论文标题

3D活动性手性液滴中的旋转和推进

Rotation and propulsion in 3d active chiral droplets

论文作者

Carenza, Livio Nicola, Gonnella, Giuseppe, Marenduzzo, Davide, Negro, Giuseppe

论文摘要

手学是生物系统研究的一个反复主题,在该研究中,由化学能的内部转化为工作,主动过程驱动了积极的过程。细菌鞭毛,肌动蛋白丝和微管束是活性系统,也是内在手性的。尽管有一些探索性尝试捕获手性与运动之间的关系,但到目前为止,尚未对内在的手性系统进行分析。为了解决知识的这一差距,我们在这里研究内部活性力和扭矩对嵌入各向同性液体中的胆固醇液晶(CLC)的三维液滴的影响。我们考虑在液滴表面的液晶主管切向锚定。与在nematics中发生的情况相反,中等扩展活性导致液滴旋转,胆汁液体的活性液滴表现出更为复杂和多样化的行为。我们发现,扩展的力偶极活性稳定了复杂的缺陷构型,其旋转动力学夫妇旋转到热力学手性,以推动螺钉状的液滴运动。取而代之的是,偶极扭矩活性可能会拧紧或放松胆固醇螺旋,如果调整后,可以用振动的角速度旋转为零均值为零。

Chirality is a recurrent theme in the study of biological systems, in which active processes are driven by the internal conversion of chemical energy into work. Bacterial flagella, acto-myosin filaments and microtubule bundles are active systems which are also intrinsically chiral. Despite some exploratory attempt to capture the relations between chirality and motility, no intrinsically chiral system has ever been analyzed so far. To address this gap in knowledge, here we study the effects of internal active forces and torques on a three-dimensional droplet of cholesteric liquid crystal (CLC) embedded in an isotropic liquid. We consider tangential anchoring of the liquid crystal director at the droplet surface. Contrary to what happens in nematics, where moderate extensile activity leads to droplet rotation, cholesteric active droplets exhibit a lot more complex and variegated behaviors. We find that extensile force dipole activity stabilises complex defect configurations whose orbiting dynamics couples to thermodynamic chirality to propel screw-like droplet motion. Instead, dipolar torque activity may either tighten or unwind the cholesteric helix, and if tuned can power rotations with an oscillatory angular velocity of zero mean.

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