Federal Circuit disposition — 25-1705

N OTE: This disposition is nonprecedential.
United States Court of Appeals
for the Federal Circuit
______________________
IN RE: KWANGJIN SONG,
Appellant
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2025-1705
______________________
Appeal from the United States Patent and Trademark
Office, Patent Trial and Appeal Board in No. 18/199,940.
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Decided: February 18, 2026
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K WANGJIN SONG, Rockwell, NC, pro se.
MARY L. K ELLY , Office of the Solicitor, United States
Patent and Trademark Office, Alexandria, VA, for appel-
lee John A. Squires. Also represented by K AKOLI
CAPRIHAN, N ICHOLAS T HEODORE MATICH , IV, ROBERT J.
MCMANUS .
______________________
Before D YK, HUGHES , and STOLL , Circuit Judges.
P ER CURIAM .
Kwangjin Song appeals pro se from a decision of the
Patent Trial and Appeal Board (“Board”) affirming an
examiner’s final rejection of several claims of patent
application No. 18/199,940 as anticipated or obvious over
Case: 25-1705 Document: 36 Page: 1 Filed: 02/18/2026

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IN RE: SONG 2
U.S. Patent Publication No. 2018/0043656 to Song et al.
(published Feb. 15, 2018) (“Song ’656”) and U.S. Patent
Publication No. 2016/0243525 to Song et al. (published
Aug. 25, 2016) (“Song ’525”). We affirm.
BACKGROUND
Appellant Kwangjin Song is the inventor of patent
application No. 18/199,940, filed on May 20, 2023, which
appellant prosecuted pro se. The application is directed to
a “porous separator film” which may be used as a separa-
tor dividing the positive and negative electrodes of certain
battery types. J.A. 28.1 The independent claim at issue
in this appeal is claim 1, which recites:
A multilayer porous separator film comprising at
least one oriented layer, the at least one oriented
layer comprising:
a) a matrix polymer selected from the group of a
first polymer having a crystalline melting tem-
perature (“Tm”) or a glass transition tempera-
ture (“Tg”) of 180° C. or higher, a second
polymer other than the first polymer, and
combinations thereof;
b) an open and interconnecting pore structure
characterized by a plurality of open and inter-
connecting pores, a Gurley air permeability of
1 sec/100 cc or greater, and a porosity of 90 %
or less; and
c) an ionic conductivity characterized by a Mac-
Mullin number (“N M”) of 1 to 15.
J.A. 100.
1 Citations to “J.A.” refer to the corrected joint ap-
pendix filed by the parties. Dkt. No. 24.
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IN RE: SONG 3
The examiner rejected claims 1, 2, 4, 6–9, 12–21, 23,
and 25–39 (the “contested claims”). Each contested claim
was rejected as anticipated by or obvious over two prior-
art references. First, the examiner rejected each contest-
ed claim under 35 U.S.C. § 102(a)(1) as anticipated by
Song ’656. Song ’656 is directed to an “oriented multi-
layer porous film,” and the corresponding patent applica-
tion is the subject of an appeal that we also decide today
upholding the rejection of the application. See In re Song,
No. 2025-1653. Song ’656 discloses manufacturing pro-
cesses that are identical to those in the appealed applica-
tion. Compare J.A. 36–49 ¶¶ 64–103; J.A. 50–57 ¶¶ 108–
27; J.A. 61–72 ¶¶ 139–75, with J.A. 487–92 ¶¶ 61–100;
J.A. 492–96 ¶¶ 102–27; J.A. 496–504 ¶¶ 132–68. The
examiner additionally rejected all contested claims as
unpatentable over Song ’525, determining claims 1, 2, 4,
6–9, 12–21, 23, 25–27, 38, and 39 to be anticipated by
Song ’525 and claims 28–37 to be obvious under 35 U.S.C.
§ 103 over Song ’525.2 Song ’525 is directed to a “method
for producing a novel multilayer sorbent polymeric mem-
brane comprising . . . a plurality of interconnecting pores.”
J.A. 464 ¶ 6. Appellant appealed to the Board, and the
Board affirmed.
