NOTE: This disposition is nonprecedential.

United States Court of Appeals 

for the Federal Circuit ______________________

ARBMETRICS, LLC,

Plaintiff-Appellant

v.

DEXCOM INC.,

Defendant-Appellee

______________________

2020-1510

______________________

Appeal from the United States District Court for the 

Southern District of California in No. 3:18-cv-00134-JLSMSB, Judge Janis L. Sammartino.

______________________

Decided: December 31, 2020

______________________

TIMOTHY EDWARD GROCHOCINSKI, Nelson Bumgardner 

Albritton P.C., Orland Park, IL, argued for plaintiff-appellant. Also represented by JOSEPH P. OLDAKER. 

 RICHARD T. MULLOY, DLA Piper LLP (US), San Diego, 

CA, argued for defendant-appellee. Also represented by 

STANLEY JOSEPH PANIKOWSKI, III; STUART ERIC POLLACK, 

New York, NY. 

 ______________________

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2 ARBMETRICS, LLC v. DEXCOM INC.

Before WALLACH, TARANTO, and CHEN, Circuit Judges.

CHEN, Circuit Judge.

This appeal arises from an infringement action Arbmetrics, LLC (Arbmetrics) filed in the United States District Court for the Southern District of California against 

Dexcom Inc. (Dexcom). Arbmetrics asserts that Dexcom’s 

Continuous Glucose Monitoring (CGM) systems infringe

U.S. Patent No. 6,343,225 (’225 patent). Based on the district court’s claim constructions of either “emulsion” or “oxygen dissolving substance,” the parties stipulated that 

Dexcom’s accused products do not infringe the ’225 patent. 

See Arbmetrics, LLC v. Dexcom, Inc., No. 3:18-cv-00134, 

2019 WL 7290541 (S.D. Cal. Dec. 30, 2019) (Claim Construction Order). Pursuant to the stipulation, the district 

court entered final judgment of noninfringement in favor of 

Dexcom. J.A. 2–4 (Stipulation); J.A. 7–8 (Final Judgment). 

Because we conclude that the district court did not err in 

its claim construction of oxygen dissolving substance, we 

affirm.

BACKGROUND

The ’225 patent relates to “the field of electrochemical 

devices for detection and measurement purposes and more 

specifically an enzyme emulsion for use in an implantable 

miniature polarographic glucose sensor.” ’225 patent col. 1 

ll. 4–7. The glucose sensor of the ’225 patent is useful for 

long-term monitoring of blood glucose levels of individuals 

suffering from diabetes. Implantation of the device is 

“[p]referably . . . beneath the surface of the skin” or near 

the peritoneal cavity, putting the sensor directly in contact 

with biological fluids such as peritoneal or interstitial fluid, 

but not blood. Id. at col. 3 ll. 40–42, col. 6 ll. 58–67 (“All of 

the body tissues come into glucose equilibrium with the 

blood fairly rapidly[,] . . . [such that] placement of the device in contact with the blood is not . . . required.”). The 

sensor includes a conductive electrode in contact with a stabilized enzyme emulsion comprising: (1) an oxidase 

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enzyme (e.g., glucose oxidase) and (2) a compound in which 

oxygen is extremely soluble (e.g., a perfluorocarbon liquid). 

Id. at Abstract. The enzyme emulsion can be stabilized by 

crosslinking the proteins (i.e., the oxidase enzyme and any 

carrier proteins) in the emulsion to form a gel. Id. at col. 8 

ll. 29–41, col. 9 ll. 16–25.

Measurement of the blood glucose level occurs via an 

electrochemical reaction. Id. at col. 2 ll. 43–58. In the presence of oxygen, the oxidase enzyme oxidizes glucose, generating hydrogen peroxide. Id. The hydrogen peroxide 

then acts as an “electron carrier,” moving “electrons from 

glucose (by way of glucose oxidase) to the electrode.” Id. at 

col. 11 ll. 34–39. At the surface of the electrode, removal of 

electrons from hydrogen peroxide results in a measurable 

current. Id. Therefore, hydrogen peroxide serves as a “direct measure” of blood glucose levels. Id. at col. 2 ll. 52–54. 

