A dispenser for the delivery of a droplet of a liquid comprises a housing which defines an outlet orifice, a tip seal, biased against the housing to seal the outlet orifice, and a dosing pump for pumping a liquid to the outlet nozzle. The dispenser further comprises an actuation pump configured to provide a hydraulic opening force to the tip seal for opening of the outlet orifice. Preferably the actuation pump is configured to operate at a higher pressure than the dosing pump.