Aerosol-generating system with motor

A method of providing a liquid aerosol-forming substrate during generation of aerosol, the method comprising:

• storing liquid aerosol-forming substrate in a liquid storage portion in a stand-alone cartridge, the liquid storage portion including a movable wall and an outlet, the stand-alone cartridge further including
• a piston connected to the movable wall, and
• a lead screw connected to the piston;
• inserting the stand-alone cartridge in a compartment in a main assembly that includes a pump, the pump further including a micro stepper motor having a drive shaft, such that
• the stand-alone cartridge, the piston, the lead screw, the drive shaft of the micro stepper motor, and the micro stepper motor are in longitudinal alignment along a longitudinal axis of the main assembly, and
• the outlet of the liquid storage portion is configured to direct a flow of liquid aerosol-forming substrate from the liquid storage portion to a vaporizer of the main assembly;
• and
• delivering liquid aerosol-forming substrate from the outlet of the liquid storage portion, the delivering including
• the lead screw translating a rotation of the drive shaft of the micro stepper motor into an axial movement of the piston and a corresponding axial movement of the movable wall, and
• axially moving the movable wall toward the liquid storage portion to cause a particular amount of liquid aerosol-forming substrate to be delivered from the outlet of the liquid storage portion to the vaporizer of the main assembly, causing a reduction of a volume of the liquid storage portion.