A Three-Dimensional DNA Double-Helix Micromixer Enabling Rapid Mixing of High-Viscosity Fluids

Rapid and uniform mixing of high-viscosity fluids remains a critical challenge in microfluidics. The inertial effects are strongly suppressed at high viscosity, making it difficult to generate chaotic advection. To address this limitation, a three-dimensional micromixer inspired by the DNA double-helix structure is proposed. The three-dimensional helix microchannel introduces additional torsional forces to generate revolution flows, in addition to the centrifugal forces, which leads to Dean vortices. Fluids not only rotate along the microchannel axis but also revolute along the helix axis. This is analogous to planetary motion, in which a planet spins on its own axis while simultaneously revolving around the sun. Such revolution effects lead to rotation–revolution flows, which significantly enhances chaotic advection. It was found that for 10 cSt silicone oils, the DNA micromixer achieved mixing performance above 98% at Re = 40, outperforming the planar serpentine and splitting-and-recombining (SAR) micromixers. Even for higher-viscosity fluids, the DNA micromixer achieved mixing performance above 95% at Re = 60 for 50 cSt silicone oil and at Re = 120 for 100 cSt silicone oil, whereas that of the traditional passive micromixers fell below 36%. This work demonstrates that the rotation–revolution flows induced by the three-dimensional helix microchannels could effectively intensify chaotic advection, providing an efficient pathway for high-viscosity fluids mixing.