Ultrathin, flexible, and high-performance bacterial cellulose/copper nanowires film for broadband electromagnetic interference shielding and photothermal conversion

The swift advancement in wearable electronics, implantable medical devices, fifth communications, unmanned aerial vehicles, and military stealth technology leads to a surge of highly flexible multifunctional films. The enhancement of electromagnetic radiation and the demand for normal operation in extreme environments has posed substantial challenges for flexible films with outstanding electromagnetic interference (EMI) shielding and other functionality. In this paper, ultra-thin, flexible Janus bacterial cellulose (BC)/cooper nanowires (CuNWs) films are prepared via using microwave-assisted hydrothermal technique and vacuum filtration methods, which are used as broadband EMI shielding materials and photothermal conversion materials. In addition, the optimum reaction conditions for preparing CuNWs were investigated in detail. BC/CuNWs films have outstanding mechanical properties, with stress of 43.1-77.3 MPa under the strain of 4.1-7.3%. When the mass of CuNWs is 10 mg, the conductivity of BC/CuNWs films can reach 140700.4 S m-1. Ultra-strong EMI shielding effectiveness of 68.71 dB in frequency range of 8-12.4 GHz and over 56 dB can be achieved in the broad frequency of 6-26.5 GHz for BC/CuNWs film with an ultra-thin thickness of 30 μm. The specific EMI shielding effectiveness of BCu-4 film is up to 2290.33 dB mm-1. In addition, BC/CuNWs films exhibit outstanding photothermal conversion and the saturation temperature of BCu-4 film reach up to 75 oC under irradiation of one sun light. In this work, we provide a simple and collaborative strategy for fabricating ultra-thin, flexible multifunctional films with EMI shielding and photothermal conversion which can be used to solve EMI problems in modern electronic technology.