Advancing micromixing techniques: the role of surface acoustic waves and fluid–structure interaction in non-newtonian fluids

This study numerically investigated the enhancement of micromixing efficiency through integrating surface acoustic waves (SAWs) and hyper-elastic channel walls, modeled using a power-law fluid representative of human blood flow. The governing equations are systematically divided into zeroth, first, and second orders based on perturbation theory. This facilitates the development of a fully coupled two-way fluid–structure interaction (FSI) framework implemented via the Arbitrary Lagrangian–Eulerian (ALE) method. The combination of SAWs and hyper-elastic materials demonstrated a marked improvement in mixing efficiency, increasing from 0 to 0.99, alongside a significant reduction in pressure drop within the microchannel. The interaction between SAWs and the deformable walls induces localized instabilities and shear stresses that effectively disrupt the laminar flow, promoting enhanced mixing. The study highlights the critical role of hyper-elastic walls in modulating normal forces on the fluid and reducing pressure drop, offering insights into the interaction between fluid viscosity, acoustic pressure fields, and flow dynamics. These findings provide a framework for designing micromixers with optimized efficiency and reduced channel length, offering practical advancements in microfluidic systems.