Halliburton Energy Services, Inc. (“Halliburton”) appeals from a final judgment of the United States District Court for the Eastern District of Texas. Halliburton Energy Services, Inc. v. M-I LLC, No. 6:05-CV-155 (E.D.Tex. Nov. 20, 2006) (“Judgment Order”). The district court granted summary judgment in favor of MI LLC (“M-I”), holding that independent claims 1-3 and 5 and their asserted dependent claims of U.S. Patent No. 6,887,832 B2 (“the '832 patent”) were invalid as indefinite under 35 U.S.C. § 112, ¶ 2. We heard oral argument on November 7, 2007. Because a claim term in each asserted claim lacked clear meaning to the ordinary artisan, we affirm.
I.
Halliburton is the assignee of the '832 patent, which relates to oil field drilling fluids that are fragile gels. In the process of drilling such wells, drilling fluid is used for a variety of purposes, such as “removing drill cuttings from the wellbore, cooling and lubricating the drill bit, aiding in support of the drill pipe and drill bit, and providing a hydrostatic head to maintain the integrity of the wellbore walls and prevent well blowouts.” '832 patent col.l 11.27-31.
The '832 patent claims recite certain fragüe gel drilling fluids. Claim 1 for example recites:
1. A method for conducting a drilling operation in a subterranean formation using a fragile gel drilling fluid comprising:
(a) an invert emulsion base;
(b) one or more thinners;
(c) one or more emulsifiers; and
(d) one or more weighting agents, wherein said operation includes running casing in a borehole.
(emphasis added).
During prosecution, Halliburton distinguished the claims of the '832 patent from prior art fluids by stating that the claims were “limited to” a “fragile gel” drilling fluid or the method of using a “fragile gel” drilling fluid. Thus, although the term “fragile gel” appears only in the preamble of the asserted independent claims, Halliburton concedes that the claimed drilling fluids are limited to those that are “fragile gels.”
Pitney Bowes, Inc. v. Hewlett-Packard Co.,
A “fragüe gel” as used herein is a “gel” that is easüy disrupted or thinned, and that liquifies or becomes less gel-like and more liquid-like under stress, such as caused by moving the fluid, but which quickly returns to a gel when the movement or other stress is alleviated or removed, such as when circulation of the fluid is stopped, as for example when drilling is stopped. The “fragileness” of the “fragile gels” of the present invention contributes to the unique and sur *1247 prising behavior and advantages of the present invention. The gels are so “fragile” that it is believed that they may be disrupted by a mere pressure wave or a compression wave during drilling. They seem to break instantaneously when disturbed, reversing from a gel back into a liquid form with minimum pressure, force and time and with less pressure, force and time than known to be required to convert prior art fluids from a gel-like state into a flowable state.
'832 patent eol.2 11.26-42.
In May 2005, Halliburton sued M-I in the United States District Court for the Eastern District of Texas, alleging that MI’s Rheliant drilling mud system infringed certain claims of the '832 patent. M-I moved for summary judgment of invalidity, arguing that the asserted claims of the '832 patent were invalid for indefiniteness, lack of enablement, and/or lack of written description. After holding a combined
Markman
and motion hearing to address claim construction disputes as well as MI’s motion for summary judgment of invalidity, the district court granted M-I’s motion for summary judgment, finding that all asserted claims of the '832 patent were invalid as indefinite.
Halliburton Energy Serv., Inc. v. M-I LLC,
First, the district court looked at the definition of fragile gel in the specification and found that it was too subjective and unclear because it relied on terms such as “easily transitions,” “easily disrupted or thinned,” “less gel-like,” “more liquid-like,” “quickly returns to a gel,” “break instantaneously,” and “minimum pressure, force, and time.” Id. at 817. Additionally, the district court rejected Halliburton’s argument that Figure 3 (depicted below) and Figure 4 1 of the '832 patent distinguish the invention from the prior art. Id. at 822-23.
*1248 [[Image here]]
SF fluids are prior art fluids whereas ACCOLADE™ fluids have the characteristics of the invention of the '832 patent. '832 patent col.4 I.65-col.5 1.7. In Figure 3, at around the 70 minute mark, the height of the curve when stress is applied represents the strength of the gel that the fluid forms at rest, and the speed at which the curve falls back on itself indicates how quickly the gel breaks (i.e., transitions back to a liquid state). The district court found that this graph did not delineate the bounds of the invention because both prior art fluids and fluids of the invention exhibit the same shape curves (the curves of the 12.1 SF, 12.65 ACCOLADE, and 15.6 ACCOLADE fluids all fall directly back on themselves).
