Device and method for repetitive needleless injection

1. A device for repetitive needleless injection of a liquid into a surface, the device comprising:

a handheld unit that includes at least a cell that is fillable with the liquid, and a propulsion mechanism configured to apply a sequence of pressure pulses to the liquid, each pulse of the sequence of pressure pulses to eject a micro-jet of the liquid from the cell via an orifice between the cell and an exterior of the handheld unit with a velocity that is sufficient to enable the micro-jet to penetrate into the surface;

a reservoir that is connected to the cell by a conduit to enable the liquid to flow from the reservoir to the cell to replace the liquid that is ejected in the micro-jet; and

a controller that is configured to operate the propulsion mechanism repeatedly so as to eject the sequence of the micro-jets,

wherein the propulsion mechanism comprises an impulse generator configured to displace an actuation surface to generate the pulse and a plunger configured to move linearly to transmit the pulse to the cell, and

wherein the impulse generator is configured to expand to compress a propulsion resilient element and to contract to enable expansion of the propulsion resilient element to distally propel the plunger.

2. The device of claim 1 , wherein the orifice is separated from the cell by an outlet unidirectional valve that is configured to enable flow of the liquid from the cell to the orifice and to prevent inflow from the orifice to the cell.

3. The device of claim 2 , wherein the outlet unidirectional valve comprises a stopper that is separable from an aperture.

4. The device of claim 1 , wherein a connection of the conduit to the cell comprises an inlet unidirectional valve to enable the liquid to flow from the conduit to the cell and to prevent backflow of the liquid from the cell to the conduit.

5. The device of claim 4 , wherein the orifice is separated from the cell by an outlet unidirectional valve that is configured to enable flow of the liquid from the cell to the orifice and to prevent inflow from the orifice to the cell.

6. The device of claim 1 , wherein the impulse generator comprises a piezoelectric crystal.

7. The device of claim 6 , wherein the impulse generator comprises a mechanical amplifier.

8. The device of claim 1 , wherein the plunger is bonded to the actuation surface.

9. The device of claim 1 , wherein the plunger is provided with a retraction mechanism that is configured to retract the plunger after application of the pulse by the actuation surface.

10. The device of claim 9 , wherein the retraction mechanism comprises a spring.

11. The device of claim 1 , wherein the controller is configured to control operation of the propulsion mechanism so as to control one or both of an amplitude of the pulse and a rise time of the pulse.

12. The device of claim 11 , wherein the controller is configured to control said one or both of an amplitude of the pulse and a rise time of the pulse in accordance with an indicated dose or a penetration depth.

13. The device of claim 1 , wherein the controller is configured to control operation of the propulsion mechanism so as to control a repetition rate for generation of the pulses.

14. The device of claim 1 , wherein the reservoir comprises a liquid level sensor to sense a level of the liquid in the reservoir and the controller is configured to stop operation of the propulsion mechanism when the sensed liquid level is below a threshold level.

15. The device of claim 1 , wherein the reservoir and the conduit are enclosed within the handheld unit.