MXene/polyurethane auxetic composite foam for electromagnetic interference shielding and impact attenuation

Lightweight electromagnetic interference (EMI) shielding and impact attenuating materials are vital to protect delicate components in portable electronics. While conductive foams are intriguing for lightweight EMI shielding, their impact attenuating properties remain unexplored. Herein, a MXene/auxetic polyurethane (MX/ APU) composite foam is developed for multifunctional EMI shielding and impact attenuation. The MX/APU composite presents a superior EMI shielding effectiveness (SE) of 76.2 dB, 31.2% higher than its non-auxetic counterpart at the same density owing to the larger specific surface area arising from the auxetic structure. Given its ultralow density of 0.063 g cm-3, it yields a specific SE of 1210 dB cm3 g-1, placing it among the best candidates for lightweight applications. The negative Poisson's ratio of MX/APU composite foam also delivers multifunctionalities of impact attenuation, reducing the peak force by 51.4% compared to a non-auxetic foam. This work provides a conceptually new approach to design lightweight multifunctional materials using auxetic structures.