Supercontraction forces in spider dragline silk depend on hydration rate
Supercontraction forces in spider dragline silk depend on hydration rate
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DOI：
10.1016/j.zool.2008.11.003
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发表时间：
2009-01-01
期刊：
影响因子：
2
通讯作者：
Blackledge, Todd A.
中科院分区：
文献类型：
--
作者：
Agnarsson, Ingi;Boutry, Cecilia;Blackledge, Todd A.
蜘蛛牵引丝具有许多理想和特殊的性质，是仿生研究的模型生物聚合物。“超收缩”指的是牵引丝纤维被浸湿后急剧收缩的现象。在受约束的真丝纤维中，超收缩在临界湿度类似于70%相对湿度(RH)的情况下产生40-50兆帕的巨大应力。这种应力可以在雨或露水的重量下保持网的张力，并可用于机器人、传感器技术和其他应用的工业中。我们自己的发现表明，超收缩可以在比之前报道的更广泛的范围内产生压力，从10到140兆帕。在这里，我们表明，超收缩应力的变化取决于环境达到引起超收缩的临界湿度的速率。缓慢的湿度增加，持续几分钟，导致相对较低的超收缩应力，而快速增加湿度，超过几秒钟，通常导致较高的超收缩应力。热重分析表明，慢速超收缩纤维吸水较少，热稳定性与快速超收缩纤维不同。这表明蜘蛛丝根据超收缩发生的速度而实现不同的分子构型。最终，依赖于速率的超收缩可能提供一种机制，为各种应用定制丝绸或仿生纤维的特性。(C)2009年爱思唯尔股份有限公司。版权所有。
Spider dragline silk is a model biological polymer for biomimetic research due to its many desirable and unusual properties. 'Supercontraction' describes the dramatic shrinking of dragline silk fibers when wetted. In restrained silk fibers, supercontraction generates substantial stresses of 40-50 MPa above a critical humidity of similar to 70% relative humidity (RH). This stress may maintain tension in webs under the weight of rain or dew and could be used in industry for robotics, sensor technology, and other applications. Our own findings indicate that supercontraction can generate stress over a much broader range than previously reported, from 10 to 140 MPa. Here we show that this variation in supercontraction stress depends upon the rate at which the environment reaches the critical level of humidity causing supercontraction. Slow humidity increase, over several minutes, leads to relatively low supercontraction stress, while fast humidity increase, over a few seconds, typically results in higher supercontraction stress. Slowly supercontracted fibers take up less water and differ in thermostability from rapidly supercontracted fibers, as shown by thermogravimetric analysis. This suggests that spider silk achieves different molecular configurations depending upon the speed at which supercontraction occurs. Ultimately, rate-dependent supercontraction may provide a mechanism to tailor the properties of silk or biomimetic fibers for various applications. (C) 2009 Elsevier GmbH. All rights reserved.