NOTE: This disposition is nonprecedential.

 

United States Court of Appeals 

for the Federal Circuit ______________________ 

TENNANT CO.,

Appellant

v.

OXYGENATOR WATER TECHNOLOGIES, INC.,

Appellee

______________________ 

2022-2304

______________________ 

Appeal from the United States Patent and Trademark 

Office, Patent Trial and Appeal Board in No. IPR2021-

00625.

______________________ 

Decided: July 23, 2024

______________________ 

OLIVER RICHARDS, Fish & Richardson P.C., San Diego, 

CA, argued for appellant. Also represented by NITIKA 

GUPTA FIORELLA, DOUGLAS E. MCCANN, JOSEPH B.

WARDEN, Wilmington, DE.

 J. DEREK VANDENBURGH, Carlson, Caspers, Vandenburgh & Lindquist, P.A., Minneapolis, MN, argued for appellee. Also represented by NATHAN D.LOUWAGIE, HANNAH 

MOSBY O'BRIEN, AARON W. PEDERSON. 

______________________ 

Case: 22-2304 Document: 48 Page: 1 Filed: 07/23/2024
2 TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 

Before DYK, REYNA, and STOLL, Circuit Judges.

DYK, Circuit Judge. 

Tennant Co. (“Tennant”) appeals from a decision of the 

Patent and Trial Appeal Board (“Board”) finding that 

claims 13, 14, and 17–27 of U.S. Patent No. RE45,415E (the 

“’415 patent”) were not unpatentable as anticipated or obvious. We conclude that substantial evidence supports the 

Board’s finding that the claim limitation requiring nanobubbles was not shown to be inherent in the prior art by

Tennant’s testing of the prior art or by establishing that 

the prior art used the same spacing of the electrodes as the

’415 patent. However, because the Board failed to address 

Tennant’s argument that the prior art practiced all the 

claimed parameters of the ’415 patent and thus inherently 

anticipated the claimed nanobubbles limitation, we reverse 

and remand. 

BACKGROUND

Oxygenator Water Technologies, Inc. (“OWT”) is the 

owner of the ’415 patent. The patent is directed to a 

method for oxygenating water by “generat[ing] very small 

microbubbles and nanobubbles of oxygen in an aqueous 

medium, which bubbles are too small to break the surface 

tension of the medium, resulting in a medium supersaturated with oxygen.” ’415 patent, col. 2, l. 67–col. 3, l. 3. 

Claim 13 of the ’415 patent is the only independent claim 

at issue on appeal, and it provides:

13. A method for producing an oxygenated aqueous 

composition comprising:

flowing water at a flow rate no greater than 

12 gallons per minute through an electrolysis emitter comprising an electrical power 

source electrically connected to an anode 

electrode and a cathode electrode contained 

in a tubular housing,

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TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 3

causing electricity to flow from the power 

source to the electrodes, and,

producing the composition comprising a 

suspension comprising oxygen microbubbles and nanobubbles in the water, the microbubbles and nanobubbles having a 

bubble diameter of less than 50 microns, 

wherein:

the electrode is separated at a critical distance from the cathode such 

that the critical distance is from 

0.005 inches to 0.140 inches;

the power source produces a voltage no greater than about 28.3 

volts and an amperage no greater 

than about 13 amps,

the tubular housing has an inlet 

and an outlet and a tubular flow 

axis from the inlet to the outlet;

the water flows in the inlet, out the 

outlet, is in fluid connection with 

the electrodes, and the water flowing into the inlet has a conductivity 

produced by the presence of dissolved solids such that the water 

supports plant or animal life. 

’415 patent, col. 11, ll. 20–45. 

Tennant petitioned for inter partes review of claims 13, 

14, and 17–27 of the ’415 patent alleging anticipation over 

two prior art references, U.S. Patent No. 3,891,535 

(“Wikey”) and U.S. Patent No. 4,917,782 (“Davies”), and obviousness over either Wikey in combination with other 

prior art references or Davies in combination with other 

prior art references. The Board first found that 

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4 TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 

“[Tennant’s] testing does not sufficiently demonstrate that 

Wikey inherently discloses nanobubbles.” J.A. 28. Second, 

the Board found that “[Tennant’s] reliance on milkiness

and supersaturation to demonstrate the presence of nanobubbles [wa]s also unsupported.” J.A. 28. Third, the Board

found that “the ’415 patent itself does not necessarily 

equate a certain critical distance of electrodes with the formation of nanobubbles or microbubbles, to the exclusion of 

all other variables.” J.A. 26. For the dependent claims, the 

Board found that “[e]very dependent claim challenged . . . 

includes the microbubbles and nanobubbles limitation of 

claim 13, and, accordingly, [Tennant] does not make its 

case as to these dependent claims.” J.A. 31. In summary, 

the Board determined that Tennant “ha[d] not shown by a 

preponderance of the evidence that claims 13, 14, and 17–

27 of the ’415 patent are unpatentable” as anticipated or 

obvious. J.A. 2. Tennant appeals. 

