United States Patent 6,977,042: Scope, Claims, Expiration, and Patent Landscape for Microstructured Filters and Nebulizers

U.S. Patent No. 6,977,042 protects a silicon-and-glass microstructured filter architecture used in inhalation nebulizers. Its central limitation is a flat base plate with integral projections arranged in mutually juxtaposed zig-zag rows, creating narrow passages covered by a second plate. The patent also claims dimensional relationships, cascade arrangements, passage geometries, etching processes, anodic bonding, and a nebulizer incorporating the filter.

The patent issued on December 20, 2005, to Boehringer Ingelheim-related interests. Its practical exclusivity ended in approximately February 2021 based on the 20-year term measured from the U.S. filing date, subject to any patent-term adjustment shown in the USPTO record. The patent is therefore not a current barrier to independent manufacture of the claimed filter or nebulizer architecture. It also is not an Orange Book-listed drug patent and does not support a conventional Hatch-Waxman Paragraph IV challenge.

What technology does U.S. Patent 6,977,042 protect?

The patent covers a microstructured filter made from two plates:

A substantially flat base plate.
Integral projections extending from the base plate.
Passages between the projections that carry fluid from inlet to outlet.
A cover plate secured over the projections and passages.
At least two projection rows arranged in a zig-zag and mutually juxtaposed configuration.

The claimed design is a microfabricated flow path rather than a conventional porous membrane. Fluid moves through defined channels formed by the geometry of the projections, base plate and cover plate. The architecture is particularly suited to producing fine aerosol droplets in an inhalation device.

The patent specification identifies silicon as a base-plate material and glass as a cover-plate material. The plates may be joined by anodic bonding. The base plate can be formed using isotropic, anisotropic or combined etching techniques. These manufacturing limitations are reflected in claims 22 through 25. [1]

What are the independent claims in U.S. Patent 6,977,042?

Claims 1 and 26 are the principal independent claims. Claim 27 depends from claim 26.

Claim 1: microstructured filter

Claim 1 requires every element below:

Element	Requirement
Filter structure	An inlet for unfiltered fluid and an outlet for filtered fluid
Base plate	Substantially flat
Projections	Multiple projections extending from the base plate
Integration	Each projection must be an integral component of the base plate
Passages	Projections are spaced apart by passages forming the fluid path
Cover	A cover plate securable to the base plate
Enclosure	Cover plate covers the projections and passages
Arrangement	Projections are in at least two rows
Geometry	Rows extend in a zig-zag configuration
Relationship	Rows are mutually juxtaposed across the filter

The strongest limiting features are the integral projections, the covered microchannels and the zig-zag arrangement of at least two rows. A device using separately attached posts, a porous membrane or straight parallel channels without the required row relationship would present a stronger non-infringement position against claim 1.

Claim 26: nebulizer

Claim 26 independently claims a nebulizer containing the same basic filter architecture. It repeats the base plate, cover plate, integral projections, passages and zig-zag rows. Because claim 26 is an independent apparatus claim, an accused product may infringe claim 26 even if it does not practice any of the narrower dimensional or manufacturing limitations in claims 2 through 25.

Claim 27: nozzle assembly

Claim 27 narrows claim 26 by requiring a nozzle in assembly with the filter. The claim links the microstructured filter to a nebulizer nozzle but does not, on its face, require a particular drug, aerosol particle size, nozzle material or therapeutic indication.

How do claims 2 through 25 narrow the patent scope?

Claims 2 through 25 define technical subfeatures. They fall into five main groups.

Spacing and hydraulic geometry

Claims 2, 5, 10, 11, 17, 19, 20 and 21 address the relationship between the cover plate, base plate and passages.

Claim 11 is especially specific. It requires passages with:

Length of 5 to 50 micrometers;
Height of 2.5 to 25 micrometers;
Width of 2.5 to 25 micrometers; and
Approximately constant cross-section.

Claim 10 requires the passage length to be at least twice the entry-side height. Claim 12 narrows claim 11 to substantially square passages.

Claims 19 through 21 address cover-to-base spacing within a row. The spacing may be substantially constant, may increase toward the outlet, or may linearly increase from the inlet end toward the outlet end.

These claims are useful for identifying specific commercial implementations, but they do not expand claim 1. They only apply when the base claim is met.

