Document ID: s3://data.kl3m.ai/documents/govinfo/USCOURTS/USCOURTS-ca13-19-01648/USCOURTS-ca13-19-01648-0/pdf.json

Parties Involved:
Alere Toxicology Services, Inc.
Cross-Appellant
Alere, Inc.
Cross-Appellant
Innovacon, Inc.
Cross-Appellant
Instant Technologies, Inc.
Cross-Appellant
Rembrandt Diagnostics, LP
Appellant

Document Text:

NOTE: This disposition is nonprecedential.

United States Court of Appeals 

for the Federal Circuit ______________________

REMBRANDT DIAGNOSTICS, LP,

Plaintiff-Appellant

v.

ALERE, INC., ALERE TOXICOLOGY SERVICES, 

INC., INNOVACON, INC., INSTANT 

TECHNOLOGIES, INC.,

Defendants-Cross-Appellants

______________________

2019-1595, 2019-1648

______________________

Appeals from the United States District Court for the 

Southern District of California in No. 3:16-cv-00698-CABNLS, Judge Cathy Ann Bencivengo.

______________________

Decided: April 10, 2020 

______________________

JOSEPH F. JENNINGS, Knobbe, Martens, Olson & Bear, 

LLP, Irvine, CA, argued for plaintiff-appellant. Also represented by JARED C. BUNKER; ASHLEY C. MORALES, San 

Diego, CA. 

 JASON M. WILCOX, Kirkland & Ellis LLP, Washington, 

DC, argued for defendants-cross-appellants. Also 

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2 REMBRANDT DIAGNOSTICS, LP v. ALERE, INC.

represented by HANNAH LAUREN BEDARD, JOHN C.

O'QUINN; JAMES F. HURST, AMANDA J. HOLLIS, Chicago, IL.

 ______________________

Before WALLACH, MAYER, and STOLL, Circuit Judges.

STOLL, Circuit Judge.

These appeals arise from an action for patent infringement. Rembrandt Diagnostics, LP sued Alere, Inc., Alere 

Toxicology Services, Inc., Innovacon, Inc., and Instant 

Technologies, Inc. (collectively, “Alere”), alleging that 

Alere’s products infringe claims 3–6 and 10 of Rembrandt’s 

U.S. Patent No. 6,548,019, directed to devices for collecting 

and assaying biological fluid samples. Prior to trial, Rembrandt stipulated to a judgment of noninfringement of 

claims 3–6 in light of the district court’s construction of a 

disputed claim limitation. During the trial, the district 

court construed another disputed claim limitation, and the 

jury rendered a verdict of noninfringement and no invalidity as to claim 10. Rembrandt now challenges the district 

court’s constructions of the two disputed claim limitations. 

Alere cross-appeals, requesting that this court order a new 

trial on validity of claim 10 if it remands for a new trial on 

infringement of that claim. Because we conclude that the 

intrinsic evidence supports Rembrandt’s proposed constructions, we vacate the district court’s judgments and remand for further proceedings as to claims 3–6 and a new 

trial on both infringement and validity for claim 10.

BACKGROUND

I

The ’019 patent “relates to immunoassay devices and 

methods for collection and assaying of biological fluids, particularly urine.” ’019 patent col. 1 ll. 15–17; see also id.

at Abstract. In particular, the patent discloses a “means 

for controlling assay sample fluid flow through an assay 

test strip,” wherein “fluid flow control is accomplished by 

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placing the assay test strip within a flow control channel in 

which the ambient pressure within the flow control channel is maintained in substantial equilibrium with the ambient pressure outside the flow control channel.” 

Id. at col. 1 ll. 40–47. “By avoiding the formation of a pressure gradient within the flow control channel,” the device 

of the ’019 patent minimizes “the risk of oversaturation of 

the test strip on introduction into an assay sample fluid.” 

Id. at col. 1 ll. 48–55. 

Figure 3 illustrates a front view of the preferred embodiment of the ’019 patent. Id. at col. 2 ll. 18–19. 

