Growth and characterization of transition layer featuring metal nanoparticles to improve adhesion properties between magnetron sputtered nickel and polyimide

Metal-polymer films are widely used for flexible sensors and actuators, enduring various mechanical loads and facing the risk of structural damage. In this work, a method of manipulating the metal-polymer interface characteristics by metal nanoparticles in the transition layer is presented to prevent film fracture and restrain electrical failures. A transition layer with nickel (Ni) nanoparticles is grown on the surface of polyimide (PI) film through the stages of ring cleavage, ion exchange, and reduction. Further, the research investigates the influence of three parameters — the concentration of ring cleavage solution, the time of ring cleavage, and the concentration of reductant — on the thickness and particle morphology of the transition layer. After depositing ∼ 200 nm Ni film by magnetron sputtering, the film with a transition layer can withstand twice more than the maximum tensile force of untreated Ni-PI films when the resistance change reaches 10 %. The transition layer featuring metal nanoparticles increases the shear strength between Ni and PI by over 50 %. This method has been proposed for the first time, which considerably improves the adhesion properties of these two widely used materials, which provides a fine application prospect in flexible electronics.