基础微流体限域中微泳者的几何控制运动性
Geometry-Controlled Motility of Microswimmers in elementary microfluidic confinements
AI总结：
本文研究衣藻在不同PDMS微流体几何限域中的运动，发现几何可调控其运动模式，为微泳者输运的被动控制提供了新途径。
AI中文摘要：
微泳者在限域环境中的运动性是活性物质物理学的基础问题，直接关系到微流体应用及对复杂自然生境中微生物行为的理解。尽管衣藻（Chlamydomonas Reinhardtii，CR）等带鞭毛微藻的跑- tumble动态在本体悬浮液中已得到充分表征，但基础几何限域对其游动的改变程度仍未被充分理解，尤其是空间接触与流体动力学相互作用的相对贡献。本文通过单粒子追踪和统计分析，实验研究单个CR细胞在不同复杂度PDMS微流体几何结构中的轨迹。结果显示，直通道内的细胞聚集在壁附近并沿通道轴线排列，该行为可通过空间活性布朗粒子模拟定性复现，但呈现出与流体动力学壁耦合一致的限域依赖速度增强；在直径小于 persistence长度L₀~350微米的圆形空腔中，细胞从本体活性布朗运动探索转变为准圆形沿壁轨迹；在哑铃形几何中，隔间间停留长度反映纯几何预测，即使在强限域下也无显著流体动力学贡献。综上，这些结果表明环境几何可选择性放大或抑制活性生物悬浮液中的运动模式，为工程化微流体网络中微泳者输运的被动控制开辟了途径。
英文摘要：
The motility of microswimmers in confined environments is a fundamental problem in active matter physics, with direct implications for microfluidic applications and the understanding of microorganism behavior in complex natural habitats. Although the run-and-tumble dynamics of flagellated microalgae such as Chlamydomonas Reinhardtii (CR) are well characterized in bulk suspension, the extent to which elementary geometric confinements alter their swimming remains insufficiently understood, particularly regarding the relative contributions of steric contact versus hydrodynamic interactions. Here, we experimentally investigate the trajectories of individual CR cells in a diversity of PDMS microfluidic geometries of growing complexity using single-particle tracking and statistical analysis. We show that cells in straight channels accumulate near walls and align along the channel axis, a behavior qualitatively reproduced by steric Active Brownian Particle simulations, yet showing a confinement-dependent velocity enhancement consistent with hydrodynamic wall coupling. In circular cavities with diameter below the persistence length L_0 ~350 microns, cells transition from bulk active Brownian exploration to quasi-circular wall-following trajectories. In dumbbell geometries, inter-compartment dwell length reflect purely geometric predictions, evidencing no measurable hydrodynamic contributions even for strong confinements. Together, these results demonstrate that environmental geometry can selectively amplify or suppress motility modes in active biological suspensions, opening avenues for the passive control of microswimmer transport in engineered microfluidic networks.
