Laboratory of Bio-inspired Nanomechanics Giuseppe Maria Pugno, Department of Structural Engineering, Politecnico di Torino, Torino, Italy.
PLoS One. 2012;7(2):e30500. doi: 10.1371/journal.pone.0030500. Epub 2012 Feb 8.
Spider silks display generally strong mechanical properties, even if differences between species and within the same species can be observed. While many different types of silks have been tested, the mechanical properties of stalks of silk taken from the egg sac of the cave spider Meta menardi have not yet been analyzed. Meta menardi has recently been chosen as the "European spider of the year 2012", from the European Society of Arachnology. Here we report a study where silk stalks were collected directly from several caves in the north-west of Italy. Field emission scanning electron microscope (FESEM) images showed that stalks are made up of a large number of threads, each of them with diameter of 6.03 ± 0.58 µm. The stalks were strained at the constant rate of 2 mm/min, using a tensile testing machine. The observed maximum stress, strain and toughness modulus, defined as the area under the stress-strain curve, are 0.64 GPa, 751% and 130.7 MJ/m(3), respectively. To the best of our knowledge, such an observed huge elongation has never been reported for egg sac silk stalks and suggests a huge unrolling microscopic mechanism of the macroscopic stalk that, as a continuation of the protective egg sac, is expected to be composed by fibres very densely and randomly packed. The Weibull statistics was used to analyze the results from mechanical testing, and an average value of Weibull modulus (m) is deduced to be in the range of 1.5-1.8 with a Weibull scale parameter (σ(0)) in the range of 0.33-0.41 GPa, showing a high coefficient of correlation (R(2) = 0.97).
蜘蛛丝通常表现出很强的机械性能，即使在不同物种和同一物种内也会存在差异。虽然已经测试了许多不同类型的丝，但来自洞穴蜘蛛 Meta menardi 卵囊丝的丝茎的机械性能尚未得到分析。Meta menardi 最近被欧洲蛛形学会选为“2012 年欧洲蜘蛛”。在这里，我们报告了一项研究，其中直接从意大利西北部的几个洞穴中收集了丝茎。场发射扫描电子显微镜（FESEM）图像显示，丝茎由大量的纤维组成，每个纤维的直径为 6.03 ± 0.58 µm。使用拉伸试验机以 2mm/min 的恒定速率对丝茎进行拉伸。观察到的最大应力、应变和韧性模量（定义为应力-应变曲线下的面积）分别为 0.64 GPa、751%和 130.7 MJ/m³。据我们所知，这种观察到的巨大伸长率从未在卵囊丝的丝茎中报道过，这表明在宏观丝茎中有一个巨大的微观展开机制，作为卵囊的延续，它预计由非常密集和随机包装的纤维组成。使用威布尔统计对力学测试结果进行了分析，并推断出威布尔模数（m）的平均值在 1.5-1.8 范围内，威布尔尺度参数（σ（0））在 0.33-0.41 GPa 范围内，显示出很高的相关性系数（R²=0.97）。