We have jurisdiction pursuant to 28 U.S.C. 

§ 1295(a)(4)(A).

DISCUSSION

We first consider the question of anticipation. “Anticipation is a question of fact that we review for substantial 

evidence.” HTC Corp. v. Cellular Commc’ns Equip., LLC, 

877 F.3d 1361, 1368 (Fed. Cir. 2017). Substantial evidence 

is “such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.” Consol. Edison 

Co. of New York v. NLRB, 305 U.S. 197, 229 (1938). “A 

claim is anticipated if a single prior art reference discloses 

all the claimed limitations arranged or combined in the 

same way as in the claim.” HTC Corp., 877 F.3d at 1368; 

see also 35 U.S.C. § 102. The prior art reference can disclose each limitation of the claimed invention either expressly or inherently. Eli Lilly & Co. v. Los Angeles 

Biomedical Rsch. Inst. At Harbor-UCLA Med. Ctr., 849 

F.3d 1073, 1074 (Fed. Cir. 2017).

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TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 5

The Board found that both Wikey and Davies “appear[] 

to disclose each limitation of claim 13 except ‘microbubbles 

and nanobubbles having a bubble diameter of less than 50 

microns.’” J.A. 22, 40–41. Although there seems to have 

been no issue as to whether Wikey and Davies disclose microbubbles, the Board noted that neither Wikey nor Davies

disclosed nanobubbles, which is a requirement of claim 13 

of the ’415 patent. The issue is therefore whether Wikey or 

Davies discloses the nanobubble limitation. Tennant 

makes four distinct arguments in support of its position. 

Tennant first contends that its testing of the devices 

from Wikey and Davies demonstrates anticipation. Tennant’s expert re-created the device disclosed in Wikey and 

tested to see if it produced microbubbles and nanobubbles. 

“Microbubble” is defined as “a bubble with a diameter less 

than 50 microns.” ’415 patent, col. 4, ll. 10–11. “Nanobubble” is “a bubble with a diameter less than that necessary 

to break the surface tension of water,” ’415 patent, col. 4, 

ll. 12–13, which Tennant’s expert testified was “[r]oughly 

100 nanometers” (0.1 microns), J.A. 6048. The expert used 

an imaging tool which showed that the Wikey device created microbubbles. Likewise, the expert re-created the device from Davies, and testing showed that it also produced 

microbubbles. However, Tennant’s expert admitted “that 

none of the testing [he] performed determined whether or 

not there were nanobubbles in the water.” J.A. 6049, 70:1–

3. The Board did not err in concluding that the testing did 

not detect the presence of nanobubbles.

Second, Tennant argues that even if the testing did not 

directly detect nanobubbles, it demonstrated that the water was supersaturated, and that this was sufficient to 

show the presence of nanobubbles. Tennant points to the 

specification of the ’415 patent which describes “an oxygen 

emitter which . . . generates very small microbubbles and 

nanobubbles of oxygen in an aqueous medium, which bubbles are too small to break the surface tension of the medium, resulting in a medium supersaturated with oxygen.” 

Case: 22-2304 Document: 48 Page: 5 Filed: 07/23/2024
6 TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 

’415 patent, col. 2, l. 66–col. 3, l. 3. Tennant contends that

“the presence of nanobubbles was tested according to the 

only parameters provided by the ’415 patent (i.e. that they 

supersaturate water, see [J.A.] 73 at 4:12–15).” Appellant’s 

Opening Br. at 35. However, the ’415 patent defines “nanobubble” as “a bubble with a diameter less than that necessary to break the surface tension of water. Nanobubbles 

remain suspended in the water, giving the water an opalescent or milky appearance.” ’415 patent, col. 4, ll. 12–15. 

The specification describes that nanobubbles result in 

supersaturation, but Tennant has not shown that the reverse is true. The Board found that supersaturation does 

not show the presence of nanobubbles. The Board’s decision is supported by substantial evidence. Tennant’s expert admitted that “dissolved oxygen” does not “tell us 

anything about the size of the bubbles that are in the water.” J.A. 6050, 76:9–14. Additionally, Tennant presents 

no evidence that the water it tested had a milky appearance or that supersaturation gives the water a milky appearance. Tennant’s tests of Wikey and Davies showed 

that the “[v]ast majority of bubbles disappear[ed] within 1 

minute” and “no bubbles [were] visible after 3 hours.” J.A. 

