A labyrinth split and merge micromixer for bioanalytical applications

Abstract

A planar split and merge (SAM) passive micromixer with labyrinthine microchannels is proposed to efficiently mix biomolecular solutions by combining several advantages of existing micromixer designs in one realization. First, to demonstrate the labyrinth-SAM micromixer advantages, it is compared with three passive micromixers of different geometries, i.e., a zigzag, a spiral, and a linear one, with respect to their mixing efficiency, by means of a computational study. The geometrical specifications are imposed from flexible printed circuit (FPC) technology which is used for their fabrication and the diffusion coefficient from the applications to be implemented, i.e., the mixing of biochemical reagents. The computations include the numerical solution of continuity, Navier–Stokes, and mass conservation equations in 3d. It is demonstrated that the labyrinth-SAM micromixer exhibits the highest mixing efficiency. Specifically, compared to a linear micromixer, which shows a mixing efficiency of 0.328, the spiral micromixer improves the mixing efficiency by 8 %, the zigzag by 11 %, and the SAM by 92 %; the diffusion coefficient of the biomolecules is 10−10 m2/s, the Reynolds number is 0.5, and the volume of each micromixer is 2.54 μl. Second, the proposed SAM micromixer is realized simply and inexpensively, with a small footprint, implementing FPC technology, commonly available in the production lines of printed circuit board manufacturers. Finally, its mixing efficiency is experimentally evaluated by means of fluorescence microscopy, while it is further validated for enzymatic digestion of DNA. The latter is achieved even within 30 s of sufficient mixing of DNA and enzyme solutions through the SAM. Despite the numerous works on micromixers, the labyrinth-SAM is a novel design of an efficient passive micromixer. The efficiency together with its simplicity, which is manifested by (a) the planar (and not complex three-dimensional) geometry, (b) the two-inlet, instead of multiple-inlet, configuration, (c) the small number of fabrication steps, and (d) the compatibility with mass production, makes the proposed micromixer a good candidate for integration in bioanalytical miniaturized platforms.