Preparation Of Graphene Conductive Ink And Its Preformace In Inkjet Printing

As electronic products are developing in the direction of flexible,lightweight,miniaturization,inkjet printing technology as an alternative to the traditional methods used in the manufacture of electronic devices such as screen printing,offset printing and etching has become an promising research direction.Inkjet printing graphene technology combines the advantages of inkjet printing,such as material-to-write technology,low cost and large-scale production,and graphene which owns excellent physical properties.This research mainly discusses the feasibility of using graphene as a printing ink in the field of printed electronics.In this paper,graphene was used as the core material of conductive ink.Graphene printing ink was prepared by two methods: An ink in which ethyl cellulose is used as a stabilizer and a binder,and a conductive pattern processing method in which a conventional NMP-based ink is used but after printing hot pressing method is performed.The preparation of graphene-based inks and the inkjet printing of the graphene-based inks were carried out.The surface morphology,electrical and mechanical properties of the inkjet printing patterns were studied.Above all,the research not only realized the preparation of graphene-based ink,but also obtained the highperformance printing patterns compared with the current research in this field.It was found that when the graphene was prepared by liquid phase exfoliation,the ultrasonic time and the initial concentration of graphite both have an important effect on the thickness and defect of graphene sheets in the printing ink.When the ultrasonic time was 3 h,and the initial concentration of graphite is 4% w/v,the graphene sheets with the diameter range from 60 to 120 nm and the thickness less than 5 layers can be obtained with fewer defects which meet the size requirements of inkjet printing.In the study of the morphology of printing patterns on the flexible substrate,it was found that the patterns printed using the ink which contained larger flakes have better topography profiles and uniform solute distribution.The inkjet printing conductive patterns which were inkjet printed using ink contains ethyl cellulose was annealed at 300 °C for 30 min.The conductivity was 2.352×104 S/m with the transmittance of 89%(λ = 550 nm).Thanks to ethyl cellulose as the binder,the contact resistance between the layers of the graphene sheets were significantly reduced.The resistivity increased by only 1.5% with the bending cycle increased from 100 times to 500 times.Meantime,although some researchers have studied the graphene-based inks of NMP system,due to the low solid content of ink and the high contact resistance between graphene sheets,the electrical conductivity is low.In this study,the inkjet printing graphene patterns were hot-pressed.When the printing layers were 12 layers,hot-pressing temperature was 170 ℃,hot-pressing time was 5min and hot-pressing pressure was 5 MPa,the conductivity of the conductive pattern can reach 7.892×104 S/m with the transmittance of 86%(λ=550 nm).The resistivity increases only 0.16% after 500 bending cycles,and the resistivity increases by 0.18% in the case of folding 180o.