Electric droplet charging

Keywords Discrete polydisperse spray Electric droplet charging Extension nozzle Ink-jet printing Monodisperse droplet stream Monodisperse spray Multihole orifice Modulated jet excitation Nozzle hole shapes Rapid prototyping Rayleigh-type jet break-up Solder ball production... 

Two additional stabilizing influences will be summarized next that of viscoelastic films and that of solid-particle films. In general, where electrical surface charge is an important determinant of stability, it is easier to formulate a very stable O/W emulsion than a W/O emulsion because the electric double layer thickness is much greater in water than in oil. (This is sometimes incorrectly stated in terms of greater charge being present on droplets in an O/W emulsion.) However, there are ways to effectively stabilize W/O emulsions. 

Table I summarizes the experimentally determined resistivity characteristics for the nine formulations investigated. On the basis of Equation 6 and these data, a high degree of spray charge-ability by the electrostatic induction process could be predicted for all the pesticide samples tested. For these particular pesticide formulations, laboratory spray tests confirmed excellent droplet charging to greater than 10 mC/kg. Similar electrical resistivity measurements will serve as a suitable predictor of the chargeability of other formulations of interest in the electrostatic pesticide-spraying process.

The droplets are produced with an commercial piezo-driven injector. Upon generation, they are charged weakly by influence of an electric field at the nozzle tip. This charge is needed for the electrodynamic levitation. By varying the charge to mass ratio between - -10 C/kg and —10 C/kg we were able to prove that in this range the nucleation rate is not influenced by the droplet charge. 

Spraying capillaries for ESI (a) Nebulization and droplet charging by the electric field only, (b) Pneumatically assisted electrospray or ionspray and (c) Tri-coaxial probe with sheath flow. 

Figure 1.4 Evaporation and discharge of a positively charged water droplet in nitrogen gas at ambient pressure and 317 K and a weak (51 Vcm ) electric field, (a) Variation of droplet diameter with time. Also plotted (smooth curve) is the predicted change in diameter due to evaporation of a neutral water droplet in a vapor-free N2 gas at 317 K. (b) Variation of droplet charge with time,...

Note EHI has important features in common with ESI i) an electrolytic solution is sprayed by the mere action of an electrostatic field, ii) upon which it forms a mist of electrically highly charged droplets, from which Hi) the analyte ions are liberated into the gas phase for subsequent mass analysis. 

Electrical Current, I, due to the Charged Droplets. Charge and Radius of Droplets... 

Considering the requirements for charge balance in such a continuous electric current device and the fact that only electrons can flow through the metal wire supplying the electric potential to the electrodes, one comes to the conclusion that the electrophoretic charge separation mechanism [of droplet charging and formation] requires that the [positive-ion] electrospray process should involve an electrochemical conversion of ions to electrons [within the metal ES capillary[. 

The assistance of a high-velocity gas flow or ultrasonic vibration is used in electrospray mass spectrometry. In a simple approximation, the pneumatic or ultrasonic nebulizer takes care of aerosol formation, while the electric field does the droplet charging. When... 

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