Mixing mechanisms of high-viscosity fluids in asymmetric Tesla valve micromixers: Numerical and experimental investigation

High-viscosity biological fluids are widely employed in medical diagnostics and drug delivery, and understanding their microscale mixing behavior is essential for achieving high process efficiency. Previous studies have confirmed the feasibility of mixing high-viscosity fluids in symmetric Tesla micromixers. Compared with symmetric configurations, the asymmetric Tesla design induces stronger flow perturbations and more complex vortical structures, while its performance in handling high-viscosity biological fluids remains insufficiently characterized. In this work, the mixing characteristics of two high-viscosity fluids in an asymmetric Tesla valve micromixer are investigated through a combination of numerical simulations and experimental validation. The results show that as the number of Tesla valves increases, the frequency of flow disturbances rises at the curved sections and the junctions between adjacent units, thereby enhancing the mixing efficiency. The mixing efficiency increases with flow velocity and gradually approaches saturation when the Reynolds number (Re) exceeds 200, reaching a value of approximately 0.88. When the Schmidt number (Sc) exceeds 1000, the mixing process within the channel becomes primarily governed by convective transport, and further enhancement of mixing efficiency therefore requires higher flow rates. In the studied configuration, an increase in the valve angle results in a longer curved flow path within each unit and a shorter overall channel length, thereby enhancing the formation of stronger secondary vortices and simultaneously reducing the pressure drop. At a valve angle of 60°, the Tesla valve attains a mixing efficiency of 0.91 at Re = 300, with a pressure drop reduced by 5.33 × 109 Pa compared to the 30° configuration. These findings provide valuable insights into the design of asymmetric Tesla for efficient mixing of high-viscosity biological fluids.