Design of Superior Spider Silk: from Nanostructure to Mechanical Properties

¹ National University of Singapore
² Department of Physics, National University of Singapore
³ Department of Biological Science, National University of Singapore

^* To whom correspondence should be addressed. E-mail: phyliuxy{at}nus.edu.sg.

Submitted on May 16, 2006
Revised on June 20, 2006
Accepted on 21 August 2006

	Abstract

Spider dragline silk is of practical interest because of their excellent mechanical properties. However, the structure of this material is still largely unknown. In this paper, we report a new model of the hierarchical structure of silk based on the SEM and AFM images. This hierarchical structure includes -sheet, polypeptide chain network and silk fibril. It turns out that an exceptionally high strength of the spider dragline silk can be obtained by decreasing the size of the crystalline nodes in the polypeptide chain network while increasing the degree of orientation of the crystalline nodes. Based on this understanding, how the reeling speed affects mechanical properties of spider dragline silk can be understood properly. Hopefully, the understanding obtained in this study will shed light on the formation of spider silk, and consequently, on the principles for the design of ultra strong silk.

Key Words: AFM, X-ray scattering, hierarchical structure, reeling speed