Particle cassettes

A method of producing a particle cassette for a needleless syringe device which alleviates problems of providing a chamber for the confinement of particles which is hermetically sealed from the environment. A predetermined force is applied in the longitudinal direction to push first and second cassette parts together so as to cause plastic deformation of a portion of the first cassette part so as to create said hermetically sealed chamber. The cassette parts are preferably made of PETG and have bonded thereto rupturable membranes preferably made of PET. The sealing is preferably achieved at the end of a protrusion on the first cassette part which is tapered and which interacts with the membrane of the second cassette part.