Id. Fig. 3. In this embodiment, the sample loading zone 

(30) of the assay test strip (22) partially extends beyond the 

opening of the flow control channel (34). The specification 

explains that “[a]ssay sample fluid control in this embodiment . . . is accomplished by disposing assay test strip 22 

within a flow control channel.” Id. at col. 5 ll. 57–59.

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Figure 4 illustrates a cross-section of the top portion of 

Figure 3. Id. at col. 2 ll. 20–21. 

Id. Fig. 4. The flow control channel “has five liquid impervious walls 35, 35A, 35B, 35C and backing 28, and one liquid pervious side consisting of an opening 36 through 

which sample loading zone 30 of assay test strip 22 protrudes.” Id. at col. 6 ll. 11–16; see also id. at col. 6 ll. 38–40

(“Open end 36 has an opening 37 which is loosely fitted 

around test strip 22, whose sample loading zone 30 protrudes beyond opening 37.”). 

Figure 6 shows a “front view of an assay sample fluid 

collection device of the invention, into which is inserted the 

dipstick assay means of” Figures 3 and 4. Id. at col. 2 

ll. 24–27. 

Id. Fig. 6. 

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Claim 1, the only independent claim of the ’019 patent,

recites the two disputed claim limitations:

1. A device for collecting and assaying a sample of 

biological fluid, the device comprising:

(a) a flow control channel defined by at least one 

liquid pervious side joined to liquid impervious 

sides, wherein the internal dimensions of the flow 

control channel are sufficient to permit placement 

therein of an assay test strip;

(b) an assay test strip within the flow control channel, wherein the assay test strip has a sample loading zone therein, and wherein further the assay test 

strip is disposed within the flow control channel so 

the sample fluid contacts the sample loading zone 

at a liquid pervious side of the flow control channel; 

and

(c) a sample fluid container having a base, an open 

mouth, and walls connecting the base to the 

mouth;

wherein the flow control channel is disposed inside 

the sample fluid container with the liquid pervious 

side oriented toward the base of the sample fluid 

container so that the assay sample fluid, when 

added to the container, is delivered to the sample 

loading zone of the assay test strip by entry 

through a liquid pervious side of the flow control 

channel without migration through an intermediate structure, and wherein entry of fluid into the 

flow control channel creates an ambient pressure 

within the flow control channel equivalent to the 

ambient pressure outside of the flow control channel, thereby eliminating a pressure gradient along 

which excess sample fluid could flow into the flow 

control channel.

Id. at col. 8 l. 42–col. 9 l. 2 (emphases added).

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The claims at issue on appeal are dependent claims 3–

6 and 10. Claim 10 requires that “all of the assay test 

strips” in the device “are disposed in a single flow control 

channel.” Id. at col. 10 ll. 5–6. None of the limitations of 

claims 3–6 or 10 is in dispute. 

II

Rembrandt accused four Alere urine test cup products

of infringing claims 3–6 of the ’019 patent: the iCup DX Pro, 

AmediCheck, DrugSmart, and UScreen.1 Rembrandt alleged that these four products were copies of the preferred 

embodiment illustrated in Figures 3, 4, and 6 of the 

’019 patent. Rembrandt also accused a fifth Alere urine 

test cup product—the iCup A.D.—of infringing claim 10. 

Rembrandt alleged that unlike the other four accused products, the assay test strips of the iCup A.D. are disposed in

a single flow control channel, as required by claim 10, and 

do not protrude from the end of the channel. 

As noted above, there are two claim limitations at issue 

on appeal: “the assay test strip is disposed within the flow 

control channel” in claim 1 and the claims that depend from 

claim 1 (the “disposed within” limitation); and “entry of 

fluid into the flow control channel creates an ambient pressure within the flow control channel equivalent to the ambient pressure outside of the flow control channel” in 

1 In a parallel inter parties review proceeding, Rembrandt disclaimed claims 1, 9, and 11–15 of the ’019 patent, 

leaving only claims 2–5 in dispute. Because the Board did 

not institute review of all claims and grounds in the IPR 

petition, this court vacated the Board’s patentability determinations as to claims 2–5, and remanded for the Board to 

review all claims and grounds included in the petition pursuant to SAS Institute, Inc. v. Iancu, 138 S. Ct. 1348 (2018). 

