There is provided an aerosol-forming cartridge for an electrically operated aerosol-generating system. The cartridge includes a base layer, at least one aerosol-forming substrate disposed on the base layer and including a liquid nicotine source, and an electric heater including at least one heating element configured to heat the at least one aerosol-forming substrate. The base layer and the at least one aerosol-forming substrate are in contact at a contact surface that is substantially planar. The electric heater and one or both of the base layer and the at least one aerosol-forming substrate are in contact at a contact surface that is substantially planar and substantially parallel to the contact surface between the base layer and the at least one aerosol-forming substrate.