Halliburton,
The district court also noted that Halliburton’s proposed additional limitation to the term “fragile gel,” that it contains no or only low amounts of organophilic clay or lignite, was improperly imported from the specification, which states that the fragile gel of certain embodiments of the invention of the patent preferably does not have these clays. Id. at 824. The court found that the doctrine of claim differentiation further counseled against this construction because dependent claims added the limitation that the fluid is “substantially free of organophilic clay.” Id. at 824-25.
In November 2006, the court issued a final judgment that all asserted claims of the '832 patent were proven invalid as indefinite, held that all other issues of infringement and validity were moot, and dismissed M-I’s counterclaims without prejudice. This timely appeal followed. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).
*1249 II.
We review both a district court’s grant of summary judgment and a conclusion that a claim is indefinite under 35 U.S.C. § 112, ¶ 2
de novo. Datamize, LLC v. Plumtree Software, Inc.,
35 U.S.C. § 112, ¶ 2 requires that the specification of a patent “conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the applicant regards as his invention.” Because claims delineate the patentee’s right to exclude, the patent statute requires that the scope of the claims be sufficiently definite to inform the public of the bounds of the protected invention, i.e., what subject matter is covered by the exclusive rights of the patent. Otherwise, competitors cannot avoid infringement, defeating the public notice function of patent claims.
Athletic Alternatives, Inc. v. Prince Mfg., Inc.,
This court has applied the definiteness requirement of 35 U.S.C. § 112, ¶ 2 in numerous circumstances. For example, we have held claims indefinite where a claim recites means-plus-function elements without disclosing corresponding structure in the specification,
Biomedino, LLC v. Waters Techs. Corp.,
Of course, claims are not indefinite merely because they present a difficult task of claim construction. Instead, “[i]f the meaning of the claim is discernible, even though the task may be formidable and the conclusion may be one over which reasonable persons will disagree, we have held the claim sufficiently clear to avoid invalidity on indefiniteness grounds.”
Exxon Research & Eng’g Co. v. United States,
In this case, the district court found that the asserted claims, which contained the limitation that the drilling fluid be a “fragile gel,” were indefinite. “Only claims ‘not amenable to construction’ or ‘insolubly ambiguous’ are indefinite.”
Datamize,
Halliburton argues that “fragile gel” as used in the asserted claims is definite and has a three-part definition:
1) A gel that easily transitions to a liquid state upon the introduction of force (e.g., when drilling starts) and returns to a gel when the force is removed (e.g., when drilling stops); and
2) At rest, is capable of suspending drill cuttings and weighting materials; and
3)Contains no organophilic clay or or-ganophilic lignite or can contain low amounts of organophilic clay or lignite individually or in combination so that the fragile gel can still easily transition between a gel and liquid state and suspend drill cuttings and weighting materials.
We address the third part of Halliburton’s definition (no or low organophilic clay or lignite) first, and conclude that “fragile gels” that have no or low organophilic clay or lignite are merely preferred embodiments of the invention covered by certain dependent claims, and thus “fragile gel” as used in the independent claims is not limited to those embodiments.
The specification of the '832 patent states that one of the advantages of the invention is that it “suspends drill cuttings through its gel or gel-like characteristics, without need for organophilic clays to add viscosity to the fluid.” '832 patent col.2 11.48-51 (emphasis added). It also states that “preferably no organophilic clays are added to the drilling fluid for use in the invention.” Id. at col.3 11.51-53 (emphasis added).
Contrary to Halliburton’s argument, nothing in the specification of the '832 patent requires the fragile gel drilling fluid *1251 as claimed to have low or no organophilic clay. Instead, the specification merely says there is no need for such clays. Absence of need for a component does not necessarily mean that that component is absent, or present only in low amounts. Additionally, the specification states that “preferably” none of these clays are added; this strongly suggests that absence of clays is simply a preferred embodiment. This reading is reinforced by the dependent claims: claims 20, 58, 95, 125 add the limitation that the fluid is “substantially free of organophilic clay.” Thus, a requirement of low or no organophilic clays is not properly part of the construction of “fragile gel” as contained in the asserted independent claims.