Alere, Inc. v. Rembrandt Diagnostics, LP, 791 F. App’x 173, 

178 (Fed. Cir. 2019).

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claim 1 and the claims that depend from claim 1 (the 

“equivalent to” limitation).

Prior to trial, the district court construed the “disposed 

within” limitation to require that “the assay test strip is 

disposed entirely within the flow control channel.” Rembrandt Diagnostics, L.P. v. Innovacon, Inc., No. 16–698, 

2017 WL 6059129, at *4 (S.D. Cal. Dec. 7, 2017) (Claim 

Construction Op.) (emphasis added). Rembrandt had proposed that the limitation should be “accorded its plain and 

ordinary meaning” and that, to the extent the court construed the limitation, it should mean “the assay test strip 

is placed or arranged within the flow control channel.”

J.A. 2932. The district court rejected this proposed construction, which would allow the assay test strip to “protrude at the pervious end such that the sample loading 

zone of the strip extends beyond the channel in the manner 

described in the specification and depicted in Figure 3.” 

Claim Construction Op., 2017 WL 6059129, at *3 (citations 

omitted). While acknowledging that a “claim interpretation that excludes a preferred embodiment from the scope 

of the claim is rarely, if ever, correct,” the district court 

nonetheless determined that the “unambiguous” claim language and the prosecution history “result[ed] in the exclusion of a preferred embodiment that teaches the loading 

zone can protrude from the channel.” Id. at *4 (citations 

omitted).

Following the district court’s construction of the “disposed within” limitation, Rembrandt stipulated to the district court’s entry of judgment that none of accused 

products iCup DX Pro, AmediCheck, DrugSmart, or 

UScreen infringed claims 3–6 of the ’019 patent “because 

the test strips in such products are not ‘disposed entirely 

within the flow control channel.’” Pretrial Order at 3, Rembrandt Diagnostics, LP v. Alere, Inc., No. 16–698 (S.D. Cal. 

Nov. 19, 2018), ECF No. 312. 

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The case then proceeded to a jury trial solely concerning the validity of claim 10 and the iCup A.D. product’s alleged infringement thereof. During the trial, the district 

court construed the “equivalent to” limitation in claim 1 to 

mean “equal to.” J.A. 10941 at 434:12–17. The district 

court rejected Rembrandt’s proposed construction of the

disputed limitation to mean “in equilibrium with.” The district court thereafter instructed the jury that “equivalent 

to” was defined as “equal to.” The jury found that the iCup 

A.D. product did not infringe claim 10, and that claim 10 

was not invalid for anticipation or obviousness. 

Rembrandt and Alere appeal. We have jurisdiction 

pursuant to 28 U.S.C. § 1295(a)(1).

DISCUSSION

We start by addressing Rembrandt’s challenge to the 

district court’s constructions of the two disputed claim limitations: the “disposed within” limitation and the “equivalent to” limitation. We then turn to Alere’s cross-appeal, in 

which it contends that if this court remands for a new trial 

on infringement for claim 10, it should order a new trial on 

validity as well.

I

Claim construction based on the intrinsic evidence is a 

question of law that this court reviews de novo. Trustees of 

Columbia Univ. v. Symantec Corp., 811 F.3d 1359, 1362 

(Fed. Cir. 2016). “The construction of claim terms based on 

the claim language, the specification, and the prosecution 

history are legal determinations.” Id. The two claim construction disputes in this case present close questions. 

Based on our review of the claim language, specification, 

and prosecution history, however, we conclude that the district court erred in construing the disputed claim limitations.

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A

We consider first Rembrandt’s challenge to the district 

court’s construction of “disposed within.” At the outset, we 

recognize that the language of claim 1 is ambiguous. The 

parties’ arguments focus on two specific phrases in claim 1. 

