Leaf-inspired nanofibrous mat-based composites for liquid–gas phase change-driven dynamically adaptive electromagnetic interference shielding†

Smart-response electromagnetic interference (EMI) shielding composites are fascinating in aerospace, military and protective textile applications. However, the majority of current EMI shielding composites are either absorption- or reflection-dominant and the self-tuning shielding mechanism is limited because it mainly depends on the composite thickness. Herein, inspired by leaves, a bionic bilayer composite structure of a PAN–PVP nanofibrous mat/COOH-CNTs aerogel and a PAN–PVP nanofibrous mat/COOH-CNTs film (PAF) is built with the aerogel as an electromagnetic absorption layer and the film as an electromagnetic reflection layer. The composite's reflection and absorption of incident electromagnetic waves are modulated by simulating photosynthesis and transpiration. PAF's unique gradient structure allows for 95% light absorption as well as rapid water absorption and diffusion. In addition, through water absorption and liquid–gas phase change, the EMI shielding effectiveness of PAF can be self-tuned between 64.4 dB and 35.9 dB, with a ΔSE of 28.5 dB, and the absorption power coefficient can be adjusted between 0.31 and 0.71, which regulates the EMI shielding mechanism. This may be because adsorbed water promotes electron transfer within the composite. Meanwhile, the PAF also exhibits good infrared stealth performance. This innovative work provides an effective strategy to design and construct dynamically adaptive EMI shielding composites.