2 Appellant is listed as an inventor on both prior art
references and argued during prosecution that appellant’s
own patent publications should not be prior art, citing
§ 102(b)(2). Section 102(b) provides that a disclosure is
not prior art under certain circumstances when the dis-
closure’s subject matter is obtained from the same inven-
tor. § 102(b)(2). However, § 102(b)(2) can only disqualify
prior art cited under § 102(a)(2). Id. Here, the examiner
cited the references as printed publications under
§ 102(a)(1). The examiner correctly determined that the
exception under § 102(b)(2) does not apply to disqualify
Song ’656 or Song ’525, which were both published before
the critical date of the appealed application.
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IN RE: SONG 4
Appellant timely appeals. We have jurisdiction under
28 U.S.C. § 1295(a)(4)(A).
D ISCUSSION
“To anticipate a claim, a prior art reference must dis-
close every limitation of the claimed invention, either
expressly or inherently.” Rapoport v. Dement, 254 F.3d
1053, 1057 (Fed. Cir. 2001). A prior art reference need
not use the same language as the invention to be antici-
pating. Adasa Inc. v. Avery Dennison Corp., 55 F.4th 900,
913 (Fed. Cir. 2022). Rather, the question is whether the
reference enables a person of ordinary skill in the art
(“POSA”) to practice the invention as claimed without
undue experimentation. Am. Calcar, Inc. v. Am. Honda
Motor Co., 651 F.3d 1318, 1341 (Fed. Cir. 2011). A claim
is unpatentable as obvious “if the differences between the
claimed invention and the prior art are such that the
claimed invention as a whole would have been obvious” to
a person of ordinary skill in the art (“POSA”) at the
effective filing date. 35 U.S.C. § 103. A single prior-art
reference may render a claim obvious if a POSA would
have been motivated to modify the prior art to arrive at
what is claimed. Arendi S.A.R.L. v. Apple Inc., 832 F.3d
1355, 1361 (Fed. Cir. 2016).
I
Appellant’s arguments are primarily directed to the
rejection of independent claim 1 as anticipated over
Song ’656.
Song ’656 discloses a “porous film having excellent
ionic conductivity and electrical insulation for use as a
separator” in certain electrical battery types. J.A. 484
¶ 10.
Appellant argues that the Board misconstrued claim 1
by not reading the preamble as limiting. Specifically,
appellant urges that Song ’656, which discloses a “porous
film,” does not disclose the “separator film” of the claimed
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IN RE: SONG 5
invention, as recited in the preamble. Appellant’s Br. 22.
The Board concluded that the word “separator” indicates
only the intended use of the film and that claim 1 recites
a structurally complete device without the preamble. We
agree with the Board’s conclusion. The specification does
not suggest any structural meaning of “separator” for the
film itself but explains that a “separator is located be-
tween positive and negative electrodes in an electrochem-
ical cell.” J.A. 25. The positive and negative electrodes
are not part of the claimed structure; the word “separator”
thus merely explains where the claimed film might be
used advantageously. And in any event, Song ’656 dis-
closes “a porous film . . . for use as a separator.” J.A. 484
¶ 10.
With respect to the “open and interconnecting pore
structure” limitation, the Board determined that appel-
lant’s application and Song ’656 disclose identical meth-
ods, such that the resulting pore structures would
necessarily be the same, and observed that appellant did
not identify any differences. Appellant argues that the
Board erred in determining that the process disclosed in
Song ’656 inherently produces the claimed pore structure.
Appellant points to the range of “distinctly different
structures and properties” that may result from the
disclosed process. Appellant’s Br. 29 (citing J.A. 94–96
¶¶ 255–57).
We note that appellant described some of the result-
ing films as having “clogged or collapsed pores” rather
than open pores, J.A. 94 ¶ 255, suggesting that some
version of the process, as identically disclosed in
Song ’656, does not necessarily result in the claimed open
and interconnected pore structure. See MEHL/Biophile
Int’l Corp. v. Milgraum, 192 F.3d 1362, 1365 (Fed. Cir.
1999). But anticipation does not need to rely on an inher-
ency theory when Song ’656 explicitly discloses the open
and interconnected pore structure. J.A. 501 ¶ 174 (“a
fibrous matrix interconnected with a plurality of open
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IN RE: SONG 6
pores” (reference numbers omitted)). We further note
that Figures 2A and 2B in the appealed application,
showing electron micrographs of “interconnecting
pores . . . for an unfilled and filled separator film,” appear
to be identical to Figures 2A and 2B in Song ’656, showing
a micrograph of “a typical [polyolefin]-based separator
film and a filled Example separator film.” Compare
J.A. 32 ¶ 45, 108, with J.A. 480, 485 ¶ 45. Additionally,
appellant concedes that Song ’656 discloses an open pore
structure with interconnecting pores. Appellant’s Br. 25
(“As shown above, the ’656 application disclosed an open
pore structure, characterized by [Gurley number] and
channeled in the [normal direction] by a plurality of
interconnecting pores.”).