First, the device of claim 1 comprises an “assay test strip” 

that is “disposed within the flow control channel so the 

sample fluid contacts the sample loading zone at a liquid 

pervious side of the flow control channel.” ’019 patent col. 8 

ll. 42–54 (emphases added). Second, the device is arranged 

in such a way that the “assay sample fluid, when added to 

the container, is delivered to the sample loading zone of the 

assay test strip by entry through a liquid pervious side of 

the flow control channel without migration through an intermediate structure.” Id. at col. 8 ll. 57–64 (emphasis 

added). 

Both parties present reasonable arguments about how 

the disputed limitation should be understood based on this 

claim language. Alere contends that the district court’s 

construction is correct because if the test strip were to “protrude” from the flow control channel, the sample fluid 

would contact the strip before the fluid reaches the channel. Thus, according to Alere, the fluid would not “contact”

the test strip’s loading zone “at” the liquid pervious side of 

the channel, as required by claim 1; instead, the contact 

would happen on the protruding portion of the strip outside

of the channel. In addition, the fluid would not be “delivered” to the test strip’s loading zone “by entry through” the 

liquid pervious side of the channel, as also required by 

claim 1. 

Rembrandt’s broader construction—which encompasses devices with protruding test strips—also finds support in the claim language. Rembrandt contends that 

claim 1 does not require that the sample fluid contact the 

test strip’s loading zone “first and only precisely at the 

opening of the flow control channel and nowhere else.” 

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Appellant’s Resp. Br. 5 (emphasis in original). In Rembrandt’s view, “at” is not limited to “the singular spot of 

entry to the flow control channel” and, in fact, such a construction “would exclude a device in which the test strip is 

entirely within the flow control channel but does not extend 

to being flush with it.” Id. Rembrandt also contends that 

claim 1 does not require that the “fluid be delivered to the 

test strip ‘only’ by entry through the channel opening and 

nowhere else.” Id. In sum, the claim language does not 

definitively support one construction over the other. 

We turn next to the specification, which “is the single 

best guide to the meaning of a disputed term.” Phillips 

v. AWH Corp., 415 F.3d 1303, 1315 (Fed. Cir. 2005) (quoting Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 

1582 (Fed. Cir. 1996)). There is no dispute that the district 

court’s construction excludes the preferred embodiment of 

the ’019 patent, as depicted in Figures 3 and 4. Claim Construction Op., 2017 WL 6059129, at *4. By contrast, Rembrandt’s proposed construction encompasses the preferred 

embodiment. There is also no dispute that, in describing 

the preferred embodiment, the specification uses nearly 

identical language as the disputed claim language. Compare ’019 patent col. 8 ll. 51–52 (“the assay test strip is disposed within the flow control channel” (emphasis added)), 

with id. at col. 5 ll. 57–59 (“Assay sample fluid control in 

this embodiment of the invention is accomplished by disposing assay test strip 22 within a flow control channel 

. . . .” (emphases added)). 

Turning next to the prosecution history, we are not persuaded that the prosecution history includes a clear and 

unmistakable surrender of claims directed to a preferred 

embodiment in which test strips protrude. Nor are we persuaded that any of the inventors’ statements otherwise require a claim construction that would omit a preferred 

embodiment.

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Claim 1 was initially drafted to recite a method comprising the step of “disposing an assay test strip within the 

flow control channel,” wherein the “assay test strip is disposed within the flow control channel so the sample loading 

zone is flush with, or protrudes from, a liquid pervious side 

of the flow control channel.” J.A. 11517 (emphasis added). 

The Patent Office rejected claim 1 as anticipated by, and 

for obviousness-type double patenting over, related 

U.S. Patent Application No. 09/192,969. The ’969 application issued as U.S. Patent No. 6,379,620 (Tydings). 

Tydings shares an inventor with the ’019 patent and 

discloses and claims a device that Rembrandt refers to as 

the inventors’ “first generation drug test cup design.” Appellant’s Br. 8. Like the device recited in claim 1 of the 

’019 patent, Tydings discloses a device that uses assay test 

strips, as illustrated in Figure 3 of Tydings:

Tydings Fig. 3. The prior art Tydings device is also depicted in Figures 1 and 2 of the ’019 patent. 

