Particles larger than about 250 ⁇ m can also be delivered from these devices, with the upper limitation being the point at which the size of the particles would cause untoward pain and/or damage to the target tissue. The term " hypospray", although better known within science fiction, originates from a jet injector known as the Hypospray; it has been cited within several scientific articles.

Robert Hingson partook in numerous health expeditions with his charity, Brother's Brother Foundation. Initially, the actuating lever 66 is provided in a primed position in which the powder cavity 55 is oriented at 45° from the position in which it is aligned with the particle inlet passage 10 . the Venturi effect is not essential for this purpose and other methods of introducing the particles into the flow may be utilized.Similarly, the second convergence 9 has a much reduced flow cross-section relative to the flow cross-section of the chamber 8. This invention relates to needleless syringes for use in delivering particles into target tissue of a subject, for example skin or mucosa. Vented spacers were fitted to the end of the device nozzle so as to keep the devices at a fixed distance from the target surface and at right angles to it. the device is so constructed and arranged that substantial boundary layer separation between the wall of the nozzle and the gas jet is avoided thus enabling the particles accelerated out of the exit nozzle in the gas jet to be distributed across substantially the full width of the nozzle's downstream exit.

This will cause gas flow to be routed from the downstream point 72 to the upstream point 73 due to the pressure differential in use. and diverges to provide the bore of the nozzle 15 with a 10 mm exit diameter at the nozzle's downstream exit 19 .

the flat, main downstream face 6 of the sonic nozzle 4 is spaced upstream from the upstream face 7 of nozzle 2 . This sonic nozzle 4 is provided with an aperture which forms a first convergence or constriction 5 to the flow of gas through the main body 1. the particles being accelerated can be distributed across substantially the full cross-section of the nozzle at the nozzle's downstream exit. The radially innermost end of the particle inlet passage 10 opens into the particle entrainment chamber 8 and the radially outer end of the passage 10 is arranged to communicate with a particle source 11 containing a payload of particles. a sonic nozzle 41 Provided at the upstream end of the particle entrainment chamber 39 is a sonic nozzle 41 , whose central aperture forms the first convergence or constriction 42 to the flow of gas from the gas source.