Dough‐Like Aramid Nanofiber Putty‐Assisted Design of Free‐Standing Liquid Metal‐Based Films for Ultrahigh Electromagnetic Interference Shielding

Gallium‐based liquid metal (LM) is expected to be an ideal candidate for flexible electromagnetic interference (EMI) shielding materials in wearable electronics due to its excellent electrical conductivity and extraordinary fluidity. However, it is difficult to fabricate LM as a free‐standing material due to its high surface tension and unmanageable fluidity, as well as its poor compatibility with other materials. Herein, a processing strategy is developed to fabricate free‐standing LM‐based films by vacuum filtration with the assistance of dough‐like aramid nanofiber (ANF) putty. The ANF putty improves the compatibility of ANF and LM, and also greatly improves the stability, reliability, and processability of ANF. Rational design of the structure enables the preparation of LM/ANF films with ANF as the nanobridge connecting LM micro/nanodroplets, and ANF‐LM‐ANF sandwich films with ANF as the shells, LM layer as the core. The LM/ANF film (tensile strength: 5.4 MPa) exhibits an ultrahigh EMI SE of up to 105.9 dB (8.0–12.4 GHz) at a thickness of 60 μm. While the ANF‐LM‐ANF sandwich film has higher mechanical strength (33.1 MPa), and also has good EMI shielding properties. The average EMI SE of the 10 μm thick sandwich film exceeds 45 dB in the X‐band.