The Preparation Of Microwires Fine Conductive Patterns Based On Microcontact Printing

Printed electronics has been developed for the unique advantages of large area and flexibility compared with silicon microelectronic technology. High resolution is necessary for printed electronics product, such as thin film transistor(TFT) and TCF(transparent conductive film) However, traditional printing techniques can only achieve 50-100 μm resolution, which still have some gap with the demand of less than20 μm for the electronic products. The resolution has been one of the bottlenecks of the printing electronics industry, and new printing techniques must be developed.As a soft lithography technologie, microcontact printing(μCP) has the unique advantages in the preparation of fine pattern. At first, μCP was used to modify the surface properties by transferring thiol to the Au substrate using PDMS stamp. Then hundreds of nanometers width patterns can be acquired by self-assembly technology and etching technique. Later, more materials were used to transfer, for example, micro- and nano- particles.This paper aims to acquire fine conductive pattern of silver nanoparticles based on μCP, and silver nanoparticles ink was used to transferring materials. Firstly, the silver nanoparticles dispersion was synthesized via the liquid phase reduction method,and the dispersion was concentrated and dispersed in the solvent and conductive ink for μCP was acquired with different solid contents(30%、40%、50%). The printed pattern was showed very homogeneous and high-resolution when solid content was40% and surface tension was 30.51 mN/m.Secondly, from the point of the surface energy of material, the influence of the surface energy of PDMS stamp, conductive ink and PET substrate to μCP pattern was explored. The precondition of μCP, namely,the relationship between material surface energies,ink?(30.51 mN/m)<PDMS?(155.94 mJ/m2) <PET?(175.22 mJ/m2), was obtained. Furthermore,influence factors to the process of μCP and printed patterns were discussed, such as temperature, amount of feeded ink, pressure of dipped ink, the printing pressure. Andthe printed single line was more fine than flexible printing with uniformity σ = 0.58,line width d=9.33 μm, ink thickness h=210 nm, roughness Ra=129.34 nm, resistance R=100 Ω, which was obtained at the best transfer prined conditions: T = 60 ℃, V = 5μl, Fink = 0.3 N, Fprined = 0.8 N. Finally, flexible metal grid transparent electrodes were prepared using the μCP method based on the transferring the line pattern and the influence of spacing of the grid to the light transmittance and the conductivity was discussed. The result showed that the performance of metal grid transparent electrodes prined by μCP was not better enough than ITO which was the mainstream product in market. However, μCP provids a new method for preparing fine conductive patterns.The research work lays the foundation for the application of μCP in the preparation of printing electronics devices.