Hermetic stretchable seals enabled by a viscoplastic surface effect

Elastic seals safeguard stretchable electronics from reactive species in the surrounding environment. However, elastic contact with device modules and the intrinsic small-molecule permeability of elastomers limit the hermeticity of devices. Here we present a viscoplastic surface effect in polymeric elastomers for deriving sealing platforms with high hermeticity and large stretchability, made possible by controlling phase separations of partially miscible polar plastics within the near-surface region of block copolymer elastomers. The resulting viscoplastic surface allows the elastomer to form defect-free interfaces regardless of their size, materials chemistry and geometry. This capability facilitates the airtight integration of device modules to mitigate side leakage and enable the seamless assembly of high-potential gas barriers to prevent bulk penetration. A multilayer seal that incorporates scavenging components demonstrates properties that are as hermetic as aluminium foil while being stretchable like a rubber band. This breakthrough extends the operational lifetime of perovskite optoelectronics, hydrogel thermoelectrics and implantable bioelectronics without sacrificing their stretchability or efficiency.