The US Court of Appeals for the Federal Circuit explained (again) that when a claim separately recites multiple structural limitations, infringement requires separate corresponding structures. A single component that sequentially or multifunctionally performs the claimed functions is not enough. Magnolia Medical Technologies, Inc. v. Kurin, Inc., Case No. 24-2001 (Fed. Cir. Mar. 6, 2026) (Lourie, Hughes, Freeman, JJ.)
Magnolia Medical sued Kurin for infringement of two patents directed to devices designed to reduce contamination of blood samples by skin microbes during venipuncture. The claimed devices divert the initial portion of blood, which is most susceptible to contamination, into a separate reservoir before collecting the remainder of the sample. Kurin manufactures the Kurin Lock, which separates the initial blood sample from the remaining sample using a porous plug. That plug initially functions as a vent, allowing air to escape, and then expands as it absorbs blood, closing its pores and forming a seal.
The representative claim of one of the asserted patents recites a device comprising a fluid reservoir “at least partially defined by a seal member and a vent.” The representative claim of the other patent recites a “diverter.”
During claim construction, the district court construed “diverter” as a means‑plus‑function term under § 112(f). Because the Kurin Lock lacked a corresponding diverter structure, the parties stipulated noninfringement of that patent.
The district court did not expressly construe the “seal” and “vent” limitations of the other patent at Markman. At trial, however, the jury found that Kurin infringed that patent.
Kurin moved for judgment as a matter of law (JMOL), arguing that it did not infringe because the Kurin Lock did not include separate seal and vent structures. Instead, a single porous plug performed both functions at separate times. The district court agreed and granted JMOL of no infringement. Magnolia appealed.
The Federal Circuit affirmed, rejecting Magnolia’s argument that the district court had improperly adopted a new claim construction at the JMOL stage. While courts may not introduce a materially different construction after trial, they may elaborate on what is inherent in the plain and ordinary meaning of a claim. The Federal Circuit reiterated its prior holdings that when a claim separately lists structural limitations, the plain and ordinary meaning requires separate corresponding structures. Here, the district court merely clarified that requirement, it did not change the construction.
The Federal Circuit found that the asserted claim required separate structures. The use of “comprising,” the introduction of “a” before both “seal” and “vent,” and the use of “and” between them all pointed to distinct components. The specification further reinforced that the seal and vent were described as separate structures.
The Federal Circuit also affirmed the district court’s construction of “diverter” as a means plus function limitation. Although the claim did not use the word “means,” Kurin successfully showed that the term failed to recite sufficient structure, triggering § 112(f).
Practice note: This case is a reminder that when multiple structural elements are separately recited in a claim, courts are likely to require separate physical structures in the accused device, even if a single component can perform the functions of multiple elements over time. Drafters should consider whether functional language, structural consolidation, or explicit disclosure of multifunctional components is necessary to avoid unintentionally narrowing claim scope.
