标题： 限制几何结构决定了外部剪切应力对微管-驱动蛋白活性流体中主动应力驱动流动的影响 显示英文标题

标题： Confinement geometry governs the impact of external shear stress on active stress-driven flows in microtubule-kinesin active fluids

摘要： 活性流体产生内部主动应力，并对如超流和自适应转变等外部力表现出独特的响应。然而，限制几何如何影响这些响应仍不明确。在此，我们研究了在外加剪切应力下两种几何结构中的微管-驱动蛋白活性流体。在板状限制（窄间隙腔体）中，外加应力在整个系统中传播，导致应力竞争和运动学转变，使动力学从以主动应力为主转变为以剪切应力为主。在转变过程中，我们估计主动应力约为1.5 mPa。模拟支持这种转变源于应力竞争。相反，在环状限制（环形系统）中，外力局部作用，引发微型腔流动，触发自组织重新配置，而不是直接卷入。这些发现表明，活性流体对外部强迫的响应不仅取决于施加应力的大小，还取决于限制几何如何引导和重新分布该应力，揭示了一种通过结合静态几何设计与动态外部刺激来控制活性流体行为的新方法，实现实时调节流动模式。这种控制策略可能应用于微流控系统，其中如微机械执行器等外部输入可以动态调节固定设备几何内的活性流体行为，实现混沌流与有序流之间的转换，用于混合、分选或定向传输等任务。 显示英文摘要

摘要： Active fluids generate internal active stress and exhibit unique responses to external forces such as superfluidity and self-yielding transitions. However, how confinement geometry influences these responses remains poorly understood. Here, we investigate microtubule-kinesin active fluids under external shear stresses in two geometries. In slab-like confinement (a narrow-gap cavity), external stresses propagated throughout the system, leading to stress competition and a kinematic transition that shifted dynamics from active stress-dominated to shear stress-dominated flow. At the transition, we estimate the active stress to be ~1.5 mPa. Simulation supported that this transition arises from stress competition. In contrast, in ring-like confinement (a toroidal system), external forces acted locally, inducing a mini cavity flow that triggered self-organized reconfiguration rather than direct entrainment. These findings show that the response of active fluids to external forcing depends not only on the magnitude of the applied stress but also on how confinement geometry directs and redistributes that stress, revealing a new approach to controlling active fluid behavior by combining static geometrical design with dynamic external stimuli for real-time modulation of flow patterns. Such control strategies may be applied to microfluidic systems, where external inputs such as micromechanical actuators can dynamically tune active fluid behavior within fixed device geometries, enabling transitions between chaotic and coherent flows for tasks such as mixing, sorting, or directed transport.