Submitted to Proceedings of the Royal Society BWe investigate the rheological properties of microliter quantities of the spinning
material extracted ex vivo from the major ampullate gland of a Nephila clavipes spider
using two new micro-rheometric devices. A sliding plate micro-rheometer is employed to
measure the steady-state shear viscosity of ~1µL samples of silk dope from individual
biological specimens. The steady shear viscosity of the spinning solution is found to be highly shear-thinning with a power-law index consistent with values expected for liquid crystalline solutions. Calculations show that the viscosity of the fluid decreases ten-fold as it flows through the narrow spinning canals of the spider. By contrast, measurements in a microcapillary extensional rheometer show that the transient extensional viscosity (i.e. the viscoelastic resistance to stretching) of the spinning fluid increases more than one hundred-fold during the spinning process. Quantifying the properties of native spinning solutions provides new guidance for adjusting the spinning processes of synthetic or genetically-engineered silks to match those of the spider.NASA (Biologically-Inspired Technologies), ISN (Institute For Soldier Nanotechnologies, MIT
