Electrospray

Electrospray is the name for a procedure for the atomization of liquids with the aid of an electric field. The resulting spray contains fine, highly unipolar charged droplets with a narrow size distribution. The physical principle is based on the instability of a Taylor cone.

The field strength required for atomization of the liquid is relatively high and highly dependent on the electrical conductivity and the surface tension of the liquid. If the conductivity and / or the surface tension of the liquid is very high, it can lead to partial discharge ( corona discharge) or to the complete discharge of the ambient gas come before the atomization of the liquid used.

Under atmospheric conditions ( for example, ambient air) electrolytic fluids are atomized as a rule. Application examples are eg electrostatic surface coatings (paint, corrosion protection, medical inhalation aerosols ) or analytical devices ( mass spectrometer ). In vacuo also much higher field strengths can be used without a gas discharge occurs. This use is made of, for example, to produce metal ions having a high energy for the ion-etching or ion propulsion for satellites.

In laboratory experiments, a low melting point metals ( tin solder, Wood's metal, gallium and indium) were dispersed in a gaseous environment to produce monodisperse fine metal particles and granular films on surfaces. However, the very high electric field strengths necessary require the use of electro-negative gases ( electrical extinguishing gas such as sulfur hexafluoride, SF6) at increased pressure in order to prevent premature discharge gas before the sputtering begins.