Localized Electroosmosis (LEO) Induced by Spherical Colloidal Motors
Localized Electroosmosis (LEO) Induced by Spherical Colloidal Motors
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DOI：
10.1021/la402262z
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发表时间：
2014-03-18
期刊：
影响因子：
3.9
通讯作者：
Velegol, Darrell
中科院分区：
文献类型：
--
作者：
Chiang, Tso-Yi;Velegol, Darrell
实验数据表明，胶体（催化）马达的速度随着马达颗粒尺寸的增大而减小。然而，先前的电动力学模型已经表明，至少对于极薄的双层和反应有限的催化来说，球体的胶体电机速度与尺寸无关。虽然已经计算出了扩散限制催化中电机转速的大小依赖性，但大多数电机实验都是在反应限制条件下进行的。这个明显的矛盾使我们从通常的电动方程式开始，研究电机速度(U)是如何随距离墙壁(5)的变化而变化的。一个关键的发现是，胶体马达和附近壁面之间的相互作用产生了局部电渗透（LEO）流场，可以显著改变壁面附近的马达速度。由于大型电机颗粒通常比小型电机更靠近壁面，因此LEO至少为电机速度的大小依赖性提供了一种解释。此外，LEO提供了一种在毛细血管和微通道中创建流场的新方法。
Experimental data show that the speed of colloidal (catalytic) motors decreases as the size of the motor particles increases. However, previous electrokinetic models have shown that the colloidal motor speed for spheres is independent of size, at least for the case of infinitesimally thin double layers and reaction-limited catalysis. Although a size dependence of motor speed has been calculated for diffusion-limited catalysis, most motor experiments are done in the reaction-limited regime. This apparent contradiction led us to examine how motor speed (U) changes with distance (5) from a wall, starting from the usual electrokinetic equations. A key finding is that interactions between a colloidal motor and a nearby wall produce a localized electroosmotic (LEO) flow field that can significantly alter the motor speed near the wall. Because large motor particles typically settle closer to the wall than small motors, LEO thus provides at least one explanation of the size dependence of motor speed. Furthermore, LEO provides a new method of creating flow fields in capillaries and microchannels.