Ultra-bendable and durable Graphene Urethane composite/silver nanowire film for flexible transparent electrodes and electromagnetic-interference shielding

Abstract

Foldable and rollable smart electronic devices are exposed to humidity, cyclic fatigue due to repeated bending, and the radiation or interference environment of electromagnetic waves, thereby necessitating countermeasures. Herein, an ultra-bendable and durable polymer composite/silver nanowire film with a high figure of merit was fabricated via the wet sintering of silver nanowires and a hydrophobic silane-functionalized graphene urethane rubber (HS/G UR) overcoat on a polyethylene terephthalate (PET) substrate. The sintered silver nanowire (SSN) film exhibits a threshold radius of curvature (RoC) of 0.8 mm, which is approximately 17 times lower than that of indium tin oxide on a 100-mu m-thick PET substrate and is highly suitable for foldable displays. The HS/G UR/SSN film with an HS-functionalized graphene nanoflake-embedded urethane composite overcoat showed a highly reduced threshold RoC of 0.43 mm and remarkably increased the cyclic-bending durability due to the enhanced adhesion between the NW and the substrate. After being bent 300,000 times at a RoC of 2 mm, the electrical resistance of the HS/G UFt/SSN film with a 25-mu m-thick PET substrate showed no change and the contact angle remained constant due to the HS-functionalized composite overcoat. The electromagnetic-interference shielding effectiveness of the HS/G UR/SSN film also showed little decrease after the bending test involving 300,000 cycles and a high-temperature and high-humidity durability test at 85 degrees C and 85% relative humidity for 500 h. The results show that the HS/G UR/SSN film has excellent flexibility and durability, making it suitable for use in transparent electrodes and/or electromagnetic-interference shields for future flexible devices.