The present invention relates to an aerosol-generating system comprising a liquid storage portion (3) for storing liquid aerosol-forming substrate, a vaporiser comprising a heating element (7) with an internal passage and a micro pump (5) configured for delivering liquid aerosol-forming substrate from the liquid storage portion to the internal passage of the heating element, wherein the vaporiser is configured for heating the delivered liquid aerosol-forming substrate in the internal passage to a temperature sufficient to volatilize at least a part of the delivered liquid aerosol-forming substrate. The present invention further relates to a cartridge for an aerosol-generating system, wherein the cartridge comprises the liquid storage portion of the aerosol-generating system. The present invention further relates to a method for generating aerosol.