标题： Janus微泳器是不良的水动力混合器 显示英文标题

标题： Janus microswimmers are poor hydrodynamic mixers

摘要： 由自促微泳者产生的流体流动被提出作为一种机制，以增强微观和纳米尺度上的质量传输和混合。 在这里，我们实验研究了模型二维“活性浴”中光催化二氧化硅-二氧化钛Janus微球在集体行为开始前的不同微泳者密度下增强示踪粒子扩散率的能力。 受我们实验结果与之前生物微生物结果之间相似性的启发，我们随后使用一般的蠕动框架对我们的Janus微泳者进行建模，特别是将它们视为中性蠕动体。 数值模拟准确地捕捉了我们的观察结果，提供了对示踪粒子传输微观机制的见解，并使我们能够扩展超出实验系统的参数空间。 我们发现强有力的证据表明，在活性Janus浴中，近场相互作用主导了示踪粒子扩散率的增强，从而根据尺度论证确定了由化学微泳者增强示踪粒子传输的操作窗口。 基于这种论证，我们认为对于许多化学活性胶体系统，仅靠流体力学可能不足以诱导具有大扩散系数的被动组分的显著混合。 显示英文摘要

摘要： The generation of fluid flows by autophoretic microswimmers has been proposed as a mechanism to enhance mass transport and mixing at the micro- and nanoscale. Here, we experimentally investigate the ability of model 2-D "active baths" of photocatalytic silica-titania Janus microspheres to enhance the diffusivity of tracer particles at different microswimmer densities below the onset of collective behaviour. Inspired by the similarities between our experimental findings and previous results for biological microorganisms, we then model our Janus microswimmers using a general squirmer framework, specifically treating them as neutral squirmers. The numerical simulations faithfully capture our observations, offer an insight into the microscopic mechanism underpinning tracer transport, and allow us to expand the parameter space beyond our experimental system. We find strong evidence that near-field interactions dominate enhancements in tracer diffusivity in active Janus baths, leading to the identification of an operating window for enhanced tracer transport by chemical microswimmers based on scaling arguments. Based on this argumentation, we suggest that for many chemically active colloidal systems, hydrodynamics alone is likely to be insufficient to induce appreciable mixing of passive components with large diffusion coefficients.