3D Printing of Liquid Metals: Recent Advancements and Challenges

The development of flexible electronics (FEs) has rapidly accelerated in numerous fields due to their exceptional deformability, bending, and stretchability. Room-temperature gallium-based liquid metals (LMs) are considered as efficient conductive materials for FEs due to their outstanding electrical conductivity and intrinsic flexibility. Recently, 3D printing has become a promising technique for fabricating FEs. However, the poor printability due to high surface tension and fluidity offers huge challenges in the 3D printing of LMs. This review summarizes the effective strategies to address these challenges. It primarily focuses on three points: 1) how to improve the printability of LM and its wettability with the substrate, 2) how to select the appropriate printing method to improve the printing speed and ensure the resolution of printing structure, and 3) how to provide perfect encapsulation for LM-based FEs with 3D printing. Following a brief introduction, the mainstream printing technologies and recent developments in the 3D printing of LMs are provided, with an emphasis on the selection of printing method, improvement of printability, encapsulation, and conductivity activation. Then, the revolutionary changes attained after 3D printing of LMs are specifically focused upon. Finally, opinions and potential directions for this thriving discipline are explored.