A specialized ultrasonic device is not required to produce micron fine aerosol powders. All one needs is a used and cleaned print head assembly and its piezo pulse circuitry. Nozzle apertures are typically 25-50 micron and if the material is suspended, in weak concentration, in a solution which quickly evaporates but doesn't harm the spores it should produce moderate quantities of fine powder quickly.
If smaller sizes are desired a field ring charged to 1000-3000v DC can be placed around and in front of the nozzles. If operated in sync with the nozzle pulses it can cause a the emerging droplets to cascade to nanometer size via the electrospray effect (now becoming common in drug production). See http://www.essex.ac.uk/bs/staff/colbeck/index.htm#appas
