Aerosols are useful for a variety of purposes such as applying deodorant, spraying pesticides and air conditioning. By carefully controlling the droplet size, the aerosol can be efficiently delivered for the particular application.
Instead of the aerosol droplet being a solid sphere it would be
interesting to make hollow spheres - bubbles.
This could be achieved by running liquid down the outside of a hollow needle and gas through the inside of the needle. As the droplet forms at the tip of the needle, gas is pulsed into it. This could be done with an array of needles to make a large quantity of mist. The liquid could be encouraged to run down the needle by any force such as gravity, centrifugal, electrostatic etc.
The microbubbles would be useful to lower the average density of the droplets.
If the microbubbles were filled with a light gas (eg helium)the mist would float eerily. One application of this would be for cooling outdoor areas. Obviously for this application it would be preferable to choose a material you would want to be coated in such as a water/ethanol mix.
The material would also need to have physical properties (viscosity, surface tension etc.) conducive to microbubble formation.