Tsinghua University develops ultra-fast flexible electronic manufacturing technology

Recently, the Department of Biomedical Engineering of Tsinghua University School of Medicine and the Institute of Physics and Chemistry of the Chinese Academy of Sciences, for the first time in Science China Materials, reported a universal ultra-fast flexible electronic manufacturing technology. In a few seconds, a large-area high-precision complex liquid metal circuit is printed, which is far faster than the various electronic processing technologies that have been developed so far. The corresponding method is named SMART Printing according to its English abbreviation. The first author of the article is Guorui, a third-year doctoral student in the Department of Biomedical Engineering. The author of the communication is Professor Liu Jing.

Smart printing technology operation process and printed conductive patterns

As we all know, printed circuit boards play an important role in people's daily lives, and they have a wide range of applications in industrial production, national defense security, and medical health. The traditional printed circuit board preparation process is very complicated and needs to be processed through more than a dozen processes. The whole process is time-consuming and power-consuming, and is accompanied by a large amount of environmental pollution. In recent years, flexible electronics has sprung up and is receiving increasing attention. Unlike traditional rigid boards, flexible boards can be bent, folded, or stretched at will, making them of great value in areas such as wearables, portable medical, and electronic skin.

Liu Jing group, who has more than ten years of research experience in liquid metal flexible electronics, based on a large number of previous studies on the properties of liquid metal materials, found that a mixture of gallium-based alloys and solid metal particles (Ni) which are liquid at room temperature can be prepared. Semi-liquid metal material (Ni-EGaIn) with high viscosity and plasticity. There is a huge difference in the adhesion of such materials on different substrate surfaces, and the use of this difference allows for the rapid printing of patterned liquid metal circuits.

Multilayer circuit prepared by smart printing technology

The experiment confirmed that the semi-liquid metal material has extremely high adhesion on the PU film, and the adhesion on the toner is poor. To this end, the research team first introduced a laser printing method to deposit a toner pattern onto a paper coated with a PU film, and then by means of a semi-liquid metal material on the two types of substrates, a significant difference in adhesion, by rolling coating, In a very short time (<10s), the semi-liquid metal material is selectively printed on the target part of the A4 size paper, and it can be said that the required circuit is instantaneously produced.

Large area conductive pattern prepared by smart printing technology

The flexible circuit prepared by this technology has the highest precision of 50 μm and can maintain the stability of the circuit connection during the bending and folding process of the substrate. The study further pointed out that the new method is more universal, and the semi-liquid metal material also has higher adhesion on more base materials such as flexible silica (Ecoflex) surface. Based on this phenomenon, a semi-liquid metal ink material can also be deposited on a target portion of the surface of the flexible silica gel by a transfer method, thereby rapidly preparing a stretchable flexible circuit.

Using the above manufacturing principles, the research team has produced a series of flexible and stretchable functional circuits, such as multilayer circuits, large-area circuits, and stretchable sensors. The test demonstrates the excellent electrical stability and adaptability of each corresponding device. Recyclable advantages.

Stretchable sensor functional electronic circuits and performance prepared and assembled using smart printing technology

The implementation of the method established in this paper does not require complicated equipment, and the manufactured flexible circuit can be used in wearable medical equipment, which provides new technologies and tools for the rapid manufacture of wearable medical and personalized electronic health products, and has a very important science. Meaning and application value.