Appellant also argues that the prior art fails to antici-
pate claim 1 because the “open and interconnecting pore
structure” of the claim is improved over the prior art pore
structure. But the distinctions identified by appellant,
such as “multiple form factors” and “complete in-plane
interconnectivity” between pores, are not recited in
claim 1. Appellant’s Br. 25–26. These unrecited proper-
ties do not distinguish the claim from the prior art.
We affirm the Board’s decision with respect to
Song ’656.
II
The Board also correctly rejected claims 1, 2, 4, 6–9,
12–21, 23, 25–27, 38, and 39 based on anticipation by
Song ’525. Song ’525 discloses a “multilayer sorbent
polymeric membrane” comprising “a plurality of intercon-
necting pores.” J.A. 464 ¶ 6. The “wide range of applica-
tions” of the Song ’525 membrane includes “separation
and purification of gases and fluids.” J.A. 464 ¶ 2. Appel-
lant’s arguments for all claims rejected on this ground
rest on the same arguments presented as to claim 1.
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IN RE: SONG 7
Regarding the “open and interconnecting pore struc-
ture” limitation, the Board concluded that a person of
ordinary skill would have understood that the Song ’525
membrane would either absorb or adsorb a material and
reasoned that in an absorbent membrane, “the pore
structure must be open and interconnecting to permit a
material to be absorbed into it.” J.A. 7. Appellant argues
that the Board erred in concluding that the absorbent
membrane must be an open and interconnecting pore
structure. We understand appellant’s argument to be
that the Board’s theory is one of inherent anticipation and
that the Board did not establish that a membrane can
only be made absorbent by having open and interconnect-
ing pores.
As with the Song ’656 ground, we find it unnecessary
to determine if the method of Song ’525 inherently dis-
closes an open and interconnecting pore structure because
it directly discloses the structure. The examiner observed
that Figure 2 of Song ’525 is identical to Figure 2B in the
appealed application, which appellant describes as show-
ing “a plurality of open, interconnecting pores” in the
specification of the appealed application. J.A. 75 ¶ 183;
compare J.A. 460, with J.A. 108. We agree that these two
figures depict the same film in all relevant respects.
Song ’525 thus discloses an open and interconnecting pore
structure by appellant’s own description.
Appellant’s remaining arguments are directed at
properties that are not recited as limitations in claim 1.
Appellant argues that the prior art membrane was thick
and weak compared to the film of claim 1, but claim 1
recites no thickness or strength limitations. We reject
appellant’s argument that the preamble’s recitation of
“separator film” should limit and distinguish the claim for
the same reason as discussed for the Song ’656 ground.
The Board did not err in rejecting claims 1, 2, 4, 6–9, 12–
21, 23, 25–27, 38, and 39 as anticipated by Song ’525.
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IN RE: SONG 8
Claims 28–37 were rejected as obvious over Song ’525.
The examiner found that the configuration of layer struc-
tures recited in these claims were obvious to try in light of
the disclosure in Song ’525 that layers can comprise
different materials such as polyolefin, polar polymer,
sorbent polymer, and coating polymers. Appellant does
not dispute that such configurations were obvious to try
but argues only that Song ’525 is “unanalogous” to the
appealed application. Appellant’s Br. 40. Appellant
forfeited this argument by not raising it before the Board.
See In re Google Tech. Holdings LLC, 980 F.3d 858, 863
(Fed. Cir. 2020). But in any event, appellant’s argument
that the multilayer polymer membrane of Song ’525 is not
from an analogous field of endeavor as the multilayer
polymer film of the appealed application is unpersuasive.
The Board did not err in rejecting claims 28–37 as obvious
over Song ’525.
We affirm the Board’s decision with respect to
Song ’525.
III
We have considered appellant’s other arguments and
find them unpersuasive. We affirm the Board’s decision.
AFFIRMED
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