Federal Circuit Finds That Prosecution History Estoppel Is Limited To Claim Element Having Function

In Aquatex Industries v. Techniche Solutions, 81 USPQ2d 1865 (Fed. Cir. 2007), Aquatex is the assignee of U.S. Patent No. 6,371,977 (“the ‘977 patent”).  The ‘977 patent claims a method for cooling a person through evaporation by use of a multi-layered, liquid-retaining composite material in evaporative cooling garments.  Claim 1 of the ‘977 patent claims a method performed using a device “comprising a fiberfill batting material, and hydrophilic polymeric fibers that absorb at least 2.5 times the fiber’s weight in water.”  The defendant Techniche performs a method similar to the method recited in claim 1 of the ‘977 patent, using a commercially available product called Vizorb® as its filler layer. Vizorb® is an airlaid non-woven fabric predominantly made of cellulouse fluffed pulp, incorporating both natural and synthetic fibers. 

In 2004, Aquatex sued Techniche for contributory infringement, asserting that Techniche made a product which its customers used to perform the method recited in claim 1 of its ‘977 patent.  Techniche conceded that most of the claim limitations were satisfied, but asserted that Vizorb®, which Techniche used in its product, did not satisfy the “fiberfill batting material” limitation of claim 1.  Specifically, Techniche argued that only a batting material using exclusively synthetic fibers satisfied the “fiberfill” limitation of claim 1, and that Techniche’s Vizorb® material used both natural and synthetic fibers. 

The District Court construed the term “fiberfill” to require only synthetic batting material, and therefore held that Techniche did not literally infringe claim 1.  The District Court also found that the claim of infringement under the doctrine of equivalents was barred by prosecution history estoppel.  During prosecution, Aquatex had amended its claims to distinguish the Zafiroglu prior art patent, U.S. Patent No. 4,897,297, by narrowing its claims to claim a method that cooled by evaporation, whereas Zafiroglu cooled through use of a compress and involved only slight evaporation over time.  Based on the prosecution history, the District Court concluded that Aquatex was estopped from arguing that Techniche’s accused product was equivalent. 

On appeal, the Federal Circuit affirmed the District Court’s finding of no literal infringement.  However, the Federal Circuit remanded the case to determine whether Techniche’s Vizorb® material infringed the “fiberfill” limitation of claim 1 under the doctrine of equivalents.  The Federal Circuit noted that the subject matter surrendered by Aquatex during prosecution, which related to evaporation, bore no relation to the composition of the fiberfill batting material. 

On remand, the District Court re-considered whether the defendant Techniche’s product infringed claim 1 under the doctrine of equivalents.  In its defense, Techniche argued that: (1) Aquatex was barred by amendment estoppel from asserting the doctrine of equivalents, (2) its product did not include the equivalent of fiberfill batting, and (3) Aquatex failed to provided particularized testimony and linking argument as to the insubstantiality of the differences between the claimed invention and the accused device, or with respect to the “function, way, result” test.  The District Court again held that Aquatex’s narrowing amendments made during prosecution surrendered the subject matter within which Techniche’s products falls, holding that Techniche did not infringe claim 1 under the doctrine of equivalents. 

On appeal, the Federal Circuit held that, although the District Court misapplied the doctrine of equivalents in concluding that the defendant Techniche’s product did not infringe claim 1, the plaintiff failed to provide particularized testimony and linking argument in support of infringement under the doctrine of equivalents.   Specifically, the District Court misapplied the doctrine of equivalents because the narrowing amendment related to evaporation, while the limitation at issue related to the composition of filling material.  The amendment was directed to a completely different claim limitation – the requirement that the overall method of cooling of the garment be by evaporation.  Thus, Aquatex surrendered no claim to the characteristics of the fiberfill during prosecution and was not barred from asserting equivalents as to the “fiberfill batting material” limitation. 

While agreeing that the District Court had misapplied doctrine of prosecution history estoppel, the Federal Circuit found that there was harmless error since, in order to prove infringement under the doctrine of equivalents, Aquatex was required to provide particularized testimony and linking argument on a limitation-by-limitation basis as to the insubstantiality of the differences between the claimed invention and the accused device or process, or with respect to the function, way, result test.  Texas Instruments, Inc. v. Cypress Semiconductor Corp., 90 F.3d 1558 (Fed. Cir. 1996).  Here, Aquatex failed to provide particularized testimony from an expert or person skilled in the art that specifically addressed equivalents on a limitation-by-limitation basis, instead relying solely on legal argument and generalized testimony.  Aquatex therefore failed to demonstrate a genuine issue of material fact that would prevent the grant of summary judgment, and so the Federal Circuit affirmed the decision of the District Court granting summary judgment of noninfringement to the defendant Techniche.

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