The Tydings device uses a wicking material, such as 

filter paper or fiber glass, which “extends substantially the 

full length of the backing” of the cup. Id. at col. 2 ll. 40–45. 

As shown in Figure 3, the “top portion of the reagent strip 

12 is bent over the top edge 15 of the backing 8 and overlapped onto the wicking paper 10.” Id. at col. 2 ll. 65–67. 

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Urine “wicks up the wicking material 10 until it reaches 

the overlapped portions of the assay strips 12,” and then 

“wicks over the top edge of the backing 8 and down the assay strips 12.” Id. at col. 3 ll. 25–28. “The urine wicking 

down the assay strips 12 will react with the chemical 

agents” on the strip and “will give positive, negative or inconclusive test results.” Id. at col. 3 ll. 28–31. 

In its response to the examiner’s office action, the applicants distinguished Tydings on the ground that the 

claimed invention:

provides a flow control channel whereby the sample is delivered directly to the sample loading 

zone 30 of assay strip 22 through a liquid pervious 

side 36 (as opposed to having the fluid migrate 

through an intermediate structure, such as wicking material 10 of FIGS. 1 and 2 [the ’969 device]

. . . ).

J.A. 11613 (underlining omitted). In addition, the applicants amended claim 1 to recite a device and added the requirement that “the assay sample fluid, when added to the 

container, is delivered directly to the sample loading zone 

through a liquid pervious side of the flow control channel.” 

J.A. 11601 (emphasis added). 

The patent examiner was not convinced and maintained the rejections based on Tydings. The applicants 

thereafter amended claim 1 to recite, in relevant part, that 

“the assay test strip is disposed within the flow control 

channel so the sample fluid contacts the sample loading 

zone at a liquid pervious side of the flow control channel.” 

J.A. 11674 (emphases added). At the same time, the applicants removed the requirement that the test strip’s sample 

loading zone “is flush with, or protrudes from,” a liquid pervious side of the channel. Id. The applicants further

amended the claim to recite that fluid is “delivered directly 

to the sample loading zone of the assay test strip through 

a liquid pervious side of the flow control channel without 

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migration through an intermediate structure.” Id. (emphasis added). The applicants reiterated to the examiner that, 

in contrast to the Tydings device, the claimed invention did 

not use an intermediate structure. 

Shortly thereafter, the applicants further amended 

claim 1 to recite that “the assay sample fluid, when added 

to the container, is delivered to the sample loading zone of 

the assay test strip by entry through a liquid pervious side 

of the flow control channel without migration through an 

intermediate structure,” and removed the requirement 

that the fluid is delivered “directly” to the loading zone. 

J.A. 11688 (emphasis added). The applicants explained 

that their invention “improves upon previous devices by 

preventing the flooding of test strips by constructing a flow 

channel around the strips,” and that the liquid pervious 

side of the channel “limit[s] the rate at which sample will 

flow into the channel to contact the sample loading zone on 

the assay strips.” J.A. 11686 (emphases added). 

Alere’s argument that the applicants’ amendments 

during prosecution support a narrower construction has 

some merit. Ultimately, however, we disagree with Alere 

and the district court that the applicants narrowed the 

scope of claim 1 during prosecution to cover only devices 

with test strips that are disposed “entirely” within the flow 

control channel. In particular, the applicants did not 

merely remove “protrudes from” in claim 1; rather, they removed “is flush with, or protrudes from.” J.A. 11674. In 

addition, the applicants never distinguished the Tydings

device (or any other prior art device) on the ground that the 

claimed test strips cannot protrude beyond the channel. 

