Swimming of deformable microcapsules and droplets

本研究计画主要针对可变形微胶囊或液滴式自推进游泳器进行理论研究。我们研究了由于水动力和可变形性的相互作用而通常发生在可变形的自推进胶囊或液滴中的两个问题：A）由于水动力，自推进微胶囊或液滴在游泳过程中会变形，这反过来改变了周围流体的速度场，从而改变了所得的游泳速度。我们将开发理论和模拟方法，以解决弹性微胶囊或液滴变形的耦合问题，流体动力学流体流动周围（和内部）的游泳者，并最终负责泳动效应的表面活性剂的反应物的扩散。特别是，我们研究胶囊和液滴游泳推进自泳。B）可变形微胶囊可以使用循环形状变化作为机械游动机制。耦合一个简单的振荡控制参数的滞后形状的变化足以引起游泳运动。这种游泳机制的滞后形状的变化将在理论上进行研究，相对于可能实现的游泳者构造的热响应性聚合物凝胶进行全球滞后的形状变化引发的局部膨胀和收缩。

This research project is focused on the theoretical investigation of self-propelling deformable microcapsule or droplet-based swimmers. We study two problems that occur generically for deformable self-propelled capsules or droplets due to the interplay of hydrodynamic forces and deformability: A) Because of hydrodynamic forces, a self-propelled microcapsule or droplet will deform during swimming, which changes in turn the velocity field of the surrounding fluid and, thus, the resulting swimming velocity. We will develop theoretical and simulation methods in order to solve the coupled problem of elastic microcapsule or droplet deformation, of the hydrodynamic fluid flow around (and inside) the swimmer and, eventually, of the diffusion of reactants of surfactants responsible for phoretic effects. In particular, we study capsule and droplet swimmers propelling by autophoresis. B) A deformable microcapsule can use cyclic shape changes as a mechanical swimming mechanism. Coupling a hysteretic shape change to a simply oscillating control parameter suffices to induce swimming motion. This swimming mechanism by hysteretic shape changes will be investigated theoretically with respect to possible realizations by swimmers constructed from thermo-responsive polymer gels undergoing global hysteretic shape changes triggered by local swelling and shrinking.