Surface wrinkles are commonly observed in soft polymer nanofibers produced in electrospinning. This paper studies the conditions of circumferential wrinkling in polymer nanofibers under axial stretching. A nonlinear continuum mechanics model is formulated to take into account the combined effects of surface energy and nonlinear elasticity of the nanofibers on wrinkling initiation, in which the soft nanofibers are treated as incompressible, isotropically hyperelastic neo-Hookean solid. The critical condition to trigger circumferential wrinkling is determined and its dependencies upon the surface energy, mechanical properties, and geometries of the nanofibers are examined. In the limiting case of spontaneous circumferential wrinkling, the theoretical minimum radius of soft nanofibers producible in electrospinning is determined, which is related closely to the intrinsic length $l_0=\gamma /E$ of the polymer (γ: the surface energy; E: a measure of the elastic modulus), and compared with that of spontaneous longitudinal wrinkling in polymer nanofibers. The present study provides a rational understanding of surface wrinkling in polymer nanofibers and a technical approach for actively tuning the surface morphologies of polymer nanofibers for applications, e.g., high-grade filtration, oil-water separation, tissue scaffolding, etc.

中文翻译：

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聚合物纳米纤维的周向起皱。

通常在静电纺丝中生产的软聚合物纳米纤维中观察到表面皱纹。本文研究了在轴向拉伸下聚合物纳米纤维的周向起皱条件。建立了一个非线性连续力学模型，以考虑到纳米纤维的表面能和非线性弹性对起皱的综合影响，在这种模型中，柔软的纳米纤维被视为不可压缩的各向同性超弹性新霍克固体。确定触发圆周起皱的临界条件，并检查其对纳米纤维的表面能，机械性能和几何形状的依赖性。在自发圆周起皱的极限情况下，确定了可在静电纺丝中生产的软纳米纤维的理论最小半径，${升}_0=\gamma /Ë$聚合物纳米纤维的自发纵向起皱皱纹比较（γ：表面能；E：弹性模量的度量）。本研究为聚合物纳米纤维的表面起皱提供了合理的理解，并为主动调整聚合物纳米纤维的表面形貌提供了一种技术方法，例如高级过滤，油水分离，组织支架等。