Electrospray apparatus for producing uniform submicrometer droplets

An apparatus for analyzing submicron droplets and particles, including:

• an electrospray means having an electrospray inlet and a discharge, for receiving a liquid sample at the electrospray inlet and electrostatically generating multiple substantially uniformly sized electrically charged droplets of the liquid sample at the discharge;
• a means for supplying the liquid sample to the electrospray means at a controlled rate;
• and an evaporation means defining a droplet evaporation region proximate the electrospray discharge and extending downstream thereof, for reducing the size of the droplets by evaporation as the droplets progress downstream through the evaporation region, to form an aerosol of the liquid sample;
• a charge neutralizing means for reducing the charge of each droplet as the droplet progresses through the evaporation region by an amount sufficient to prevent droplet fragmentation due to Coulombic forces, whereby said aerosol is substantially monodisperse;
• a particle separation means disposed downstream of the evaporation region, for receiving the aerosol from the electrospray means and for separating particles of the aerosol based on the electrical mobility of the particles;
• and
• a particle counting means disposed downstream of the particle separation means, for counting the particles received from the separation means.

A process for forming multiple submicron droplets generally uniform in size, including the steps of:

• providing a liquid sample at a steady supply rate to an electrospray device, and generating multiple, substantially uniformly sized, electrically charged droplets of the liquid sample at a discharge of the electrospray device;
• transporting the electrically charged droplets downstream of the discharge through an evaporation region, to controllably reduce the size of the droplets by evaporation as the droplets progress through the evaporation region;
• while so transporting the droplets, reducing the electrical charge of each droplet as it emerges from the discharge;
• and thereafter continually reducing the electrical charge of each droplet as it is so transported to prevent the droplet from disintegrating due to repulsive Coulombic forces.