Instead, the applicants expressly distinguished the 

Tydings device on the basis that Tydings used an intermediate structure, and amended the claims to exclude the use 

of such intermediate structure. And although the additions of the “by entry” and “contact . . . at” language in 

claim 1 were made in conjunction with, or shortly after, removal of the “flush with, or protrudes from” language, 

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these additions were also made when the applicants 

amended claim 1 to exclude the use of an intermediate 

structure. Alere emphasizes that claim 1 was amended to 

exclude the protruding strips embodiment while still covering the flush strips embodiment based on the added language that “the sample fluid contacts the sample loading 

zone at a liquid pervious side of the flow control channel.” But, as we have already discussed, this language is 

at best ambiguous and does not require a construction that 

the strips must be contacted only at a particular location. 

Contrary to the district court’s suggestion, Elekta Instrument S.A. v. O.U.R. Scientific International, Inc., 

214 F.3d 1302 (Fed. Cir. 2000), does not “compel[] adopting 

[a] construction excluding [the preferred] embodiment” of 

protruding strips based on the applicants’ amendments in 

this case. Claim Construction Op., 2017 WL 6059129, at *4 

(citing Elekta, 214 F.3d at 1308). In Elekta, the claim at 

issue expressly required gamma units with radiation 

sources “only within a zone extending between latitudes 

30°–45°.” 214 F.3d at 1306. The preferred embodiment 

disclosed sources between 0°–45°, and the district court 

construed the claim to cover sources beginning at 0° and 

extending to a point between 30°–45°. Id. at 1306–07. We

held that the district court’s construction was inconsistent 

with the “unambiguous” claim language, which “controls 

over any contradictory language in the written description.” Id. at 1308. In light of the unambiguous claim language and the prosecution history—in which the 

applicants expressly limited their invention to sources located exclusively between 30° and 45°—this court held that 

this was the “rare case” in which the construction must exclude the preferred embodiment. Id. Here, in contrast, neither the claim language nor the prosecution history 

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demonstrates that claim 1 is “susceptible of only one reasonable construction.”2 Id.

We have considered Alere’s other arguments, but we do 

not find them persuasive. Although Rembrandt’s challenge presents a close issue, we conclude that the claim language, specification, and prosecution history are more 

aligned with a broader construction that would not exclude

the preferred embodiment. Accordingly, we construe the 

“disposed within” limitation to mean “the assay test strip 

is placed or arranged within the flow control channel.”

B

We next consider Rembrandt’s challenge to the district 

court’s construction of the “equivalent to” limitation, along 

with the district court’s jury instruction based thereon. 

“An erroneous instruction regarding claim interpretation 

that affects the jury’s decision on infringement is grounds 

for a new trial.” Ecolab, Inc. v. Paraclipse, Inc., 285 F.3d 

1362, 1373 (Fed. Cir. 2002). “A party seeking to alter a 

judgment based on erroneous jury instructions must establish that ‘those instructions were legally erroneous,’ and 

that ‘the errors had prejudicial effect.’” Id. (quoting Advanced Display Sys., Inc. v. Kent State Univ., 212 F.3d 

1272, 1281 (Fed. Cir. 2000)). Whether a jury instruction is 

legally erroneous is a question of law. Id. (citing Brooktree 

2 Alere cites North American Container, Inc. 

v. Plastipak Packaging, Inc., 415 F.3d 1335 (Fed. Cir. 2005)

and Uship Intellectual Properties, LLC v. United States, 

714 F.3d 1311 (Fed. Cir. 2013), for the proposition that 

claim limitations may be construed to exclude a preferred 

embodiment if the prosecution history compels that result. 

Unlike this case, each of those cases involved narrowing 

amendments or remarks that clearly removed the preferred embodiments from the claim scope.

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Corp. v. Advanced Micro Devices, Inc., 977 F.2d 1555, 1570 

(Fed. Cir. 1992)).

This claim construction issue also presents a close 

question. Based on our review of the claim language, specification, and prosecution history, however, we conclude 

that Rembrandt’s proposed construction of the “equivalent 

to” limitation to mean “in equilibrium with” is more consistent with the intrinsic record than the construction 

adopted by the district court. We also conclude that Rembrandt has demonstrated that the jury instruction was erroneous and prejudicial.

