Due to the advantages of environmental protection, low cost and flexibility, flexible printed circuit is expected to replace the traditional electronic devices based on lithography technology. Ink jet printing technology can directly realize the patterning of metal nanoparticles, which is one of the most promising methods to prepare nano printed electronic devices. However, the application of ink-jet printing technology in the field of high-precision, high integrated circuit preparation is limited due to the spread and integration of ink droplets.

With the support of NSFC, the Ministry of science and technology and the Chinese Academy of Sciences, song Yanlin research group, the Key Laboratory of green printing, Institute of chemistry, Chinese Academy of Sciences, deeply and systematically studied the interaction between printing ink drops and substrate, and carried out a series of extensive and in-depth research in the field of controllable high-precision printing and printing technology by regulating the wetting behavior of ink drops on the substrate surface Research. They have successfully prepared a series of high-precision patterns by adjusting the characteristics of ink, substrate and other materials: using the “coffee ring” phenomenon to prepare high-precision conductive patterns of metal nanoparticles with a linewidth of up to 5 μ M.

The development of the technology of full print multilayer embedded flexible circuit

High precision three-dimensional functional pattern is printed by the triphase line slip phenomenon of printing ink drop; a series of special three-dimensional column structures with controllable shape are prepared by the dynamic retraction of triphase line induced by magnetic field; high precision micro pit and groove structures are prepared by the soft substrate “ink-jet printing”; the precision is up to 3 by controlling the nano materials to be assembled and printed on the printing electrode template 0 nm conductive pattern. They use these printed and printed functional patterns to realize applications such as plasma light wave transmission, high sensitive detection, quantum dot pattern, biological cell separation, microfluidic channel and high-precision flexible circuit preparation.

On the basis of the above research, they print conductive ink containing nano particles on polymerizable liquid substrate, cleverly use the dynamic wrapping effect of liquid substrate on the printing ink drop, and realize the direct preparation of high-precision embedded conductive silver wire. Because of the influence of the viscosity and surface tension of the ink jet printing conductive ink, it is very challenging to realize its internal fusion into a line in another liquid. They solved this problem by adjusting the rheological behavior of the liquid substrate and the properties of nano silver conductive ink, realized the controllable wrapping of the liquid substrate on the ink drop, effectively inhibited the diffusion of the ink drop and the “coffee ring” effect.

The development of the technology of full print multilayer embedded flexible circuit

Based on this, the conductive silver wire with a width of about 1-2 μ m was prepared by using a common commercial printer with a hole diameter of 25 μ m, which is about 20 times more accurate than the conventional ink-jet printer. The prepared high-precision circuit is directly embedded in the substrate to avoid subsequent packaging steps. Electrical tests show that the embedded micro cable prepared by this method has excellent conductivity. They further used this “liquid film embedded printing” method to directly print layer by layer to realize the multi-layer circuit preparation, achieving the integration of 60 μ m transparent film embedded three-layer circuit.

The “liquid film embedded printing” is a universal method, which is also suitable for carbon nanotubes, graphene and other conductive materials. It is of great significance to improve the precision and integration of printing circuit and prepare ultra-high transparent embedded electronic devices. It also lays a technical foundation for printing and preparing high integrated and high-precision three-dimensional structure circuit.

       

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