Physics Department E14 and T37, TU Munich, D-85748 Garching, Germany.
Phys Rev Lett. 2022 Feb 4;128(5):058002. doi: 10.1103/PhysRevLett.128.058002.
Suspended microparticles subjected to ac electrical fields collectively organize into band patterns perpendicular to the field direction. The bands further develop into zigzag shaped patterns, in which the particles are observed to circulate. We demonstrate that this phenomenon can be observed quite generically by generating such patterns with a wide range of particles: silica spheres, fatty acid, oil, and coacervate droplets, bacteria, and ground coffee. We show that the phenomenon can be well understood in terms of second order electrokinetic flow, which correctly predicts the hydrodynamic interactions required for the pattern formation process. Brownian particle simulations based on these interactions accurately recapitulate all of the observed pattern formation and symmetry-breaking events, starting from a homogeneous particle suspension. The emergence of the formed patterns can be predicted quantitatively within a parameter-free theory.
悬浮在介质中的微粒在交流电场中会共同排列成与电场方向垂直的条带图案。这些条带进一步发展成锯齿状图案，观察到颗粒在其中循环运动。我们证明，通过使用广泛的颗粒（如二氧化硅球、脂肪酸、油和凝聚液滴、细菌和研磨咖啡）来产生这种图案，可以很普遍地观察到这种现象。我们表明，根据二级电动流的原理，可以很好地理解这种现象，该原理正确预测了图案形成过程中所需的流体动力学相互作用。基于这些相互作用的布朗粒子模拟准确地再现了所有观察到的图案形成和对称破缺事件，从均匀的颗粒悬浮液开始。在无参数理论中可以定量预测形成图案的出现。
