Electrolysis: processes – compositions used therein – and methods – Electroforming or composition therefor
Reexamination Certificate
1999-09-09
2001-05-22
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electroforming or composition therefor
C205S122000
Reexamination Certificate
active
06235177
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the field of liquid dispensing, and in particular to the aerosolizing of fine liquid droplets. More specifically, the invention relates to the formation and use of aperture plates employed to produce such fine liquid droplets.
A great need exists for the production of fine liquid droplets. For example, fine liquid droplets are used in for drug delivery, insecticide delivery, deodorization, paint applications, fuel injectors, and the like. In many applications, it may be desirable to produce liquid droplets that have an average size down to about 0.5 &mgr;l. For example, in many medical applications, such a size is needed to insure that the inhaled drug reaches the deep lung.
U.S. Pat. Nos. 5,164,740; 5,586,550; and 5,758,637, the complete disclosures of which are herein incorporated by reference, describe exemplary devices for producing fine liquid droplets. These patents describe the use of aperture plates having tapered apertures to which a liquid is supplied. The aperture plates are then vibrated so that liquid entering the larger opening of each aperture is dispensed through the small opening of each aperture to produce the liquid droplets. Such devices have proven to be tremendously successful in producing liquid droplets.
Another technique for aerosolizing liquids is described in U.S. Pat. No. 5,261,601 and utilizes a perforate membrane disposed over a chamber. The perforate membrane comprises an electroformed metal sheet using a “photographic process” that produces apertures with a cylindrical exit opening.
The invention provides for the construction and use of other aperture plates that are effective in producing fine liquid droplets at a relatively fast rate. As such, it is anticipated that the invention will find even greater use in many applications requiring the use of fine liquid droplets.
SUMMARY OF THE INVENTION
The invention provides exemplary aperture plates and methods for their construction and use in producing fine, liquid droplets at a relatively fast rate. In one embodiment, a method is provided for forming an aperture plate. The method utilizes a mandrel that comprises a mandrel body having a conductive surface and a plurality of nonconductive islands disposed on the conductive surface such that the islands extend above the conductive surface. The mandrel is placed within a solution containing a material that is to be deposited onto the mandrel. Electrical current is then applied to the mandrel to form an aperture plate on the mandrel, with the apertures having an exit angle that is in the range from about 30° to about 60°, more preferably from about 41° to about 49°, and still more preferably about 45°. Construction of the aperture plate to have such an exit angle is particularly advantageous in that it maximizes the rate of droplet production through the apertures.
In one particular aspect, the islands have a geometry that approaches a generally conical shape or a dome shape having a circular base, with the base being seated on the mandrel body. Conveniently, the islands may have a base diameter in the range from about 20 microns to about 200 microns, and a height in the range from about 4 microns to about 20 microns.
In another particular aspect, the islands are formed from a photoresistent material using a photolithography process. Conveniently, the islands may be treated following the photolithography process to alter the shape of the islands. In another aspect, the aperture plate is removed from the mandrel, and is formed into a dome shape. In still another aspect, the material in the solution that forms the aperture plate may be a material such as a palladium nickel alloy, palladium cobalt, or other palladium or gold alloys.
The invention further provides an exemplary aperture plate that comprises a plate body having a top surface, a bottom surface, and a plurality of apertures that taper in a direction from the top surface to the bottom surface. Further, the apertures have an exit angle that is in the range from about 30° to about 60°, more preferably about 41° to about 49°, and more preferably at about 45°. The apertures also have a diameter that is in the range from about 1 micron to about 10 microns at the narrowest portion of the taper. Such an aperture plate is advantageous in that it may produce liquid droplets having a size that are in the range from about 2 &mgr;m to about 10 &mgr;m, at a rate in the range from about 4 &mgr;L to about 30 &mgr;L per 1000 apertures per second. In this way, the aperture plate may be employed to aerosolize a sufficient amount of a liquid medicament so that a capture chamber that may otherwise be employed to capture the aerosolized medicament will not be needed.
The aperture plate may be constructed of a high strength and corrosion resistant material. As one example, the plate body may be constructed from a palladium nickel alloy. Such an alloy is corrosion resistant to many corrosive materials particularly solutions for treating respiratory diseases by inhalation therapy, such as an albuterol sulfate and ipratroprium solution, which is used in many medical applications. Further, the palladium nickel alloy has a low modulus of elasticity and therefore a lower stress for a given oscillation amplitude. Other materials that may be used to construct the plate body include gold, gold alloys, and the like.
In another aspect, the plate body has a portion that is dome shaped in geometry. In one particular aspect, the plate body has a thickness in the range from about 20 microns to about 70 microns.
In another embodiment, the invention provides a mandrel for forming an aperture plate. The mandrel comprises a mandrel body or plate having a conductive, generally flat top surface and a plurality of nonconductive islands disposed on the conductive surface. The islands extend above the conductive surface and have a geometry approaching a generally conical or dome shape. Such a mandrel is particularly useful in an electroforming process that may be employed to form an aperture plate on the mandrel body. The shaped nonconductive islands when used in such a process assist in producing apertures that have an exit angle in the range from about 30° to about 60°, more typically in the range from about 41° to about 49°, and still more typically at about 45°.
In one aspect, the islands have a base diameter in the range from about 20 microns to about 200 microns, and a height in the range from about 4 microns to about 20 microns. In another aspect, the islands may have an average slope in the range from about 15° to about 30° relative to the conductive surface. Conveniently, the islands may be formed from a photoresist material using a photolithography process. The islands may be treated following the photolithography process to further shape the islands.
In still another embodiment, the invention provides a method for producing a mandrel that may be employed to form an aperture plate. According to the method, an electroforming mandrel body is provided. A photoresist film is applied to the mandrel body, and a mask having a pattern of circular regions is placed over the photoresist film. The photoresist film is then developed to form an arrangement of nonconductive islands that correspond to the location of the holes in the pattern. Following this step, the mandrel body is heated to permit the islands to melt and flow into a desired shape. For example, the islands may be heated until they are generally conical or dome shaped in geometry and have a slope relative to the surface of the mandrel body. Optionally, the steps of applying the photoresist film, placing a mask having a smaller pattern of circular regions over the photoresist film, developing the photoresist film and heating the mandrel body may be repeated to form layers of a photoresist material and thereby further modify the shape of the nonconductive islands.
In one aspect, the photoresist film has a thickness in the range from about 4 microns to about 15 microns. In another aspect, the mandrel body is heated t
Baker Gary
Borland Scott
Aerogen, Inc.
Gorgos Kathryn
Smith-Hicks Erica
Townsend and Townsend / and Crew LLP
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