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吸盘手套配乳液,树蛙想扒哪儿就扒哪儿

 2018/11/8 9:04:19 《最新论文》 作者:Frontiers in Zoology 我有话说(0人评论) 字体大小:+

论文标题:Tree frog attachment: mechanisms, challenges, and perspectives

期刊:Frontiers in Zoology

作者:Julian K. A. Langowski, Dimitra Dodou, Marleen Kamperman and Johan L. van Leeuwen

发表时间:2018/08/23

数字识别码:10.1186/s12983-018-0273-x

原文链接:https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-018-0273-x?utm_source=WeChat&utm_medium=Website_linksSocial_media_organic&utm_content=CelZha-MixedBrand-multijournal-Multidisciplinary-China&utm_campaign=ORG_AWA_CZH_BMCWechat_dailyposts_blogs

微信链接:https://mp.weixin.qq.com/s/UuXBx2s3Wb3T26MYn89KDQ

原文作者:Julian K. A. Langowski, Dimitra Dodou, Marleen Kamperman and Johan L. van Leeuwen

树蛙有一种神奇的能力:从光滑的玻璃到粗糙的木头,它能够吸附于或干或湿的各种表面。在Frontiers in Zoology发表的一篇文章中,作者之一的Julian Langowski向我们描述了几种树蛙超强吸附能力的可能机制。

吸附在平滑表面上的灰绿树蟾(Hyla cinerea )。

J.K.A. Langowski

即使在某些充满挑战性的条件下,树蛙仍能用脚趾端的软垫把自己牢牢固定在上面,连一些又湿又滑的表面也不例外。研究树蛙的吸附能力不仅能让我们进一步解读这种动物的演化和生态,还能促进开发以其为灵感的相关产品,例如全天候轮胎(全雨胎)、手术夹具等。虽然几个世纪来的研究让我们获得很多关于树蛙吸附能力的重要信息,但仍然缺乏对树蛙吸附能力的全面而彻底的了解。荷兰瓦格宁根大学和研究院的Julian Langowski在最近一篇发表在Frontiers in Zoology的综述文章里总结了对树蛙吸附能力的研究,并解释了与其有关机制的知与未知。

树蛙足垫表面样式的示意图概述。摘自:Langowski et al. (2018): Tree frog attachment: mechanisms, challenges, and perspectives.Frontiers in Zoology, 15:32.

树蛙足垫底部的表面存在有特别的纹路。足垫表面的皮肤细胞组成被通道形成的网络所环绕的六角形柱。而每个细胞的表面也被一个“纳米支柱”覆盖,并被通道分隔,于是在足垫表面形成微米级到纳米级有层次的纹理。这种纹理被认为有降低足垫硬度的作用。事实上,这些足垫的有效硬度大约为25kPa,几乎比所有的生物材料都要柔软,这或许是让足垫完美地契合任何自然界中硬度更大的表面的原因。

足垫的弹性可能导致足垫和表面之间产生范德瓦尔斯力(van der Waals forces),也就是分子之间近距离产生的吸引力,而让树蛙成功吸附在物体表面。我们对足垫和表面之间的距离和产生的范德瓦尔斯力之间的关系进行了敏感性分析。分析结果显示,足垫和表面的高度契合能够产生大量范德瓦尔斯力。此外,足垫的纹理也有可能让树蛙用吸力吸附表面,类似头足类动物的吸盘,或者昆虫爪和牛蒡种子毛刺的机械联锁。

另外,树蛙可以向足垫表面的通道网络分泌粘液。这些粘液通常用于控制温度、皮肤呼吸和防御,此外也有可能帮助吸附。比如,粘液成为连接足垫和表面的毛细管液体桥梁。普遍的理论是,这种液体桥梁会引起毛细管粘附,例如被水紧紧粘在一起的两块玻璃。粘液随着足垫的移动还可能导致流体动力的接触力。然而,现有的分析模型不能充分地量化每种机制对树蛙吸附的贡献。

