Chinese Researchers Look to Functional Electronics 3D Printing by Liquid Metal Injection

In 2014, researchers from the Chinese Academy of Sciences (CAS), together with Tsinghua University researchers, published a paper in Science China Technological Sciences, titled “Liquid Phase 3D Printing for Quickly Manufacturing Conductive Metal Objects with Low Melting Point Alloy Ink.” The paper, which discussed how to more quickly and affordably 3D print using metal materials, was ahead of the curve, as 3D metal printing is now one of the fastest growing aspects of the 3D printing technology field. The researchers postulated that unconventional methods, like liquid phase 3D printing, could potentially solve the issues. The two Chinese educational institutions didn’t stop their work with 3D liquid metal printing there, but soldiered on, and recently published some brand-new research.

XJet liquid metal inks.

Family-owned Vader Systems and Israel-based startup XJet are two of the bigger players in the liquid metal 3D printing game, while 3D printing artist Ioan Florea used liquid metal 3D printing techniques to make his stunning Gran Torino piece of abstract art. Tsinghua University’s Jing Liu, who was a co-author on the 2014 paper, also co-authored a research paper published earlier this month in Materials & Design, titled “3D printing for functional electronics by injection and package of liquid metals into channels of mechanical structures.” Other co-authors of this paper include Jin-Rong Lu and Yong-Ze Yu, both with the Technical Institute of Physics and Chemistry at the Chinese Academy of Sciences (TIPCCAS).

The research paper presents a more “developed approach” of how the scientists were able to incorporate mechanical structures and liquid metals for functional electronics.

“With the fabrication freedom and high efficiency introduced by 3D printing, such technology has been explored in the electronic manufacturing processes. In the present work, we reported a developed method for the fabrication of functional electronics with liquid phase electronic circuits. The technique involves printing hollow channels within elastomer structures via fused deposition modeling (FDM), then injecting and encapsulating liquid metal to form electrical traces. The process parameters in printing elastomer objects and the design of hollow channels were investigated via the extrusion experiments. The influence of flow rates on liquid metal injection was also studied under pressure injection. Based on these discussions and validations, the relationships between process parameters and the printing structures were demonstrated, and the flexible substrate with hollow channels was successfully printed by optimization of the process parameters. Moreover, a probe signal circuit has been fabricated to demonstrate the ability of injecting and packaging liquid metal into 3D printed structures for functional electronics,” the paper states.

Graphical abstract of research paper

In layman’s terms, the liquid metal channels are formed into a flexible 3D printed part through the use of an injection technique. The researchers concluded that layer thickness, as well as the heating temperature, might play an important role in printing elastomer material into mechanical structures that feature hollow channels. Elastomers are versatile, with both thermal and electrical insulation, which is why they’re so popular in smart biomedical devices and electronics; these applications both need adaptable, flexible material, and elastomers fit the bill.

The circular channel is the best option to use in order to reduce the geometry of the structure’s hollow channels. Then, the lower flow rates will improve the liquid metal’s overall fill effect. The technology could be used in a variety of applications, due to its inherent flexibility. Discuss in the Liquid Metal forum at 3DPB.com.