CyTek Biosciences Inc v. Beckman Coulter Inc

1. Case Identification

• Case #: IPR2025-01319
• Patent #: 11,703,443
• Filed: July 17, 2025
• Petitioner(s): Cytek Biosciences, Inc.
• Patent Owner(s): Beckman Coulter, Inc.
• Challenged Claims: 1-4, 6, 7, 9, 10, 11, 13, 15-18

2. Patent Overview

• Title: FLOW CYTOMETER
• Brief Description: The ’443 patent discloses a wavelength division multiplexer (WDM) for use in a flow cytometer. The WDM is designed to separate collected fluorescent and scattered light into distinct color bands for photodetection using a series of filters and mirrors, including at least one curved mirror, arranged in a zig-zag configuration.

3. Grounds for Unpatentability

Ground 1: Obviousness over Goodman in view of Oostman - Claims 1-4, 6, 7, 9, 10, 11, 13, 15-18 are obvious over Goodman in view of Oostman.

• Prior Art Relied Upon: Goodman (Patent 6,542,306) and Oostman (Patent 6,683,314).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the combination renders the challenged claims obvious by substituting the superior WDM design from Goodman into the flow cytometer system of Oostman. Oostman disclosed a complete flow cytometer system with multiple lasers, a flow cell, a light collector, and optical fibers that route light to bulky, polygonal WDMs for analysis. Goodman, from the analogous art of optical communications, taught a compact and efficient zig-zag WDM using a transparent optical block, a set of wavelength-selective filters (e.g., dichroic filters), and a set of reflectors (e.g., curved mirrors) that relay light between the filters before it is directed to a set of detectors.
  • Petitioner asserted that for independent claims 1 and 18, Goodman disclosed all elements of the WDM itself: a set of filters, at least one curved mirror configured to receive and reflect light between the filters, and a set of corresponding detectors. Oostman provided the broader flow cytometer context required by the preambles and dependent claims, including the light sources, flow cell for particle passage, and the optical element (light collector) that gathers scattered and fluorescent light and delivers it via optical fibers to the WDM.
  • Motivation to Combine: Petitioner contended that a person of ordinary skill in the art (POSITA) would have been motivated to replace Oostman's large, complex, and difficult-to-align polygonal WDM with Goodman's well-known zig-zag design. The motivation stemmed from a desire to improve Oostman's system by achieving a more compact, scalable, modular, and cost-effective design. Goodman's WDM, built within a monolithic optical block, directly addressed these common engineering goals by reducing the system's footprint and simplifying manufacturing and alignment compared to Oostman's multi-component, open-air configuration. The ’443 patent itself acknowledged that WDM techniques from the optical communication industry (Goodman's field) were readily adaptable for fluorescence light detection.
  • Expectation of Success: A POSITA would have had a reasonable expectation of success in this combination. The integration was presented as a predictable substitution of one known type of WDM for another to achieve known benefits. Goodman was explicitly designed to be easily incorporated into other optical systems. Furthermore, the underlying principles of demultiplexing light are nearly identical between optical communications and flow cytometry detection, involving separating a multi-wavelength light signal received from an optical fiber into constituent bands for detection.

4. Key Claim Construction Positions

• "first" / "second" (Claim 9): The parties disputed the construction of these terms in the underlying litigation. Petitioner argued that under either its proposed "sequential" construction or the Patent Owner's "distinguishing" construction, Goodman's disclosure of a specific sequence of filters and mirrors in its zig-zag path (e.g., first filter 22a, first mirror 24a, second filter 22b, etc.) rendered the claim obvious.
• "collimated beam" (Claim 10): Petitioner noted a dispute over whether this term requires perfectly parallel rays or "nearly parallel" rays. Petitioner argued that Goodman taught reflectors that can be collimating mirrors, which inherently produce a collimated beam (parallel rays) that would satisfy either construction. Therefore, the dispute was immaterial to the obviousness analysis.

5. Arguments Regarding Discretionary Denial

• §314(a) / Fintiv: Petitioner argued against discretionary denial under Fintiv, stating that the co-pending district court litigation was in its very early stages. At the time of filing, claim construction briefing had just begun, and no claim construction rulings had been issued, indicating that an inter partes review (IPR) would be a more efficient resolution.
• §325(d): Petitioner asserted that denial under §325(d) would be inappropriate because the primary references, Goodman and Oostman, were not considered or discussed by the Examiner during the prosecution of the ’443 patent. Although the references were cited in a large Information Disclosure Statement (IDS) for a parent application, the Examiner noted that only a cursory review was performed due to the sheer volume, and the applicant never specifically raised them for "higher degree consideration." Petitioner also highlighted that the European Patent Office (EPO) had rejected nearly identical claims in a counterpart application based on these same references.

6. Relief Requested

• Petitioner requests institution of an IPR and cancellation of claims 1-4, 6, 7, 9, 10, 11, 13, and 15-18 of the ’443 patent as unpatentable.