Katuri Jaideep, Uspal William E, Popescu Mihail N, Sánchez Samuel
Institute for Bioengineering of Catalonia (IBEC), The Barcelona Institute of Science and Technology (BIST), Baldiri Reixac 10-12, 08028 Barcelona Spain.
Department of Mechanical Engineering, University of Hawaii at Manoa, 2540 Dole Street, Holmes Hall 302, Honolulu, HI 96822, USA.
Sci Adv. 2021 Apr 30;7(18). doi: 10.1126/sciadv.abd0719. Print 2021 Apr.
Chemically active Janus particles sustain non-equilibrium spatial variations in the chemical composition of the suspending solution; these induce hydrodynamic flow and (self-)motility of the particles. Direct mapping of these fields has so far proven to be too challenging. Therefore, indirect methods are needed, e.g., deconvolving the response of "tracer" particles to the activity-induced fields. Here, we study experimentally the response of silica particles, sedimented at a wall, to active Pt/silica Janus particles. The latter are either immobilized at the wall, with the symmetry axis perpendicular or parallel to the wall, or motile. The experiments reveal complex effective interactions that are dependent on the configuration and on the state of motion of the active particle. Within the framework of a coarse-grained model, the behavior of tracers near an immobilized Janus particle can be captured qualitatively once activity-induced osmotic flows on the wall are considered.
具有化学活性的Janus粒子会维持悬浮溶液化学成分的非平衡空间变化；这些变化会引发流体动力流以及粒子的（自）运动性。事实证明，直接绘制这些场图极具挑战性。因此，需要采用间接方法，例如对“示踪”粒子对活性诱导场的响应进行反卷积处理。在此，我们通过实验研究了沉积在壁面上的二氧化硅粒子对活性铂/二氧化硅Janus粒子的响应。后者要么固定在壁面上，对称轴垂直或平行于壁面，要么处于运动状态。实验揭示了复杂的有效相互作用，这些相互作用取决于活性粒子的构型和运动状态。在粗粒度模型的框架内，一旦考虑到壁面上活性诱导的渗透流，就可以定性地捕捉到示踪粒子在固定Janus粒子附近的行为。
