Multifunctional Janus composite films with spontaneous gravity-induced asymmetric gradient for absorption-dominated electromagnetic interference shielding and high-efficiency thermal management

Abstract

With the rapid advancement of high-power electronics, developing advanced multifunctional electromagnetic interference (EMI) shielding materials that simultaneously realize high shielding effectiveness (SE), low reflection, and mechanical adaptability remains a critical challenge. This work presents a gravity-driven assembly strategy to construct asymmetric gradient structures by spatially distributing low-density MXene nanosheets@hollow Fe₃O₄ nanospheres (MXene@HFO) and high-density silver-coated tetraneedle ZnO whiskers (T-ZnO@Ag) within a waterborne polyurethane (WPU) matrix. The self-organized Janus architecture optimizes impedance matching and enables a multiple “absorption-reflection-reabsorption” loss mechanism. The resulting composite film achieves absorption-dominated EMI shielding with an SE of 72.4 dB and an absorption coefficient (A) of 0.54. Notably, it also exhibits exceptional mechanical properties, including over 400% reversible stretchability, robust durability for 1000 cycles, and strain-responsive shielding tunability, addressing key limitations in practical applications. Moreover, the interconnected conductive network delivers rapid Joule heating (174°C in 30 s at 2.5 V) and high thermal conductivity (9.53 W m⁻¹ K⁻¹), enabling efficient thermal management. The proposed multifunctional film holds great promise for next-generation electronics requiring simultaneous EMI protection and thermal management, while the one-step fabrication methodology offers scalability advantages suitable for industrial production.