Device and method for repetitive needleless injection

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;
• a controller that is configured to operate the propulsion mechanism repeatedly so as to eject the sequence of the micro-jets;
• and
• a unidirectional valve to enable flow of the liquid from the reservoir to the cell and to prevent backflow of the liquid from the cell to the reservoir,
• wherein the propulsion mechanism comprises:
• an impulse generator configured to displace an actuation surface to generate the pulse;
• a plunger configured to move linearly to transmit the pulse from the actuation surface to the cell, and
• a restoration mechanism to retract the plunger;
• and wherein a plunger rod of the plunger is configured to slide back and forth within a neck of the handheld unit, and wherein the plunger rod and the actuation surface are placed in contact and separated intermittently during operation of the propulsion mechanism.