Monn Michael A, Weaver James C, Zhang Tianyang, Aizenberg Joanna, Kesari Haneesh
School of Engineering, Brown University, Providence, RI 02912; and.
Wyss Institute for Biologically Inspired Engineering and.
Proc Natl Acad Sci U S A. 2015 Apr 21;112(16):4976-81. doi: 10.1073/pnas.1415502112. Epub 2015 Apr 6.
To adapt to a wide range of physically demanding environmental conditions, biological systems have evolved a diverse variety of robust skeletal architectures. One such example, Euplectella aspergillum, is a sediment-dwelling marine sponge that is anchored into the sea floor by a flexible holdfast apparatus consisting of thousands of anchor spicules (long, hair-like glassy fibers). Each spicule is covered with recurved barbs and has an internal architecture consisting of a solid core of silica surrounded by an assembly of coaxial silica cylinders, each of which is separated by a thin organic layer. The thickness of each silica cylinder progressively decreases from the spicule's core to its periphery, which we hypothesize is an adaptation for redistributing internal stresses, thus increasing the overall strength of each spicule. To evaluate this hypothesis, we created a spicule structural mechanics model, in which we fixed the radii of the silica cylinders such that the force transmitted from the surface barbs to the remainder of the skeletal system was maximized. Compared with measurements of these parameters in the native sponge spicules, our modeling results correlate remarkably well, highlighting the beneficial nature of this elastically heterogeneous lamellar design strategy. The structural principles obtained from this study thus provide potential design insights for the fabrication of high-strength beams for load-bearing applications through the modification of their internal architecture, rather than their external geometry.
为了适应各种对身体要求苛刻的环境条件，生物系统进化出了多种多样坚固的骨骼结构。一个这样的例子是偕老同穴，它是一种生活在沉积物中的海洋海绵，通过由数千根锚状骨针（长的、毛发状的玻璃纤维）组成的灵活固着装置固定在海底。每根骨针都覆盖着倒刺，其内部结构由一个二氧化硅实心核心和围绕它的同轴二氧化硅圆柱体组件组成，每个圆柱体由一层薄的有机层隔开。每个二氧化硅圆柱体的厚度从骨针的核心到其外围逐渐减小，我们推测这是一种重新分布内部应力的适应方式，从而增加每根骨针的整体强度。为了评估这一假设，我们创建了一个骨针结构力学模型，在该模型中我们固定了二氧化硅圆柱体的半径，以使从表面倒刺传递到骨骼系统其余部分的力最大化。与天然海绵骨针中这些参数的测量结果相比，我们的建模结果相关性非常好，突出了这种弹性非均质层状设计策略的有益性质。因此，从这项研究中获得的结构原理为通过改变其内部结构而非外部几何形状来制造用于承重应用的高强度梁提供了潜在的设计思路。
