The Importance of a Filament-like Structure in Aerial Dispersal and the Rarefaction Effect of Air Molecules on a Nanoscale Fiber: Detailed Physics in Spiders’ Ballooning
The Importance of a Filament-like Structure in Aerial Dispersal and the Rarefaction Effect of Air Molecules on a Nanoscale Fiber: Detailed Physics in Spiders’ Ballooning
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丝状结构在空中传播中的重要性以及空气分子对纳米级纤维的稀疏效应：蜘蛛气球飞行中的详细物理学
DOI：
10.1093/icb/icaa063
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发表时间：
2020
影响因子：
2.6
通讯作者：
Koref, Iván Santibáñez
中科院分区：
文献类型：
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作者：
Cho, Moonsung;Koref, Iván Santibáñez
许多飞行昆虫利用膜状结构飞行，这被称为“翅膀”。然而，一些蜘蛛使用丝纤维进行空中传播。众所周知，蜘蛛可以分散数百公里，并以这种方式上升到离地面几公里的地方。然而，由于缺乏定量数据，人们对蜘蛛的膨胀机制知之甚少。最近，Cho等人发现了以前未知的关于蜘蛛膨胀丝的类型和物理特性的信息。根据数据，一只重20毫克的蟹蛛同时纺出50-60根气球状的丝，这些丝约200纳米厚，3.22米长，用于飞行。基于这些物理尺寸的气球丝，这些类似于磁共振的结构的意义是解释的理论分析，审查流体动力学的各向异性颗粒（如长丝或高细长体）。(1)该被动式结构是在低雷诺数流态下产生（或在被动飞行的情况下收获）流体动力的实质上有效的几何形状。(2)多个纳米级纤维是细纤维的物理特性的结果，其阻力与其长度成比例，但不与其直径成比例。由于纤维的这种非线性特性，对蜘蛛来说，纺多根细的气球状纤维比纺一根粗的蜘蛛丝更能产生拖曳力，因为蜘蛛可以使用相同数量的丝原液来最大化它们对气球状纤维的拖曳力。(3)纤维的平均厚度200 nm受到膨胀纤维的机械强度和空气分子在纳米级纤维上的稀疏效应的限制，因为如果纤维的厚度变得比100 nm薄，则纤维上的滑动条件可能占主导地位。
Many flying insects utilize a membranous structure for flight, which is known as a “wing.” However, some spiders use silk fibers for their aerial dispersal. It is well known that spiders can disperse over hundreds of kilometers and rise several kilometers above the ground in this way. However, little is known about the ballooning mechanisms of spiders, owing to the lack of quantitative data. Recently, Cho et al. discovered previously unknown information on the types and physical properties of spiders’ ballooning silks. According to the data, a crab spider weighing 20 mg spins 50–60 ballooning silks simultaneously, which are about 200 nm thick and 3.22 m long for their flight. Based on these physical dimensions of ballooning silks, the significance of these filament-like structures is explained by a theoretical analysis reviewing the fluid-dynamics of an anisotropic particle (like a filament or a high-slender body). (1) The filament-like structure is materially efficient geometry to produce (or harvest, in the case of passive flight) fluid-dynamic force in a low Reynolds number flow regime. (2) Multiple nanoscale fibers are the result of the physical characteristics of a thin fiber, the drag of which is proportional to its length but not to its diameter. Because of this nonlinear characteristic of a fiber, spinning multiple thin ballooning fibers is, for spiders, a better way to produce drag forces than spinning a single thick spider silk, because spiders can maximize their drag on the ballooning fibers using the same amount of silk dope. (3) The mean thickness of fibers, 200 nm, is constrained by the mechanical strength of the ballooning fibers and the rarefaction effect of air molecules on a nanoscale fiber, because the slip condition on a fiber could predominate if the thickness of the fiber becomes thinner than 100 nm.