Structure of the menisci of leaky dielectric liquids during electrically-assisted evaporation of ions

An understanding of the processes enabling field-assisted evaporation ofions from leakydielectric liquids, i.e.,liquids that are substantially less conductive thanliquid metals, has historically been elusive in comparison to those of conventional electrohydrodynamic emission modes such as that of the cone-jet. While selectionic liquids have been shown to yield nearly monodisperse beams of molecularions under certain conditions, the dearth of direct observation (visualization) and theoretical insight has precluded a fundamental appreciation for the inherent mechanics. In this paper, we present a family of equilibriummeniscus structures that shed measurable charge when themeniscus is large in relation to a characteristic emission scale. Such structures reside in a region of parameter space where empirical evidence suggests that steady emission may occur and also where stationary interfaces have not been reported before. In this regime, we show (i) that the macroscopic shape of themeniscus may vary only with the appliedelectric field; (ii) that the feeding flow is very germane to the emission characteristics, unlikeliquid metalion sources; and (iii) that while the balance of stresses governing the interface shape may in some cases be very similar to that of the classical Taylor cone, the widespread notion of a ubiquitous 49 ° half-angle is unfounded. Further study of this family may be helpful in elucidating a number of outstanding questions surrounding the pureion mode.

Source: Applied Physics Letters - December 6, 2016 Category: Physics Authors: Chase Coffman, Manuel Mart ínez-Sánchez, F. J. Higuera and Paulo C. Lozano Source Type: research