High Deformability and High Thermal Conductivity Film Using Polymer Nanosheets and Liquid Metal

The development of highly deformable electronic devices is advancing rapidly, and thermal management within these devices become a significant challenge. Traditional thermal dissipation materials, such as copper or graphite sheets, are rigid and incompatible with flexible device architectures. Alternative materials, like stretchable polymers, offer poor thermal conductivity, thereby limiting their heat dissipation capacity. Attempts to enhance polymer performance by incorporating rigid materials, such as metals or graphene, generally result in compromised deformability despite improved thermal conductivity.<br/>Gallium-based liquid metals, including GaInSn and EGaIn, represent a novel class of thermal management materials that combine high thermal conductivity with excellent deformability and biocompatibility. However, their corrosive nature towards some metals poses additional challenges. To address this, there is a need for heat-dissipating materials that simultaneously offer high thermal conductivity, deformability, electrical insulation, and corrosion resistance. One approach involves the development of composite materials by embedding liquid metal in polymer matrices. Nevertheless, this technique significantly reduces thermal conductivity, achieving less than one-third that of the pure liquid metal due to the high polymer content.<br/>In this study, we developed a heat-dissipating material that encapsulates liquid metal within a nanoscale polymer film, enhancing both thermal conductivity and material deformability. This encapsulation prevents corrosion and maintains high deformability and insulation. The thickness of the liquid metal layer is 200 µm, surrounded by a polymer film with a thickness of less than 500 nm. The thermal conductivity of the resulting heat transfer sheet in the in-plane direction is 28.6 W/mK, approximately six times higher than that of conventional materials.<br/>To demonstrate its effectiveness, the heat-dissipating sheet was integrated into a stretchable electronic device, positioned between an LED and a stretchable substrate. The device's thermal performance was evaluated by powering the LEDs under mechanical deformation. It was observed that the temperature of the LEDs with the heat-dissipating sheet was approximately 20°C lower compared to the control setup without the sheet. This finding underscores the capability of the liquid metal sheet to enhance thermal diffusion under both static and dynamic conditions.