Zhang Jianli, Zhang Yuanxing, Bevan Michael A
Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Chem Phys. 2020 Feb 7;152(5):054905. doi: 10.1063/1.5142609.
A method is reported to determine equilibrium concentration profiles and local phase behavior of colloids on multi-dimensional energy landscapes. A general expression is derived based on local particle concentration and osmotic pressure differences that are balanced by forces on colloids due to energy landscape gradients. This analysis is applied to colloidal particles in high frequency AC electric fields within octupolar electrodes, where the energy landscape can be shaped in two dimensions. These results are also directly applicable to any particles having induced dipoles in spatially non-uniform electromagnetic fields. Predictions based on modeling colloids with an effective hard disk equation of state indicate inhomogeneous solid and fluid states coexisting on different shaped energy landscapes including multiple minima. Model predictions show excellent agreement with time-averaged Brownian dynamic simulations at equilibrium. Findings demonstrate a general approach to understand colloidal phase behavior on energy landscapes due to external fields, which could enable control of colloidal microstructures on morphing energy landscapes and the inverse design of fields to assemble hierarchically structured colloidal materials.
本文报道了一种确定胶体在多维能量景观上的平衡浓度分布和局部相行为的方法。基于局部粒子浓度和渗透压差异推导出一个通用表达式，这些差异由能量景观梯度作用于胶体的力来平衡。该分析应用于八极电极内高频交流电场中的胶体粒子，其中能量景观可在二维空间中形成。这些结果也直接适用于在空间非均匀电磁场中具有感应偶极子的任何粒子。基于用有效硬球状态方程对胶体进行建模的预测表明，在包括多个极小值的不同形状能量景观上，不均匀的固态和流体态共存。模型预测与平衡时的时间平均布朗动力学模拟结果显示出极好的一致性。研究结果展示了一种理解由于外部场导致的胶体在能量景观上的相行为的通用方法，这可能有助于控制在变化的能量景观上的胶体微观结构以及逆向设计用于组装分层结构胶体材料的场。
