Patent ID: 7718296

Claim:
A liquid fuel cartridge having bistable structures, comprising: a housing; a storage unit that is placed in the housing and stores a liquid fuel, the storage unit comprising a plurality of bistable structures that are connected in a row, wherein each bistable structure has bistable states corresponding to a full state and an exhausted state with respect to an amount of liquid fuel contained therein, wherein each bistable structure comprises: at least one pair of wall portions; a roof portion; and a flexible portion that connects the wall portions and the roof portion, wherein the flexible portion has a sufficient stiffness to support the roof portion at a raised position when the bistable structure contains liquid fuel and has a sufficient flexibility to allow the roof portion to collapse to a lowered position when the bistable structure has been emptied of fuel, and wherein the plurality of bistable structures are arranged in a sequence with respect to the fuel outlet and wherein a stiffness of the flexible portion of each bistable structure is successively increased from a bistable structure farthest from the fuel outlet to a bistable structure closest to the fuel outlet, so that when the storage unit is filled with liquid fuel, the roof portion of each of the bistable structures is in the raised position and when the storage unit is emptied of liquid fuel, the bistable structures collapse in sequence beginning with the bistable structure that is farthest from the fuel outlet; a fuel outlet that is connected to an end of the storage unit and that extends to an outside of the housing; and one or more windows through which the bistable states of the bistable structures are detected.