The invention relates to a fluid delivery device (2, 2') for delivering a fluid into a human or animal body. The fluid delivery device (2, 2') comprises a fluid chamber (4, 4') for receiving a fluid, an oscillator (6, 6') for imparting oscillations to at least a portion of the fluid and a control for controlling the oscillator (6, 6'). The oscillator (6, 6') comprises a vibrator (8, 8') and a resonator (10, 10'). The resonator (10, 10') has a main body (12, 12'), defining an interior volume (14, 14'), and a neck (16, 16'). The neck (16, 16') is connected to the main body (12, 12') and in fluid communication with the interior volume (14, 14'). The vibrator (8, 8') is configured to impart vibrations to the resonator (10, 10'). The control is configured to control operation of the vibrator (8, 8') so as to impart vibrations to the resonator (10, 10') at a resonance frequency of the resonator (10, 10') or at a frequency which is within ± 20% of a resonance frequency of the resonator (10, 10'). The invention further relates to a method of operating the fluid delivery device (2, 2').
