Abstract.

Geometric confinements are frequently encountered in the biological world and strongly affect the stability, topology, and transport properties of active suspensions in viscous flow. Based on a far-field analytical model, the low-Reynolds-number locomotion of a self-propelled microswimmer moving inside a clean viscous drop or a drop covered with a homogeneously distributed surfactant, is theoretically examined. The interfacial viscous stresses induced by the surfactant are described by the well-established Boussinesq-Scriven constitutive rheological model. Moreover, the active agent is represented by a force dipole and the resulting fluid-mediated hydrodynamic couplings between the swimmer and the confining drop are investigated. We find that the presence of the surfactant significantly alters the dynamics of the encapsulated swimmer by enhancing its reorientation. Exact solutions for the velocity images for the Stokeslet and dipolar flow singularities inside the drop are introduced and expressed in terms of infinite series of harmonic components. Our results offer useful insights into guiding principles for the control of confined active matter systems and support the objective of utilizing synthetic microswimmers to drive drops for targeted drug delivery applications.

Graphical abstract

中文翻译：

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对清洁和表面活性剂覆盖液滴中活性微泳剂的分析描述。

摘要。

几何限制在生物界经常遇到，并且强烈影响粘性流中活性悬浮液的稳定性，拓扑和运输特性。基于远场分析模型，理论上研究了在干净的粘性液滴或覆盖有均匀分布的表面活性剂的液滴内部移动的自行式微泳器的低雷诺数运动。表面活性剂引起的界面粘性应力由成熟的Boussinesq-Scriven本构流变模型描述。此外，活性剂以偶极力为代表，并研究了游泳者与围护液滴之间的流体介导的流体动力学耦合。我们发现表面活性剂的存在通过增强其重新定向而显着改变了被包裹的游泳者的动力学。引入了Stokeslet速度图像和液滴内部偶极流动奇点的精确解，并用无穷次谐波分量表示。我们的结果为控制受限活性物质系统的指导原则提供了有用的见解，并支持了利用合成微泳器驱动液滴以达到靶向药物输送应用的目标。

图形概要