Martinez-Pedrero Fernando, Cebers Andrejs, Tierno Pietro
Departament d'Estructura i Constituents de la Matèria, Universitat de Barcelona, 08028, Barcelona, Spain.
Faculty of Physics and Mathematics, University of Latvia, Zellu 23, LV-1002, Riga, Latvia.
Soft Matter. 2016 Apr 20;12(16):3688-95. doi: 10.1039/c5sm02823j.
We combine experiments and theory to investigate the orientational dynamics of dipolar ellipsoids, which self-assemble into elongated ribbon-like structures due to the presence of a permanent magnetic moment, perpendicular to the long axis in each particle. Monodisperse hematite ellipsoids are synthesized via the sol-gel technique and arrange into ribbons in the presence of static or time-dependent magnetic fields. We find that under an oscillating field, the ribbons reorient perpendicular to the field direction, in contrast with the behaviour observed under a static field. This observation is explained theoretically by treating a chain of interacting ellipsoids as a single particle with orientational and demagnetizing field energy. The model allows us to describe the orientational behaviour of the chain and captures well its dynamics at different strengths of the actuating field. The understanding of the complex dynamics and assembly of anisotropic magnetic colloids is a necessary step for controlling the structure formation, which has direct applications in different fluid-based microscale technologies.
我们结合实验和理论来研究偶极椭球体的取向动力学，由于每个粒子中存在垂直于长轴的永久磁矩，这些偶极椭球体自组装成细长的带状结构。通过溶胶 - 凝胶技术合成单分散赤铁矿椭球体，并在静态或随时间变化的磁场中排列成带。我们发现，在振荡场下，带会重新取向至垂直于场方向，这与在静态场下观察到的行为相反。通过将相互作用的椭球体链视为具有取向和退磁场能量的单个粒子，从理论上解释了这一观察结果。该模型使我们能够描述链的取向行为，并很好地捕捉其在不同强度驱动场下的动力学。理解各向异性磁性胶体的复杂动力学和组装是控制结构形成的必要步骤，这在不同的基于流体的微尺度技术中有直接应用。
