TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Device: The fuel supply comprises at least two inner liners (preferably flexible inner liners), an absorbent material between the inner liners, potential energy storage element(s) acting on the liner containing fuel, a third liner, and a movable guide arm mounted on the fuel supply. Preferred Method: The guide arm is moved from a first position to a second position before the fuel supply is inserted into the electronic device. After the fuel supply is inserted, the guide arm returns to the original position to retain the fuel supply inside the electronic device. Preferred Component: The reactant compartment comprises a gas permeable and liquid impermeable membrane. It also comprises a liner containing the reactants. The fuel compartment comprises a liner containing the fuel. The fuel cartridge further comprises a valve (26) and a pump (24) to transport fuel from the fuel compartment to the reaction chamber. The outer casing is flexible and substantially impermeable to hydrogen gas. The fuel compartment and the reactant compartment are separated by, a movable wall (18) that forms a seal with the walls of the reactant compartment and fuel compartment. The seal comprises a wiper (20) or an o-ring pressing against the walls of the reactant compartment and fuel compartment. One of the liners contains fuel and is in fluid communication with a valve connecting the liner to a fuel cell. The spring potential energy storage element comprises a spring. The guide arm is spring-biased. It comprises a cover that seals a shut-off valve connecting the fuel supply to a fuel cell in the electronic device before its first use, and protects the shut-off valve. The outer casing comprises internal ribs to guide the movement of the liner and the potential energy storage element, when fuel is transported into or out of the liner. The bag is shrink wrapped to the fuel supply. Preferred Function: The valve selectively allows hydrogen gas to pass through to the fuel cell. Preferred Condition: The walls of the fuel compartment and the reactant compartment are integrally formed. The fuel supply has a size and a dimension that can be received in a compartment in an electronic device. The inner liner is in fluid communication with a valve connecting the inner liner to the fuel cell inside the electronic device. The guide arm is mounted co-axially with but spaced from a control valve connecting the fuel supply to a fuel cell in the electronic device. The movable guide arm is rotatable, bendable, flexible, and slidable.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The fuel comprises sodium borohydride. The liquid reactant comprises sodium borate. The reaction chamber comprises platinum or ruthenium, and a catalyst. The liquid reactant further reacts with an additional reactant to produce a gas to increase the pressure within the reactant compartment to push fuel out of the fuel compartment. The additional reactant is a metal and a catalyst. Preferred Condition: Hydrogen gas passes through the membrane to the fuel cell. It is stored within the outer casing.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The fuel comprises sodium borohydride. The liquid reactant comprises sodium borate. The reaction chamber comprises platinum or ruthenium, and a catalyst. The liquid reactant further reacts with an additional reactant to produce a gas to increase the pressure within the reactant compartment to push fuel out of the fuel compartment. The additional reactant is a metal and a catalyst. Preferred Condition: Hydrogen gas passes through the membrane to the fuel cell. It is stored within the outer casing.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The fuel comprises methanol.    TECHNOLOGY FOCUS - POLYMERS - Preferred Component: The spring potential energy storage element also comprises foam. The foam comprises multiple zones of different porosity, where the zone of highest porosity is space farthest from the liner. It defines vent holes.