander baffle structures were used to compare the mixing efficiency. The modified staggered baffle structure has lower capillary flow resistance and faster speed compared with the meander one. Conversely, the meander baffle structure has higher mixing efficiency at lower flow speed with enough diffusion time than the modified staggered one. The effective channel height of the trigger valve was simulated to be between 220 and 434 μm for merging two fluids at negative capillary pressure. The experiments also verified the trigger value worked at the channel height of 351 μm for two fluids merged together to flow forward but it failed at 169 μm height for only one fluid flow without merging. The mixer with the meander baffle structure performed wiht the best mixing efficiency of 94% among the design structures because of the long flow time and short average diffusion length in the mixing zone.