Spider orb webs are multifunctional, acting to absorb prey impact energy and transmit vibratory information to the spider. This paper explores the links between silk material properties, propagation of vibrations within webs and the ability of the spider to control and balance web function. Combining experimental and modelling approaches, we contrast transverse and longitudinal wave propagation in the web. It emerged that both transverse and longitudinal wave amplitude in the web can be adjusted through changes in web tension and dragline silk stiffness, i.e. properties that can be controlled by the spider. In particular, we propose that dragline silk supercontraction may have evolved as a control mechanism for these multifunctional fibres. The various degrees of active influence on web engineering reveals the extraordinary ability of spiders to shape the physical properties of their self-made materials and architectures to affect biological functionality, balancing trade-offs between structural and sensory functions.
Controlled reeling is a powerful tool to investigate the details of silk processing. However, consistent forced reeling of silkworms is hindered by the significant degree of behaviorally induced variation caused by the animal. This paper proposes silkworm paralysis as a novel method to control the animal and thus in vivo spinning conditions. Using these methods, we achieve low and consistent reeling forces during the collection of over 500 m of individual silk fiber while monitoring filament variability, morphology, and properties. Novel techniques to measure the irregular silk cross-sectional areas lead to the more accurate calculation of the true engineering values and mechanical property variation of individual silk fibers. Combining controlled reeling and accurate thread measurement techniques allows us to present the relative contributions of processing and behavior in the performance envelope of Bombyx mori silk.
Sonic properties of spider silks are measured independent of the web using laser vibrometry and ballistic impact providing insights into Nature's design of functionalized high‐performance materials. Through comparison to cocoon silk and other industrial fibers, we find that major ampullate silk has the largest wavespeed range of any known material.
The forced reeling of silkworms offers the potential to produce a spectrum of silk filaments, spun from natural silk dope and subjected to carefully controlled applied processing conditions. Here we demonstrate that the envelope of stress-strain properties for forced reeled silks can encompass both naturally spun cocoon silk and unnaturally processed artificial silk filaments. We use dynamic mechanical thermal analysis (DMTA) to quantify the structural properties of these silks. Using this well-established mechanical spectroscopic technique, we show high variation in the mechanical properties and the associated degree of disordered hydrogen-bonded structures in forced reeled silks. Furthermore, we show that this disorder can be manipulated by a range of processing conditions and even ameliorated under certain parameters, such as annealing under heat and mechanical load. We conclude that the powerful combination of forced reeling silk and DMTA has tied together native/natural and synthetic/unnatural extrusion spinning. The presented techniques therefore have the ability to define the potential of Bombyx-derived proteins for use in fibre-based applications and serve as a roadmap to improve fibre quality via post-processing.
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