  The formation of drops of a complex fluid, for instance including dissolved
polymers and/or solid particles, has practical implications in several
industrial and biophysical processes. In this Letter, we experimentally
investigate the generation of drops of a viscoelastic suspension, made of
non-Brownian spherical particles dispersed in a dilute polymer solution. Using
high-speed imaging, we characterize the different stages of the detachment. Our
experiments show that the particles primarily affect the initial Newtonian
necking by increasing the fluid viscosity. In the viscoelastic regime,
particles do not affect the thinning until the onset of the blistering
instability, which they accelerate. We find that the transition from one regime
to another, which corresponds to the coil-stretch transition of the polymer
chains, strongly depends on the particle content. Considering that the presence
of rigid particles increase the deformation of the liquid phase, we propose an
expression for the local strain rate in the suspension, which rationalizes our
experimental results. This method could enable the precise measurement of local
stresses in particulate suspensions.

Soft Condensed Matter;Fluid Dynamics