An aerosol-generating system may include a liquid storage portion configured to hold liquid aerosol-forming substrate, a vaporizer including a heating element with an internal passage at least partially defined by a surface of the heating element, and a micro pump configured to deliver liquid aerosol-forming substrate from the liquid storage portion to the internal passage of the heating element, such that the vaporizer is configured to heat the delivered liquid aerosol-forming substrate at the internal passage to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate. The micro pump may be configured to deliver a particular amount of liquid aerosol-forming substrate to the internal passage based on the micro pump performing an individual pump cycle.