MAGNOLIA MEDICAL TECHNOLOGIES, INC. v. KURIN, INC.

Authored by: Jeremy J. Gustrowsky

When blood is drawn from a patient, microbes on the skin can contaminate the sample, leading to false-positive test results and unnecessary treatments. Both Magnolia Medical Technologies and Kurin developed devices to solve this problem by separating and discarding the initial blood drawn (the portion most likely to carry skin contaminants) from the sample actually sent for testing. Magnolia sued Kurin in the District of Delaware, alleging that Kurin’s product, the “Kurin Lock,” infringed claims of U.S. Patent No. 10,039,483 and U.S. Patent No. 9,855,001. After a jury found infringement of the ‘483 patent, the district court overturned the verdict. The Federal Circuit affirmed.

The central issue with the ‘483 patent was whether two separately listed claim limitations, a “vent” and a “seal member,” required two physically distinct structures. In the Kurin Lock, both functions are performed by a single component: a porous plug. Before blood reaches it, the plug’s pores are open and it acts as a vent, letting air escape. Once blood contacts the plug, the material swells, the pores close, and it becomes a seal. Both parties’ experts agreed on this point. The district court relied on the Federal Circuit’s prior decision in Becton, Dickinson & Co. v. Tyco Healthcare Group to hold that when a patent claim lists elements separately, the plain meaning implies those elements must be separate structures. Because the Kurin Lock used one structure for both roles, the court granted judgment as a matter of law of no infringement.

Magnolia argued that this separate-structure requirement was a new claim construction improperly introduced after trial, depriving it of the chance to argue infringement under that theory to the jury. The Federal Circuit disagreed, explaining that the district court was not adopting a new construction but merely clarifying what was already inherent in the plain and ordinary meaning of the claim language. Under Becton, when limitations are listed separately and connected by “and,” the natural reading is that distinct components are required. The specification of the ‘483 patent supported this reading, as it described the vent and seal as separate structures. Magnolia’s claim differentiation argument (pointing to a dependent claim that also recited the vent and seal as separate) was found unpersuasive because that dependent claim narrowed how the two structures interact, giving it independent meaning without requiring the broader claim to encompass a single-structure reading.

The Federal Circuit also upheld the district court’s construction of the term “diverter” in the ‘001 patent as a means-plus-function limitation under 35 U.S.C. § 112(f). Although the claim recited some structural features of the diverter (an inlet and two outlets), the court found these were insufficient to perform the function of directing fluid down one of two paths. Magnolia’s own expert undermined its position by describing a “diverter” as including “at least” an inlet and two outlet branches, which the court read as an admission that the term lacks a sufficiently definite structural meaning and instead generically captures any structure performing that function. Because the Kurin Lock did not practice the specific structures disclosed in the specification, the stipulated non-infringement of the ‘001 patent stood.

This case reinforces two important drafting lessons for patent practitioners. First, when a claim lists structural elements separately, courts will likely require an accused product to have corresponding separate structures. Second, when a claim term does not convey sufficiently definite structure to a person of ordinary skill, it risks being treated as a means-plus-function term, possibly narrowing its scope to the examples disclosed in the specification.