Printed electronics, which is based on the printing principle, is a newly emerging additive manufacturing technology. It has many advantages for electronics making such as large area, flexibility, personalized and low cost compared to conventional electronics manufacturing. There are generally three typical conductive inks used in printed electronics: conductive carbon ink, conductive polymer and metal conductive ink. However, post-treatments via high temperature curing process are often needed after such printing, so as to improve conductivities as well as reliability of these inks and the printed products. This makes the fabrication process somewhat complicated. Besides, the complex preparation process of the nano materials and inks thus formed also raised the application cost. As a new class of conductive ink, the liquid metal is becoming an important research area. Such ink material owns unique merits such as high electronic conductivity, simple preparation process, requesting no post-processing and so on. To further push forward the research along this direction, this article is dedicated to present an overview on the research advancement of the physical and chemical properties of the liquid metal ink and related typical printing methods over the world. Prospective directions worth of pursuing were outlined.
