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1. Electrically Insulating Flexible Films with Quasi‐1D van der Waals Fillers as Efficient Electromagnetic Shields in the GHz and Sub‐THz Frequency Bands

   https://doi.org/10.1002/adma.202007286  

   Barani, Zahra ; Kargar, Fariborz ; Ghafouri, Yassamin ; Ghosh, Subhajit ; Godziszewski, Konrad ; Baraghani, Saba ; Yashchyshyn, Yevhen ; Cywiński, Grzegorz ; Rumyantsev, Sergey ; Salguero, Tina T. ; et al ( February 2021 , Advanced Materials)

   Polymer composite films containing fillers comprising quasi‐1D van der Waals materials, specifically transition metal trichalcogenides with 1D structural motifs that enable their exfoliation into bundles of atomic threads, are reported. These nanostructures are characterized by extremely large aspect ratios of up to≈10⁶. The polymer composites with low loadings of quasi‐1D TaSe₃fillers (<3 vol%) reveal excellent electromagnetic interference shielding in the X‐band GHz and extremely high frequency sub‐THz frequency ranges, while remaining DC electrically insulating. The unique electromagnetic shielding characteristics of these films are attributed to effective coupling of the electromagnetic waves to the high‐aspect‐ratio electrically conductive TaSe₃atomic‐thread bundles even when the filler concentration is below the electrical percolation threshold. These novel films are promising for high‐frequency communication technologies, which require electromagnetic shielding films that are flexible, lightweight, corrosion resistant, inexpensive, and electrically insulating.

    

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2. Dual‐Functional Graphene Composites for Electromagnetic Shielding and Thermal Management

   https://doi.org/10.1002/aelm.201800558  

   Kargar, Fariborz ; Barani, Zahra ; Balinskiy, Michael ; Magana, Andres Sanchez ; Lewis, Jacob S. ; Balandin, Alexander A. ( October 2018 , Advanced Electronic Materials)

   The synthesis and characterization of epoxy‐based composites with few‐layer graphene fillers, which are capable of dual‐functional applications, are reported. It is found that composites with certain types of few‐layer graphene fillers reveal an efficient total electromagnetic interference shielding, SE_tot≈ 45 dB, in the important X‐band frequency range,f= 8.2 −12.4 GHz, while simultaneously providing high thermal conductivity,K≈ 8 W m⁻¹K⁻¹, which is a factor of ×35 larger than that of the base matrix material. The efficiency of the dual‐functional application depends on the filler characteristics: thickness, lateral dimensions, aspect ratio, and concentration. Graphene loading fractions above the electrical and thermal “percolation thresholds” allow for strong enhancement of both the electromagnetic interference shielding and heat conduction properties. Interestingly, graphene composites can block the electromagnetic energy even below the electrical percolation threshold, remaining electrically insulating, which is an important feature for some types of thermal interface materials. The dual functionality of the graphene composites can substantially improve the electromagnetic shielding and thermal management of airborne systems while simultaneously reducing their weight and cost.

    

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3. Layer‐by‐Layer Assembly of Cross‐Functional Semi‐transparent MXene‐Carbon Nanotubes Composite Films for Next‐Generation Electromagnetic Interference Shielding

   https://doi.org/10.1002/adfm.201803360  

   Weng, Guo‐Ming ; Li, Jinyang ; Alhabeb, Mohamed ; Karpovich, Christopher ; Wang, Hang ; Lipton, Jason ; Maleski, Kathleen ; Kong, Jaemin ; Shaulsky, Evyatar ; Elimelech, Menachem ; et al ( September 2018 , Advanced Functional Materials)

   Lightweight, flexible, and electrically conductive thin films with high electromagnetic interference (EMI) shielding effectiveness are highly desirable for next‐generation portable and wearable electronic devices. Here, spin spray layer‐by‐layer (SSLbL) to rapidly assemble Ti₃C₂T_xMXene‐carbon nanotube (CNT) composite films is shown and their potential for EMI shielding is demonstrated. The SSLbL technique allows strategic combinations of nanostructured materials and polymers providing a rich platform for developing hierarchical architectures with desirable cross‐functionalities including controllable transparency, thickness, and conductivity, as well as high stability and flexibility. These semi‐transparent LbL MXene‐CNT composite films show high conductivities up to 130 S cm⁻¹and high specific shielding effectiveness up to 58 187 dB cm²g⁻¹, which is attributed to both the excellent electrical conductivity of the conductive fillers (i.e., MXene and CNT) and the enhanced absorption with the LbL architecture of the films. Remarkably, these values are among the highest reported values for flexible and semi‐transparent composite thin films. This work could offer new solutions for next‐generation EMI shielding challenges.

    

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4. Highly Stretchable Polymer Composite with Strain‐Enhanced Electromagnetic Interference Shielding Effectiveness

   https://doi.org/10.1002/adma.201907499  

   Yao, Bin ; Hong, Wei ; Chen, Tianwu ; Han, Zhubing ; Xu, Xinwei ; Hu, Renchao ; Hao, Jianyu ; Li, Changhao ; Li, He ; Perini, Steven E. ; et al ( February 2020 , Advanced Materials)

   Polymer composites with electrically conductive fillers have been developed as mechanically flexible, easily processable electromagnetic interference (EMI) shielding materials. Although there are a few elastomeric composites with nanostructured silvers and carbon nanotubes showing moderate stretchability, their EMI shielding effectiveness (SE) deteriorates consistently with stretching. Here, a highly stretchable polymer composite embedded with a three‐dimensional (3D) liquid‐metal (LM) network exhibiting substantial increases of EMI SE when stretched is reported, which matches the EMI SE of metallic plates over an exceptionally broad frequency range of 2.65–40 GHz. The electrical conductivities achieved in the 3D LM composite are among the state‐of‐the‐art in stretchable conductors under large mechanical deformations. With skin‐like elastic compliance and toughness, the material provides a route to meet the demands for emerging soft and human‐friendly electronics.

    

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5. Ultrathin MXene film interaction with electromagnetic radiation in the microwave range

   https://doi.org/10.1063/5.0176575  

   Rakhmanov, Roman ; Shuck, Christopher Eugene ; Al_Hourani, Jamal ; Ippolito, Stefano ; Gogotsi, Yury ; Friedman, Gary ( November 2023 , Applied Physics Letters)

   The quick progress in communication technologies demands superior electromagnetic interference (EMI) shielding materials. However, achieving a high shielding effectiveness (SE) with thin films, which is needed for microscale, flexible, and wearable devices, through absorption of EM radiation remains a challenge. 2D titanium carbide MXene, Ti3C2Tx, has been shown to efficiently reflect electromagnetic waves. In this paper, we investigated the electromagnetic shielding of ultrathin printed Ti3C2Tx films and recorded absorption up to 50% for 4 nm-thick films. This behavior is explained by impedance matching. Analysis of the sheet impedance in the X-band frequency range allows us to correlate the EMI shielding mechanism with the electrical conductivity measured within the same range. The average bulk in-plane conductivity for 4 to 40 nm-thick films reaches 106 S/m, while the average relaxation time is estimated at around 2.3 ps. Our figures of merit are similar to those reported for ultrathin metal films, such as gold, showing that an abundant MXene material can replace noble metals. We demonstrate that the MXene conductivity mechanism does not change from direct current to THz. The conventional method of reporting EMI SE is correlated with absolute values of transmitted, reflected, and absorbed power, which allows us to interpret previous results on MXene EMI shielding. Considering the easy deposition of thin MXenes films from solution onto a variety of surfaces, our findings offer an attractive alternative for shielding microscale devices and personal electronics.

    

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