Dual-Network MXene/Polyurethane Composite Foams for Both Stretchable and Compressible Electromagnetic Interference Shielding and Strain Sensors

Miniaturized and wearable electronic products require electromagnetic interference shielding (EMI) materials with sensing functions to cope with complex application situations. Herein, an effective dual-network structure is designed to fabricate two-dimensional transition metal carbides and nitrides/bacterial cellulose-thermoplastic polyurethane (MXene/BC-TPU) foams with intriguing EMI shielding property and piezoelectric sensing ability under both compressive and tensile strains. Anisotropic MXene/BC aerogels, as conductive networks, with impressive conductivity (1912 S m^-1), ultrahigh EMI shielding effectiveness (SE) of 86 dB, and absolute SE up to 63,608 dB cm² g^-1 can be built by directional freezing. Interpenetrated neuro-like TPU network is embedded into the MXene/BC aerogels by controllable coagulation to provide elasticity. Inheriting the elastic TPU network, the light weight MXene/BC-TPU foams show superb elasticity and remarkable fatigue resistance suffering both compressive and tensile strains with a wide strain range (-80-80%). Meanwhile, benefiting from the separated conductive MXene/BC network and the elastic TPU network, the MXene/BC-TPU foams display an outstanding EMI SE (76 dB) with an EMI SE retention of 86.8% after 5000 compression-release cycles and an EMI SE retention of 69.7% after 100 stretch-release cycles, respectively. Furthermore, the MXene/BC-TPU foams reveal stable resistance signal output as piezoresistive sensors in a wide strain range of -80-80%. The highly conductive, stretchable, and compressible MXene/BC-TPU foams are suitable as EMI shielding and motion monitoring materials for wearable electronics.