 United States Court of Appeals for the Federal Circuit

                                       2007-1149


                      HALLIBURTON ENERGY SERVICES, INC.,

                                                        Plaintiff-Appellant,

                                            v.

                                        M-I LLC
                      (doing business as M-I Drilling Fluids L.L.C.),

                                                        Defendant-Appellee.



      Edward D. Manzo, Cook, Alex, McFarron, Manzo, Cummings & Mehler, Ltd., of
Chicago, Illinois, argued for plaintiff-appellant. With him on the brief were Monte M.
Bond and David L. Patterson, Dykema Gossett PLLC, of Dallas, Texas.

       John R. Keville, Howrey LLP, of Houston, Texas, argued for defendant-appellee.
With him on the brief were Stephen H. Cagle and Richard L. Stanley. Of counsel on the
brief was S. Calvin Capshaw, Brown McCarroll LLP, of Longview, Texas.

Appealed from: United States District Court for the Eastern District of Texas

Judge Leonard Davis
 United States Court of Appeals for the Federal Circuit

                                       2007-1149


                      HALLIBURTON ENERGY SERVICES, INC.,

                                                              Plaintiff-Appellant,
                                            v.


                                       M-I LLC
                     (doing business as M-I Drilling Fluids L.L.C.),

                                                              Defendant-Appellee.


  Appeal from United States District Court for the Eastern District of Texas in case no.
                        6:05-CV-155, Judge Leonard E. Davis

                            __________________________

                             DECIDED: January 25, 2008
                            __________________________


Before MICHEL, Chief Judge, BRYSON, Circuit Judge, and FOGEL, ∗ District Judge.

MICHEL, Chief Judge.

      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 M-I 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.


      ∗
             Honorable Jeremy Fogel, District Judge, United States District Court for
the Northern District of California, sitting by designation.
§ 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.1 ll.27-31.

       The ’832 patent claims recite certain fragile 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., 182 F.3d 1298, 1305 (Fed. Cir. 1999) (“If the claim

preamble, when read in the context of the entire claim, recites limitations of the claim,




2007-1149                                       2
or, if the claim preamble is ‘necessary to give life, meaning, and vitality’ to the claim,

then the claim preamble should be construed as if in the balance of the claim.”)

(citations omitted). The specification defines “fragile gels” as follows:

       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. The “fragileness” of the “fragile gels” of the present invention
       contributes to the unique and surprising 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 col.2 ll.26-42.

        In May 2005, Halliburton sued M-I in the United States District Court for the

Eastern District of Texas, alleging that M-I’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 M-I’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, 456 F. Supp. 2d 811, 825 (E.D. Tex. 2006).

       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,”




2007-1149                                     3
“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.




SF fluids are prior art fluids whereas ACCOLADETM fluids have the characteristics of the

invention of the ’832 patent. ’832 patent col.4 l.65 – col.5 l.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


       1
              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.


2007-1149                                    4
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, 456 F. Supp. 2d at 820. The primary difference between

these fluids is the height of the curves (i.e., the strength of the gels formed), but the

district court found that Halliburton had produced no evidence of “precisely how high the

vertical leg of a fluid’s L-shaped curve must reach—i.e., how ‘strong’ a gel must be—for

that fluid to exhibit ‘fragile gel behavior.’” Id.

       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).




2007-1149                                        5
                                            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., 417 F.3d 1342, 1347 (Fed. Cir. 2005).

      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., 73 F.3d 1573, 1581 (Fed. Cir. 1996) (“[T]he primary purpose of

the requirement is ‘to guard against unreasonable advantages to the patentee and

disadvantages to others arising from uncertainty as to their [respective] rights.’”)

(quoting Gen. Elec. Co. v. Wabash Appliance Corp., 304 U.S. 364, 369, (1938)). The

Supreme Court has stated that “[t]he statutory requirement of particularity and

distinctness in claims is met only when [the claims] clearly distinguish what is claimed

from what went before in the art and clearly circumscribe what is foreclosed from future

enterprise.” United Carbon Co. v. Binney & Smith Co., 317 U.S. 228, 236 (1942).

      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., 490 F.3d 946, 950 (Fed. Cir.