The plain claim language suggests a broader meaning 

of “equivalent to” than “equal to.” Claim 1 recites, in relevant part, that the “entry of fluid into the flow control channel creates an ambient pressure within the flow control 

channel equivalent to the ambient pressure outside of the 

flow control channel, thereby eliminating a pressure gradient along which excess sample fluid could flow into the flow 

control channel.” ’019 patent col. 8 l. 64–col. 9 l. 2 (emphasis added). Similar to the oft-used claim term “substantially,” we consider “equivalent,” as used in claim 1, to be a 

term of degree that does not require mathematical precision. See Ecolab, Inc. v. Envirochem, Inc., 264 F.3d 1358, 

1367 (Fed. Cir. 2001) (“[T]he term ‘substantially’ is a descriptive term commonly used in patent claims to ‘avoid a 

strict numerical boundary to the specified parameter.’” (quoting Pall Corp. v. Micron Seps., 66 F.3d 1211, 

1217 (Fed. Cir. 1995))). Indeed, as Rembrandt correctly observes, the patent law doctrine of equivalents refers to the 

legal comparison of two elements that are, in fact, different, 

which supports that “equivalent” is not limited to “equal.”

If the applicants meant “equal,” they would have used the 

word “equal” rather than the broader word “equivalent.” Claim 1 neither uses the term “equal” nor refers to a 

numerical measurement, numerical comparison between 

pressures, or even the pressure unit of measurement—pascals.

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The specification also supports a broader interpretation of the claim language. The specification repeatedly 

uses terms other than “equal” to describe achieving the 

claimed result of “eliminating a pressure gradient along 

which excess sample fluid could flow into the flow control 

channel.” For example, the specification teaches:

By maintaining substantial ambient pressure equilibrium about the flow control channel, no pressure 

gradient is allowed to form along which fluid outside the flow control channel will flow into the flow 

control channel.

Id. at col. 6 ll. 28–31 (emphasis added); see also id. at Abstract, col. 1 ll. 42–47, col. 5 ll. 57–64, col. 5 l. 64–col. 6 l. 2, 

col. 6 ll. 23–31, 47–51 (referring to “equilibrium” or “substantial equilibrium”). Like claim 1, the specification never 

uses the term “equal” when discussing air pressure, nor 

does it mention pascals, pressure tests, or numerical measurements. Thus, the specification further supports Rembrandt’s construction, which “captures immaterial and 

insubstantial differences in the two pressures,” Appellant’s 

Br. 56, over a construction that requires mathematical 

equality.

We understand the district court’s view that “equivalent” could mean “equal” given the applicants’ statements 

during prosecution about the pressures inside and outside 

the channel being “equalized.” Specifically, the applicants 

argued that “the liquid pervious side of the channel serves 

as a pressure equalizer,” J.A. 11611 (emphasis added), and 

that the “present invention utilizes equalized pressure,” 

J.A. 11650 (emphasis added). But even “equalized pressure” does not mean the pressures are mathematically, 

precisely equal. For instance, when explaining the “ambient pressure” limitation and distinguishing the Tydings device, the applicants described their invention as using a 

flow control channel to create a “pressure equilibrium.” 

J.A. 11672; see also J.A. 11611 (“The present invention 

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improves upon previous devices by preventing the flooding 

of test strips by constructing a flow channel so the air pressure within it stays in substantial equilibrium with the air 

pressure outside of it.” (emphasis added)).

We have considered Alere’s other arguments, but we do 

not find them persuasive. We conclude that the district 

court’s construction imposes a mathematical or numerical 

rigor of exactness that is not supported by the intrinsic evidence. Accordingly, we construe the “equivalent to” limitation to mean “in equilibrium with.” We also hold that the 

jury instruction that included the district court’s construction was prejudicial and requires the verdict of noninfringement of claim 10 to be set aside.

II

We next turn to the issue raised in Alere’s cross-appeal. 

Because we have determined that the district court’s construction of the “equivalent to” limitation was erroneous, 

we conclude that a new trial will be necessary to determine 

whether the asserted prior art anticipates or renders obvious claim 10 under the correct construction of the “equivalent to” limitation. 

