Structural Design for EMI Shielding: From Underlying Mechanisms to Common Pitfalls

Interfacial jamming and assembly, facilitated by nanoparticle surfactant (NPS) complexation, demonstrate a remarkable efficacy in stabilizing multiphase systems, evident in structured liquid streams and structured Pickering emulsions. However, the utilization of structured liquid templates to tune multiple porosity levels of ultra‐flyweight aerogels is barely discussed. In this study, a structured Pickering emulsion is prepared through mixing an aqueous dispersion of graphene oxide (GO) with an organic (hexane) solution containing an active ligand. The emulsion is jetted into the same organic phase, resulting in “dual jamming”. This process produced worm‐like aerogels with porosity that can be precisely tailored at four different levels: i) voids between filaments, ii) cavities produced by evaporation of trapped hexane droplets, iii) pores generated from sublimation of water in the bulk of GO emulsion, and iv) microscopic regions trapped between GO flakes or fractures/holes within GO nanosheets. These aerogels exhibit ultra‐low density (1.67–2.3 mg cm−3), high compressibility, and shape recovery. The multi‐scale porosity, created by structural design, endows aerogels with a record‐level fluid sorption capacity (e.g., 615 g g−1 for chloroform). Additionally, the aerogels demonstrate an absorption‐dominant electromagnetic interference (EMI) shielding mechanism, achieving a remarkable specific EMI shielding (SSE/t) of 67 178 dB cm2 g−1.

A Journey from Structured Emulsion Templates to Multifunctional Aerogels

Isari,

Ghaffarkhah,

Hashemi

et al. 2024

Absorption‐Dominant Electromagnetic Interference (EMI) Shielding across Multiple mmWave Bands Using Conductive Patterned Magnetic Composite and Double‐Walled Carbon Nanotube Film

Park,

Hwang,

Lee

et al. 2024

The revolution of millimeter‐wave (mmWave) technologies is prompting a need for absorption‐dominant EMI shielding materials. While conventional shielding materials struggle in the mmWave spectrum due to their reflective nature, this study introduces a novel EMI shielding film with ultralow reflection (<0.05 dB or 1.5%), ultrahigh absorption (>70 dB or 98.5%), and superior shielding (>70 dB or 99.99999%) across triple mmWave frequency bands with a thickness of 400 µm. By integrating a magnetic composite layer (MCL), a conductive patterned grid (CPG), and a double‐walled carbon nanotube film (DWCNTF), specific resonant frequencies of electromagnetic waves are transmitted into the film with minimized reflection, and trapped and dissipated between the CPG and the DWCNTF. The design factors for resonant frequencies, such as the CPG geometry and the MCL refractive index, are systematically investigated based on electromagnetic wave propagation theories. This innovative approach presents a promising solution for effective mmWave EMI shielding materials, with implications for mobile communication, radar systems, and wireless gigabit communication.

Environmentally Stable and Highly Crystalline MXenes for Multispectral Electromagnetic Shielding up to Millimeter Waves

Iqbal,

Kwon,

Hassan

et al. 2024

Advanced electronics and telecommunication devices rely on electromagnetic (EM) waves of a wide frequency range during their operation, thereby necessitating the development of efficient and ultrathin materials for electromagnetic interference (EMI) shielding across multispectral EM waves, particularly those exceeding 100 GHz, equivalent to millimeter wavelengths. Here, this study reveals that highly crystalline Ti3C2Tx MXene exhibits excellent EMI shielding performance across a multispectral frequency range from 100 kHz to 110 GHz, along with outstanding environmental stability and processability for solution coating and film fabrication. Notably, the highly crystalline Ti3C2Tx MXene films exhibit the highest electrical conductivity (18,000 S cm−1) and remarkable environmental stability (maintaining >95% electrical conductivity over one year), coupled with effective EMI shielding (up to 106 dB at 110 GHz with an ultrathin thickness of 10 µm), surpassing five other MXenes, including Nb2CTx, V2CTx, conv.‐Ti3C2Tx, Ti3CNTx, and Mo2Ti2C3Tx, and different synthetic materials. Furthermore, increasing the thickness, electrical conductivity, and frequency enhances the shielding performance. These results demonstrate the potential of applying MXenes to next‐generation portable electronics, radar systems, and autonomous vehicles. This study also provides insight into the fundamental shielding mechanisms related to material thickness, electrical conductivity, and frequency of EM waves.