Abstract: A nebuliser for nebulising liquid droplets, including: a housing; at least one piezoelectric substrate (2) accommodated within the housing and having a transducer surface (2a) upon which is located at least one electroacoustic transducer (48) for generating acoustic wave energy within the at least one piezoelectric substrate (2), and an opposing non-transducer surface (2b); a liquid supply system for supplying a liquid to at least one of the transducer and non-transducer surfaces, the liquid supply system including a reservoir (3) for accommodating the liquid, and at least one relatively rigid supply conduit in contact with the at least one piezoelectric substrate (2) for supplying the liquid from the reservoir (3) to the at least one piezoelectric substrate (2); and a sensor for detecting a volume of liquid on the at least one piezoelectric substrate (2).