“The Federal Rules of Civil Procedure allow the courts 

to grant partial new trials so long as the issues are ‘distinct 

and separable.’” Commil USA, LLC v. Cisco Sys., Inc., 

720 F.3d 1361, 1371 (Fed. Cir. 2013) (citing Fed. R. Civ.

P. 59), vacated in part, 575 U.S. 632 (2015). “A court’s authority to grant a partial new trial is likewise constrained 

by the Seventh Amendment.” Id. (citing Gasoline Prod. Co. 

v. Champlin Refining Co., 283 U.S. 494, 500 (1931)). 

“Where the practice permits a partial new trial, it may not 

properly be resorted to unless it clearly appears that the 

issue to be retried is so distinct and separable from the others that a trial of it alone may be had without injustice.” Id. (quoting Gasoline Prod., 283 U.S. at 500).

“A partial new trial should not be granted where the issues 

to be retried are ‘so interwoven’ with other issues in the 

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REMBRANDT DIAGNOSTICS, LP v. ALERE, INC. 19

case ‘that the former cannot be submitted to the jury independently of the latter without confusion and uncertainty.’” Id. (quoting Gasoline Prod., 283 U.S. at 500).

It is true, as Rembrandt asserts, that infringement and 

validity are distinct issues and that this court previously 

stated that it “routinely orders a partial new trial on infringement, while upholding an earlier verdict on validity.” Commil, 720 F.3d at 1371 (first citing Cardiac 

Pacemakers, Inc. v. St. Jude Med., Inc., 381 F.3d 1371, 

1374 (Fed. Cir. 2004); then citing Comaper Corp. v. Antec, 

Inc., 596 F.3d 1343, 1354–55 (Fed. Cir. 2010)). Rembrandt 

contends that the correct construction of “equivalent to” 

was “not material to the jury’s rejecting Alere’s challenge 

to the validity of claim 10” because the evidence showed 

that the asserted prior art reference “failed to meet the 

‘equivalent to’ limitation even under the correct construction.” Appellant’s Resp. Br. 33. 

The testimony of Alere’s expert, however, demonstrates that the infringement and validity issues are intertwined. See, e.g., J.A. 11077–78 at 570:5–571:9; J.A. 11117 

at 610:18–20. Alere would suffer an injustice if it were not 

permitted to challenge the validity of claim 10 under Rembrandt’s proposed construction in a new trial if Rembrandt 

has another opportunity to prove infringement. See Commil, 720 F.3d at 1371. Although Rembrandt cites testimony by its expert that the asserted prior art reference 

does not disclose “a flow control channel and flow control 

capability as required by claim 10” to show that a new trial 

on invalidity is unnecessary, Appellant’s Resp. Br. 36 (citing J.A. 11130–32 at 623:25–625:9), Alere identifies contrary testimony of both parties’ experts that the reference 

does, in fact, disclose all the elements of claim 10, CrossAppellant’s Resp. Br. 4–6 (citing J.A. 11068 at 561:4–21; 

J.A. 11078–81 at 571:10–574:4; J.A. 11138–41 at 631:13–

634:15). Thus, a reasonable jury could find based on the 

evidence that the asserted prior art teaches the “equivalent 

to” limitation under the correct construction.

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20 REMBRANDT DIAGNOSTICS, LP v. ALERE, INC.

Accordingly, we remand for a new trial on both infringement and validity of claim 10 under the correct construction of the “equivalent to” limitation.

CONCLUSION

For the foregoing reasons, we vacate the district court’s 

judgment of noninfringement as to claims 3–6 and remand 

for further proceedings under the proper construction of 

the “disposed within” limitation. We also vacate the district court’s judgment of noninfringement and validity as

to claim 10 and remand for a new trial on the issues of infringement and validity of that claim under the proper construction of the “equivalent to” limitation.

VACATED AND REMANDED

COSTS

Costs to Appellant.

Case: 19-1648 Document: 3 Page: 20 Filed: 04/10/2020