A challenge in developing glucose sensors is the limited 

amount of oxygen available to the oxidase enzyme. Id. at 

col. 4 ll. 10–13. Unlike glucose, oxygen is poorly soluble in 

biological fluids, resulting in a high glucose-to-oxygen ratio. Id. at col. 3 ll. 33–45. As a consequence, implantable 

glucose sensors “effectively measure [the amount of] oxygen instead of, or together with, [the amount of] glucose.” 

Id. at col. 4 ll. 10–17. Emulsifying the oxidase enzyme in 

the sensor with a compound in which oxygen is extremely 

soluble, as described in the invention of the ’225 patent, 

creates an oxygen reservoir, increasing the amount of oxygen available to the oxidase enzyme, reducing the electrode’s sensitivity to oxygen, and correcting the glucoseoxygen imbalance. Id. at col. 5 ll. 20–25, col. 8 l. 61–col. 9 

l. 6. Oxygen is no longer the limiting agent in the electrochemical reaction, enabling accurate measurement of blood 

glucose levels.

In January 2018, Arbmetrics filed a patent infringement action against Dexcom asserting infringement of 

claims 1, 2, 5, 7, and 8 of the ’225 patent. J.A. 2. During 

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4 ARBMETRICS, LLC v. DEXCOM INC.

claim construction, the district court construed seven 

terms. On appeal, Arbmetrics disputes five of these constructions. Claims 1 and 5 include the terms at issue.

Claim 1 is directed to an implantable sensor and recites:

1. An implantable sensor for sensing a concentration of an organic substrate, the sensor comprising:

a conductive electrode; and

a stabilized enzyme emulsion in contact with the 

electrode, the enzyme emulsion comprising:

an oxidase enzyme that quantitatively oxidizes the 

organic substrate;

a water immiscible oxygen dissolving substance 

emulsified into intimate contact with the enzyme 

to provide oxygen; and

a protein crosslinking agent to crosslink and insolubilize the enzyme forming a stabilized gel comprising crosslinked protein and particles of said 

oxygen dissolving substance.

’225 patent at claim 1 (emphases added to disputed terms).

Claim 5 depends from claim 1 and recites:

5. The implantable sensor of claim 1, wherein the 

oxygen dissolving substance is selected from the 

group consisting of perfluorocarbons, silicone oils, 

fluorosilicone oils, aromatic and aliphatic hydrocarbon oils or solids, carotenoids and steroids.

Id. at claim 5 (emphases added to disputed terms).

Relevant to this appeal, the district court adopted the 

following construction for oxygen dissolving substance: “a 

substance in which oxygen is preferentially soluble in comparison to water.” Claim Construction Order, 2019 WL 

7290541, at *9. The district court rejected Arbmetrics’s

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proposal to construe oxygen dissolving substance to mean 

“a substance (a particular kind of matter with uniform 

properties) having a higher oxygen solubility or higher oxygen permeability than at least one of a hydrocarbonaceous 

polymer and an oxyhydrocarbon polymer.” Id. at *8; J.A. 

1727. 

In view of the Claim Construction Order, the parties 

stipulated the following: “Arbmetrics and Dexcom agree 

that all of Dexcom’s accused products do not meet either 

the ‘emulsion’ or the ‘oxygen dissolving substance’ limitations of all asserted claims of the ʼ225 patent as construed 

by the [district court].” J.A. 2. The district court then entered final judgment of noninfringement in favor of Dexcom. J.A. 7–8. Arbmetrics appeals to this court. We have 

jurisdiction over the appeal pursuant to 28 U.S.C.

§ 1295(a)(1).

DISCUSSION

Arbmetrics challenges the district court’s construction 

of the following terms: “oxygen dissolving substance,” 

“emulsion,” “in contact with,” “electrode,” and “hydrocarbon oils or solids.” We address only the district court’s construction of oxygen dissolving substance as it dispositive in 

view of Arbmetrics’s stipulation of noninfringement. See

Starhome GmbH v. AT&T Mobility LLC, 743 F.3d 849, 854 

(Fed. Cir. 2014) (“Where, as here, a plaintiff concedes noninfringement by stipulation, we need only address the district court’s construction of the pertinent claim [term].”); 

see also Altiris, Inc. v. Symantec Corp., 318 F.3d 1363, 1368 

(Fed. Cir. 2003) (noting that when a party stipulates to 

noninfringement following claim construction, “we need 

only address the district court’s construction of the [relevant] claims”).

