Ultrathin and flexible electromagnetic interference shielding films by interface-confinement strategy
Electromagnetic interference (EMI) shielding technology is evolving from traditional bulky metal enclosures toward ultrathin, conformable, and flexible films. However, as the thickness of the shielding layer decreases, the electromagnetic wave absorption efficiency significantly deteriorates, leading to a marked decline in overall shielding performance. To overcome this intrinsic 'thickness–performance dilemma', porous structural designs are often employed to enhance multiple internal reflections and absorption. Nevertheless, such strategies typically suffer from uncontrollable thickness, poor spatial uniformity, and low process compatibility. To address these challenges, a joint team from the Gwangju Institute of Science and Technology and Seoul National University proposed an embedded MXene-in-metal (EXIM) shielding strategy. By embedding a non-porous MXene layer within a metallic film, a metal–MXene–metal heterolamellar architecture was constructed. Remarkably, this ultrathin structure achieves an EMI shielding effectiveness of ~70 dB at only ~1 μm thickness (up to 80 dB at 1.9 μm), breaking the conventional trade-off between reduced thickness and performance degradation. The superior performance originates from the conductivity contrast between the metal and MXene layers, which forms electromagnetic confinement wells. The localized electromagnetic waves undergo multiple polarization losses induced by interfacial dipoles, resulting in efficient energy absorption at thin thicknesses. The study further reveals that the EMI shielding performance of EXIM films primarily depends on the number of metal–MXene heterointerfaces rather than the total thickness. Multilayer stacking (e.g., Cu/Ti3C2Tx/Cu) notably enhances absorption efficiency while imparting excellent isotropy and flexibility. Moreover, introducing a Cr–Al dual-metal passivation layer effectively suppresses MXene oxidation, ensuring long-term operational reliability. The EXIM films are compatible with conventional fabrication and packaging techniques, including physical vapor deposition and spray coating, enabling scalable and large-area production. Practical demonstrations in USB 3.0 chips and flexible Schottky diodes confirm their outstanding capability in mitigating Bluetooth interference and blocking electromagnetic noise. This work is pioneering in that it introduces a new shielding mechanism based on conductivity contrast-induced electromagnetic confinement, achieves ultrahigh shielding effectiveness and mechanical flexibility within an ultrathin (<2 μm) structure, and elucidates a dipole-dominated interfacial polarization loss mechanism that provides theoretical insights into the design of 2D-material-based heterostructured shielding systems. Moreover, it opens up a new path for EMI shielding to shift from 'thick structure reflection' to 'heterogeneous interface confined absorption', providing a novel solution for realizing free-form, interference-free intelligent electronic packaging.