Cooperative properties of thermophoretic microswimmers

由于它们与生物系统的相似性及其潜在的实际应用，例如在芯片实验室设备中，合成微游泳者正迅速受到越来越多的关注。自传递效应是一种有效的、有前途的人工微游泳体设计策略。热泳泳者解释了不均匀的表面加热，因此它们在存在外部加热（例如激光照明或磁刺激）的情况下，由于自身产生的局部温度梯度而推进。我们已经开发的微游泳模拟模型，目前功能是微二聚体，Janus胶体和微齿轮。溶剂与微游体表面相互作用的细节决定了电泳力的亲热或疏热特性，而这一特性将是决定微游体行为的关键，以及颗粒的大小和形状。通过这种方式，不同的微二聚体在流体动力学上表现得像推动者、推动者或中性粒子；这是为了在周围流体的驱动下产生吸引、排斥或中性的粒子间相互作用。这些流体动力相互作用将与具有相同或不同方向的流体相互作用共存。这些不同机制之间的相互作用，以及由此产生的各种行为，在很大程度上仍未得到探索。本项目的主要目的是通过介观模拟研究具有多个游泳者的溶液和游泳者与被动粒子的混合物的性质。这项研究将主要对Janus胶体、二聚体、三聚体以及最终的其他游泳体形状进行研究。特别令人感兴趣的是三聚体，考虑到珠的大小和三个珠的组成，它提供了高度的不对称程度。这可能会导致游泳者有大的持续运动，不同的不对称相互作用，也可以沿着椭圆轨道运动，以及大范围的手性相互作用。对这些游泳者的集体行为的调查将显示出群集、群集和各种类型的同步运动等重要现象。一些自组装的结构预计将长期使用，但情况仍有待确定。具有重要潜在应用前景的现象的例子是电泳游泳者的定向运动，以及游泳者围绕被动电泳颗粒的组装，这将使货物运输和交付到指定区域成为可能。

Due to their similitude with biological systems and their potential practical applications, for example in lab-on-a-chip devices, synthetic microswimmers are receiving rapidly increasing attention. Self-phoretic effects have shown to be an effective and promising strategy to design such artificial microswimmers. Thermophoretic swimmers account for inhomogeneous surface heating, such that they propel due to the presence of self-generated local temperature gradients in the presence of external heating, for example by laser illumination or magnetic stimulation. The microswimmer simulation models that we have already developed and that are currently functional are microdimers, Janus colloids, and microgears. The details of the solvent interactions with the microswimmer surface determines the thermophilic or thermophobic character of the phoretic forces, and this character will be crucial to determine the microswimmer behavior, together with the particle size and shape. In this way, different microdimers have shown to hydrodynamically behave like pushers, pullers, or neutral particles; this is to generate attractive, repulsive, or neutral interparticle interactions driven by the surrounding fluid. These hydrodynamic interactions will coexist with the phoretic interactions which can have the same or different directions. The interplay of these different mechanisms, and the variety of resulting behaviors is still largely unexplored. The main purpose of this project is to investigate, by means of mesoscopic simulations the properties of solutions with multiple swimmers and of mixtures of swimmers with passive particles. This research will be performed mainly with Janus colloids, dimers, trimers, and eventually other swimmers shapes. Of particular interest are the trimers, which offer a high possible degree of asymmetry, considering the bead sizes and composition of the three beads. These might result in swimmers with a large persistent motion, different asymmetric interactions, and also moving with elliptical orbits, and with large range of chiral interactions. The investigation of the collective behavior of these swimmers will display important phenomena like clustering, swarming, and various types of synchronized motion. Some of the self-assembled structures are expected to be long-lived, under circumstances still to be identified. Examples of phenomena with important potential applications are the directed motion of phoretic swimmers, and the assembly of swimmers around a passive phoretic particle, which would enable to transport and deliver cargo to designated areas.