title: Wire-in-a-nozzle as a new droplet-on-demand electrogenerator.
abstract: Many engineering applications assume the generation of single spherical droplets on demand. Piezo and thermo droplet-on-demand (DOD) instruments are not able to produce droplets with a broad range of size distributions from the same nozzle. We show that this challenge can be resolved using the principles of electrostatic generation and capillarity. A thin conductive wire threaded through a needle can be used as the droplet electrogenerator (or DOD generator). By applying a weak-bias electric field, one can deliver a drop from the needle edge to the free wire tip. When the drop moves toward the wire tip, it leaves behind a thin coating film. The capillary pressure of this cylindrical film helps isolate the droplet from the liquid source: the film spontaneously thins, breaking the connection between the droplet and the liquid source. The detachment of a pendant drop from the wire is then achieved by applying a short voltage pulse. Using the wire-in-a-needle nozzle, we were able to produce single droplets ranging from 50 to 500 μm, and we were able to deposit them with controlled velocity in a prescribed position. Therefore, the proposed method offers new opportunities in fields dealing with the DOD applications.
authors.affiliation: School of Materials Science & Engineering, Clemson University, 161 Sirrine Hall, Clemson, South Carolina 29634, United States.
authors.forename: Taras
authors.initials: T
authors.lastname: Andrukh
authors.forename: Binyamin
authors.initials: B
authors.lastname: Rubin
authors.forename: Konstantin G
authors.initials: KG
authors.lastname: Kornev
mesh_terms: D055615:Electrical Equipment and Supplies; D010316:Particle Size; D055672:Static Electricity; D013499:Surface Properties