Claim construction is a question of law. Teva Pharms. 

USA, Inc. v. Sandoz, Inc., 135 S. Ct. 831, 841–42 (2015). 

“[W]hen the district court reviews only evidence intrinsic 

to the patent (the patent claims and specifications, along 

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with the patent’s prosecution history),” we review that construction de novo. Id. at 841. We review any “subsidiary

factual findings [on extrinsic evidence] under the ‘clearly 

erroneous’ standard.” Id. at 838.

Arbmetrics argues that the district court’s construction 

of oxygen dissolving substance is “incorrect for two reasons: 

(1) it incorrectly defines the term in relation to the [oxygen] 

solubility of water instead of adopting the patentee’s disclaiming statements made during prosecution, and (2) it 

defines the term only in relation to solubility instead of solubility or permeability.” Appellant’s Br. at 22. Pointing to 

the prosecution history, Arbmetrics contends that patentee 

excluded graphite, nylon, polyethylene, and polystyrene 

from the definition of oxygen dissolving substance when 

distinguishing the invention over the prior art, an “unequivocal disclaimer that must be accounted for in the construction of the term ‘oxygen dissolving substance.’” Id. at 

23. Regarding inclusion of permeability as an alternative 

to solubility in the term’s construction, Arbmetrics argues 

that “the ’225 patent specification uses the concepts of oxygen permeability and solubility interchangeably in the 

context of a material’s ‘oxygen dissolving’ properties.” Id.

at 27. Arbmetrics thus concludes “that the term ‘oxygen 

dissolving substance’ should be construed to mean: ‘a substance having a higher oxygen solubility or higher oxygen 

permeability than particles of graphite, polyethylene, polystyrene, and nylon.’” Id. at 28. We disagree.

While we begin our claim construction analysis with 

the language of the claim itself, see Phillips v. AWH Corp., 

415 F.3d 1303, 1312 (Fed. Cir. 2005) (en banc), the claims 

“do not stand alone. Rather, they are part of ‘a fully integrated written instrument,’ . . . consisting principally of a 

specification that concludes with the claims,” id. at 1315 

(quoting Markman v. Westview Instruments, Inc., 52 F.3d 

967, 978 (Fed. Cir. 1995) (en banc)). “For that reason, 

claims ‘must be read in view of the specification, of which 

they are a part.’” Phillips, 415 F.3d at 1315 (quoting

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Markman, 52 F.3d at 979). Additionally, we recognize that 

“the prosecution history can often inform the meaning of 

the claim language by demonstrating how the inventor understood the invention.” Id. at 1317. But the prosecution 

history “is less useful for claim construction” than the claim 

language and written description. Id. 

The written description supports the district court’s 

use of water rather than substances such as graphite and 

polyethylene as the benchmark for construing oxygen dissolving substance. A goal of the ’225 patent’s invention is 

to address “impediments to successful implantable glucose 

sensors.” ’225 patent col. 3 ll. 33–45. These impediments 

include the limited availability of oxygen—due to its poor 

solubility—in the biological fluids surrounding the sensor. 

Id. Because the oxygen dissolving substance functions to 

resolve this issue by concentrating oxygen in the sensor, 

that substance must be one in which oxygen has a greater

solubility than it does in the surrounding biological fluids. 

See Apple Comput., Inc. v. Articulate Sys., Inc., 234 F.3d 

14, 25 (Fed. Cir. 2000) (“[A] claim must be interpreted in 

light of the teachings of the written description and purpose of the invention described therein.”). 

