A three-dimensional spiral-splitting and re-combining microreactor based on Dean vortex-interface shear coupling enhanced chaotic mixing for the uniform high-throughput synthesis of nano-alumina

• 3D-TSM couples Dean vortices and interface stretching, breaking 2D’s mixing-throughput trade-off in millimeter channels. • 99.96 % mixing efficiency at Re =600 (69 % higher than 2D SAR and 3D S-shaped structures) via simulations and experiments. • Single-channel throughput >100 mL/min with 0.0002 Pa pressure drop for high-throughput low-energy scaling. • Nano-alumina: 71 nm particles (vs. 105 nm via beaker) with concentrated distribution and 15 % higher crystallinity. Traditional 2D channel microreactors suffer from low and uneven mixing efficiency. Reducing channel size restricts throughput, while increasing size weakens mass transfer due to thicker laminar flow, creating a performance bottleneck. A novel 3D spiral-split and recombine (3D-TSM) microreactor is proposed, coupling Dean vortex enhancement of spiral channels with interface stretching of split-and-recombine units. Its performance is validated via CFD simulations and Villermaux/Dushman parallel competitive reactions. The key mechanism is the synergistic coupling of spiral channel-induced Dean vortices and split-recombine interface shear, generating 3D chaotic mixing that splits fluids into micron-scale sublayers and shortens diffusion distance by 78 %. This reduces the inertial mixing threshold to Re >200, achieving 97 % mixing efficiency at Re =600 (69 % higher than 2D SAR and 3D S-shaped structures) with single-channel flux >100 mL/min and pressure drop 0.0002 Pa. For nano-alumina synthesis, uniform supersaturation regulation via precise mixing reduces average particle size to 71 nm (vs. 105 nm via beaker mixing), narrows size distribution, and improves crystallinity.