The mechanical energy of an actuator is used for producing vibration alerts in a portable electronic device. The same mechanical energy is also utilized to control the flow of fuel or to mix the fuel in a fuel cell of the portable electronic device. Thus, the flow of fuel into a reaction area of a fuel cell is controlled or fuel is mixed in a fuel storage area of a fuel cell assembly. Such fuel flow control and mixing is performed passively whenever a vibration alert occurs, or is performed actively in response to monitoring the status of the fuel cell assembly.