Federal Circuit Affirms USPTO Rejection of Multilayer Porous Separator Film Patent
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📋 Case Summary
| Case Name | In re: Kwangjin Song |
| Case Number | 25-1705 (Fed. Cir.) |
| Court | Federal Circuit, Appeal from USPTO |
| Duration | Apr 2025 – Feb 2026 295 Days |
| Outcome | USPTO Rejection Affirmed |
| Patent at Issue | |
| Technology Area | Multilayer Porous Separator Films |
Case Overview
The Parties
👤 Applicant
Named inventor and applicant seeking patent protection for a multilayer porous separator film technology, represented by Liso Plastics LLC.
🏛️ Respondent
John A. Squires, Under Secretary of Commerce for Intellectual Property and Director of the USPTO, representing the agency’s examination and appeal decisions.
Patent Application at Issue
This case involved US Patent Application No. US18/199940 (Publication No. US20240047826A1), directed to a multilayer porous separator film technology, a critical component in lithium-ion batteries.
- • US20240047826A1 — Multilayer porous separator film architecture for lithium-ion batteries
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The Verdict & Legal Analysis
Outcome
The Federal Circuit issued a clean AFFIRMANCE of the USPTO’s underlying patentability rejection. The court’s order states unambiguously: “THIS CAUSE having been considered, it is ORDERED AND ADJUDGED: AFFIRMED.” No damages were at issue given the administrative nature of the proceeding. The affirmance operates to finalize the USPTO’s rejection, preventing issuance of patent claims as presented by Song.
Key Legal Issues
The verdict cause is classified as **Patentability / Invalidity-Cancellation Action** — indicating the USPTO’s rejection, as affirmed by the Federal Circuit, rested on substantive patentability grounds under the Patent Act. While specific legal basis is not detailed, common grounds include Obviousness (35 U.S.C. § 103), Anticipation (35 U.S.C. § 102), or Lack of enablement/written description (35 U.S.C. § 112). The Federal Circuit’s affirmance confirms the agency’s reasoning was legally sound and supported by substantial evidence.
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⚠️ Patentability Challenges & Analysis
This case highlights critical IP prosecution risks in advanced materials and battery technology. Choose your next step:
📋 Understand Patentability in this Area
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High Patentability Bar
Generic multilayer separator film designs
Dense Prior Art
In battery materials sector
Importance of Differentiation
For successful claim prosecution
✅ Key Takeaways
For Patent Attorneys & Litigators
Federal Circuit affirmances in *in re* patentability appeals reflect strong deference to USPTO findings — identify legal error, not factual disagreement, as the core appellate argument.
Search related case law →Dense prior art in battery materials demands heightened claim differentiation at the prosecution stage.
Explore prior art tools →For R&D Teams & Innovators
Document invention conception and reduction-to-practice thoroughly to support written description requirements and overcome rejections.
Improve invention documentation →Engage patent counsel early in advanced materials development to ensure claim architecture survives both examination and appellate review.
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