Abstract: Fabricating a capacitor include using a first etching solution to etch a first sheet of material so as to generate a spent etchant. At least one chemical component is recovered from the spent etchant. A second etching solution is used to etch a second sheet of material. The second etchant includes at least one of the chemical components that was recovered from the spent etchant.

Abstract: A capacitor is fabricated by generating a sheet of material that has a first active region that includes tunnels extending into an electrode metal. The sheet of material has a first inactive region that includes the electrode metal but does not include the tunnels extending into the electrode metal. The first inactive region has a first shape that includes multiple first projections that each projects from a perimeter of a circle. An electrode is removed from the sheet of material such that the electrode includes a portion of the inactive region. Additionally or alternately, fabricating a capacitor include using a first etching solution to etch a first sheet of material so as to generate a spent etchant. At least one chemical component is recovered from the spent etchant. A second etching solution is used to etch a second sheet of material. The second etchant includes at least one of the chemical components that was recovered from the spent etchant.