Max-Planck-Institut für Intelligente Systeme, Heisenbergstraße 3, 70569 Stuttgart, Germany.
Soft Matter. 2018 Jul 25;14(29):6043-6057. doi: 10.1039/c8sm01102h.
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.
在化学活性粒子存在的情况下，附近的化学惰性粒子可以响应浓度梯度并通过扩散泳动移动。研究了两种情况下的运动性质：首先，固定的反应性球体和移动的惰性球体，其次，自由移动的反应性和惰性球体。对这些系统进行了连续反应-扩散和 Stokes 方程的解析求解，并进行了动力学的微观模拟。尽管两个系统中球体的相对速度非常相似，但流线和流速场的局部和全局结构却发现大不相同。对于自由移动的球体，当两个球体相互靠近时，通过扩散泳动由惰性球体产生的流将反应性球体拖向它。这导致能够在溶液中自行推进的自组装二聚体马达。二聚体形成时的流场方向发生变化。二聚体中球体大小的比例影响流场的特性，这一特征表明，在这种反应性系统中，通过改变球形胶体粒子的尺寸可以操纵活性自组装。
