The present invention refers to an ultrasonic device comprising an ultrasound transducer; and a disk-shaped metallic low-frequency ultrasound (NFLUS) resonator being mechanically connected with the ultrasound transducer on one side of the resonator; a container with an opening on its bottom side and being arranged on the other side of the disk-shaped resonator such that the opening is facing the disk-shaped resonator; an elastic sealing element arranged between the disk-shaped resonator and the container for sealing the container around the opening; and means for supplying a pressing force such that the container is tightened on the resonator during ultrasonication, but can be repeatedly disassembled and assembled after ultrasonication.