2. Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
Max-Planck-Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany.
Phys Rev Lett. 2016 Apr 1;116(13):138301. doi: 10.1103/PhysRevLett.116.138301. Epub 2016 Mar 29.
We experimentally investigate active motion of spherical Janus colloidal particles in a viscoelastic fluid. Self-propulsion is achieved by a local concentration gradient of a critical polymer mixture which is imposed by laser illumination. Even in the regime where the fluid's viscosity is independent of the deformation rate induced by the particle, we find a remarkable increase of up to 2 orders of magnitude of the rotational diffusion with increasing particle velocity, which can be phenomenologically described by an effective rotational diffusion coefficient dependent on the Weissenberg number. We show that this effect gives rise to a highly anisotropic response of microswimmers in viscoelastic media to external forces, depending on its orientation.
我们通过实验研究了粘性流体中具有各向异性的球形 Janus 胶体粒子的主动运动。通过激光照射施加临界聚合物混合物的局部浓度梯度来实现自推进。即使在流体粘度与粒子引起的变形速率无关的情况下，我们发现随着粒子速度的增加，旋转扩散率显著增加了 2 个数量级，这可以用依赖于 Weissenberg 数的有效旋转扩散系数来唯象描述。我们表明，这种效应导致微游泳者在粘弹性介质中对外力的响应具有高度各向异性，这取决于其取向。
