Heat units using a solid fuel capable of undergoing an exothermic metal oxidation-reduction reaction propagated without an igniter

Inventors

Sharma, Krishnamohan • Lei, Mingzu

Assignees

Alexza Pharmaceuticals Inc

Abstract

A heating unit comprising an electrically conductive substrate. A solid fuel layer comprising a metal reducing agent, a metal containing oxidizing agent and a binder is coated on a surface of the substrate, the solid fuel layer having a solid fuel surface spaced from the substrate. A first electrode coupled to the substrate. A second electrode coupled to the solid fuel surface. A power supply is configured to be selectively coupled to the first and second electrodes to provide a voltage between the metallic substrate and the solid fuel surface. The voltage acts to propagate an exothermic metal oxidation-reduction reaction without the use of an igniter.

Core Innovation

A heating unit is described that propagates an exothermic metal oxidation-reduction reaction without an igniter by applying a voltage between an electrically conductive substrate and a spaced solid-fuel surface via first and second electrodes. The solid fuel layer includes a metal reducing agent, a metal-containing oxidizing agent, and an inorganic binder. The reaction is described as igniter-free propagation of a thermite reaction by electrical actuation using a power supply.

The solid fuel is applied as a coating formed by coating a portion of the interior surface of the conductive substrate with a slurry of solid fuel and solidifying the slurry. A first electrode is coupled to the conductive substrate, and a second electrode is coupled to the surface of the solid fuel. This structure is positioned so that the electrical voltage is applied between the conductive substrate and the spaced solid-fuel surface to activate the reaction.

In drug supply embodiments, the heated substrate vaporizes a drug film, and aerosol delivery embodiments are described where the vaporization occurs within seconds. The disclosed formulations include metal reducing agent, metal-containing oxidizing agent, and inorganic binder selections, including Laponite® silicate-based binder, and evaluation of how applied voltage, resistance/capacitance, and solid fuel layer characteristics affect activation without an igniter.

Claims Coverage

The disclosed claims include one independent claim directed to a method of making a heating unit, with dependent claims that refine the selection of components in the solid fuel slurry. Overall, the claim set specifies four inventive aspects: coating an interior surface of a conductive substrate with a slurry of solid fuel, solidifying the slurry, coupling electrodes to the conductive substrate and solid fuel surface, and constraining the slurry components by named material selections in dependent claims.

The claim coverage centers on making an igniter-free heating unit by forming a solid fuel layer on an interior surface of an electrically conductive substrate from a slurry that includes a metal reducing agent, a metal-containing oxidizing agent, and an inorganic binder, then solidifying the slurry and coupling a first electrode to the conductive substrate and a second electrode to the solid fuel surface. Dependent claims narrow the component selections by specifying particular metals for the reducing agent, particular compounds for the oxidizing agent, and an inorganic silicate-based binder.

Stated Advantages

Documented Applications