Scalable, Highly Conductive and Micro-Patternable Mxene Films for Enhanced Electromagnetic Interference Shielding

2D transition metal carbides and nitrides (MXenes) have accumulated tremendous interest recently as a result of their high conductivity, aspect ratio, and excellent figures of merit in numerous application areas.[1–3] Freestanding films of MXenes are important for versatility in their incorporation into roll-to-roll production to allow for large-scale fabrication. Vacuum assisted filtration is currently the state-of-the-art for fabrication of freestanding MXene films, however methods that increase the active film area are beneficial for large-scale production and wide use of this material. Aqueous-based solution casting onto hydrophilic substrates is a useful way to make MXene coatings but they cannot be delaminated from the substrate to yield a freestanding film. In this work, we show that it is possible to fabricate Ti₃C₂T_x MXene freestanding films through simple drop-casting onto hydrophobic substrates. MXene films prepared using this technique have greater alignment of MXene flakes due to repulsive interactions between the substrate and the Ti₃C₂T_x MXenes and allows for facile delamination of the film from the substrate. We show that freestanding drop-cast MXene films can be fabricated in large areas (>125 cm²) and thicknesses (23.2 µm) while maintaining high electronic conductivity (~7,000 S cm^-1). Drop-cast MXene films can also be micropatterned in three-dimensions (3D) simply by using commercially available microstructured plastics as substrates (Figure 1). These 3D-patterned MXene films exhibit a 38% increase in EMI shielding efficiency normalized to thickness and density (EMI SSE/t) as compared to their unpatterned counterparts, yielding EMI SSE/t as high as 48,800 dB cm² g^-1. The results presented here represent a step forward in the advancement of the prospect of MXene industrialization, opening the door for progression in design of novel prototypes of MXene devices.

[1] G.-M. Weng, J. Li, M. Alhabeb, C. Karpovich, H. Wang, J. Lipton, K. Maleski, J. Kong, E. Shaulsky, M. Elimelech, Y. Gogotsi, A.D. Taylor, Layer-by-Layer Assembly of Cross-Functional Semi-transparent MXene-Carbon Nanotubes Composite Films for Next-Generation Electromagnetic Interference Shielding, Adv. Funct. Mater. 28 (2018) 1803360. https://doi.org/10.1002/adfm.201803360.

[2] J. Lipton, G. Weng, M. Alhabeb, K. Maleski, F. Antonio, J. Kong, Y. Gogotsi, A.D. Taylor, Mechanically strong and electrically conductive multilayer MXene nanocomposites, Nanoscale. 11 (2019) 20295–20300. https://doi.org/10.1039/C9NR06015D.

[3] M. Mariano, O. Mashtalir, F. Antonio, W.-H. Ryu, B. Deng, F. Xia, Y. Gogotsi, A. Taylor, Solution-processed Titanium Carbide MXene films examined as highly transparent conductors, Nanoscale. 8 (2016) 16371–16378. https://doi.org/10.1039/C6NR03682A.