Bauman Moscow State Technical University, 2nd Baumanskaya str. 5, 105005 Moscow, Russia.
J Chem Phys. 2021 Sep 21;155(11):114107. doi: 10.1063/5.0060705.
Anisotropic particles are widely presented in nature, from colloidal to bacterial systems, and control over their interactions is of crucial importance for many applications, from self-assembly of novel materials to microfluidics. Placed in rapidly rotating external electric fields, colloidal particles attain a tunable long-range and many-body part in their interactions. For spherical colloids, this approach has been shown to offer rich capabilities to construct the tunable interactions via designing the internal structure of particles and spatial hodographs of external rotating fields, but in the case of anisotropic particles, the interactions remain poorly understood. Here, we show that tunable interactions between anisotropic rod-like and spheroidal colloidal particles in rotating electric or magnetic fields can be calculated and analyzed with the diagrammatic technique we developed in the present work. With this technique, we considered an in-plane rotating electric field, obtained the long-range asymptotics of the anisotropic interactions, calculated the tunable interactions between particles rotating synchronously, and found conditions for rotator repulsion. We compared the mechanisms providing tunable interactions to those for orientational (Keesom), induction (Debye), and dispersion (London) interactions in molecular systems and found that the tunable interactions between anisotropic particles represent a novel kind of dipole-like interaction. The method can be directly generalized for magnetically induced interactions, 3D systems, and fields with spatial hodographs. The results provide significant advance in theoretical methods for tunable interactions in colloids and, therefore, are of broad interest in condensed matter, chemical physics, physical chemistry, materials science, and soft matter.
各向异性粒子广泛存在于自然界中，从胶体到细菌系统，控制它们的相互作用对于许多应用至关重要，从新型材料的自组装到微流控。在快速旋转的外电场中，胶体粒子获得了可调谐的长程和多体相互作用。对于球形胶体，这种方法已被证明可以通过设计粒子的内部结构和外部旋转场的空间时标来提供构建可调谐相互作用的丰富能力，但在各向异性粒子的情况下，相互作用仍然知之甚少。在这里，我们表明，在旋转电场或磁场中各向异性棒状和扁球状胶体粒子之间的可调相互作用可以用我们在本工作中开发的图论技术来计算和分析。利用该技术，我们考虑了一个面内旋转电场，获得了各向异性相互作用的长程渐近，计算了同步旋转粒子之间的可调相互作用，并找到了转子排斥的条件。我们将提供可调相互作用的机制与分子系统中的取向（凯泽姆）、感应（德拜）和色散（伦敦）相互作用的机制进行了比较，发现各向异性粒子之间的可调相互作用代表了一种新型的偶极子相互作用。该方法可以直接推广到磁诱导相互作用、3D 系统和具有空间时标的场。该结果为胶体中可调相互作用的理论方法提供了重要进展，因此在凝聚态物质、化学物理、物理化学、材料科学和软物质中具有广泛的兴趣。