We next review the remainder of Halliburton’s proposed definition. The first two parts of Halliburton’s definition (i.e., that fragile gels are those that easily transition to a liquid state upon the introduction of force and return to a gel when the force is removed, and those that are capable of suspending drill cuttings and weighting materials at rest) are indeed supported by the specification. Regarding the first part, the specification states:
A “fragile gel” as used herein is a “gel” that is easily disrupted or thinned, and that liquifies or becomes less gel-like and more liquid-like under stress, such as caused by moving the fluid, but which quickly returns to a gel when the movement or other stress is alleviated or removed, such as when circulation of the fluid is stopped, as for example when drilling is stopped.
'832 patent col.2 11.26-33. And regarding the second part:
When drilling is stopped while using a drilling fluid of the present invention, and consequently the stresses or forces associated with drilling are substantially reduced or removed, the drilling fluid forms a gel structure that allows it to suspend drill cuttings and weighting materials for delivery to the well surface.
Id. at col.2 11.43-48.
The fact that Halliburton can articulate a definition supported by the specification, however, does not end the inquiry. Even if a claim term’s definition can be reduced to words, the claim is still indefinite if a person of ordinary skill in the art cannot translate the definition into meaningfully precise claim scope. Having reviewed the remaining two parts of Halliburton’s proposed construction, both individually and in combination, in the context of the intrinsic record and the knowledge of a person of ordinary skill in the art, we hold that the ambiguity as to the scope of “fragile gel” cannot be resolved.
Halliburton argues that the first part of its definition (i.e., a gel that easily transitions from gel to liquid and back again) is sufficiently objective so that a skilled artisan would understand the limits of the claimed “fragüe gel.” Halliburton primarily focuses on the L-shaped curve shown in Figure 3 of the '832 patent. 3 *1252 According to Halliburton, a person of ordinary skill in the art would have interpreted Figure 3 as requiring that fragile gels of the invention exhibit “L-shaped” curves when tested with an off-the-shelf Brook-field viscometer. Figure 3 shows Brook-field test data for two fluids of the '832 patent (ACCOLADE) and two prior art fluids (SF). Halliburton argues that the key feature of the L-shaped curve is that it falls directly back onto itself when force is applied. While Halliburton admits that the prior art 12.1 SF fluid also exhibits this very same feature, it notes that the heavier 15.6 SF fluid does not. Halliburton argues, however, that whether the pri- or art (i.e., 12.1 SF fluid) is covered by the claim as construed is properly addressed in validity challenges of other types (anticipation, obviousness, etc.) rather than in claim construction or in evaluating definiteness. We disagree that the evaluation of a claim’s definiteness cannot include whether the patent expressly or at least clearly differentiates itself from specific prior art. Such differentiation is an important consideration in the definiteness inquiry because in attempting to define a claim term, a person of ordinary skill is likely to conclude that the definition does not encompass that which is expressly distinguished as prior art.
Of course, that is not to suggest that a claim can never be definite and yet read on the prior art. For example, a claim that recites a specific numeric range for a physical property may be definite even though prior art products fell within that range. In such a case, a person of ordinary skill in the art would know the boundaries of the claim, and the focus would properly be on other validity challenges (e.g., anticipation).
This case presents a different situation, however. Here, in describing Figure 3, the figure on which Halliburton primarily relies in asserting that “fragile gel” is definite, the patent specification stated that Figure 3 distinguished the fluids of the invention (ACCOLADE) from the prior art fluids (SF):
FIG. 3 indicates superior response and performance by the drilling fluids of the present invention. Not only do the fluids of the present invention build up more gel when at rest, which enables the fluids of the invention to better maintain weight materials and drill cuttings in suspension when at rest — a time prior art fluids are more likely to have difficulty suspending such solid materials— but the fluids of the present invention nevertheless surprisingly provide less resistance to the sheer, which will result in lower ECDs as will be discussed further below.
'832 patent col.6 II.5-14 (emphases added). A person of ordinary skill would not have ignored these explicit teachings, but rather would have looked to Figure 3 to try to determine the bounds of the claims.
*1253
Thus, we reject Halliburton’s assertion that a “fragile gel” can be defined by an L-shaped curve alone because the specification does not distinguish how the “fragile gels” claimed in the '832 patent performed differently than the disclosed prior art— how much more quickly the gels broke when stress was imposed or how much more quickly the gels reformed when stress was removed. Halliburton’s failure to distinguish the fragileness of the drilling fluids of the invention from the close prior art (the 12.1 SF fluid that exhibited the L-shaped curve behavior) is fatal.
