Research in inhalation toxicology requires the ability to generate stable aerosol concentrations of a respirable particle size in a consistent manner from day to day and experiment to experiment.
Aerosol deposition in the upper airways of the human is generally achieved by a particle size between about 2.5 and 10 microns (μm) aerosol mass median aerodynamic diameter (MMAD) with the larger particles depositing in the larger airways.
Deposition in the lower airways is achieved between 0.5 and 2.5 μm MMAD with maximal alveolar deposition occurring with particles of about 1.2 μm MMAD or smaller. For inhalation studies using small research animals, the range of the upper airways is approximately 2.0 to 6.0 μm MMAD and for the lower airways 0.5 to 2.0 μm MMAD.
In addition to inhalation studies, other research areas in the life and physical sciences, various manufacturing processes, and certain systems or products require precise and accurate atomization to produce aerosols having a small particle size at low to ultra-low, yet stable, concentrations. Various methods of generating such aerosols are in use but suffer from a number of limitations including an inability to function with ultra-low liquid flow rates, degradation by organic solvents, and inconsistent flow rates.
Army scientists and engineers have developed a micro-atomizer to produce stable aerosol concentrations having an aerosol MMAD from 1 – 6 microns with liquid feed rates of 10 to 1000 microliters per hour. The micro-atomizer includes a liquid channel in the shape of a thick wall tube and a cap having an aerosol outlet orifice whereby a liquid-gas contact space is formed by the internal surface of the cap and the flat end of the liquid channel.
Pressurized carrier gas and the liquid to be aerosolized are allowed to come into contact inside a precisely formed liquid-gas contact space. The desired aerosol characteristics are accurately established, stable, and reproducible.
- Capable of generating aerosols at liquid flow rates in the microliter per minute range or lower in a reproducible and consistent manner
- Materials arr substantially impermeable and nonreactive to the liquids and air or other carrier gasses
- Numerous combinations of carrier gas flow rate, liquid feed, and carrier gas pressure can be used to tune MMAD and particle counts
- US patent 8,882,085 available for license