Figure 3.

(a) Without forcing, a non-viscoelastic aqueous thread focused by an immiscible non-viscoelastic oil phase (hexadecane) breaks up into droplets 2 mm downstream of the cross junction in the channel with a square cross section of $80\times 80\mu {\mathrm{m}}^2$. This breakup length corresponds well with the theoretical prediction for a confined thread that has an undisturbed radius $r_0=14\mu \mathrm{m}$ and flows at a velocity of $U=4.5\mathrm{mm}\mathrm{/}\mathrm{s}$). Fluid properties: ${\eta }_i=22\mathrm{mPas},{\eta }_e=3.3\mathrm{mPas},\gamma =0.2\mathrm{mN}\mathrm{/}\mathrm{m}$. (b) The same experiment with the piezo-electric bending disc operating at 100 mV.