After Schrader has failed to demonstrate that a claim is obvious based on printed publications in an inter partes review, it is estopped under 35 U.S.C. § 315(e)(2) from later raising in district court an invalidity challenge relying on a physical product that presents the same "grounds" as the printed publications. Even if the "evidence" (i.e., the physical product) was not available during the IPR, the "grounds" (i.e., obviousness) raised by the physical product and the printed publications are "materially identical", and Schrader is estopped since the grounds could reasonably have been raised during the IPR.
There is a circuit split on this issue and the Federal Circuit has yet to weigh in.