Dispensing particles under atmospheric and vacuum conditions using an electrostatic device

Abstract

Experiments were conducted to determine the operational characteristics of an electrostatic device that dispenses micrometer-size particles continuously without the use of a carrier gas. The dispenser’s operational performance was determined under different operating conditions based upon four independent experimental variables: the environmental pressure in which the dispenser was operated, its interelectrode spacing, the applied voltage, and the type of particle used. Measurements were made of the dispenser’s operating current and voltage, particle mass dispensing efficiency, and dispensed particle mass flow rate, current, and velocity. An increase in the strength of the dispenser’s internal electric field was found to produce an increase in operating current and dispensed particle velocity, current, and mass flow rate. The measured average charge acquired by a particle and the particle average velocity under vacuum conditions were predicted using single particle theory. All temporal measurements of the dispensed particle mass were correlated nondimensionally, independent of the particle type, interelectrode spacing, and applied voltage. The dispensing efficiency under atmospheric conditions, when expressed as a function of the strength of the internal electric field above the minimum field required for particle levitation against gravity, was shown to be independent of particle type.