Structure of the menisci of leaky dielectric liquids during electrically-assisted evaporation of ions
Abstract
An understanding of the processes enabling field-assisted evaporation of ions from leaky dielectric liquids, i.e., liquids that are substantially less conductive than liquid metals, has historically been elusive in comparison to those of conventional electrohydrodynamic emission modes such as that of the cone-jet. While select ionic liquids have been shown to yield nearly monodisperse beams of molecular ions 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 equilibrium meniscus structures that shed measurable charge when the meniscus 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 the meniscus may vary only with the applied electric field; (ii) that the feeding flow is very germane to the emission characteristics, unlike liquid metal ion 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 pure ion mode.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 05, 2016
- Source ID
- 10.1063/1.4971778
Entities
People
- Chase Coffman
- F. J. Higuera
- Manuel Martı́nez-Sánchez
- Paulo Lozano
Organizations
- Air Force Office of Scientific Research
- Massachusetts Institute of Technology
- National Aeronautics and Space Administration