DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom.
Phys Rev Lett. 2019 Oct 4;123(14):148005. doi: 10.1103/PhysRevLett.123.148005.
Suspensions of spherical active particles often show microphase separation. At a continuum level, coupling their scalar density to fluid flow, there are two distinct explanations. Each involves an effective interfacial tension: the first mechanical (causing flow) and the second diffusive (causing Ostwald ripening). Here we show how the negative mechanical tension of contractile swimmers creates, via a self-shearing instability, a steady-state life cycle of droplet growth interrupted by division whose scaling behavior we predict. When the diffusive tension is also negative, this is replaced by an arrested regime (mechanistically distinct, but with similar scaling) where division of small droplets is prevented by reverse Ostwald ripening.
球形活性粒子的悬浮液通常会表现出微相分离。在连续体水平上，将它们的标量密度与流体流动耦合，有两种截然不同的解释。每一种都涉及到一个有效的界面张力：第一种是力学的（导致流动），第二种是扩散的（导致奥斯特瓦尔德成熟）。在这里，我们展示了收缩游泳者的负力学张力如何通过自剪切不稳定性产生液滴生长的稳态生命周期，其分裂被中断，我们预测了其标度行为。当扩散张力也为负时，就会出现一种被阻止的状态（在机械上不同，但具有相似的标度），其中小液滴的分裂被反向奥斯特瓦尔德成熟所阻止。