2007-1149                                   6
2007), includes a numeric limitation without disclosing which of multiple methods of

measuring that number should be used, Honeywell Int’l, Inc. v. Int’l Trade Comm’n, 341

F.3d 1332, 1340 (Fed. Cir. 2003), and contains a term that is “completely dependent on

a person’s subjective opinion,” Datamize, 417 F.3d at 1350. We have also stated that a

claim could be indefinite if a term does not have proper antecedent basis where such

basis is not otherwise present by implication or the meaning is not reasonably

ascertainable. Energizer Holdings, Inc. v. Int’l Trade Comm’n, 435 F.3d 1366, 1370-71

(Fed. Cir. 2006). The common thread in all of these cases is that claims were held

indefinite only where a person of ordinary skill in the art could not determine the bounds

of the claims, i.e., the claims were insolubly ambiguous.

      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, 265 F.3d 1371,

1375 (Fed. Cir. 2001) (citations omitted).       Proof of indefiniteness requires such an

exacting standard because claim construction often poses a difficult task over which

“expert witnesses, trial courts, and even the judges of this court may disagree.” Id.

Nevertheless, this standard is met where an accused infringer shows by clear and

convincing evidence that a skilled artisan could not discern the boundaries of the claim

based on the claim language, the specification, and the prosecution history, as well as

her knowledge of the relevant art area.




2007-1149                                    7
       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, 417 F.3d

at 1347 (citing Novo Indus., L.P. v. Micro Molds Corp., 350 F.3d 1348, 1353 (Fed. Cir.

2003); Honeywell, 341 F.3d at 1338; Exxon Research, 265 F.3d at 1375). Because we

conclude that neither Halliburton’s proposed definition nor any other possible

construction resolves the ambiguity in the scope of the term “fragile gel,” we agree with

the district court that claims containing that term are indefinite. 2

       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 organophilic lignite or can
                 contain low amounts of organophilic clay or lignite individually or

       2
                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., 439 F.3d 1312, 1320 (Fed. Cir. 2006) (“[M]ere
statements of disagreement with the district court as to the existence of factual disputes
do not amount to a developed argument.”) (citations omitted); see also United States v.
Dunkel, 927 F.2d 955, 956 (7th Cir. 1991) (“A skeletal ‘argument’, really nothing more
than an assertion, does not preserve a claim. . . . Judges are not like pigs, hunting for
truffles buried in briefs.”).


2007-1149                                      8
                 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 ll.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 ll.51-53 (emphasis added).

       Contrary to Halliburton’s argument, nothing in the specification of the ’832 patent

requires the fragile gel drilling fluid 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.




2007-1149                                     9
          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 ll.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 ll.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



2007-1149                                       10
artisan would understand the limits of the claimed “fragile gel.” Halliburton primarily

focuses on the L-shaped curve shown in Figure 3 of the ’832 patent. 3 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 Brookfield viscometer. Figure 3 shows Brookfield 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 prior art (i.e., 12.1 SF fluid) is covered by the claim as

construed is properly addressed in validity challenges of other types (anticipation,


       3
              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 ll.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 equipment 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 rest”). Under the doctrine of claim differentiation, “the presence of a dependent
claim that adds a particular limitation gives rise to a presumption that the limitation in
question is not present in the independent claim.” Phillips v. AWH Corp., 415 F.3d
1303, 1315 (Fed. Cir. 2005) (en banc). While claim differentiation is a presumption that
can be rebutted, Andersen Corp. v. Fiber Composites, LLC, 474 F.3d 1361, 1370 (Fed.
Cir. 2007), Halliburton’s argument that the presumption is rebutted in this case is
unpersuasive.


2007-1149                                    11
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 ll.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.




2007-1149                                    12
       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., 927 F.2d 1200, 1218 (Fed. Cir. 1991) (holding that the term “at least about” was

indefinite because the patent provided no guidance as to where the line should be

drawn between the numerical value of the prior art cited in the prosecution history and

the close numerical value in the patent); see also Verve, LLC v. Crane Cams, Inc., 311

F.3d 1116, 1119-20 (Fed. Cir. 2002) (recognizing that guidance as to measurement of a

term of degree can come from the intrinsic record or from the knowledge of a person of

ordinary skill in the art).

