MEASUREMENT OF THE AERODYNAMIC DRAG FORCE ON SINGLE AEROSOL-PARTICLES

The 'picobalance' (quadrupole) was used to measure the aerodynamic drag force on individual solid particles and droplets by suspending the object in a laminar jet of gas introduced through the bottom electrode. Particles ranging in diameters from about 1 to 150 mu m can be studied in this manner. The dc voltage required to maintain the particle position against the opposing forces of aerodynamic drag and gravity was measured to determine the drag force. The flow velocity at which the aerodynamic drag force balances the gravitational force yields information on the aerodynamic size, and the dc voltage required to suspend the particle against gravity with no flow provides a measure of the particle mass.