Room temperature self-healing and high gas barrier properties of elastomer composites incorporated with liquid metal

Abstract

Flexible electronic devices require stretchable packaging materials that provide a hermetic seal. However, conventional soft materials often exhibit strong gas permeability, making it difficult to achieve stable operation, which requires films with high deformability, self-healing capability, and gas barrier functionality. In this study, a layer by layer (LBL) method was employed to uniformly coat a controllable thickness of liquid metal (LM) onto a designed and synthesized self-healing thermoplastic polyurethane (TPU) film, successfully developing a stretchable gas barrier film (TPU/LM) with high gas barrier properties. The designed polyurethane film significantly enhanced the adhesion of the liquid metal, effectively preventing leakage. The experimental results show that the water vapor transmission rate (WVTR) of the TPU/LM composite film with a thickness of 40 μm is 4.04g/(m²·day). Compared to the film without LM, the gas barrier performance has been improved by approximately 16 times. Additionally, there is a significant enhancement in nitrogen (N₂) barrier, with a permeation rate reaching 4.0*10⁻¹⁷ cm³ cm/(cm²·s·Pa), effectively blocking the N₂ permeation. This demonstrates the universality of the TPU/LM in gas barrier applications. Furthermore, the TPU/LM film also demonstrated excellent electromagnetic shielding effectiveness. The self-healing capability of the stretchable gas barrier film allows it to recover its initial gas barrier performance after mechanical damage. Humidity-sensitive resistors encapsulated with TPU/LM exhibited stable operation in both air and 90 % humidity environments, confirming the superior barrier properties of the TPU/LM. Generally, the developed TPU/LM is suitable for packaging applications in the next generation of flexible electronic devices.