Anticipate This!™ | Patent and Trademark Law Blog

Mukherjee v. Chu.

Posted in Opinion Commentary by Jake Ward on March 2, 2007

 Recitation in the specification that a particular element was “critical” was used to invalidate claims under 35 U.S.C. § 112, ¶1.

(Fed. Cir. 2007, 06-1450), nonprecedential 


Mukherjee appealed the decision of the BPAI holding Mukherjee’s claims in Interference No. 105,281 unpatentable for failure to comply with the written description requirement of 35 U.S.C. § 112, ¶1.

Section 112,¶1 recites that:

The specification shall contain a written description of the invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains, or with which it is most nearly connected, to make and use the same, and shall set forth the best mode contemplated by the inventor of carrying out his invention.

The technology at issue in Mukherjee’s U.S.Serial No. 09/795,915 relates to rechargeable lithium-sulfur batteries. The Mukherjee application disclosed that in addition to sulfur, the cathodes of the batteries contain an Electroactive Transition Metal Chalcogenide1 (“ETMC”) composition. As defined in the Mukherjee application, ETMC is “an electroactive material having a reversible lithium insertion ability, wherein the transition metal is at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Nb, Mo, Ta, W, Co, Ni, Cu, Y, Zr, Ru, Rh, Pd, Hf, Re, Os, and Ir, and the chalcogenide is at least one selected from the group consisting of O, S, and Se.”

Noticeably absent from the claims at issue in the interference was any requirement that the cathode contain an ETMC. That is, the claims at issue failed to recite ETMC as a limitation.

Written description is a question of fact, judged from the perspective of one of ordinary skill in the art as of the relevant filing date.The BPAI had conducted an extensive (64-page) analysis the Mukherjee application to determine whether it provided written description support for the claims at issue.  In particular, the BPAI observed that the Detailed Description of the Invention Section continued with the notion that an ETMC cathode is a distinguishing feature of the invention.   For example, the Detailed Description states:

The present invention also pertains to the design and configuration of composite cathodes of the present invention. The relative configuration of the electroactive sulfur-containing cathode material and the electroactive transition metal chalcogenide composition in the composite cathode is critical. In all cases, in order to retard out-diffusion of anionic reduction products from the cathode compartment in the cell, the sulfur-containing cathode material must be effectively separated from the electrolyte or other layers or parts of the cell by a layer of an electroactive transition metal chalcogenide composition. (Emphasis mine and CAFC).

Based on the review of the entire specification, the BPAI found that the application does not disclose non-ETMC cathodes as the invention or alternatives to the invention and does not characterize ETMC as an optional part of the cathode.  Expert testimony was also provided to assert that it would have been clear to one of skill in the art that the Mukherjee invention was limited to ETMC cathodes because it was the presence of chalcogenide in the cathode that overcame the drawbacks of previous sulfur batteries. 

In light of the above, the CAFC held that there is substantial evidence to support the Board’s determination that the Mukherjee application does not comply with the written description requirement of 35 U.S.C. § 112, ¶1.  A reasonable person would find the testimonial and documentary evidence sufficient to support the Board’s finding. 


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