Storage-stable, fluid dispensing device using a hydrogen gas generator

• US 5,707,499 A
• Filed: 10/06/1995
• Issued: 01/13/1998
• Est. Priority Date: 10/06/1995
• Status: Expired due to Term

• Current Assignee: Microlin LLC
• Original Assignee: Ceramatec, Inc.
• Inventors: Joshi, Ashok V., Gordon, John H., McEvoy, John J.
• Primary Examiner(s): Valentine, Donald R.
• Application Number:
  US08/539,998
• Time in Patent Office: 830 Days
• Field of Search: 204/265, 204/266, 204/228, 204/292, 204/293, 204/295
• US Class Current: 204/230.5
• CPC Class Codes: A61M 2005/14204 with gas-producing electrochemical cell
• CPC Class Codes: A61M 5/145 using pressurised reservoirs, e.g. pressurised by means of pistons
• CPC Class Codes: H01M 12/06 with one metallic and one gaseous electrode
• CPC Class Codes: H01M 16/00 Structural combinations of different types of electrochemical generators
• CPC Class Codes: H01M 2300/0014 Alkaline electrolytes
• CPC Class Codes: H01M 2300/0085 Immobilising or gelification of electrolyte
• CPC Class Codes: H01M 4/42 Alloys based on zinc
• CPC Class Codes: H01M 4/50 of manganese
• CPC Class Codes: H01M 4/628 Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
• CPC Class Codes: H01M 4/86 Inert electrodes with catalytic activity, e.g. for fuel cells
• CPC Class Codes: H01M 4/9016 Oxides, hydroxides or oxygenated metallic salts
• CPC Class Codes: H01M 50/109 of button or coin shape
• CPC Class Codes: H01M 50/119 Metals
• CPC Class Codes: H01M 50/121 Organic material
• CPC Class Codes: H01M 50/124 having a layered structure
• CPC Class Codes: H01M 50/216 adapted for button or coin cells
• CPC Class Codes: H01M 50/545 formed by the casing of the cells cup shaped terminals adapted for cells having curved cross-section H01M50/56
• CPC Class Codes: H01M 6/12 with flat electrodes
• CPC Class Codes: H01M 6/26 Cells without oxidising active material, e.g. Volta cells
• CPC Class Codes: H01M 6/38 by mechanical means
• CPC Class Codes: Y02E 60/36 : Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

A storage stable fluid delivery device including a gas generator in which moisture (water) is involved in the gas generation reaction in which moisture containment is utility to prevent or retard water loss as disclosed. The moisture containment may be a moisture impermeable membrane as a permanent part of the device and may be utilized in conjunction with the gas generator when the membrane has high gas permeability for the gas being generated. The fluid delivered by such device is typically a liquid having some particular utility in its environment. The liquid dispensed may be a pharmaceutical or some other liquid having a beneficial or curative effect upon an animal or human patient or it may be a liquid such as an insecticide, fumigant, fragrance or other liquid having a relatively high vapor pressure.

Claims

1. A storage stable fluid delivery device comprising a liquid chamber containing a liquid to be dispensed, a flexible wall or movable piston positioned between said liquid chamber and a gas chamber into which gas flows from a gas generator structured to produce hydrogen at a substantially constant rate over a period of time such that the fluid flows from the liquid chamber through an outlet as the gas enters the gas chamber, said gas generator containing moisture which participates in the generation of the gas;

sealing means to prevent substantial permeation of water vapor from the gas generator to the environment during storage; and

wherein the gas generator is an electrochemical gas generating cell comprising a gas-evolving cathode composed of at least a hydrophobic gas permeable layer and a current collector, and an electroactive metal anode wherein said anode is electronically isolated from said cathode by an insulative means which is both ionically and electronically insulative;

an aqueous electrolyte adapted to be in ionic communication with said anode and cathode;

wherein said electrolyte is in contact with said electroactive metal anode during storage;

wherein said gas generating cell contains enough moisture in the electrolyte to sustain water vapor losses due to permeation or leakage during storage, to be consumed in the electrode reactions, to humidify the generated gas, and to remain ionically conductive during the life of the device;

wherein the anode and cathode are connected through an electric circuit consisting of a means to complete the circuit at the time of activation;

and a hydrogen permeable moisture barrier means present to permit small amounts of hydrogen generated inadvertently during storage before the electrical circuit means is activated to substantially permeate out of the device and

said barrier means having sufficiently low water vapor permeation to prevent the escape of substantial water vapor.

2. The device of claim 1, wherein the hydrogen permeable, moisture barrier which prevents substantial permeation of water vapor from the gas generator to the environment during storage is an intermediate moisture vapor barrier positioned between the gas generator cathode current collector and the gas chamber.

3. The device of claim 2, wherein barrier disruption means is associated with said hydrogen permeable, intermediate moisture vapor barrier to permit rapture of said barrier after the gas generator is activated so that the flow of gas from the gas generator to the gas chamber is not substantially impeded by said barrier after the device has been activated.

4. The device of claim 2, wherein said hydrogen-permeable moisture barrier is expansible and cooperates with the gas discharge port between said gas generator and said gas chamber to expose said port when said barrier is expanded by gas generation.

5. The device of claim 2, wherein said hydrogen permeable moisture barrier is a metallized film of a polymeric membrane having a metal coating of a thickness of about 0.3-1.5×

10^-6 inches adhered thereto.

6. The device as in claim 2, wherein said hydrogen permeable moisture barrier is a polymeric material selected from the class consisting of polychlorotrifluoroethylene, polychlorotrifluoroethylene copolyethylene, polyvinylidene chloride, high density polyethylene, oriented polypropylene, polytetrafluoroethylene PFA, and polytetrafluoroethylene-co-hexafluoropropene, low density polyethylene, linear low density polyethylene, and polyester, or combination of one or more of these materials with another material.

