In the presence of a chemically active particle, a nearby chemically inert particle can respond to a concentration gradient and move by diffusiophoresis. The nature of the motion is studied for two cases: first, a fixed reactive sphere and a moving inert sphere, and second, freely moving reactive and inert spheres. The continuum reaction–diffusion and Stokes equations are solved analytically for these systems and microscopic simulations of the dynamics are carried out. Although the relative velocities of the spheres are very similar in the two systems, the local and global structures of streamlines and the flow velocity fields are found to be quite different. For freely moving spheres, when the two spheres approach each other the flow generated by the inert sphere through diffusiophoresis drags the reactive sphere towards it. This leads to a self-assembled dimer motor that is able to propel itself in solution. The fluid flow field at the moment of dimer formation changes direction. The ratio of sphere sizes in the dimer influences the characteristics of the flow fields, and this feature suggests that active self-assembly of spherical colloidal particles may be manipulated by sphere-size changes in such reactive systems.

中文翻译：

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化学活性和惰性颗粒之间的扩散电泳诱导的相互作用†

在存在化学活性粒子的情况下，附近的化学惰性粒子可以响应浓度梯度并通过扩散电泳移动。在两种情况下研究了运动的性质：第一，固定的反应性球和移动的惰性球，第二，自由移动的反应性和惰性球。解析了这些系统的连续反应扩散方程和斯托克斯方程，并对动力学进行了微观模拟。尽管在两个系统中球体的相对速度非常相似，但发现流线的局部和整体结构以及流速场却大不相同。对于自由移动的球体，当两个球体彼此接近时，惰性球体通过扩散电泳产生的流会将反应性球体拖向它。这将导致能够在溶液中自我推进的自组装二聚体电动机。二聚体形成时的流体流场改变方向。二聚体中球体尺寸的比率会影响流场的特性，并且此特征表明球形胶体颗粒的主动自组装可能会受到此类反应系统中球体尺寸变化的控制。