Compact microfluidic T-channel-mixer via tunable pulsatile actuation and fluid rheology

Enhancing microfluidic heat and mass transfer requires improved mixing, which is challenging under laminar, low Reynolds number flows. Traditional reliance on diffusive transport often demands longer channels, compromising the compactness, which is essential for integration into microsystems. We explore a novel strategy integrating pulsatile flow actuation at the inlet in a T-shaped micromixer with fluid rheology tuning to enhance transport characteristics while maintaining a compact footprint. We investigate the effect of pulsed flow through perpendicular inlets on mixing performance for fluids with different rheological behaviors—shear-thinning, Newtonian, and shear-thickening—using finite element simulations. Mixing efficiency, quantified by a mixing index derived from instantaneous concentration, is shown to improve across all fluid types with the introduction of pulsing. Notably, shear-thinning fluids exhibit the greatest enhancement, achieving a 25.6% increase in mixing under optimal conditions (Strouhal number, St = 0.0003–0.0006, velocity ratio > 5). Alternating-phase pulsing further amplifies mixing, enabling 80% mixing with channel lengths reduced by 28.5%, 23.8%, and 21.6% for shear-thinning, Newtonian, and shear-thickening fluids, respectively, compared to steady-state operation. Our results highlight that pulsatile actuation—particularly in alternate-phase mode—effectively boosts interfacial area and chaotic advection without adding system complexity. This actuator-driven approach offers a versatile and efficient design strategy for compact micromixers, with significant potential for advancing thermal management, chemical synthesis, and environmental microfluidic applications. Pulsatile mixing thus emerges as a promising solution for enhancing both mixing efficiency and heat/mass transfer in next-generation microfluidic devices.