6548, 6556, 6562. The specification provides that “[the device] forms bubbles which are too small to break the surface 

tension of the fluid. These bubbles remain suspended indefinitely in the fluid and, when allowed to build up, make 

the fluid opalescent or milky. Only after several hours 

do[es] . . . the water clear[].” A’415 patent, col.4, ll. 32–37. 

Thus, Tennant failed to show that supersaturation demonstrated the existence of nanobubbles. 

Third, Tennant argues that both Wikey and Davies inherently produce microbubbles and nanobubbles because 

they both “describe[] an anode and cathode spaced at the 

‘critical distance,’ and given the ’415 patent’s teachings 

that the ‘critical distance’ is the critical factor in the creation of microbubbles and nanobubbles, the Board should 

have found Wikey [and Davies] inherently anticipate[] the 

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TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 7

bubble size limitation.” Appellant’s Opening Br. at 34; see 

also Appellant’s Opening Br. at 47. Tennant relies on the 

’415 patent’s abstract which states that “[w]hen the anode 

and cathode are separated by a critical distance, very small 

microbubbles and nanobubbles of oxygen are generated.” 

J.A. 62. 

The Board found “that the ’415 patent itself does not 

necessarily equate a certain critical distance of electrodes 

with the formation of nanobubbles or microbubbles, to the 

exclusion of all other variables.” J.A. 26. The Board’s finding is supported by substantial evidence. Tennant’s expert, 

Dr. Tremblay, testified that “a person of skill in the art 

reading the ’415 patent would understand . . . that many 

things other than spacing of the electrodes are going to 

have an effect on the bubble size created using devices described in the patent.” J.A. 6039, 30:24–31:5.

Finally, Tennant argues that Wikey and Davies “met 

all of the limitations of independent claim 13 as they relate 

to the parameters of the device—i.e., the voltage used, the 

amperage used, the shape of the housing, the inlet, the outlet, the fluid flow, and even the ‘critical distance.’” Appellant’s Opening Br. at 33. The Board found that both Wikey 

and Davies “appear[] to disclose each limitation of claim 13 

except ‘microbubbles and nanobubbles having a bubble diameter of less than 50 microns.’” J.A. 22, 40–41. And, Tennant argues, “when all claimed parameters are present—

as in Wikey—microbubbles and nanobubbles are inherently formed.”1 Appellant’s Reply Br. at 7. For support, 

1 OWT contends that parameters other than those 

found in the claim limitations affects the production of microbubbles and nanobubbles. This appears to contradict 

OWT’s representations made during prosecution of the ’415 

patent. And even if other parameters affect bubble size, 

nothing in the specification discloses any such requirement 

Case: 22-2304 Document: 48 Page: 7 Filed: 07/23/2024
8 TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 

Tennant points to In re King, which holds that “if a previously patented device, in its normal and usual operation, 

will perform the function which an appellant claims in a 

subsequent application . . . then such application . . . will 

be considered to have been anticipated by the former patented device.” 801 F.2d 1324, 1326 (Fed. Cir. 1986); see 

also In re Ackenbach, 45 F.2d 437, 439 (C.C.P.A. 1930).

Tennant made this same argument to the Board in its 

IPR petition, contending that “[t]he Wikey emitter has the 

same configuration as claim 12 and therefore produces the 

same result – namely, a suspension comprising microbubbles and nanobubbles.” J.A. 121–22; see also J.A. 24–25 

(The Board noting that “[Tennant] also replies that claim 

13 specifies voltage, current, and flow rate limits that, combined with the critical distance, create microbubbles and 

nanobubbles, and that Wikey teaches values for each of 

these variables falling within the claimed ranges”); J.A. 

112 (“Wikey discloses a tubular water electrolysis emitter 

having an anode separated from a cathode by the claimed 

critical distance in combination with the claimed voltage, 

amperage and flow rate. The Wikey emitter therefore produces a suspension comprising microbubbles and nanobubbles in the water, as the ’415 patent acknowledges.”). 

Tennant’s expert testified that “Wikey not only discloses the claimed anode and cathode separation distance 

in combination with the claimed voltage, it inherently provides the claimed current and flow rates,” J.A. 528, and 

“Davies not only discloses the anode and cathode separation distance in combination with the claimed voltage and 

flow rate of the ’415 patent, it also inherently provides the 

claimed current,” J.A. 559. However, the Board did not address this argument, finding only that Wikey’s and Davies’

or describes how to manipulate those parameters to produce microbubbles and nanobubbles.

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TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 9

disclosure of the “critical distance” was insufficient to inherently disclose production of nanobubbles. 

