In a recent case, Bio-Rad Laboratories, Inc. v. 10X Genomics Inc., the Federal Circuit affirmed the district court decision that the “tangentiality” exception to prosecution history estoppel can be used to show infringement under the doctrine of equivalents of an amended claim limitation.
The facts of the case are simple.
During prosecution, the claims were amended by adding terms to distinguish the claimed invention from the prior art.
Specifically, the inventors argued that the invention was directed to non-fluorinated microchannels which would not react with fluorinated surfactants.
The accused products at issue contained microchannels coated with a fluorine-containing coating resin.
An amendment narrowing the scope of the claims is presumed to be a surrender of all equivalents within “the territory between the original claim and the amended claim.” Festo I, 535 U.S. at 740.
This presumption can be overcome if the patentee can show that one of the following “exceptions” to prosecution history estoppel applies: (1) the rationale underlying the amendment bears no more than a tangential relation to the equivalent in question; (2) the equivalent was unforeseeable at the time of the application; or (3) there was some other reason suggesting that the patentee could not reasonably be expected to have described the equivalent. Id. at 740–41.
The District Court framed the issue on (1), the “tangentiality” exception.
According to the District Court the amendment was tangential to the accused equivalent because while the amendment submitted during prosecution was made to distinguish the invention from the fluorinated channels found in the prior art, the accused products were found to have negligible quantities of fluorine with no function and unreactive with the microchannels.
Therefore, according to the District Court, the accused product fell within the” non-fluorinated limitation” under the doctrine of equivalents.
The Federal Circuit agreed and held that the patentee was not barred from asserting that negligible amounts of fluorine in the microchannels is equivalent to “non-fluorinated microchannels.”
This decision is important because it protects the patentee from accused devices that perform the same function, in the same way, to achieve the same result.
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Silvia Salvadori, PhD