Selective Infiltration in Polymer Hybrid Thin Films as a Gas-Encapsulation Layer for Stretchable Electronics

The infiltration depth and water vapor transmission rate (WVTR) were explored in a variety of Al₂O₃-polymer hybrid layers as thin gas barrier films by filling the free volumes of polymers in the subsurface region with Al₂O₃ using the atomic layer infiltration (ALI) method. Among all, the prepared Al₂O₃-polyethylene terephthalate (PET), Al₂O₃-polyimide, and Al₂O₃-Nylon 6 hybrid thin layers with the infiltration depth in the nanometer ranges showed extremely low WVTR values (<10^-6 g m^-2 day^-1) in a Ca dot corrosion test. Furthermore, we observed selective infiltration among the two polymers [perfluoroalkoxy alkane (PFA) and PET] by a preferential growth of Al₂O₃ in the PET polymer that might be based on effective functional group anchoring in the ALI process. Then, we demonstrated a novel strategy by employing such a selective infiltration procedure and encapsulating individual segments of 144 Ca dots by Al₂O₃-PET hybrid thin films on the PFA polymer substrate rather than wrapping the whole thing together for the stretchable gas-encapsulation film. Regardless of stretching, it showed an extremely low WVTR (<10^-7 g m^-2 day^-1) and is proposed as a highly promising hermetic sealing alternative in stretchable, flexible, and foldable electronic display technologies.