Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Langmuir. 2011 Aug 16;27(16):9781-91. doi: 10.1021/la2017038. Epub 2011 Jul 21.
Single-particle longitudinal motion and pairwise lateral motion was investigated while the particles were excited by an oscillating electric field directed normally to an electrode proximate to the particles. The electrode was polarized over a range of potential insufficient to drive electrochemical reactions, a range called the "ideally polarizable region". The particles' motion was qualitatively dependent on the choice of electrolyte despite the absence of electrochemical reactions. As when electrochemical reactions were not explicitly excluded, the phase angle θ between particle height and electric field correlated with the particles' separation or aggregation during excitation. A simple harmonic oscillator model of the particles' response, including colloidal and hydrodynamic forces and including the Basset force not previously cited in this context, showed how θ can increase from 0° at low frequencies, cross 90° at ∼100 Hz, and then increase to 180° as frequency was increased. The model captured the essence of experimental observations discussed here and in earlier works. This is the first a priori prediction of θ for this problem.
当颗粒被一个垂直于靠近颗粒的电极的振荡电场激发时，研究了颗粒的单颗粒纵向运动和成对的侧向运动。电极在一个不足以驱动电化学反应的电位范围内极化，这个范围称为“理想极化区”。尽管没有电化学反应，但颗粒的运动在很大程度上取决于电解质的选择。正如当电化学反应没有被明确排除时，颗粒高度和电场之间的相位角θ与颗粒在激发期间的分离或聚集有关。颗粒响应的简谐振荡器模型，包括胶体和流体动力，以及以前在这种情况下没有引用过的巴塞特力，展示了θ如何从低频时的 0°增加，在约 100 Hz 时交叉到 90°，然后随着频率的增加增加到 180°。该模型捕捉到了这里和以前的工作中讨论的实验观察的本质。这是对此问题的θ的第一个先验预测。