Amgen, Inc. v. Chugai Pharm. Co., Ltd.,
Even if the '832 patent distinguished “fragile gels” of the invention from those of the prior art, it did not place any limit on the scope of what was invented beyond the prior art. By Halliburton’s own admission, drilling fluids which included an invert emulsion base, a thinner, an emulsifier, and a weighting agent were known in the prior art, and independent claims 1-3 and 5 are distinguishable from the prior art only because they are “fragile gels.” By failing to identify the degree of the fragility of its invention, Halliburton’s proposed definition would allow the claims to cover not only that which it invented that was superior to the prior art, but also all future improvements to the gel’s fragility. 4 While patentees are allowed to claim their inventions broadly, they must do so in a way that distinctly identifies the boundaries of their claims. The fluids of the '832 invention may provide less resistance to shear (i.e., break more quickly) than the prior art fluids, but the degree of improved speed remains ambiguous. Thus, it is unclear whether a person of ordinary skill in the art would have interpreted this claim as having an upper bound of fragility. 5
We note that where a claim is ambiguous as to its scope we have adopted a narrowing construction when doing so would still serve the notice function of the claims.
See Athletic Alternatives,
The second part of Halliburton’s definition (i.e., the fragile gel is capable of suspending drill cuttings and weighting materials at rest) fares no better because nothing in the record suggests what degree of such capability is sufficient. Halliburton argues that a person of ordinary skill would know how to measure the quantity of drill cuttings suspended in a fluid (either through laboratory measurements or in the field for example by measuring weight (or density) of the fluid when entering the borehole and when exiting the borehole), and would also know how to determine when the fluid no longer exhibited the L-shaped curve behavior when tested with a Brookfield viscometer. The fact that an artisan would know how to perform these measurements and tests, however, says nothing about whether the artisan would also know which fluids were “fragile gels” as that term is used in the claims of the '832 patent.
Assuming a person of ordinary skill would add solids incrementally, determining the effect of each addition by observing whether the fluid still maintains its fragile gel characteristics (the L-shaped curve), as Halliburton suggests, this testing protocol still does not answer the fundamental question: what quantity, weight, size and/or volume of cuttings must be suspended? Halliburton does not attempt to resolve this ambiguity, instead arguing that this limitation merely means adequate for the circumstances.
In
Geneva Pharmaceuticals, Inc. v. GlaxoSmithKline PLC,
As in Geneva Pharmaceuticals, under Halliburton’s proposed construction in this case, an artisan would not know from one well to the next whether a certain drilling fluid was within the scope of the claims because a wide variety of factors could affect adequacy (formation geology, well- *1255 bore size, depth, angle, etc.). In other words, a given fluid might be adequate to suspend drill cuttings in some formations and/or well configurations, whereas in others it would not be. When a proposed construction requires that an artisan make a separate infringement determination for every set of circumstances in which the composition may be used, and when such determinations are likely to result in differing outcomes (sometimes infringing and sometimes not), that construction is likely to be indefinite.
We also note that the two parts of Halliburton’s proposed definition discussed above (ability of the fluid to transition quickly from gel to liquid, and the ability of the fluid to suspend drill cuttings at rest) are functional, i.e., the fluid is defined “by what it does rather than what it is.”
In re Swinehart,
Although our predecessor court later recognized that “there is nothing intrinsically wrong with” using functional language in claims, it noted that in some instances, use of functional language can fail “to provide a clear-cut indication of the scope of subject matter embraced by the claim” and thus can be indefinite.
Swinehart,
When a claim limitation is defined in purely functional terms, the task of determining whether that limitation is sufficiently definite is a difficult one that is highly dependent on context (e.g., the disclosure in the specification and the knowledge of a person of ordinary skill in the relevant art area). We note that the patent drafter is in the best position to resolve the ambiguity in the patent claims, and it is highly desirable that patent examiners demand that applicants do so in appropriate circumstances so that the patent can be amended during prosecution rather than attempting to resolve the ambiguity in litigation.
A patent drafter could resolve the ambiguities of a functional limitation in a number of ways.
6
For example, the ambiguity might be resolved by using a quanti
*1256
tative metric (e.g., numeric limitation as to a physical property) rather than a qualitative functional feature. The claim term might also be sufficiently definite if the specification provided a formula for calculating a property along with examples that meet the claim limitation and examples that do not.
