An ejector mechanism, droplet delivery device and related methods or delivering small droplets to the respiratory system of a users disclosed. The ejector mechanism comprises a piezoelectric actuator and an aperture plate, the aperture plate having and a plurality of openings formed through its thickness, wherein at least the fluid entrance side of one or more of said openings is configured to provide a surface contact angle of less than 90 degrees and the piezoelectric actuator is operable to oscillate the aperture plate at a frequency to thereby generate an ejected stream of droplets during use. The droplet delivery device is automatically breath actuated by a user when the differential pressure sensor senses a predetermined pressure change. The ejector mechanism is then actuated to generate a plume of droplets having an average ejected particle diameter within the respirable size range having a diameter of less than about 4 um so as to target the respiratory system of the user.