论文标题
具有空间变化活性的活性列膜中的缺陷自我传播
Defect self-propulsion in active nematic films with spatially-varying activity
论文作者
论文摘要
我们研究具有空间变化活性的活性列膜中拓扑缺陷的动力学，并考虑两个设置：i）恒定的活动梯度，ii）活动急剧上升。恒定的（收缩）活动的恒定梯度赋予了彗星样$+1/2 $缺陷，具有有限的涡度，该涡度驱动缺陷，以减少（增加）梯度的方向使其鼻子对齐。但是，恒定的梯度不会影响$+1/2 $缺陷的已知自我推测，并且对仍然是非运动粒子的$ -1/2 $没有影响。活动的急剧跳跃就像墙壁困扰缺陷的墙壁，影响了这两种电荷的翻译和旋转运动。 $+1/2 $缺陷在接近接口时会减慢，净涡度倾向于重新定位缺陷极化，从而使其垂直于接口。 $ -1/2 $缺陷获得了对活动接口的自我推测，而涡度诱导的主动扭矩倾向于将缺陷与首选方向保持一致。阴性缺陷对壁的有效吸引与观察到主动/被动界面和物理边界的负拓扑电荷的积累一致。
We study the dynamics of topological defects in active nematic films with spatially-varying activity and consider two setups: i) a constant activity gradient, and ii) a sharp jump in activity. A constant gradient of extensile (contractile) activity endows the comet-like $+1/2$ defect with a finite vorticity that drives the defect to align its nose in the direction of decreasing (increasing) gradient. A constant gradient does not, however, affect the known self-propulsion of the $+1/2$ defect and has no effect on the $-1/2$ that remains a non-motile particle. A sharp jump in activity acts like a wall that traps the defects, affecting the translational and rotational motion of both charges. The $+1/2$ defect slows down as it approaches the interface and the net vorticity tends to reorient the defect polarization so that it becomes perpendicular to the interface. The $-1/2$ defect acquires a self-propulsion towards the activity interface, while the vorticity-induced active torque tends to align the defect to a preferred orientation. This effective attraction of the negative defects to the wall is consistent with the observation of an accumulation of negative topological charge at both active/passive interfaces and physical boundaries.
