SAW atomization application on inhaled pulmonary drug delivery

Pulmonary drug delivery transports the drug formulations directly to the respiratory tract in the form of inhaled particles or droplets. Because of the direct target treatment, it has significant advantages in the treatment of respiratory diseases, for example asthma. However, it is difficult to produce monodispersed particles/droplets in the 1-10 micron range, which is necessary for deposition in the targeted lung area or lower respiratory airways, in a controllable fashion. We demonstrate the use of surface acoustic waves (SAWs) as an efficient method for the generation of monodispersed micron dimension aerosols for the treatment of asthma. SAWs are ten nanometer order amplitude electroacoustic waves generated by applying an oscillating electric field to an interdigital transducer patterned on a piezoelectric substrate. The acoustic energy in the waves induces atomization of the working fluid, which contains a model drug, albuterol. Laser diffraction techniques employed to characterize the aerosols revealed mean diameter of the aerosol was around 3-4 μm. Parallel experiments employing a one-stage (glass) twin impinger as a lung model demonstrated a nearly 80% of atomized drug aerosol was deposited in the lung. The aerosol size distribution is relatively independent of the SAW frequency, which is consistent with our predictive scaling theory which accounts for the dominant balance between viscous and capillary stresses. Moreover, only 1-3 W powers consumption of SAW atomization suggests that the SAW atomizer can be miniaturized into dimensions commensurate with portable consumer devices.