几种可能参与树蛙吸附过程的机制。

树蛙有可能依靠多种而不仅仅是一种以上提到的机制,来保证在自然界的多种表面上运动或静止、粘附或产生摩擦力、进行可逆的运动以及重复吸附。总的来说,树蛙是一个让人着迷的模型,可以用来研究不同机制之间在一个生物粘附系统里复杂的相互影响。为了深入了解这一系统,我们需要进一步研究足垫的内部形态(例如粘附性的表面如何与内骨骼进行机械连接?)和粘液的化学成分(例如树蛙是否通过主动调整粘液的化学成分来控制吸附?)。在一篇最近发表的研究里,我们向解答这些问题迈出了第一步。我们发现足垫的表面通过一层胶原连接树蛙的骨架,而胶原很适合传递高剪切载荷

解决这些问题有助于形成一个完整的模型,这个模型中包含对足垫的功能需求、足垫的形态和多种与树蛙吸附能力有关的机制。这个模型可能会让我们对接触和吸附的基本原理产生新的理解。了解树蛙吸附也会增进我们对其他生物吸附系统(比如壁虎和昆虫)的理解并有助于探讨这些系统趋同进化的可能性。最后,树蛙吸附相关原理会激励仿生研究制造出和类似树蛙足垫的多功能产品。

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摘要:

Tree frogs have the remarkable ability to attach to smooth, rough, dry, and wet surfaces using their versatile toe pads. Tree frog attachment involves the secretion of mucus into the pad-substrate gap, requiring adaptations towards mucus drainage and pad lubrication. Here, we present an overview of tree frog attachment, with focus on (i) the morphology and material of the toe pad; (ii) the functional demands on the toe pad arising from ecology, lifestyle, and phylogenetics; (iii) experimental data of attachment performance such as adhesion and friction forces; and (iv) potential perspectives on future developments in the field. By revisiting reported data and observations, we discuss the involved mechanisms of attachment and propose new hypotheses for further research. Among others, we address the following questions: Do capillary and hydrodynamic forces explain the strong friction of the toe pads directly, or indirectly by promoting dry attachment mechanisms? If friction primarily relies on van der Waals (vdW) forces instead, how much do these forces contribute to adhesion in the wet environment tree frogs live in and what role does the mucus play? We show that both pad morphology and measured attachment performance suggest the coaction of several attachment mechanisms (e.g. capillary and hydrodynamic adhesion, mechanical interlocking, and vdW forces) with situation-dependent relative importance. Current analytical models of capillary and hydrodynamic adhesion, caused by the secreted mucus and by environmental liquids, do not capture the contributions of these mechanisms in a comprehensive and accurate way. We argue that the soft pad material and a hierarchical surface pattern on the ventral pad surface enhance the effective contact area and facilitate gap-closure by macro- to nanoscopic drainage of interstitial liquids, which may give rise to a significant contribution of vdW interactions to tree frog attachment. Increasing the comprehension of the complex mechanism of tree frog attachment contributes to a better understanding of other biological attachment systems (e.g. in geckos and insects) and is expected to stimulate the development of a wide array of bioinspired adhesive applications.

阅读论文全文请访问:

https://frontiersinzoology.biomedcentral.com/articles/10.1186/s12983-018-0273-x?utm_source=WeChat&utm_medium=Website_linksSocial_media_organic&utm_content=CelZha-MixedBrand-multijournal-Multidisciplinary-China&utm_campaign=ORG_AWA_CZH_BMCWechat_dailyposts_blogs

期刊介绍:

Frontiers in Zoology (https://frontiersinzoology.biomedcentral.com/, 3.627 - 2-year Impact Factor, 3.782 - 5-year Impact Factor) is an open access, peer-reviewed online journal publishing high quality research articles and reviews on all aspects of animal life.

来源:Frontiers in Zoology