A versatile system for stable generation of uniform droplets

Abstract

A system for the production of liquid droplets of uniform size and velocity is described. The precise control of the operating fluid provided by this system allows the generator to function in a droplet-on-demand, burst, or continuous mode of operation. The basic component of the uniform droplet generator is a radially contracting piezoelectric cylinder which forces liquid through a glass-capillary nozzle. Droplet diameters ranging from 5 to 500 μm have been produced by appropriate selection of nozzle aperture and operating mode. Further control of size, velocity, and interdroplet spacing is exercised through the voltage- and fluid-control elements of the system. In addition to its ability to operate in any orientation, the droplet generator is designed with a small cross section and a water cooling feature for operation in coflowing, elevated-temperature environments. The uniform-droplet-generation system has exhibited long-term stability in operations ranging from a single isolated droplet to a stream of calibration-standard droplets separated by center-to-center spacings of less than two diameters. Its capabilities in controlling droplet development and dynamics make it an attractive candidate for use in a wide range of liquid-droplet applications.