A multilayered unit includes a core comprising an energetic material and an activator; a support layer disposed on the core; and a protective layer disposed on the support layer, wherein the support layer and the protective layer each independently comprises a polymeric material, a metallic material, or a combination comprising at least one of the foregoing, provided that the support layer is compositionally different from the protective layer. The multilayered unit can be embedded in a component, attached to a component, or disposed between two components of a downhole assembly. The downhole assembly containing the multilayered unit has controlled disintegration in a downhole environment.