       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




2007-1149                                     13
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, 73 F.3d at 1581 (“Where there is an equal choice between a

broader and a narrower meaning of a claim, and there is an enabling disclosure that

indicates that the applicant is at least entitled to a claim having the narrower meaning,

we consider the notice function of the claim to be best served by adopting the narrower

meaning.”). In this case, however, Halliburton asks that we resolve the ambiguity in a

way that gives it the broadest possible construction (i.e., that its claim covers all future

improvements without regard to whether Halliburton invented such improvements); such

a construction would undermine the notice function of the claims because it would allow

       4
               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.
        5
               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, 265 F.3d at 1382 (holding that a
claim limitation that average particle diameter be greater than 5 μm was not indefinite
where no upper limit on particle size was given). However, when a limitation is
ambiguous as to the presence or absence of an upper bound, an inquiry into the
definiteness of that limitation is warranted.


2007-1149                                   14
Halliburton to benefit from the ambiguity, rather than requiring Halliburton to give proper

notice of the scope of the claims to competitors. Additionally, adopting the broadest

possible construction could retard innovation because cautious competitors may steer

too far around that which Halliburton actually invented, neglecting improvements that

otherwise might be made. We thus hold that the term “fragile gel” is not sufficiently

definite if construed in accordance with the first part of Halliburton’s proposed definition

because a person of ordinary skill in the art could not determine how quickly the gel

must transition to a liquid when force is applied and how quickly it must return to a gel

when the force is removed.

       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




2007-1149                                    15
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, 349 F.3d 1373, 1384

(Fed. Cir. 2003), we refused to adopt a proposed construction for “synergistically

effective amount” (“a formulation falls outside the scope of the claims if a given

antibiotic, bacteria, and disease combination provides no synergy”) because the

construction would have been indefinite. Because the patent claims at issue did not

identify the specific bacteria, we rejected the proposed construction because “a given

embodiment would simultaneously infringe and not infringe the claims, depending on

the particular bacteria chosen for analysis.” Id. We concluded that such a construction

that results in an artisan not knowing from “one bacterium to the next whether a

particular composition standing alone is within the claim scope or not” was “the epitome

of indefiniteness.” Id.

       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, wellbore 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




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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, 439 F.2d 210, 212 (CCPA 1971). The Supreme

Court in two early cases identified the dangers of using only functional claim limitations

to distinguish the claimed invention from the prior art. In General Electric, the Court

held that a vice of functional claiming occurs “when the inventor is painstaking when he

recites what has already been seen, and then uses conveniently functional language at

the exact point of novelty.” General Electric, 304 U.S. at 371 (holding claims invalid

where the grains of the claimed lighting filament were distinguished from the prior art

only because they were “of such size and contour as to prevent substantial sagging and

offsetting” of the filament during the commercially useful life of the lamp). Likewise, in

United Carbon, the Court held indefinite claims that recited only “inaccurate suggestions

of the functions of the product.” United Carbon, 317 U.S. at 234 (holding indefinite

patent claims that recited, for example, “sustantially (sic) pure carbon black in the form

of commercially uniform, comparatively small, rounded smooth aggregates having a

spongy or porous exterior”).

       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, 439 F.2d at 212-




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13 (holding that the term “transparent” was definite because the disclosure, which

showed that a substantial amount of infrared radiation was always transmitted even

though the precise degree of transparency varied depending on certain factors, was

sufficiently clear).

       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 quantitative

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, 316 F.3d



       6
              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 invention to show which such fluids fell within
the scope of the claims. Exxon Research, 265 F.3d at 1376 (stating that the patent
was lacking in “specificity that in some instances would have been easy to provide and
would have largely obviated the need to address the issue of indefiniteness” but holding
that the flaws ultimately were not “fatal”).


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1331, 1341 (Fed. Cir. 2003) (holding that, at the preliminary injunction stage, the

accused infringer had not shown a substantial question of indefiniteness, where the

claims and specification linked the claim term “vivid colored appearance” to a

calculation for differential effect and then provided examples of when differential effect

values were and were not sufficient for a “vivid colored appearance”); see also In re

Marosi, 710 F.2d 799, 803 (Fed. Cir. 1983) (finding claims definite where the applicant’s

disclosure provided “a general guideline and examples sufficient” to teach an artisan

when the claim limitation was satisfied). 7

       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.




       7
              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, 490
F.3d at 950. This statutory provision was meant to preclude the overbreadth inherent in
open-ended functional claims, such as those presented in this case which effectively
purport to cover any and all means so long as they perform the recited functions.


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       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.




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