A device for repetitive needleless injection including a handheld unit having at least a cell fillable with a liquid, and a propulsion mechanism to apply a sequence of pressure pulses to the liquid to eject a micro-jet of the liquid from the cell via an orifice 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； a controller that is configured to operate the propulsion mechanism repeatedly； and a unidirectional valve to enable flow of the liquid from the reservoir to the cell and to prevent backflow. The propulsion mechanism includes an impulse generator configured to displace an actuation surface to generate the pulse； a plunger to transmit the pulse to the cell, and a restoration mechanism to retract the plunger.
