Broad Claim Language Must Be Enabled Across Its Full Scope of Coverage

In MagSil Corp. v. Hitachi Global Storage Technologies, Inc., No. 11-1221 (Fed. Cir. Aug. 14, 2012), the Federal Circuit affirmed the district court's grant of SJ of invalidity for lack of enablement of U.S. Patent No. 5,629,922 ("the '922 patent"), assigned to the Massachusetts Institute of Technology and exclusively licensed to MagSil Corporation ("MagSil").

The '922 patent relates to read-write sensors for computer hard disk drive storage systems. The sensors use a quantum mechanical effect where the electric current can tunnel from one electrode through a thin insulating barrier layer into a second electrode. With two ferromagnetic electrodes, the tri-layer tunnel resistance changes with a change in magnetization direction. The '922 patent claims a method of manufacturing a tri-layer tunnel junction and the junction itself. The asserted claims, however, only claim the tunnel junction device.

MagSil filed suit against several defendants, including Hitachi Global Storage Technologies, Inc., Hitachi America, Ltd., Hitachi Data Systems Corporation, and Shenzhen Excelstor Technology, Ltd. (collectively "Hitachi"), alleging that their disk drive products infringed claims of the '922 patent. The non-Hitachi defendants were dismissed from the case. After claim construction proceedings, the parties filed cross-motions for SJ. The district court granted Hitachi's SJ motions of invalidity and noninfringement after finding that the limitation "a change in the resistance by at least 10% at room temperature" was not enabled by the specification. Because the asserted claims were deemed invalid, the district court also granted Hitachi's SJ motion of noninfringement.

On appeal, the Federal Circuit affirmed the district court's holdings. The Court reiterated that enablement serves a dual function in the patent system by ensuring adequate disclosure of the claimed invention and preventing overbroad claiming that might otherwise attempt to cover more than was actually invented. MagSil advocated for a broad construction of the claim terms, relying on, among other things, expert testimony that the claims cover tunnel junctions with resistive changes of 100% or more, with one of the inventors testifying that a 1000% change falls within the scope of the claims. As construed, the district court found that the asserted claims cover "resistance changes beyond 120% and up to infinity." Slip op. at 7 (quoting MagSil Corp. v. Seagate Tech., 764 F. Supp. 2d 647...