Controlled local orientation of 2D nanomaterials in 3D devices: methods and prospects for multifunctional designs and enhanced performance

Abstract

Two-dimensional (2D) nanomaterials are sheet-like crystalline solids exhibiting remarkable electrical, chemical, mechanical and optical properties. The emergence of 2D nanomaterials of diverse chemistries with unique performance at the nanometric scale provides great potential to establish enhanced functionalities at the macroscopic scale. However, transposing these nanoscopic properties into functional macroscopic devices remains a challenge due to the lack of suitable processing technologies. Recent experimental efforts to control the local orientation of 2D materials in thin films and reinforced composites have demonstrated significant advances in improving the bulk material performances and could be the key to unlock next-generation multifunctional designs. Examples of these for sensors, thermoelectrics and energy harvesting devices are provided in this review. Then, we present the recent advances and methods for achieving controlled alignment of 2D nanomaterials, including in horizontal, vertical, heterogeneous and arbitrary oriented configurations. Moreover, the advances in 3D printing technology to support aligned microstructures and its capability to build multimaterial compositions, design complex structures and scale up, are discussed in detail. Finally, we envision exciting future developments yet also challenges to realize the promises of complex multifunctional energy devices based on 2D nanomaterials with enhanced performance, sustainability, and potentially opening up new applications.