MXene 3D-AJP: Three-Dimensional Well-Oriented Freeform Networks of 2D MXene Nanosheets via Aerosol-Based 3D Printing

Next-generation microelectronic devices and energy systems will require fabrication techniques that enable the rapid spatial arrangement of 1D and 2D functional nanomaterials. Arranging atomically thin 2D nanosheets in three-dimensional (3D) space, however, is challenging due to the need for additives or support materials required for their spatial build-up. Here, we report an advanced fabrication technique that can arrange nanometer-thick micron-sized Ti₃C₂T_x MXene 2D nanosheets in self-supporting three-dimensional structures in a single printing step. This additive-free approach leverages aerosol jet 3D nanoprinting (AJP), where fluid dynamics of rapidly evaporating aerosol droplets is used to achieve precise, support-free, freestanding 3D geometries of 2D nanosheets. A real-time thickening effect during printing and van der Waals interactions between MXene nanosheets are identified as the basis of robust structure formation in 3D, offering a pathway to use 2D materials in device applications. The versatility and impact of this technique are demonstrated by constructing 3D microsupercapacitors (MSCs) with finely patterned 3D MXene electrodes. These devices exhibit a breakthrough areal capacitance of 375 mF·cm^-2 at a current density of 1.5 mA·cm^-2 (equivalent electrode capacitance of 1500 mF·cm^-2) and an energy density of 11.04 µWh·cm^-2 at a power density of 0.40 mW·cm^-2. This electrochemical performance far exceeds that of MSCs fabricated by other high-resolution patterning methods. This work paves the way for the use of 2D materials in micron-sized device systems.