Cascade and staged restriction

Claim 3 requires multiple projection rows arranged in cascade form. The passage width perpendicular to fluid flow decreases from row to row, and the inlet-side projections are larger than the outlet-side projections. The cover-to-base spacing must also correspond approximately to the passage width at the entry side of each row.

Claim 6 adds an interconnected space between adjacent projection rows. Fluid enters the space from all passages in one row and exits into all passages in the next row. This limitation describes a distributed manifold effect between successive channel rows.

Projection shapes

Claims 7 through 9 cover projections in the form of:

Straight lands;
Curved lands; or
Columns.

These claims give the patent coverage over multiple projection profiles while preserving the core base-plate and passage architecture.

Passage cross-sections

Claims 12 through 16 address passage shape:

Claim	Passage limitation
12	Substantially square cross-section
13	Barrel-shaped cross-section
14	Trapezoidal cross-section
15	Longer side of trapezoid formed by cover plate
16	Approximately square at entry and wider toward exit

The cross-section limitations may be important in claim-charting against a silicon microfabricated filter. An accused product could avoid a particular dependent claim while remaining exposed under claim 1 or claim 26.

Etching and bonding

Claims 22 through 25 address fabrication:

Wet isotropic or dry isotropic etching;
Wet anisotropic or dry anisotropic etching;
A combination of isotropic and anisotropic etching;
Silicon base plate, glass cover plate and anodic bonding.

These claims are process- and material-sensitive. A product made using molded polymer components, laser-machined metal, ceramic fabrication or a different joining method may avoid these dependent claims. It could still fall within claim 1 or claim 26 if the resulting structure satisfies the independent-claim limitations.

What is the patent expiration date for U.S. Patent 6,977,042?

The patent issued December 20, 2005. The public patent record identifies a February 16, 2001 U.S. filing date and a February 18, 2000 priority date. The statutory term for a post-June 8, 1995 utility patent generally runs 20 years from the earliest effective U.S. nonprovisional or PCT filing date, not from the foreign priority date. [1, 2]

On that basis, the ordinary term would have ended around February 16, 2021, subject to any patent-term adjustment. A foreign priority date does not independently extend the U.S. patent term. Patent-term extension under 35 U.S.C. § 156 generally applies to qualifying regulated products, but an inhaler component patent would not ordinarily receive an extension merely because it is used with an approved drug. [2, 3]

The commercial consequence is material: the patent does not presently provide enforceable U.S. exclusivity against a new filter or nebulizer that practices its claims.

What is the Orange Book status of U.S. Patent 6,977,042?

U.S. Patent 6,977,042 is not a conventional Orange Book drug patent.

The Orange Book records patents submitted by a new drug application holder for a specific approved drug product. Listed patents typically cover the active ingredient, composition, formulation, method of use or approved drug-delivery product. [4] A standalone microstructured filter patent generally does not appear as a drug-product patent unless the NDA holder submits it as a patent that claims the approved drug or an approved method of use.

The patent claims a filter and a nebulizer, not a pharmaceutical active ingredient, drug formulation or therapeutic method. Its regulatory relevance is therefore indirect. A generic drug applicant would not ordinarily address this patent through a Paragraph IV certification unless an Orange Book-listed drug product patent incorporated the same subject matter.

Does U.S. Patent 6,977,042 create Paragraph IV risk?

No conventional Paragraph IV exposure follows from the patent itself.

Paragraph IV certifications apply to patents listed in the Orange Book against a reference-listed drug. A generic applicant certifies that an Orange Book-listed patent is invalid, unenforceable or not infringed. [4, 5] Because the patent is directed to a device component and expired in approximately 2021, it does not create a current Hatch-Waxman launch block.

A company developing a competing nebulizer could face ordinary patent infringement analysis for later, unexpired patents held by the same or other parties. The existence of U.S. Patent 6,977,042 would not by itself prevent FDA approval of a drug delivered through a different nebulizer.

What FDA regulatory issues are associated with the claimed nebulizer?

The claimed filter is part of an inhalation-delivery device. FDA treatment depends on the product configuration:

A nebulizer marketed as a standalone medical device may be regulated under the medical-device framework.
A drug-nebulizer combination may be regulated as a combination product.
A drug supplied with a proprietary delivery device may have device specifications incorporated into the NDA or labeling.
A replacement or generic inhaler may require a demonstration of equivalent performance, dose delivery and clinical effect, depending on the product and regulatory pathway.

