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Electrosprays of highly conducting liquids: A study of droplet and ion emission based on retarding potential and time-of-flight spectrometry

Manuel Gamero-Castaño* and Albert Cisquella-Serra

  • Department of Mechanical and Aerospace Engineering, University of California, Irvine, California 92697, USA

  • *mgameroc@uci.edu
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Phys. Rev. Fluids 6, 013701 – Published 14 January, 2021

DOI: https://doi.org/10.1103/PhysRevFluids.6.013701

Abstract

Electrosprays of highly conducting liquids operated in the cone-jet mode produce charged nanodroplets of controllable size and molecular ions. The study of this electrospraying regime is challenging due to the lack of experimental techniques for probing these nanometric systems, and the higher complexity of the physics associated with the onset of ion field emission and self-heating. Jet parameters in the breakup region such as its radius, velocity, potential, and electrification level are key for understanding the formation of droplets and emission of ions, and useful to validate numerical models of cone jets. In the case of micron-sized jets, these quantities can be determined with the values of the retarding potentials and mass-to-charge ratios of the droplets produced by the breakup. This article uses this technique to investigate the parameters of nanometric jets. Retarding potential and mass-to-charge distributions of the beam are measured with retarding potential and time-of-flight analyzers operated in tandem. This combination makes it possible to differentiate between droplets of similar mass-to-charge ratios which, unlike in the case of micrometric jets, are needed to apply the technique. Aside from the jet parameters, the experimental characterization also reveals with great detail the composition of the beam, which includes primary ions emitted from the jet breakup; ions resulting from the desolvation of primary ions; stable primary droplets produced at the breakup; smaller droplets resulting from the Coulomb explosion of unstable primary droplets; and small primary droplets that evaporate a significant fraction of their charge in flight. An analysis of the breakup, parametrized by dimensionless numbers, explains this complexity. Although the experimental characterization only studies the electrosprays of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, the analysis is general and can be used to understand the beams of other highly conducting liquids.

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References (30)

  1. M. Cloupeau and B. Prunet-Foch, Electrostatic spraying of liquids in cone-jet mode, J. Electrost. 22, 135 (1989).
  2. M. Cloupeau and B. Prunet-Foch, Electrostatic spraying of liquids. Main functioning modes, J. Electrost. 25, 165 (1990).
  3. J. Fernández de la Mora and I. Loscertales, The current emitted by highly conducting Taylor cones, J. Fluid Mech. 260, 155 (1994).
  4. J. Rosell-Llompart and J. Fernández de la Mora, Generation of monodisperse droplets 0.3 to 4μm in diameter from electrified cone-jets of highly conducting and viscous liquids, J. Aerosol Sci. 25, 1093 (1994).
  5. A. M. Gañán-Calvo, Cone-Jet Analytical Extension of Taylor's Electrostatic Solution and the Asymptotic Universal Scaling Laws in Electrospraying, Phys. Rev. Lett. 79, 217 (1997).
  6. F. Higuera, Flow rate and electric current emitted by a Taylor cone, J. Fluid Mech. 484, 303 (2003).
  7. J. Fernández de la Mora, The fluid dynamics of taylor cones, Annu. Rev. Fluid Mech. 39, 217 (2007).
  8. A. Gañán-Calvo, J. López-Herrera, M. Herrada, A. Ramos, and J. Montanero, Review on the physics of electrospray: From electrokinetics to the operating conditions of single and coaxial Taylor cone-jets, and AC electrospray, J. Aerosol Sci. 125, 32 (2018).
  9. J. Rosell-Llompart, J. Grifoll, and I. Loscertales, Electrosprays in the cone-jet mode: From Taylor cone formation to spray development, J. Aerosol Sci. 125, 2 (2018).
  10. M. Gamero-Castaño and J. Fernández de la Mora, Direct measurement of ion evaporation kinetics from electrified liquid surfaces, J. Chem. Phys. 113, 815 (2000).
  11. M. Gamero-Castaño, Electric-Field-Induced Ion Evaporation from Dielectric Liquid, Phys. Rev. Lett. 89, 147602 (2002).
  12. M. Gamero-Castaño, Dissipation in cone-jet electrosprays and departure from isothermal operation, Phys. Rev. E 99, 061101(R) (2019).
  13. M. A. Herrada, J. M. López-Herrera, A. M. Gañán-Calvo, E. J. Vega, J. M. Montanero, and S. Popinet, Numerical simulation of electrospray in the cone-jet mode, Phys. Rev. E 86, 026305 (2012).
  14. M. Gamero-Castaño and M. Magnani, Numerical simulation of electrospraying in the cone-jet mode, J. Fluid Mech. 859, 247 (2019).
  15. A. McEwen, H. Ngo, K. LeCompte, and J. Goldman, Electrochemical properties of imidazolium salt electrolytes for electrochemical capacitor applications, J. Electrochem. Soc. 146, 1687 (1999).
  16. E. Grustán-Gutierrez and M. Gamero-Castaño, Microfabricated Electrospray Thruster Array with High Hydraulic Resistance Channels, J. Propul. Power 33, 984 (2017).
  17. M. Gamero-Castaño, Characterization of the electrosprays of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide in vacuum, Phys. Fluids 20, 032103 (2008).
  18. M. Gamero-Castaño and V. Hruby, Electrospray as a source of nanoparticles for efficient colloid thrusters, J. Propul. Power 17, 977 (2001).
  19. M. Gamero-Castaño, Retarding potential and induction charge detectors in tandem for measuring the charge and mass of nanodroplets, Rev. Sci. Instrum. 80, 053301 (2009).
  20. C. Daguenet, P. J. Dyson, I. Krossing, A. Oleinikova, J. Slattery, C. Wakai, and H. Weingaertner, Dielectric response of imidazolium-based room-temperature ionic liquids, J. Phys. Chem. B 110, 12682 (2006).
  21. J. V. Iribarne and B. A. Thomson, On the evaporation of small ions from charged droplets, J. Chem. Phys. 64, 2287 (1976).
  22. A. Gañán-Calvo, On the general scaling theory for electrospraying, J. Fluid Mech. 507, 203 (2004).
  23. M. Gamero-Castaño and V. Hruby, Electric measurements of charged sprays emitted by cone-jets, J. Fluid Mech. 459, 245 (2002).
  24. M. Gamero-Castaño, The structure of electrospray beams in vacuum, J. Fluid Mech. 604, 339 (2008).
  25. C. E. Miller and P. C. Lozano, Measurement of the dissociation rates of ion clusters in ionic liquid ion sources, Appl. Phys. Lett. 116, 254101 (2020).
  26. M. Gamero-Castaño, Energy dissipation in electrosprays and the geometric scaling of the transition region of cone-jets, J. Fluid Mech. 662, 493 (2010).
  27. J. Fernández de la Mora, On the outcome of the coulombic fission of a charged isolated drop, J. Colloid Interface Sci. 178, 209 (1996).
  28. M. Gamero-Castaño and M. Magnani, The minimum flow rate of electrosprays in the cone-jet mode, J. Fluid Mech. 876, 553 (2019).
  29. A. Gañán-Calvo, J. Dávila, and A. Barrero, Current and droplet size in the electrospraying of liquids. Scaling laws, J. Aerosol Sci. 28, 249 (1997).
  30. S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability, Dover Books on Physics Series (Dover, New York, 1981).

Outline

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Phys. Rev. Fluids 6, 013701– Published 14 January, 2021
  • Received 29 September 2020
  • Accepted 8 December 2020
Article part of CHORUS
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