Mixing enhancement via a serpentine micromixer for real-time activation of carboxyl

Abstract The amide condensation reaction is crucial for preparing biological probes with a polypeptide backbone. The traditional condensation reaction requires the monomer and condensing agent to be pre-mixed and activated by physical agitation mixing, which entail long time, require many reagents, and yield several by-products. In microfluidic mixing devices, the high specific surface area of ​​microchannel enables traditional chemical reactions to be accomplished efficiently and quickly using only trace amounts of reagents in real time. This paper presents a novel serpentine mixing channel for the activation of amino acid monomers. A number of outward convex elliptical structures are introduced to both sides of the improved serpentine microchannel, creating a Dean vortex that increases the mixing efficiency at low Reynolds condition (90% at Re = 40). Effective monomer activation can be realized directly using a micromixing reactor and leads to less by-products as verified by ultraviolet spectroscopy and high-performance liquid chromatography analysis. The practicability of the micromixer is successfully tested by utilizing it as a microreactor for the real-time activation of amino acids for the in situ synthesis of polypeptide array at a flow rate of 300 μL/min (Re = 40). The proposed micromixer has the potential to be an excellent alternative for conventional flask reactions and integrated in automated miniaturized biochip preparation systems.