Sun Mingxia, Chen Yuan, Zheng Yongmei, Zhen Mingming, Shu Chunying, Dai Zhendong, Liang Aiping, Gorb Stanislav N
Key Laboratory of the Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beichen West Road 1-5, Chaoyang District, Beijing 1000101, China; Department of Functional Morphology and Biomechanics, Zoological Institute, Kiel University, Am Botanischen Garten 1-9, D-24118 Kiel, Germany.
Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, Beihang University, Xueyuan Road 37, Haidian District, Beijing 100191, China.
Acta Biomater. 2017 Mar 15;51:408-417. doi: 10.1016/j.actbio.2017.01.022. Epub 2017 Jan 7.
The surface of the elytra in some species of aquatic beetles displays relatively low contact angles (CAs), even showing hydrophilic properties. In this study, we report on an observation that both sexes of Cybister chinensis beetle fresh elytral surface do not exhibit uniform CA, but rather a wettability gradient along the longitudinal axis in posterior direction. The wettability is very different between females and males due to the presence (female) or absence (male) of channels on the elytral surface. When a small drop of water touches the elytra surface, it tends to slide towards the anterior having a lower CA on the elytra. This gradient presumably supports a breathing-associated behavior of beetles in which they cause the tip of their abdomen to protrude into the surface of the water in order to collect an air bubble for oxygen uptake and, when floating on the surface, to keep the body inclined at a small angle to the water's surface with their heads immersed.
Hydrophobicity on surfaces is a fundamental property which has attracted great interest across all scientific disciplines, here we have demonstrated that the gradually changing chemistry of the elytral surface facilitates the tilted beetle posture on the water's surface. The mechanism of water interacting with the elytra demonstrated the most energetically favorable posture in the diving beetles. Surfaces with directional wetting properties that promote droplet drainage are of significant practical importance in many fields. The anisotropic topography and wetting properties of the elytra may inspire microfluidic devices for medical and robotic applications.
某些水生甲虫鞘翅的表面显示出相对较低的接触角（CA），甚至呈现出亲水性。在本研究中，我们报告了一项观察结果，即中华牙甲雌雄新鲜鞘翅表面的接触角并非均匀一致，而是沿后向纵轴存在润湿性梯度。由于鞘翅表面存在（雌性）或不存在（雄性）通道，雌雄之间的润湿性差异很大。当一小滴水接触鞘翅表面时，它往往会朝着鞘翅上接触角较低的前部滑动。这种梯度大概支持了甲虫的一种与呼吸相关的行为，即它们使腹部尖端突出到水面以收集气泡用于吸氧，并且当漂浮在水面上时，使身体以小角度倾斜于水面，头部浸入水中。
表面疏水性是一种基本特性，在所有科学学科中都引起了极大的兴趣，在这里我们已经证明鞘翅表面逐渐变化的化学性质有助于甲虫在水面上保持倾斜姿势。水与鞘翅相互作用的机制展示了潜水甲虫最有利的姿势。具有促进液滴排水的定向润湿性的表面在许多领域具有重要的实际意义。鞘翅的各向异性形貌和润湿性可能会启发用于医学和机器人应用的微流体装置。
