Pei Lei, Xuan Shouhu, Wu Jie, Bai Linfeng, Gong Xinglong
Langmuir. 2019 Sep 17;35(37):12158-12167. doi: 10.1021/acs.langmuir.9b01957. Epub 2019 Sep 9.
This work reports an experiment/simulation combination study on the magnetorheological (MR) mechanism of magnetic fluid based on FeO hollow chains. The decrease of shear stress versus the increasing magnetic field was observed in a dilute magnetic fluid. Hollow chains exhibited a higher MR effect than pure FeO hollow nanospheres under a small magnetic field. A modified particle level simulation method including the translational and rotational motion of chains was developed to comprehend the correlation between rheological properties and microstructures. Sloping cluster-like microstructures were formed under a weak external field (24 mT), while vertical column-like microstructures were observed under a strong field (240 mT). The decrease of shear stress was due to the strong reconstruction process of microstructures and the agglomeration of chains near the boundaries. The chain morphology increased the dip angle of microstructures and thus improved the MR effect under a weak field. This advantage made FeO hollow chains to be widely applied for small and low-power devices in the biomedical field. Dimensionless viscosity as a function of the Mason number was collapsed onto linear master curves. Magnetic fluid in Poiseuille flow in a microfluidic channel was also observed and simulated. A qualitative and quantitative correspondence between simulations and experiments was obtained.
本文报道了一项基于FeO空心链的磁流体磁流变（MR）机制的实验/模拟结合研究。在稀磁流体中观察到剪切应力随磁场增加而降低。在小磁场下，空心链比纯FeO空心纳米球表现出更高的磁流变效应。为了理解流变特性与微观结构之间的相关性，开发了一种改进的粒子水平模拟方法，该方法包括链的平移和旋转运动。在弱外场（24 mT）下形成倾斜的簇状微观结构，而在强场（240 mT）下观察到垂直柱状微观结构。剪切应力的降低是由于微观结构的强烈重构过程以及边界附近链的团聚。链形态增加了微观结构的倾角，从而在弱场下提高了磁流变效应。这一优势使得FeO空心链在生物医学领域的小型和低功率设备中得到广泛应用。无量纲粘度作为梅森数的函数被整理成线性主曲线。还观察并模拟了微流体通道中泊肃叶流中的磁流体。模拟与实验之间获得了定性和定量的对应关系。
