Obviousness

An analysis of U.S. Patent No. 12,174,106, titled "Flow cytometer," under 35 U.S.C. § 103 suggests that several of its claims may be rendered obvious by a combination of prior art references. This analysis is based on information from the patent's prosecution history, which reveals key prior art considered by the U.S. Patent and Trademark Office (USPTO) examiner.

Key Prior Art and Motivation for Combination

During the prosecution of the patent family to which U.S. Patent No. 12,174,106 belongs, the examiner cited and combined at least two key prior art references:

• U.S. Patent Publication No. 2003/0048539 to Oostman, Jr., et al. (Oostman): This reference discloses a flow cytometer.
• U.S. Patent Publication No. 2004/0165828 to Capewell (Capewell): This reference, from the field of optical communications, discloses a wavelength division multiplexer (WDM).

The motivation to combine these references, as is common in patent examination, would be to apply a known technology from one field (optical communications) to solve a known problem or to improve a device in another field (flow cytometry). A person of ordinary skill in the art of flow cytometer design would be motivated to look for more efficient and compact ways to manage and detect multiple optical signals, a problem addressed by WDM technology in the telecommunications sector.

Obviousness Analysis of Key Claims

While a full analysis would require a detailed element-by-element breakdown of every claim, a general obviousness argument can be constructed based on the combination of Oostman and Capewell.

Claim 1 of US Patent 12,174,106 describes a flow cytometer that includes:

• An optical illumination subsystem for directing a beam of light into a viewing zone.
• A composite microscope objective for imaging light scattered from and fluoresced by a particle.
• A fluidic subsystem for supplying a liquid sheath flow.
• A peristaltic pump for supplying the sample liquid.
• A wavelength division multiplexer (WDM) for separating the light from the viewing zone into multiple colored bands.

The Combination of Oostman and Capewell:

Oostman teaches a flow cytometer, which would provide the foundational elements of the claimed invention, such as the illumination system, the fluidics, and the general concept of detecting light from particles in a flow stream. However, Oostman may not have explicitly disclosed the specific WDM configuration claimed in the '106 patent.

Capewell, on the other hand, provides the detailed teachings of a WDM system for separating light into different wavelengths. A person of ordinary skill in the art, seeking to improve the optical detection system of the flow cytometer taught by Oostman, would have found it obvious to incorporate the WDM technology from Capewell. The motivation would be to create a more compact, efficient, and reconfigurable system for detecting multiple fluorescence signals, a known goal in the field of flow cytometry.

The examiner in the prosecution of a related patent explicitly stated that the claims were allowable over the combination of Oostman and Capewell, suggesting that while the combination was considered, the applicant was able to demonstrate patentable differences. However, for the purposes of this analysis, the combination itself is a strong starting point for an obviousness rejection.

For example, the '106 patent describes a WDM with a "cascaded unit-magnification image relay architecture" to extend the collimated optical path without significant beam expansion. If the specific optical arrangement in Capewell, when applied to the flow cytometer of Oostman, would result in a similar architecture to achieve the desired performance, then the claims of the '106 patent directed to this arrangement could be considered obvious.

Conclusion

The combination of U.S. Patent Publication No. 2003/0048539 to Oostman and U.S. Patent Publication No. 2004/0165828 to Capewell provides a strong basis for an obviousness challenge to at least some of the claims of U.S. Patent No. 12,174,106. A person of ordinary skill in the art would have been motivated to combine the known elements of a flow cytometer from Oostman with the advanced optical signal multiplexing techniques from Capewell to achieve a more efficient and capable instrument. The ultimate patentability of the claims would then depend on whether the specific implementation described in the '106 patent contains novel and non-obvious features that are not taught or suggested by the combination of these prior art references. As indicated by the allowance of a related patent over this combination, the applicant was able to successfully argue for the novelty and non-obviousness of their specific claims. However, the potential for an obviousness challenge based on this combination remains a critical aspect of the patent's file history.