The mechanism of shape instability for a vesicle in extensional flow
The mechanism of shape instability for a vesicle in extensional flow
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拉伸流动中囊泡形状不稳定的机制
DOI：
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发表时间：
2014
影响因子：
3.7
通讯作者：
E. Shaqfeh
中科院分区：
文献类型：
--
作者：
V. Narsimhan;A. Spann;E. Shaqfeh
摘要：当柔性囊泡置于拉伸流（平面或单轴）中时，它会经历两组独特的形状转变，据作者所知，尚未在液滴中观察到这种转变。在中等体积减小（即中等颗粒长宽比）和高延伸率下，囊泡拉伸成由长圆柱形线分隔的不对称哑铃形。在低体积减少（即高颗粒长宽比）下，囊泡以类似于液滴破裂的方式对称延伸而不受限制。在这个“爆发”阶段，偶尔会发生“珍珠化”，即囊泡在其中央颈部形成一系列周期性的珠子。在本文中，我们通过求解单个充满流体的颗粒周围的斯托克斯流动方程来描述这些看似无关的不稳定性背后的物理机制，该颗粒的界面动力学由赫尔弗里希能量控制（即膜在弯曲阻力下不可延伸）。通过检查稳态形状的线性稳定性，我们确定囊泡因其界面上的曲率变化而不稳定，类似于瑞利-高原现象。这一结果表明，囊泡的初始几何形状在其在张力下的形状转变中发挥着重要作用。通过我们的模拟和缩放分析计算出的稳定性标准与现有实验非常吻合。我们希望这项工作能够深入了解其他类型的具有几乎不可压缩膜的生物颗粒（例如细胞）的拉伸动力学。
Abstract When a flexible vesicle is placed in an extensional flow (planar or uniaxial), it undergoes two unique sets of shape transitions that to the best of the authors’ knowledge have not been observed for droplets. At intermediate reduced volumes (i.e. intermediate particle aspect ratio) and high extension rates, the vesicle stretches into an asymmetric dumbbell separated by a long, cylindrical thread. At low reduced volumes (i.e. high particle aspect ratio), the vesicle extends symmetrically without bound, in a manner similar to the breakup of liquid droplets. During this ‘burst’ phase, ‘pearling’ occasionally occurs, where the vesicle develops a series of periodic beads in its central neck. In this paper, we describe the physical mechanisms behind these seemingly unrelated instabilities by solving the Stokes flow equations around a single, fluid-filled particle whose interfacial dynamics is governed by a Helfrich energy (i.e. the membranes are inextensible with bending resistance). By examining the linear stability of the steady-state shapes, we determine that vesicles are destabilized by curvature changes on its interface, similar to the Rayleigh–Plateau phenomenon. This result suggests that the vesicle’s initial geometry plays a large role in its shape transitions under tension. The stability criteria calculated by our simulations and scaling analyses agree well with available experiments. We hope that this work will lend insight into the stretching dynamics of other types of biological particles with nearly incompressible membranes, such as cells.
影响因子：
3.4
作者：
Pan, Jianjun;Tristram-Nagle, Stephanie;Nagle, John F.
通讯作者：
Nagle, John F.
影响因子：
3.4
作者：
Rawicz, W;Olbrich, KC;Evans, E
通讯作者：
Evans, E