Abstract: Apparatus which is selectively operable at low frequencies (less than 5,000 Hz and preferably between about 100 Hz to about 1,000 Hz) breaks up jets of high-viscosity fluid into monodisperse droplets. The apparatus includes a housing having a chamber, a piston disposed in the chamber, a magnetic-coil system operably attached to the housing and to the piston, and an oscillator for driving the magnetic-coil system. The housing and the piston define a reservoir for receiving a supply of high-viscosity fluid which is acted upon by oscillating motion of the piston to impart pressure perturbations on the supply of fluid so that the fluid upon discharge from the reservoir separates and breaks up into a plurality of monodisperse droplets. Also disclosed is a method for optimizing the performance of the apparatus to minimize the power required for droplet formation.