Decoupled electronic-ionic switching in gradient liquid metal hydrogels for high-contrast and absorption-dominated EMI shielding

Abstract Simultaneously addressing the formidable challenges of reflection-induced secondary pollution and the limited dynamic range of responsive electromagnetic interference (EMI) shielding remains a critical bottleneck for intelligent electromagnetic protection. Herein, we report a gradient liquid metal hydrogel platform that enables a synergistic, decoupled electronic-ionic switching mechanism to achieve high-contrast and absorption-dominated shielding. Unlike conventional responsive hydrogels that rely on quality-deteriorating solvent exchange, swelling, or shrinking—processes that inherently compromise structural reliability—this platform achieves precise, reversible shielding control without any mass loss or structural deformation. By nanoconfining liquid metal (LM) microdroplets within a mechanically robust, aramid nanofiber-reinforced poly(vinyl alcohol) (PVA) matrix, we develop a unique phase-transition-driven “double-lock” switching mechanism. This mechanism leverages the decoupled sequential phase transitions of the LM fillers (electronic channel) and the ionic solvent (ionic channel) to realize a stable transition between electromagnetic “transparency” and “protection”. Specifically, a biomimetic gradient architecture effectively eliminates surface impedance mismatch, achieving an ultra-high EMI shielding effectiveness (SE) of 60.6 dB with a distinct absorption-dominant characteristic (A/R > 1.2). The synergistic “double-lock” system enables a remarkable dynamic switching contrast of 50.7 dB while maintaining its “green” shielding mechanism throughout all functional operational states. By synergizing this high switching contrast with a consistently absorption-dominated performance whenever active shielding is engaged, this work establishes a structure-driven paradigm for next-generation green and intelligent electromagnetic protection.