Elucidating the microscale interaction between magnetism and fluid flow is of great importance for designing micro-magnetofluidic gradient generators, micromixers, and particle sorters. Co-flowing magnetic and non-magnetic fluids can lead to instability at their interface and subsequent rapid mixing. The mismatch in the magnetisation of the fluids leads to instabilities. The present study systematically investigates the magnetofluidic spreading phenomena of both magnetic nanoparticles and non-magnetic fluorescent dye in consecutive circular chambers. Numerical simulations and experimental investigations were conducted to thoroughly evaluate the physics of magnetofluidic spreading. We show that the presence of the consecutive chambers can enhance magnetofluidic spreading by slowing down the flow and increasing the mass transfer rate transversal to the flow direction. The numerical results reveal that the magnetic force, induced by the magnetic susceptibility gradient, generates cross-sectional secondary flows that steer particles toward both the top and bottom walls. The induced secondary flow also enhances the transport of fluorescent dye, thereby leading to a higher mass transfer rate as compared to pure molecular diffusion. The findings provide further insights into the microscale spreading phenomenon of magnetic and non-magnetic particles in a magnetic field.

阐明磁性和流体流动之间的微观相互作用对于设计微磁流体梯度发生器，微混合器和颗粒分选器至关重要。共同流动的磁性和非磁性流体会导致其界面不稳定并随后迅速混合。流体磁化强度的不匹配会导致不稳定。本研究系统地研究了连续的圆形腔室中磁性纳米粒子和非磁性荧光染料的磁流体扩散现象。进行了数值模拟和实验研究，以彻底评估磁流体扩散的物理性质。我们表明，连续腔室的存在可以通过减慢流速和增加横向于流动方向的传质速率来增强磁流体扩散。数值结果表明，由磁化率梯度引起的磁力产生了横截面二次流，该二次流将粒子引向顶壁和底壁。与纯分子扩散相比，诱导的二次流还增强了荧光染料的运输，从而导致更高的传质速率。这些发现提供了对磁场中磁性和非磁性粒子的微观扩散现象的进一步见解。产生横截面二次流，该二次流将粒子引向顶壁和底壁。与纯分子扩散相比，诱导的二次流还增强了荧光染料的运输，从而导致更高的传质速率。这些发现提供了对磁场中磁性和非磁性粒子的微观扩散现象的进一步见解。产生横截面二次流，该二次流将粒子引向顶壁和底壁。与纯分子扩散相比，诱导的二次流还增强了荧光染料的运输，从而导致更高的传质速率。这些发现提供了对磁场中磁性和非磁性粒子的微观扩散现象的进一步见解。