Unraveled mechanism in silk engineering: Fast reeling induced silk toughening

We theoretically and experimentally study the mechanical response of silkworm and spider silks against stretching and the relationship with the underlying structural factors. It is found that the typical stress-strain profiles are predicted in good agreement with experimental measurements by implementing the beta-sheet splitting mechanism we discovered and verified, primarily varying the secondary structure of protein macromolecules. The functions of experimentally observed structural factors responding to the external stress have been clearly addressed, and optimization of the microscopic structures to enhance the mechanical strength will be pointed out, beneficial to their biomedical and textile applications. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3216804]