Superrepellency of underwater hierarchical structures on Salvinia leaf
Superrepellency of underwater hierarchical structures on Salvinia leaf
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槐叶属水下分层结构的超排斥性
DOI：
10.1073/pnas.1900015117
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Huiling Duan
中科院分区：
文献类型：
--
作者：
Yaolei Xiang;Shenglin Huang;Tian-Yun Huang;Ao Dong;Di Cao;Hongyuan Li;Yahui Xue;Pengyu Lv;Huiling Duan
水下湿滑气垫的不稳定性和塌陷阻碍了其应用，之后气垫甚至在荷叶等超疏水表面上也无法恢复。除了超疏水性之外，我们还提出了Salvinia叶的水下超排斥能力，它可以通过捕获补充的空气来取代微结构中的水，从而有效地和稳健地恢复无效的湿滑气垫。底座上相互连接的楔形凹槽是回收的关键，它们通过气体芯吸效应自发地将补充的空气输送到整个表面。利用3D打印技术，制作仿生人工槐叶表面，成功实现了气垫的回收。这一发现将大大扩展防水表面的水下应用。仿生超疏水表面具有许多优异的水下功能，这归因于表面结构中捕获的湿滑空气垫。然而，空气床垫容易因各种扰动而塌陷，导致完全润湿的Wenzel状态，而填充微结构的水即使在像荷叶这样的超疏水表面上也很难被排斥以完全恢复空气床垫。除了超疏水性，在这里，我们发现，漂浮的蕨类植物，Salvinia molesta，具有超排斥能力，有效地取代水的微结构与空气和鲁棒地恢复连续的空气床垫。叶表面的层次结构被证明是至关重要的恢复。表皮细胞之间的相互连接的楔形凹槽是空气在整个叶片上自发扩散的关键，由气体芯吸效应控制，以形成薄的空气膜，这为空气床垫在厚度上同步沿着毛状结构的后期生长提供了基础。受大自然的启发，采用3D打印技术制造仿生人工Salvinia表面，成功实现了连续空气床垫的完全恢复，以精确模仿Salvinia叶子的超排斥能力。这一发现将有利于防水材料的设计原理，并扩大其在水下的应用，特别是在极端环境中。
Significance Instability and collapse of the underwater slippery air mattress hinder its applications, after which the air mattress cannot be recovered even on superhydrophobic surfaces like lotus leaves. Beyond superhydrophobicity, we present the underwater superrepellent capacity of Salvinia leaves, which can efficiently and robustly recover the invalid slippery air mattress by trapping the replenished air to replace the water in the microstructures. The interconnected wedge-shaped grooves on the base are key to the recovery, which spontaneously transport the replenished air to the entire surface governed by a gas wicking effect. Using 3D printing technology, biomimetic artificial Salvinia surfaces are fabricated, which successfully achieves the recovery of the air mattress. This finding will greatly extend the underwater applications of water-repellant surfaces. Biomimetic superhydrophobic surfaces display many excellent underwater functionalities, which attribute to the slippery air mattress trapped in the structures on the surface. However, the air mattress is easy to collapse due to various disturbances, leading to the fully wetted Wenzel state, while the water filling the microstructures is difficult to be repelled to completely recover the air mattress even on superhydrophobic surfaces like lotus leaves. Beyond superhydrophobicity, here we find that the floating fern, Salvinia molesta, has the superrepellent capability to efficiently replace the water in the microstructures with air and robustly recover the continuous air mattress. The hierarchical structures on the leaf surface are demonstrated to be crucial to the recovery. The interconnected wedge-shaped grooves between epidermal cells are key to the spontaneous spreading of air over the entire leaf governed by a gas wicking effect to form a thin air film, which provides a base for the later growth of the air mattress in thickness synchronously along the hairy structures. Inspired by nature, biomimetic artificial Salvinia surfaces are fabricated using 3D printing technology, which successfully achieves a complete recovery of a continuous air mattress to exactly imitate the superrepellent capability of Salvinia leaves. This finding will benefit the design principles of water-repellent materials and expand their underwater applications, especially in extreme environments.