7. The device as in claim 1, wherein said hydrogen permeable, moisture barrier which is the shell of said gas chamber in which at least a portion of said shell is minimally hydrogen permeable.

8. The device of claim 7, wherein said at least a portion of said gas chamber shell which is at least minimally permeable to hydrogen is a metallized film of a polymer membrane material with a metal coating in the range of 0.3-1.5×

10^-6 inches in thickness.

9. The device of claim 1, wherein said hydrogen permeable, water barrier is the shell of said gas chamber, wherein said shell is at least partially comprised of a material which is at least minimally permeable to hydrogen gas having a very low moisture vapor permeability.

10. The device of claim 9, wherein the gas chamber shell is made at least partially of a material selected from the class consisting of polychlorotrifluoroethylene, polyvinylidene chloride, high density polyethylene, oriented polypropylene, low density polyethylene, linear low density polyethylene, polyester, nylon or other polymer film with metal coating in the range of 0.3-2×

10^-6 inches thickness or combination of one or more of these materials with another material.

11. The device of claim 1, wherein a direct current power supply is in said electrical circuit.

12. A device as in claim 11, wherein said direct current power supply is one or more batteries in parallel or series.

13. A device as in claim 1, wherein material of said electroactive metal anode containing at least a significant quantity of a metal selected from the class consisting of zinc, aluminum, magnesium, iron alloys and mixtures thereof.

14. A device as in claim 1, wherein an intermediate barrier is positioned between the gas generator cathode current collector and the gas chamber, said intermediate barrier having a high ratio of hydrogen to oxygen permeability such that permeation of oxygen into said electrochemical gas generating cell is inhibited but

permeation of hydrogen into said gas chamber can occur at a rate controlled by the cell structure components;

and

the onset of gas generation initiates substantially immediately after said electrochemical gas generating cell is activated by completing said electrical circuit.

15. A device as is in claim 14, wherein said intermediate barrier includes a coating of palladium, iron/titanium alloy or nickel.

16. The device of claim 1, wherein said gas generating cell has escape means to permit hydrogen to escape at a low permeation rate out of said gas chamber while said device is activated;

and wherein said shell of said gas chamber is constructed at least partially of materials with low hydrogen permeability.

17. The device of claim 1, wherein said electrochemical cell anode contains one or more anti-corrosion agents adapted to minimize premature generation of hydrogen.

18. The device of claim 1, wherein the gas generator consists of at least two adjacent compartments, a first compartment in which the substantially aqueous constituents are stored and a second compartment in which a substantially active metal is stored a divider having low moisture permeability separating said compartments during storage;

and generator activation means associated with said divider to perforate said divider at the time of activation to permit said aqueous constituents from said first compartment to flow or partially flow into said second compartment containing said active metal.

19. The device of claim 18, wherein said electrical circuit is completed at the time of activation and hydrogen is evolved at cathode at a rate which is affected by the resistance of the circuit or combination of resistance and applied voltage.

20. The device of claim 1, wherein said cathode contains ruthenium, iridium, platinum, or combinations thereof.

21. The device of claim 1

where electroactive material is incorporated into cell cap;

where all electronically conductive cathode components are mechanically attached to each other;

where electrolyte directly contacts both anode and cathode;

where an ionically conductive, electronically insulative separator between anode and cathode is not utilized.

22. The device of claim 21, wherein said cell cap is entirely made of electroactive anode material.

23. The device of claim 21, wherein said cell cap is clad or coated with electroactive anode material on the interior.

24. The device of claim 21, wherein an electroactive anode material is attached to said cell cap by mechanical bond means of integration.

29. The device of claims 1 or 28, wherein said anode comprises Zn.

25. A fluid delivery device having a hydrogen generating cell as a gas generating component comprising

a continuous solid electroactive metal anode structurally integrated as part of a cell housing;

a cathode in contact with said electrolyte;

a suitable aqueous electrolyte in contact with at least a portion of said anode and cathode;

an electrical insulator insulating the cathode and anode from one another, which is structured such that anode and cathode communicate ionically through said electrolyte;

circuitry means to electrically connect said anode and cathode; and

vent means to permit generated gas to exit said cell and enter chamber which collects gas to exert a force on fluid.

26. The device of claim 25, wherein said vent means is in communication with a membrane which has a high gas permeability and a low moisture vapor permeability.

27. The device of claim 25, wherein said hydrogen generating cell is powered by an external battery.

28. A fluid delivery device having an electrolyte-containing hydrogen generating cell as a motive component comprising

an electrically conductive housing to house said electrolyte;

said electrolyte being an aqueous material containing metallic anode particles;

a cathode material;

a separator physically separating said anode particles from the cathode;

vent means to permit flow of H₂ gas from said cell; and

vapor barrier means in communication with said electrolyte to separate said electrolyte from said flow aperture, said vapor barrier having a low moisture permeability and a high hydrogen gas permeability.

30. The device of claim 28, wherein said anode particles comprise zinc, aluminum, magnesium, iron or alloys.

31. The device of claim 28, wherein said vent means is in communication with a membrane which has a high gas permeability and a low moisture vapor permeability.

32. The device of claim 28, wherein said electrolyte is encapsulated in a rupturable envelope which, until ruptured isolates said electrolyte from the cell components.

33. The device of claim 28, wherein said cathode contains ruthenium, iridium, platinum or alloys thereof.

34. The device of claim 28, wherein said hydrogen generating cell is powered by an external battery.