Opinions — Wednesday, February 18, 2026

The Federal Circuit affirmed the Patent Trial and Appeal Board's rejection of claims in pro se appellant Kwangjin Song's patent application No. 18/199,940, directed to a multilayer porous separator film for batteries. The Board found the contested claims anticipated under § 102(a)(1) or obvious under § 103 over two prior publications, Song '656 and Song '525, both of which listed Song as an inventor. Song argued primarily that the prior art did not disclose the "open and interconnecting pore structure" recited in claim 1 and that the preamble's "separator film" language was limiting, but the court rejected both arguments.

The court's analysis turned on two key determinations that avoided reliance on inherency. First, the court held the preamble term "separator" merely described intended use rather than structural limitations, as the specification identified "separator" only as a positional reference between electrodes not part of the claimed device. Second, though Song argued the prior art process does not inherently produce the claimed pore structure because it can yield "clogged or collapsed pores," the court found explicit anticipation: Song '656 directly disclosed "a fibrous matrix interconnected with a plurality of open pores," and the identical electron micrographs in both Song '656 and the application (and likewise between Song '525's Figure 2 and the application's Figure 2B) showed the same structure, which Song himself described as having "open, interconnecting pores."

The Federal Circuit affirmed the Patent Trial and Appeal Board's determination that claims 1-4, 6, 13, 14, 17-19, and 25-27 of ST Case1Tech's U.S. Patent No. 9,270,244 were invalid as obvious over the prior art. The '244 patent relates to systems that automatically adjust audio levels in user-worn devices to improve situational awareness, specifically by employing a "voice timer" to maintain adjusted volume during conversational gaps. The appeal turned on a single claim construction issue: whether a claim limitation requiring "adjusting a mixing gain" during a voice timer mandates that the adjusting occur only after the voice timer activates, or whether maintaining previously adjusted gain levels during the timer also qualifies.

The court applied de novo review to the fully intrinsic-record-based construction and held that "adjusting" encompasses both the initial act of changing gain levels and the subsequent maintenance of those levels over time. The court rejected ST1's argument that grammar or logic required a temporal ordering of steps, finding that the specification described "maintaining" as a form of "adjusting" and depicted embodiments where gain adjustments occurred before timer activation but were maintained during the timer period. The court also rejected ST1's superfluity argument, explaining that the "activating a voice timer" step remains meaningful because it excludes embodiments where adjusting begins and ends without any timer, and noted that while a district court in parallel litigation had adopted ST1's narrower construction, the Board properly considered but declined to follow that non-binding determination under ParkerVision and the applicable regulation.

In Flip Phone Games, Inc. v. PLR Worldwide Sales Ltd., the court granted the parties' joint stipulation to voluntarily dismiss Flip Phone Games' appeal (No. 2025-2058) under Federal Rule of Appellate Procedure 42(b), with each side bearing its own costs. The order dismissed Appeal No. 2025-2058, updated the caption for the remaining appeal (No. 2025-2106), and set a briefing schedule for PLR Worldwide Sales Ltd.'s opening brief in the continuing appeal.