Samin Sela, van Roij René
Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht, The Netherlands.
Phys Rev Lett. 2015 Oct 30;115(18):188305. doi: 10.1103/PhysRevLett.115.188305. Epub 2015 Oct 29.
Gold-capped Janus particles immersed in a near-critical binary mixture can be propelled using illumination. We employ a nonisothermal diffuse interface approach to investigate the self-propulsion mechanism of a single colloid. We attribute the motion to body forces at the edges of a micronsized droplet that nucleates around the particle. Thus, the often-used concept of a surface velocity cannot account for the self-propulsion. The particle's swimming velocity is related to the droplet shape and size, which is determined by a so-called critical isotherm. Two distinct swimming regimes exist, depending on whether the droplet partially or completely covers the particle. Interestingly, the dependence of the swimming velocity on temperature is nonmonotonic in both regimes.
浸没在近临界二元混合物中的金帽双面粒子可以通过光照来驱动。我们采用非等温扩散界面方法来研究单个胶体的自推进机制。我们将这种运动归因于在粒子周围成核的微米级液滴边缘的体力。因此，常用的表面速度概念无法解释自推进现象。粒子的游动速度与液滴的形状和大小有关，而液滴的形状和大小由所谓的临界等温线决定。根据液滴是部分还是完全覆盖粒子，存在两种不同的游动状态。有趣的是，在这两种状态下，游动速度对温度的依赖性都是非单调的。
