Ultrasonic waveguide pump and method of pumping liquid

An ultrasonically driven pump for pumping liquid from a reservoir containing said liquid, said pump comprising:

• an elongate ultrasonic waveguide having longitudinally opposite first and second ends, a nodal region located longitudinally between said first and second ends of the waveguide, and an internal passage extending longitudinally within the waveguide along at least a portion of the waveguide from said first end to beyond the nodal region toward said second end of the waveguide, the waveguide having an inlet at said first end in fluid communication with said internal passage for receiving liquid from the reservoir into the waveguide, said waveguide having an outlet in fluid communication with the internal passage and spaced longitudinally from the inlet at a location longitudinally beyond the nodal region of the waveguide relative to said inlet for exhausting liquid from the pump;
• said waveguide being configured for greater longitudinal displacement at said inlet than at said outlet of the waveguide in response to ultrasonic excitation of the waveguide;
• and
• an excitation device operable to ultrasonically excite said waveguide to vibrate at least longitudinally of the waveguide.