Importantly, the solubility of oxygen in the surrounding biological fluids is close to the solubility of oxygen in 

water,1 making water a suitable proxy for the fluids. Moreover, the written description disparages water as a poor oxygen dissolving substance as compared to the examples of 

substances the patent identifies as serving as an oxygen 

dissolving substance for purposes of the invention. See, 

e.g., ’225 patent col. 10 ll. 25–30 (“Because the perfluorocarbon is emulsified into tiny particles, there is an intimate 

1 At oral argument, Arbmetrics acknowledged that 

the solubility of oxygen in the bodily fluids abutting the 

glucose sensor was close to the solubility of oxygen in water. Oral Arg. at 2:55–4:20.

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association between the oxygen carrying perfluorocarbon 

and the oxygen-requiring enzyme. This limits the distance 

that oxygen must diffuse through a poor oxygen carrier 

such as water.”); col. 13 ll. 2–4 (“An advantage is that steroids, like perfluorocarbons, are much better at dissolving 

oxygen than is water.”). We therefore agree with the district court that, in view of the written description, water is 

the correct benchmark for construing oxygen dissolving 

substance.

Turning next to the prosecution history, nothing 

therein dictates use of an alternative benchmark or construction. Arbmetrics argues that graphite, nylon, polyethylene, and polystyrene, i.e., substances allegedly 

disclaimed during prosecution, see Appellant’s Br. at 23, 

are the appropriate references for construing the term oxygen dissolving substance. But use of these substances as 

benchmarks would broaden the claims beyond what is disclosed in the written description: graphite, nylon, polyethylene, and polystyrene all have lower oxygen solubility 

than water.2 See J.A. 3483 (“Oxygen is not preferentially 

soluble in graphite—it is barely soluble at all. Nor is oxygen particularly soluble in nylon, polyethylene, or polystyrene.”). Accordingly, Arbmetrics’s suggested construction

is impermissible as “[r]epresentations [made] during prosecution cannot enlarge the content of the specification.” Biogen, Inc. v. Berlex Labs., Inc., 318 F.3d 1132, 1140 (Fed. 

Cir. 2003); see also Honeywell Int’l, Inc. v. ITT Indus., Inc., 

452 F.3d 1312, 1319 (Fed. Cir. 2006) (“Where, as here, the 

written description clearly identifies what his invention is, 

2 At oral argument, Arbmetrics explained that it 

wanted the term oxygen dissolving substance to capture a 

wider range of substances and that graphite, nylon, polyethylene, and polystyrene have a decidedly lower oxygen 

solubility than water or bodily fluids. Oral Arg. at 5:02–

5:49.

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an expression by a patentee during prosecution that he intends his claims to cover more than what his specification 

discloses is entitled to little weight.”). Arbmetrics’s proposed construction, which relies on a benchmark that is 

“barely soluble at all,” is also plainly inconsistent with the 

purpose of the invention: to create an oxygen reservoir in 

the glucose sensor through use of a substance with high 

oxygen solubility.

Last, we cannot accept Arbmetrics’s proposal to include 

permeability as an alternative to solubility in the construction of oxygen dissolving substance. Appellant’s Br. at 26, 

28 (submitting that either “higher oxygen solubility or

higher oxygen permeability” can be used as measures of a 

substance’s oxygen dissolving properties (emphasis 

added)). Although the written description may contemplate oxygen dissolving substances having both high oxygen solubility and permeability, see ’225 patent col. 8 ll. 48–

54, nothing in the claims, written description, or prosecution history supports an understanding of “oxygen dissolving substance” as having high oxygen permeability without 

high oxygen solubility. As a result, we agree with the district court that “permeability has no place in the construction of this term.” Claim Construction Order, 2019 WL 

7290541, at *8. 

Thus, we affirm the district court’s claim construction 

that an “oxygen dissolving substance” is “a substance in 

which oxygen is preferentially soluble in comparison to water.” Because the district court’s construction is correct and 

Arbmetrics conceded noninfringement by stipulation under this construction, we affirm the judgment of noninfringement. 

CONCLUSION

We have considered the parties’ remaining arguments 

but find them unpersuasive. For the foregoing reasons, we 

conclude that the district court properly construed the term 

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10 ARBMETRICS, LLC v. DEXCOM INC.

oxygen dissolving substance and properly entered final 

judgment of noninfringement. Therefore, we affirm.

AFFIRMED

COSTS

Costs to appellee.

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