Investigations into exploding droplets

The research presented stems from the direct visual observation of electrospray occurring as microscopic droplets pass through an electric discharge produced by a strong electrostatic field. This phenomenon has been called droplet electrospray or DES. An extremely fine and highly reproducibie aerosol can be produced in this manner from each droplet.; In DES, a stream of uncharged droplets with a controlled radius between 6 and 50 {dollar}mu{dollar}m and at frequencies in the 100 kllz range is produced by vibrating the capillary tip with a piezoelectric buzzer. The droplets are then charged by letting the droplet stream pass close to a 50 {dollar}mu{dollar}m diameter Pt rod electrode that is at 3kV and is producing an electric discharge in the ambient air. The charged droplets are destabilized by the surface charge and emit a fine spray of offspring droplets. These events are regular and reproducible and can therefore be observed with a stroboscopic technique. The observed droplet fission is very similar in appearance to that reported by Gomez and Tang. The gas phase ions produced by the droplet fission (droplet spray) were detected with a mass spectrometer and their relative abundances determined vs. their spatial relationships with the spraying droplets. The mass spectra of the DES-produced ions are close to identical to spectra observed with conventional electrospray and were found to be well separated in space from the ions produced by the corona discharge. The present DES results provide some important insights into the mechanism of conventional ES.