High-Performance Joule Heating and Electromagnetic Shielding Properties of Anisotropic Carbon Scaffolds

An Integrated Approach for Piezo-Electrochemical Nanoenergy Generation, Storage, and Real-Time Electromagnetic Interference Shielding Control

The extensive utilization of high-end wireless electronic equipment in medical, robotics, satellite, and military communications has created a pressing challenge for real-time electromagnetic interference (EMI) control. Herein, a piezo-powered self-chargeable supercapacitor (PPSC) architecture based on an iron-doped graphitic nitride (Fe-g-C3N4: FGN) electrode with a solid piezoelectrolyte is devised, which can provide real-time controlled EMI shielding through piezo-powered self-charging voltage (SCV). This PPSC device along with real-time SCV-controlled EMI shielding also integrates additional features like nanoenergy generation and storing capability. The results demonstrate that the PPSC device is capable of exhibiting a piezo-tuned self-charging ability of up to 669.2 mV under 9.47 N of dynamic pressing for 180 s. The SCV electrostatically modifies the PPSC device that causes destructive interference and governs the absorption of electromagnetic radiation (EMR) and controls the absorption-dominated EMI shielding up to 59.2 dB at 500 mV. Additionally, the SCV-led electrification of the PPSC device also controls a unique functional transition from the EMR reflector to the EMR absorber at ∼90 mV. Hence, this strategy of tailored absorption and reflection adjustments of EMR could also potentially contribute toward the advancement of stealth technology for military armaments with externally controlled stealth capabilities.

Remarkable Conductive Anisotropy of Ag-Coated Glass Microbeads/UV Adhesive Composites Made by Electric Field Induced Alignment

We successfully prepared highly anisotropic conductive composites (ACCs) made of Ag-coated glass microbeads/UV adhesive via electric field-induced alignment, which was achieved using custom patterned microelectrode arrays. An optimized AC electric field (2 kV/cm, 1 kHz) with pole-plate spacing (50 μm) was utilized to effectively assemble the microbeads into chain arrays, which were precisely positioned on the microelectrode arrays to construct ordered conductive channels. In this case, tangling and cross-connection of the assembled microchains could be reduced, resulting in enhanced performance of the ACCs with high conductivity as well as excellent anisotropy. With a minor loading (3 wt %), the conductivity in the alignment direction could reach ∼24.9 S/m, which was the highest among the reported ACCs to the best of our knowledge, and it could also be 6 orders of magnitude higher than that within the plane. Besides, the samples exhibited high reliability in wire connections with low resistances. Due to these fascinating properties, the ACCs demonstrate promising applications for reliable electrical interconnects and integrated circuits.

Design, Manufacturing and Functions of Pore-Structured Materials: From Biomimetics to Artificial

Porous structures with light weight and high mechanical performance exist widely in the tissues of animals and plants. Biomimetic materials with those porous structures have been well-developed, and their highly specific surfaces can be further used in functional integration. However, most porous structures in those tissues can hardly be entirely duplicated, and their complex structure-performance relationship may still be not fully understood. The key challenges in promoting the applications of biomimetic porous materials are to figure out the essential factors in hierarchical porous structures and to develop matched preparation methods to control those factors precisely. Hence, this article reviews the existing methods to prepare biomimetic porous structures. Then, the well-proved effects of micropores, mesopores, and macropores on their various properties are introduced, including mechanical, electric, magnetic, thermotics, acoustic, and chemical properties. The advantages and disadvantages of hierarchical porous structures and their preparation methods are deeply evaluated. Focusing on those disadvantages and aiming to improve the performance and functions, we summarize several modification strategies and discuss the possibility of replacing biomimetic porous structures with meta-structures.