FDA-approved Respimat products illustrate the commercial setting in which microstructured aerosol-generation technology has been used. Products such as Spiriva Respimat and Combivent Respimat are approved drug-device products, but approval of those products does not establish continuing patent protection under U.S. Patent 6,977,042. [6, 7]

What patent landscape surrounds the microstructured filter?

The relevant landscape has four layers.

The patent family

U.S. Patent 6,977,042 is part of an international patent family directed to microstructured filters and nebulizers. The family includes foreign and international filings associated with the same technical disclosure. Family members should be reviewed separately because:

Claims differ by jurisdiction;
Some foreign rights may have expired at different times;
Validation and maintenance requirements differ;
National claims may focus on the filter, nebulizer or manufacturing process.

The U.S. patent’s expiration does not establish the status of every foreign family member.

Related nebulizer patents

The broader Respimat and soft-mist inhaler portfolio includes patents covering:

Nozzle and aerosol-generation structures;
Metering chambers;
Spring-driven or energy-storage mechanisms;
Cartridge and reservoir assemblies;
Drug formulation and dose delivery;
Actuation and locking systems;
Manufacturing methods for microstructured components.

Those patents must be separated from the 6,977,042 rights. A product may be free to practice the expired filter claims but still encounter unexpired claims covering a nozzle, actuator, cartridge, formulation or complete inhaler system.

Competing device platforms

Competing inhalation technologies include jet nebulizers, vibrating-mesh nebulizers, ultrasonic nebulizers, dry-powder inhalers and pressurized metered-dose inhalers. Companies active in these categories have included Boehringer Ingelheim, PARI, Philips Respironics, Aerogen, Omron and other device manufacturers.

Most competing platforms do not inherently practice claim 1. A vibrating-mesh device, for example, may use a perforated membrane rather than integral projections and covered zig-zag microchannels. A jet nebulizer normally uses a gas jet and baffle system rather than the claimed plate architecture.

Manufacturing and know-how barriers

After patent expiration, the most relevant barriers are technical rather than exclusivity-based. They include:

High-aspect-ratio silicon etching;
Control of passage dimensions at micrometer scale;
Uniform anodic bonding;
Control of clogging and particle deposition;
Consistent aerosol droplet-size distribution;
Integration with a nozzle and metering system;
Cleaning, sterilization and extractables control;
High-volume yield and inspection.

Trade secrets, process capability and regulatory comparability may remain commercially important even when the core patent is expired. Those factors do not recreate patent exclusivity.

How strong is the patent estate for a product practicing these claims?

The historical estate was technically specific and commercially relevant, but its current legal strength is limited because the U.S. patent term has ended.

Historical strengths

The patent had several meaningful features:

A structural independent claim focused on the filter;
A second independent claim focused on a nebulizer;
Detailed dimensional claims;
Alternative projection and passage geometries;
Process claims directed to silicon microfabrication;
Material and bonding limitations;
Coverage extending from the component to the inhalation device.

The combination of integral projections and zig-zag rows would have provided a useful claim-identification framework against a closely matching microstructured filter.

Current weaknesses

The principal current weakness is expiration. An expired patent cannot support an ordinary U.S. infringement action for post-expiration conduct. The patent also does not provide current exclusivity over broad concepts such as "microstructured filter," "nebulizer" or "soft-mist inhaler."

A freedom-to-operate review must therefore shift to later patents, continuation applications, foreign rights and unexpired claims covering the commercial product’s other components.

Which companies are challenging U.S. Patent 6,977,042?

The patent does not present a current generic challenge pathway. There is no conventional Paragraph IV market challenge associated with the patent because it is not an Orange Book-listed drug patent and its U.S. term has ended.

Public litigation analysis should distinguish among:

Patent litigation involving the 6,977,042 patent itself;
Litigation involving other Respimat or soft-mist inhaler patents;
FDA disputes concerning drug-device equivalence;
Commercial disputes involving inhaler supply or licensing.

A lawsuit concerning another Boehringer inhaler patent should not be treated as litigation against U.S. Patent 6,977,042 without a patent-specific complaint, docket entry or asserted-claims record. [8, 9]

What licensing and revenue exposure is associated with the patent?

No standalone revenue figure can be assigned to U.S. Patent 6,977,042 from public drug-sales data. The patent protected a device architecture used in a commercial inhalation platform, but product revenue was generated from drug products and delivery systems, not from the patent in isolation.

