The Sandfish's Skin:Morphology,Chemistry and Reconstruction

The sandfish is a lizard having the remarkable ability to move in desert sand in a swimming-like fashion. The most outstanding adaptations to this mode of life are the low friction behaviour and the extensive abrasion resistance of the sandfish skin against sand, outperforming even steel. We investigated the topography, the composition and the mechanical properties of sandfish scales. These consist of glycosylated keratins with high amount of sulphur but no hard inorganic material, such as silicates or lime. Remarkably, atomic force microscopy shows an almost complete absence of attractive forces between the scale surface and a silicon tip, suggesting that this is responsible for the unusual tribological properties. The unusual glycosylation of the keratins was found to be absolutely necessary for the described phenomenon. The scales were dissolved and reconstituted on a polymer surface resulting in properties similar to the original scale. Thus, we provide a pathway towards exploitation of the reconstituted scale material for future engineering applications.

以砂鱼蜥头部为原型的仿生深松铲尖设计与离散元仿真

为解决传统深松机具触土部件破土困难、耕作阻力大等问题,以砂鱼蜥头部为仿生原型,采用逆向工程技术对其特殊几何特征进行提取,将量化后的几何结构特征应用于深松铲尖的设计,以期减小深松铲作业阻力和能耗。依据不同特征曲面,设计了3种仿生铲尖试样,并与凿型铲尖试样进行性能对比。建立离散元模型,求解不同铲尖垂直贯入土壤阻力;制备试样,通过万能试验机进行土壤垂直贯入实测试验;将模拟结果和实测试验结果进行对比,结果表明离散元仿真分析和实测试验结果吻合较好,最大贯入阻力的相对误差为2.47%~3.91%。使用离散元法分析仿生铲尖和凿型铲尖(T-S)在土壤分层情况下的相互作用,证实仿生铲尖比凿型铲尖具有更低的所需牵引力,其中仿生铲尖B-S-2减阻效果最好,相对于凿型铲尖,其减阻率为8.34%~19.31%。离散元分析揭示砂鱼蜥头部仿生曲线特殊的曲率变化对破土阻力有显著影响,仿生铲尖改变了土壤颗粒的流动方向,减小了铲尖上方土壤扰动范围,从而降低所需牵引力。在3种作业速度和3种耕作深度下对阻力的仿真结果与土槽试验结果进行对比,误差为10.83%~17.06%。

砂鱼蜥体表鳞片超微结构的扫描电镜观察

使用扫描电子显微镜对砂鱼蜥(Scincus scincus)体表鳞片的表面形态及其超微结构进行了观察。结果表明,砂鱼蜥体表鳞片分为表皮层和真皮层两部分,其中表皮层由4层组成,由内向外依次为发生层、生活细胞层、带有生物柔性的α-角质层和较硬的β-角质层;生活层与角质层之间称为中介层。扫描电镜下体表鳞片的形状为扇形或椭圆形,鳞片间紧密排列,形如覆瓦状。此外,体表鳞片分为背部体表鳞片和腹部体表鳞片,两者分布的条纹纹路有深有浅,宽窄不等,条纹纹路上分布有极小的微刺。体表鳞片的部位不同,微刺的高度、间距宽度、数量都不一样。砂鱼蜥背部体表鳞片不仅受到沙粒磨料磨损的损伤,而且还受到风沙冲蚀磨损的损伤。相比之下,背部体表鳞片的微刺较为尖锐,数量也较多。