Oxidation-Resistant MXene-Based Melamine Foam with Ultralow-Percolation Thresholds for Electromagnetic-Infrared Compatible Shielding

To effectively avoid the drawbacks of conventional metal-based electromagnetic interference (EMI) shielding materials such as high density and susceptibility to corrosion, a multifunctional melamine foam (MF) consisting of MXene/polydimethylsiloxane (PDMS) layers with ultralow percolation thresholds was designed through the electrostatic self-assembly and impregnation strategies. The prepared lightweight foams simultaneously show multifunctional properties including EMI shielding, infrared (IR) stealth, oxidation-resistance, and compression stability. Typically, this multifunctional foam exhibits an excellent EMI shielding efficiency (EMI SE) of 45.2 dB at X-band (8.2-12.4 GHz) with only 1.131 vol % MXene filler. Moreover, the temperature difference between the upper and lower surfaces of the foam can be maintained at 45 °C due to its unique three-dimensional (3D) porous structure and low infrared emissivity. The MF skeleton with MXene/PDMS (MFMXP) displays high hydrophobicity, which remains stable in EMI SE after 60 days of exposure to air. Additionally, it shows outstanding mechanical stability after 100 cycles of compression experiments. The lightweight stealth nanocomposite foams can operate stably in complex environments and show high potential for applications in high-tech fields such as wearable electronics, the military, and semiconductors, etc.

Ultrastrong and Hydrophobic Sandwich-Structured MXene-Based Composite Films for High-Efficiency Electromagnetic Interference Shielding

Electromagnetic interference (EMI) shielding materials are highly necessary to solve the problem of electromagnetic radiation. Transition-metal carbide/nitride (MXene) materials offer great potential for the construction of high-performance EMI shields because of their high electrical conductivity and versatile surface chemistry. However, MXene generally suffers from poor mechanical and oxidation-resistant properties, which hinders its practical applications. Herein, flexible, strong, and hydrophobic sandwich-structured composite films (H-S-MXene), consisting of a conductive MXene layer and supporting aramid nanofiber layer, were fabricated using step-by-step vacuum-assisted filtration and dip coating. Given the unique sandwich structure, hydrogen bonding interactions, and covalent cross-linking of the MXene sheets, the H-S-MXene composite films demonstrated simultaneously excellent EMI shielding and mechanical properties. The EMI shielding effectiveness of the H-S-MXene composite film with 20 wt % MXene content reached 46.1 dB at thickness of 23.2 ± 0.5 μm, and the tensile strength of the film reached 302.1 MPa, which outperformed other reported EMI shielding materials. The excellent mechanical flexibility and hydrophobicity of the H-S-MXene composite films ensured a stable EMI shielding performance, which could withstand cycled bending, torsion, and exposure to aqueous environments. These impressive features made the H-S-MXene composite films promising candidates for electronic devices and aerospace. This study provides important guidance for the rational design of stable MXene-based composites with advanced properties.

Multi-interface Assembled N-Doped MXene/HCFG/AgNW Films for Wearable Electromagnetic Shielding Devices with Multimodal Energy Conversion and Healthcare Monitoring Performances

With the progressive requirements of modern electronics, outstanding electromagnetic interference (EMI) shielding materials are extensively desirable to protect intelligent electronic equipment against EMI radiation under various conditions, while integrating functional applications. So far, it remains a great challenge to effectively construct thin films with diversiform frameworks as integrated shielding devices. To simultaneously promote electromagnetic waves (EMWs) attenuation and construct integrated multifunction, an alternating-layered deposition strategy is designed to fabricate polydimethylsiloxane packaged N-doped MXene (Ti₃CNT_x)/graphene oxide wrapped hollow carbon fiber/silver nanowire films (p-LMHA) followed by annealing and encapsulation approaches. Contributed by the synergistic effect of consecutively conductive networks and porous architectures, LMHA films exhibit satisfying EMI shielding effectiveness of 73.2 dB at a thickness of 11 μm, with a specific EMI shielding effectiveness of 31 150.1 dB·cm²·g^-1. Benefiting from the encapsulation, p-LMHA films further impart hydrophobicity and reliability against harsh environments. Besides, p-LMHA devices integrate a rapid-response behavior of the electro/photothermal and, meanwhile, function as a healthcare monitoring sensor. Therefore, it is believed that the p-LMHA films assembled by independent conductive networks with reliability offer a facile solution for practical multimodular protection of devices with integration characteristics.