Abstract
Experiments were performed to investigate the operational modes in a dual-capillary electrospraying (ES) system in the point-to-plate configuration. For a fixed distance from the capillary tip to the plate, four possible primary modes were observed with increasing of applied voltage. They are the dripping mode, silver-bullet-like mode, stable compound cone-jet mode (if attainable), and unstable cone-jet mode (or called multi-jet mode). The characteristics (i.e., the transformation of liquid meniscus shapes and spray current) of these modes and the transitions between the modes were described. Special attention was paid to identifying the sufficient conditions to establish the stable compound cone-jet mode in the dual-capillary ES system. With the designed experimental matrix for test liquid pairs (i.e., for inner and outer liquids) it was found that a stable compound cone-jet mode can be formed for miscible and partially miscible liquid pairs. For immiscible liquid pairs, two sufficient conditions were identified for the formation of stable compound cone-jet mode: (1) the liquid of low dielectric constant in the liquid pair should be used as outer liquid, and (2) the surface tensions of the liquid pair should satisfy the total or particle engulfing conditions for a three-phase interaction system at static condition. The reasoning for the two observed sufficient conditions is also given.
Highlights
Electrospraying (ES) technology has been proposed and investigated for many practical macromolecular detection, nanomaterial synthesis, monodisperse nanoparticle production, fuel injection for internal combustion engines, micro-thrusters for space propulsion, and drug delivery by inhalation (Tang, 1994; Chen and Pui, 1995; Siuzdak, 1996; Cole, 1997; Gamero-Castano and Hruby, 2001; Gomez, 2002; Kaiser et al, 2003)
Great attention has been paid to the cone-jet mode in which ES systems produce highly charged, monodisperse particles with diameters varying from a few nanometers to the supermicrometer range (Rosell-Llompart and Fernandez de la Mora 1994; Chen and Pui, 1995; Lohmann and Schmidt-Ott, 1995)
In this part of the discussion we mainly focus on the immiscible liquid pairs for cone-jet mode establishment
Summary
Electrospraying (ES) technology has been proposed and investigated for many practical macromolecular detection, nanomaterial synthesis, monodisperse nanoparticle production, fuel injection for internal combustion engines, micro-thrusters for space propulsion, and drug delivery by inhalation (Tang, 1994; Chen and Pui, 1995; Siuzdak, 1996; Cole, 1997; Gamero-Castano and Hruby, 2001; Gomez, 2002; Kaiser et al, 2003). Great attention has been paid to the cone-jet mode in which ES systems produce highly charged, monodisperse particles with diameters varying from a few nanometers to the supermicrometer range (Rosell-Llompart and Fernandez de la Mora 1994; Chen and Pui, 1995; Lohmann and Schmidt-Ott, 1995). Such highly-charged, monodisperse particles, especially with diameters in nanometer range, are much desired for nanotechnology applications. Limitations of the single-capillary technique, emerge when applying it in more complex applications
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