See Oakley, Inc. v. Sunglass Hut Int’l,
In this case, Halliburton differentiated its invention from the prior art because it was a “fragile gel.” As discussed above, Halliburton’s proposed definition of that term is not sufficiently definite because it does not adequately distinguish the fragileness of the invention from disclosed prior art, it is ambiguous as to whether an upper bound of fragileness is contemplated, and it is ambiguous as to its requisite ability to suspend drill cuttings. In other words, Halliburton’s proposed construction of “fragile gel” as used in the claims of the '832 patent is indefinite because it is ambiguous as to the requisite degree of the fragileness of the gel, the ability of the gel to suspend drill cuttings (i.e., gel strength), and/or some combination of the two. We discern no other construction that can properly be adopted that would render the claims definite.
Thus, we hold that M-I did provide clear and convincing evidence that the term “fragile gel” was indefinite, and that the district court correctly held the claims invalid on that basis.
III.
For these reasons, the district court’s grant of summary judgment of invalidity for indefiniteness is
AFFIRMED.
Notes
. Halliburton conceded at oral argument that it does not rely on Figure 4 to support its assertion that the term “fragile gel” is definite. As such, we need not address that figure directly but note only that there is no observable distinction between the relaxation rates (i.e., how quickly fluids return to gel-like state once stress is removed) of at least one of the SF (prior art) fluids and the fluids of the invention of the '832 patent.
. At oral argument, Halliburton asserted that the district court erred in finding that the asserted dependent claims stood or fell with the independent claims as to their definiteness. On appeal, Halliburton raised this issue only in a single sentence in the Summary of the Argument section of its opening brief, which did not identify the dependent claims at issue and provided no basis for finding them definite if the independent claims are indefinite. Following argument, Halliburton by letter identified the dependent claims at issue at the time of the district court’s summary judgment ruling. Nevertheless, Halliburton has presented nothing on appeal to show that this issue (i.e., whether additional limitations in the dependent claims rendered them sufficiently definite) was raised before the district court. Because Halliburton has inadequately presented this issue on appeal and failed to show it was presented below so as to preserve the issue for appeal, we deem this argument waived.
SmithKline Beecham Corp. v. Apotex Corp.,
. Halliburton also argues that other advantages of the invention provide other objective ways to delineate the scope of "fragile gel," such as lack of sag problems or lack of appreciable pressure spikes when the fragile gel drilling fluid transitions easily from a liquid to a gel and back again. '832 patent col.2 11.42-51. While these are disclosed as benefits of the invention, it is unclear how they provide an objective way of determining the scope of the claims. For example, one of the named inventors, Don Siems, testified that to determine whether there were appreciable pressure spikes, a competitor would have to compare his prior experience with other prior art fluids to his experience with fluids of the '832 patent. He also testified that pressure measurements in pressure-while-drilling equip *1252 ment can depend on factors other than the drilling fluid, such as the size of the hole and type of formation. J.A. 1323-24. Thus, it appears that these considerations (sag and pressure spikes) are as ambiguous as Figure 3, on which Halliburton primarily relies.
Additionally, these limitations both appear in dependent claims. Claims 11, 49, 87 ("no appreciable pressure spike is observed by pressure-while-drilling equipment when said drilling is resumed”); claims 19, 57, 94, 127 (“said fluid does not exhibit sag when at
. Additionally, by failing to identify the precise composition of the fluids of the invention, Halliburton’s proposed definition would allow the claims to cover fluids with added components beyond the four prior art base elements, when use of the additional components results in the same degree of fragility as the fluids of the '832 patent, even though Halliburton never contemplated such compositions.
. Of course, a claim may contain a limitation that includes no explicit upper bound at all (e.g., a claim limitation that requires “at least
5%"
of an element). Since such a limitation does not contemplate an upper bound beyond what is practically required (e.g., the total percentage must be less than 100%), the limitation may not present definiteness concerns.
See Exxon Research,
. Although not determinative on the definiteness issue, it seems clear that the patent drafter could have provided more specifics in this case, either with quantitative metrics as to how quickly the gel must break (time to break at given conditions) and how strong the gel must be (strength at given conditions), or with sufficient examples of fragile gels of the in
*1256
vention to show which such fluids fell within the scope of the claims.
Exxon Research,
. Of course, in the 1952 Patent Act, Congress authorized functional claiming, but with limits, in 35 U.S.C. § 112, ¶ 6. For so-called means-plus-function limitations, claim scope is limited to structure disclosed in the specification and equivalents. And if no structure is disclosed, the claim is indefinite.
Biomedino,