An apparatus (e.g., nebulizer) for aerosol delivery of a substance (e.g., a drug to a patient) has a mouthpiece (36); a chamber (34) holding a substance; a flexible membrane (38) having a plurality of apertures; and a vibrator (44) for vibrating the flexible membrane to form a flow of aerosol droplets of the substance that are ejected through the apertures and to the mouthpiece. The vibrator may be a piezoelectric element. A magnetic member (54) is provided on the flexible membrane and is configured to magnetically couple the flexible membrane to the vibrator. The magnetic member allows replacement of the membrane, without wasting the piezoelectric element.