Droplet pinch-off with pressure fluctuations.

Highlights • The dynamics of disturbed droplet pinch-off depends on initial perturbations. • Pressure-fluctuation-induced nonlocal flow velocity is responsible for the variations in disturbed pinch-off dynamics. • A dimensionless perturbation parameter was derivated to characterize the disturbed pinch-off. • We applied the pressure fluctuation to engineering pinch-off of droplets with highly predictable dynamics. Abstract Dynamics of Newtonian fluid pinch-off is universal, excluding the possibility of manipulating pinch-off behavior by varying initial and boundary conditions which is desirable in applications such as inkjet printing and microfluidics. Here we show that the dynamics of two-fluid pinch-off with disturbed inlet pressure (such as the profile of the conical liquid neck, cone slope, and neck thinning rate) depends on initial perturbations. The nonuniversality arises from pressure-fluctuation-induced nonlocal flow velocity that stretches the axial length scale of the pinch-off region. We renormalize the disturbed pinch-off using the linear ratio, (1 + βε), with β being the empirical constant and ε the dimensionless pressure fluctuation. We further apply the pressure fluctuation in engineering pinch-off where the disturbed and undisturbed systems have identical pinch-off dynamics but distinct material properties. Our results could provide useful guidelines for controlling the breakup of liquid threads with extreme physical properties, such as ultrahigh viscosity and ultralow interfacial tension, in inkjet printing and microfluidics for a range of applications. [ABSTRACT FROM AUTHOR]