Potential commercial exposure historically included:

Soft-mist inhalers using the claimed microstructured filter;
Product-specific cartridges and nozzles;
Combination products using the nebulizer platform;
Manufacturing supply arrangements;
Licensing or collaboration agreements relating to device technology.

The patent’s expiration removes direct U.S. royalty leverage based solely on the claimed filter. Commercial leverage may persist through unexpired companion patents, proprietary manufacturing methods, regulatory data, device qualification and brand-specific drug formulations.

How should a competing filter or nebulizer be analyzed?

A product-by-product analysis should begin with claim 1 and claim 26.

Structural claim chart

The relevant questions are:

Does the product have a substantially flat base plate?
Are the projections integral with that base plate?
Do spaces between projections form the fluid path?
Is a cover plate secured over the projections and passages?
Are the projections arranged in at least two mutually juxtaposed zig-zag rows?
Is the product a nebulizer containing that filter?
Does the nebulizer include a nozzle in assembly with the filter?

Dependent-claim review

The analysis should then test:

Passage dimensions;
Constant or varying cross-sections;
Cascade row geometry;
Projection shape;
Cover-to-base spacing;
Etching method;
Silicon and glass construction;
Anodic bonding;
Nozzle integration.

Because the patent is expired, this analysis is primarily relevant to historical infringement, damages periods, patent-family interpretation and the identification of later patents that may claim similar improvements.

Key Takeaways

U.S. Patent 6,977,042 covers a microstructured filter with integral base-plate projections, covered passages and zig-zag projection rows.
Claims 1 and 26 are the principal independent claims.
Claim 1 covers the filter; claim 26 covers a nebulizer containing the filter; claim 27 adds a nozzle.
Claims 2 through 25 narrow the invention through dimensions, cascade geometry, passage shapes, etching methods, materials and anodic bonding.
The patent issued on December 20, 2005.
Its ordinary U.S. term ended around February 16, 2021, subject to any patent-term adjustment.
The patent is not a conventional Orange Book-listed drug patent.
It does not create a current Paragraph IV barrier.
Current freedom-to-operate risk must focus on later patents covering the complete inhaler, nozzle, actuator, formulation, cartridge and manufacturing process.
The principal post-expiration barriers are manufacturing capability, regulatory qualification and unexpired companion patent rights.

FAQs

Is U.S. Patent 6,977,042 a drug patent or a device patent?

It is a device patent. Its claims cover a microstructured filter and a nebulizer, not an active pharmaceutical ingredient or drug formulation.

Does the patent cover all silicon microstructured nebulizer filters?

No. It requires specific structural relationships, including integral projections, passages covered by a plate, and at least two mutually juxtaposed rows in a zig-zag configuration.

Can a company make a similar filter in the United States today?

The patent’s U.S. term ended around 2021, so this patent alone does not block current manufacture. Later patents and foreign rights may still require review.

Does the patent cover Respimat as a brand?

No. It covers technical filter and nebulizer subject matter. Respimat products may also be covered by separate patents involving the nozzle, spring mechanism, cartridge, formulation and complete delivery system.

Are biosimilar developers exposed to this patent?

Biosimilar developers generally are not exposed through the biosimilar patent pathway because the patent claims a device, not a biologic. A biosimilar product using a proprietary nebulizer would require a separate device and patent analysis.

References

United States Patent and Trademark Office. (2005). U.S. Patent No. 6,977,042, Microstructured filter and nebulizer.
United States Code, 35 U.S.C. §§ 154, 156.
United States Patent and Trademark Office. (2024). Manual of Patent Examining Procedure, Chapter 2700: Patent term.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
Code of Federal Regulations, 21 C.F.R. § 314.101 and § 314.53.
U.S. Food and Drug Administration. (2014). Spiriva Respimat prescribing information.
U.S. Food and Drug Administration. (2016). Combivent Respimat prescribing information.
United States Patent and Trademark Office. (2024). Patent Center and Patent Examination Data System records.
U.S. Courts. (2024). Public Access to Court Electronic Records and patent litigation docket records.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	197 42 439	Sep 26, 1997

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	010946	⤷ Start Trial
Austria	228386	⤷ Start Trial
Austria	357956	⤷ Start Trial
Australia	748729	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 6,977,042