The Board’s error is particularly significant given the 

prosecution history where OWT represented that microbubbles and nanobubbles were inherently produced 

when the claim parameters of the ’415 patent were followed. The examiner rejected “[c]laims 2, 3, 5, 7, 9, 10, 13–

17, 21, 22, 26, 27, 29–32, 35, and 39–42 . . . as being anticipated by Murrell U.S. Patent 5,049,252.” Tennant Co. v. 

Oxygenator Water Techs., Inc., IPR2021-00625, Exhibit 

1102 at 216 (PTAB Mar. 9, 2021). OWT cancelled claims 

13–49 in favor of new claims 50–67. New claim 55, which, 

as amended, became claim 13 in the ’145 patent, provided

that “the combination of the critical distance, the voltage, 

amperage and the water conductivity results in the formation of a suspension comprising oxygen nanobubbles in 

the water.” Tennant, IPR2021-00625, Exhibit 1102 at 

190.2 In defending claim 55 against anticipation by Murrell, OWT submitted: 

The new claims are directed to . . . a method of producing the suspension of nanobubbles in water . . . 

[h]ence, the water and microbubbles/nanobubbles 

of oxygen suspended in the water are positively recited features of a system, a method and a suspension. In addition, the voltage, amperage, the 

separation of the electrode spacing, and the total 

solids in the water signifying viscosity and 

2 That language was ultimately deleted from claim 

13, but there was no suggestion that the change was substantive. The patent examiner had accepted claim 55 (except for a defective reissue oath, Tennant, IPR2021-00625, 

Exhibit 1102 at 167), and Tennant deleted the language after the acceptance. Tennant, IPR2021-00625, Exhibit 1102 

at 140–141. Tennant provided no explanation for the deletion. See id. at 136–153. 

Case: 22-2304 Document: 48 Page: 9 Filed: 07/23/2024
10 TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 

conductivity of the water, which can be summed by 

the phrase tap water, are positively recited features of this system. These features achieve the 

suspension of nanobubbles in water.

Id. at 196. Additionally, OWT stated that its “system, 

method and suspension” was different than Murrell’s because its “micro and nanobubbles do not rise to the surface 

[i.e., they remain suspended in the water] . . . [OWT’s] 

claims now recite the conditions needed to produce [microbubbles and nanobubbles], including voltage, amperage, 

total water solids indicating conductivity, and the electrode 

spacing.” Id. at 198. 

In other words, if the physical parameters of the claim 

were followed, it would automatically produce nanobubbles. OWT cannot make one argument when seeking issuance of its patent and the opposite argument in defending 

the patent in post-grant review and to this court. “[J]udicial estoppel[] ‘generally prevents a party from prevailing 

in one phase of a case on an argument and then relying on 

a contradictory argument to prevail in another phase.’” 

New Hampshire v. Maine, 532 U.S. 742, 749 (2001) (quoting Pegram v. Herdrich, 530 U.S. 211, 227 n.8 (2000)); see 

also Trustees in Bankr. Of N. Am. Rubber Thread Co. v. 

United States, 593 F.3d 1346, 1354 (Fed. Cir. 2010) (“Judicial estoppel applies just as much when one of the tribunals 

is an administrative agency as it does when both tribunals 

are courts.”); Tyler Refrigeration v. Kysor Indus. Corp., 777 

F.2d 687, 690 (Fed. Cir. 1985) (holding that the district 

court properly treated the Aokage reference as prior art 

“[i]n view of [patent owner’s] explicit admission” “before 

the PTO during the prosecution of the [patent]” that “the 

Aokage reference [was] prior art”); In re Nomiya, 509 F.2d 

566, 570–71 (C.C.P.A. 1975) (holding that while “[a]ppellants’ brief now questions the PTO’s use of Figs. 1 and 2 of 

their application as ‘prior art’ . . . arguing that there is no 

statutory basis for considering Figs. 1 and 2 to be ‘prior art’ 

. . . [b]y filing an application containing Figs. 1 and 2, 

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TENNANT CO. v. OXYGENATOR WATER TECHNOLOGIES, INC. 11

labeled prior art . . . appellants have conceded what is to be 

considered as prior art in determining obviousness of their 

improvement.”). 

CONCLUSION

Because the Board failed to address Tennant’s argument that Wikey and Davies disclosed all the parameters 

of the ’415 and therefore inherently produce microbubbles 

and nanobubbles, we vacate and remand. Because we vacate and remand to the Board to consider Tennant’s anticipation argument, we do not reach Tennant’s obviousness 

arguments (which depends on its contention that either 

Wikey or Davies produce nanobubbles).

VACATED AND REMANDED

COSTS

No Costs.

Case: 22-2304 Document: 48 Page: 11 Filed: 07/23/2024