Flexible and Ultrathin Waterproof Cellular Membranes Based on High‐Conjunction Metal‐Wrapped Polymer Nanofibers for Electromagnetic Interference Shielding

Abstract

Ultrathin, lightweight, and flexible electromagnetic interference (EMI) shielding materials are urgently demanded to address EM radiation pollution. Efficient design to utilize the shields' microstructures is crucial yet remains highly challenging for maximum EMI shielding effectiveness (SE) while minimizing material consumption. Herein, novel cellular membranes are designed based on a facile polydopamine‐assisted metal (copper or silver) deposition on electrospun polymer nanofibers. The membranes can efficiently exploit the high‐conjunction cellular structures of metal and polymer nanofibers, and their interactions for excellent electrical conductivity, mechanical flexibility, and ultrahigh EMI shielding performance. EMI SE reaches more than 53 dB in an ultra‐broadband frequency range at a membrane thickness of merely 2.5 µm and a density of 1.6 g cm−3, and an SE of 44.7 dB is accomplished at the lowest thickness of 1.2 µm. The normalized specific SE is up to 232 860 dB cm2 g−1, significantly surpassing that of other shielding materials ever reported. More, integrated functionalities are discovered in the membrane, such as antibacterial, waterproof properties, excellent air permeability, high resistance to mechanical deformations and low‐voltage uniform heating performance, offering strong potential for applications in aerospace and portable and wearable smart electronics.

Structural Design Strategies of Polymer Matrix Composites for Electromagnetic Interference Shielding: A Review

“…Conventional metallic materials (e.g., metal sheets, metal blocks, and metal foams, etc.) have been widely used in the field of EMI shielding due to their high electrical conductivity [ 30 – 32 ]. Park et al [ 33 ] prepared the NiFe/Cu multilayer sheets by a DC magnetron sputtering technology.…”

“…The polymer-assisted method refers to the direct deposition of conductive fillers on the surface of the polymer matrix films through laser printing, high-pressure spraying, sputtering deposition, etc., to prepare the polymer matrix EMI shielding films. The method is the main technical tool for the preparation of transparent EMI shielding films [ 30 , 135 , 136 ]. Wang et al [ 137 ] used the sputtering deposition technique to deposit copper-doped silver and indium tin oxide (ITO) films sequentially on a polyethylene terephthalate (PET) film substrate.…”

“…Conventional metallic materials (e.g., metal sheets, metal blocks, and metal foams, etc.) have been widely used in the field of EMI shielding due to their high electrical conductivity [30][31][32]. Park et al [33] Although the metal materials exhibit ultra-high EMI shielding performance, their shallow skin depth leads to the high reflectivity of electromagnetic waves, causing the secondary radiation pollution in the environment.…”

Polymer-Assisted Fabrication of Silver Nanowire Cellular Monoliths: Toward Hydrophobic and Ultraflexible High-Performance Electromagnetic Interference Shielding Materials

“…Generally, the total SE (SE T ) is influenced by reflection loss (SE R ), absorption loss 12 (SE A ), and multi-reflection ability, which correspond to the mobile charge carriers, the electric (or magnetic) dipoles, and the reflections at various surfaces or interfaces, respectively 39,46 . Considering the anisotropic microstructure of the aerogels, is similar to many other honeycomb-like porous architectures.…”

“…In particular, the metal nanofibers [33][34][35][36][37][38] exhibit favourable characteristics, such as ultrahigh aspect ratio, extraordinary electrical conductivity, and excellent mechanical flexibility, and thus, they have attracted great attention for constructing functional CPCs for EMI shielding applications. [39][40][41][42][43] Among various approaches for the fabrication of CPCs, dispersing the metal nanofibers in polymer matrix to form sufficient percolation conductive networks is the main strategy. [44][45][46] The resultant composites exhibit high EMI SE at the nanomaterial contents above a certain percolation threshold.…”