Fig. 3. (a) Radius R of necking thread formed from the ex vivo-obtained Nephila dope (measured at thread midpoint, see inset in b) in blue markers. The solid red line represents the model fit using the processability parameter of P=2.715x10^-2. (b) The transient extensional rheology of ex vivo spider dope. The extensional viscosity is shown as a function of the total strain in the material. Here, R₀ is the initial radius of the thread measured at the midpoint between the plates with a laser micrometer. The decrease of the midpoint radius R was monitored over time (see a). The extensional viscosity was then deduced from Eqn 1 and is represented by the markers. The solid line is an analytical fit of these values. For low strains, we obtain the limit _e3₀=11 400 Pa.s as expected for a Newtonian liquid. Inset, a silk thread of diameter 40 µm formed by separating the plates to a distance of 5 mm and allowing the thread to neck under the action of capillarity and viscoelastic stresses (scale bar, 1 mm).