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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 
e
30=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).
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