Abstract

A mechanism of nanomotor locomotion in a surrounding viscous fluid containing charged particles is considered. In contrast to a mechanism proposed in the literature, according to which nanomotor locomotion is induced by a concentration gradient of certain type particles produced by asymmetric chemical or electrochemical reactions occurring on the nanomotor surface, we hypothesize that nanomotor locomotion can be driven by hydrodynamic interactions in the case of identical concentrations of different-sized ions. To justify the hypothesis, the dynamics of a nanomotor surrounded by a viscous fluid is studied using the diffusion model of electrohydrodynamics and, additionally, the model of a dipolar aggregate surrounded by a cloud of equally but oppositely charged fine particles of different sizes is considered. It is assumed that the total charge of all fine particles is zero and the oppositely charged particles have identical concentrations in the ambient fluid. Computations have confirmed that the nanomotor can move in this case. The direction and speed of the motion depend substantially on both the distribution of the particles in the surrounding fluid and on their sizes. Symmetry breaking in the particle distribution gives rise to a velocity component perpendicular to the dipolar moment direction. In the case of the chemical or electrochemical mechanism of ion formation, symmetry breaking in the ion distribution can be caused by symmetry violations in the nanomotor shape or by possible impurities participating in the reaction, so, to control the nanomotor motion, an external field orienting the nanomotor in the prescribed direction has to be applied. The proposed mechanism of nanomotor locomotion can be used to control mass transfer in colloidal suspensions.

中文翻译：

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粘性流体中合成纳米电动机的运动机理

摘要

考虑了在包含带电粒子的周围粘性流体中纳米马达运动的机制。与文献中提出的机制相反，根据该机制，纳米运动的运动是由纳米运动表面上发生的不对称化学或电化学反应产生的某些类型颗粒的浓度梯度引起的，我们假设纳米运动的运动可以由流体动力相互作用驱动。相同浓度的不同尺寸离子的情况。为了证明该假设的正确性，使用电流体动力学的扩散模型研究了被粘性流体包围的纳米马达的动力学，此外，还考虑了被极性相等但带相反电荷的细小颗粒云包围的偶极聚集体模型。假定所有细颗粒的总电荷为零，并且带相反电荷的颗粒在环境流体中的浓度相同。计算已经证实，纳米电机在这种情况下可以移动。运动的方向和速度基本上取决于周围流体中颗粒的分布及其尺寸。粒子分布中的对称性破裂会产生垂直于偶极矩方向的速度分量。在离子形成的化学或电化学机理的情况下，离子分布的对称性破坏可能是由于纳米马达形状中的对称性违背或参与反应的可能杂质引起的，因此，为了控制纳米马达的运动，需要进行外部磁场定向必须按照规定的方向使用纳米马达。