ORAL REFERENCE:ICF100517OR EFFECT OF AQUEOUS ENVIRONMENT AND VISCID DROPLET ON DEFORMATION OF SPIDER THREAD Masayoshi KITAGAWA Department of Human & Mechanical Systems Engineering, Kanazawa University, Kodatsuno 2-40-20, Kanazawa, 920-8667, Japan ABSTRACT Aｓ one of serial studies on the mechanical properties of spider threads, their amino acid compositions, the microstructure of dragline, the surface tension of the viscid droplet regularly spaced on capture thread and the effect of aqueous environment on the stress-strain curve were investigated. It was shown that (1) the dragline consisted of three layers at least, (2) the surface tension of the viscid droplet was about 65mN/m and (3) the shape of stress-strain curve was fairly affected by aqueous environment surrounding the thread. KEYWORDS Spider thread, Sticky droplet, Deformation, Rubber elasticity, Microstructure, Super contraction, Aqueous environment, Surface tension 1.INTRODUCTION Some experiments on the structure and the strength of spider thread have been made on the analysis of amino acid composition, the crystalline structure, the microstructure, the mechanical properties, the effect of environment on the mechanical properties and so on using samples of spiders Nephila clavata and Argiope amoena [1,2,3,4,5,6,7]. It is interesting to note that the shape of stress-strain curve is very different between dragline and capture thread. The stress-strain curve of dragline shows a work hardening after steep yield point and breaks at small strain after elastic behavior. For capture thread, on the other hand, the curve which resembles that of rubber is upwardly concave (J-shaped) and the fracture strain, which amounts to 4 occasionally, is fairly large compared with that of dragline. The amino acid composition of capture thread without viscid droplets is nearly the same as that of dragline. Hence, the difference in the shape of the stress-strain curve between them may be attributed to the existence of viscid liquid attached to capture thread. In this paper, at first the fundamental properties of the droplet such as its shape and its surface tension are investigated, secondary the micro structure of dragline is observed using a urea super-contraction method developed by Vollrath et al. [8] and finally the effect of viscid droplet on the deformation behavior of the thread is shown. 2.EXPERIMENTAL The spiders Nephila clavata and Argiope amoena who generally constructed orb webs were used for the test, since it was easy to collect threads from their living bodies and their webs.
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