PTAB

PGR2025-00088

Cytek Biosciences Inc v. Beckman Coulter Inc

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Flow Cytometer
  • Brief Description: The ’107 patent discloses a flow cytometer that uses a wavelength division multiplexer (WDM) to analyze fluorescent and scattered light. The WDM separates light, collected by an optical fiber from a flow cell, into distinct wavelength bands using a cascaded arrangement of mirrors, filters, and an array of avalanche photodiode (APD) detectors.

3. Grounds for Unpatentability

Ground 1: Invalidity Under 35 U.S.C. § 112 for Lack of Written Description

  • Core Argument for this Ground: Petitioner argued that the challenged claims are invalid because they lack adequate written description. The claims broadly recite a WDM comprising filters, mirrors, and APDs but crucially omit a “collimating optical element,” which the specification repeatedly describes as an essential feature for the invention to be operable. Petitioner contended that every embodiment disclosed in the ’107 patent requires this element to project a collimated beam through the cascaded relay architecture, which is necessary to manage signal integrity for the noise-sensitive APDs. By omitting this critical element, the claims impermissibly cover a broader genus of inoperable or undescribed WDMs for which the inventor had not demonstrated possession.

Ground 2: Claims 1-3, 5-14, 16-18, 20-22, and 26-30 are obvious over Chandler and Goodman

  • Prior Art Relied Upon: Chandler (Patent 6,139,800) and Goodman (Patent 6,542,306).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted that Chandler disclosed a flow cytometer that used multimode optical fibers to route light to filtering, amplification, and digital conversion (FADC) units containing photodetectors, which could be APDs. Goodman, from the analogous field of optical communications, disclosed a compact, modular, and efficient WDM using a zig-zag optical path with an array of mirrors (reflectors) and filters to demultiplex light received from an optical fiber. Petitioner argued that substituting Chandler’s bulkier FADC units with Goodman’s compact WDM architecture meets all limitations of the independent claims.
    • Motivation to Combine: A Person of Ordinary Skill in the Art (POSITA) would combine these references to achieve a smaller, more cost-effective, and efficient flow cytometer, a stated goal of Chandler. A POSITA seeking to miniaturize Chandler’s system would have looked to Goodman’s well-known zig-zag WDM design as a superior alternative to Chandler’s branched filter configuration.
    • Expectation of Success: A POSITA would have had a high expectation of success because Goodman’s WDM was explicitly designed for easy incorporation into other optical systems. Furthermore, the ’107 patent itself concedes that WDM techniques from the optical communication industry are “readily adapted” for fluorescence light detection in flow cytometry.

Ground 3: Claims 1-3, 5-14, 16-18, 20-22, and 26-30 are obvious over Oostman, Goodman, and Frazier

  • Prior Art Relied Upon: Oostman (Patent 6,683,314), Goodman (Patent 6,542,306), and Frazier (Patent 8,284,402).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Oostman taught a flow cytometer using lasers, a flow cell, and detector array clusters (acting as WDMs) that receive light via multi-mode optical fibers. The combination replaces Oostman’s detector clusters with Goodman’s more compact and efficient zig-zag optical block WDM. Frazier, which discloses a similar zig-zag WDM, was cited for its express teaching that the photodetectors can be APDs.
    • Motivation to Combine: A POSITA would combine Oostman and Goodman to improve optical alignment and reduce the system footprint, key challenges in the field. The resulting system would be further combined with Frazier’s teachings to incorporate the known benefits of APDs over older photodetectors, such as smaller size and improved signal-to-noise ratios, to create a more compact and sensitive instrument.
    • Expectation of Success: Success was predictable because implementing APDs in flow cytometers was well-established by 2011, and researchers had already demonstrated the successful substitution of APDs in commercial systems. The combination involved applying known technologies to achieve predictable results.
  • Additional Grounds: Petitioner asserted additional obviousness challenges based on combinations including Hamamatsu to further support limitations related to small-area APDs. Petitioner also asserted multiple invalidity grounds under 35 U.S.C. § 112 for lack of written description and enablement regarding the terms “optical fiber” and the scope of a WDM capable of detecting a “substantially full spectrum of visible light.”

4. Key Technical Contentions (Beyond Claim Construction)

  • A core technical contention that underpinned multiple grounds was that any functional WDM as claimed, which uses noise-sensitive APDs and a cascaded relay architecture, technically requires a collimating optical element to create and maintain a collimated beam. Petitioner argued that omitting this element from the claims renders them technically deficient, as a WDM receiving non-collimated light from an extended source (like a multimode fiber) would be inoperable due to significant signal divergence and photon loss over the optical path.

5. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial would be inappropriate and stated its intent to fully brief its opposition to any such request from the Patent Owner, referencing the USPTO’s March 26, 2025 Interim Processes for PTAB Workload Management.

6. Relief Requested

  • Petitioner requests institution of Post-Grant Review and cancellation of claims 1-3, 5-14, 16-18, 20-22, and 26-30 of the ’107 patent as unpatentable.