Masa Yokoyama
Scott Daniels

The Federal Circuit’s decision this past month in ABS Global v. Cytonome was a valuable lesson in claim construction. The patent concerned a device for measuring movement of fluids within small channels, to sort, count, analyze, or test the cells or molecules in those fluids. The main claim of the patent recited (with the key claim wording highlighted):

A microfluidic assembly for use with a particle processing instrument, the microfluidic assembly comprising:

a substrate; and

a flow channel formed in the substrate, the flow channel having:

an inlet configured to receive a sample stream;

a fluid focusing region configured to focus the sample stream, the fluid focusing region having a lateral fluid focusing feature, a first vertical fluid focusing feature, and a second vertical fluid focusing feature, the lateral, the first vertical, and the second vertical fluid focusing features provided at different longitudinal locations along the flow channel, wherein a bottom surface of the flow channel lies in a first plane upstream of the first and second vertical fluid focusing features and the bottom surface of the flow channel shifts vertically upward to lie in a second plane downstream of the first and second vertical focusing features; and

an inspection region at least partially downstream of the fluid focusing region.

ABS Global requested inter partes review of the patent, arguing that the claims were anticipated by or obvious over certain prior art references. The PTO Patent Trial and Appeal Board granted the request, but ultimately issued a final written decision rejecting the ABS anticipation and obviousness arguments. Specifically, the Board construed the phrase “the sample stream” in the limitation “a fluid focusing region configured to focus the sample stream” of the main claim as covering only devices having a single stream, but not devices having multiple streams. Since the primary reference asserted by ABS disclosed only devices having multiple streams, the cited prior art failed to anticipate or make obvious the challenged claims.

On appeal, the CAFC reversed the Board’s claim construction. The Court first noted that the phrase “the sample stream”—in the limitation “a fluid focusing region configured to focus the sample stream”—includes the definite article “the,” indicating that the claim limitation refers back to the antecedent phrase “a sample stream” in the preceding claim limitation. The Court explained that the reference-back word ‘the’ gets its meaning (i.e., singular only or both singular and plural) from the meaning of the antecedent phrase, so if “a sample stream” allows multiple streams, the reference-back “the sample stream” phrase also allows multiple streams.

The Court then identified two general rules of claim construction. First, a phrase with “a” and “an” before a noun naming an object is construed to mean “one or more” such objects “unless the context sufficiently indicates otherwise.” Such a phrase is construed as singular/not plural only “where the language of the claims themselves, the specification, or the prosecution history necessitate a departure from the rule.”

Second, “[w]here the specification instructs as to the meaning of the claim term, the inventor’s lexicography governs.” Here, the specification stated that “for the purposes of the present disclosure, the term “a” or “an” entity refers to one or more of that entity. As such, the terms “a” or “an”, “one or more” and “at least one” can be used interchangeably herein” (emphasis added).

This definition in the patent itself strengthened the general understanding of “a” and “an” covering both singular and plural. The Court reviewed the remainder of the specification and the prosecution history but found nothing to contradict that general understanding.

The Court then replied to the reasoning on which the Board relied for finding that the man claim covered only devices with a single sample stream. Specifically, the Board noted that dependent claim 2 required that the “lateral fluid focusing feature is configured to introduce focusing fluid into the flow channel symmetrically with respect to a centerline of the sample stream” (emphasis added). The Board argued that if there is only one “centerline,” there can be only one “sample stream.”

The Court disagreed. For the same reasons that “a sample stream” may be singular or plural, “a centerline” may also be singular or plural. The Court therefore vacated the Board’s decision and sent the case back to the Board for it to reconsider the anticipation and obviousness issues in light of the Court’s claim construction.

Practical Tip:

Consider including in the specification the definition: “for the purposes of the present disclosure, the term “a” or “an” entity refers to one or more than one of that entity.” This definition makes the main claim broad, encompassing embodiments with one and more than one. If you do so, know that for infringement the patentee wants the claim to be broad (either one or more than one), but for validity the patentee wants the claim to be narrow (i.e., only one). Therefore, include a dependent claim limited to one only (i.e., single) and a dependent claim requiring multiple of the entity.