Preparation And Application Of Graphene-based Inks Based On Microfluidization

Graphene has shown great application prospects in printable inks due to its excellent electrical and thermal properties.Traditional graphene ink is prepared by ultrasonication and shearing.These methods are time-consuming,low yield,and require further centrifugation and drying steps,and the conductivity of the prepared graphene is generally low.Therefore,obtaining graphene with high conductivity by a simple and scalable method is still a huge challenge.In response to the above problems,this paper prepared graphene-based printable inks from expanded graphite by microfluidization.The application of graphene inks in flexible electronic devices has been explored by screen printing process.The work and results are summarized as follows:(1)Expanded graphite was used as a raw material,and ethyl cellulose is used as a binder.Graphene inks with high conductivity were prepare using high-pressure microfluidization.Morphology and structure of prepared graphene ink were characterized.The results show that the obtained ink contains 1-5 layers of graphene with few layer defects;the contact angle of the graphene ink on the polyimide film is 13.03°;under shearing forces,the prepared graphene ink exhibits shear thinning behavior;the conductivity of the graphene film prepared by blade coating is greatly improved after annealing treatment.There are porous holes on the surface after thermal treatment,and mechanical force can eliminate these holes on the surface and further increase the conductivity(up to 6.1×10~4 S/m).(2)Using polyimide as the substrate,the graphene heating film was prepared by screen printing.The results show that by adjusting the number of repeated printing,the resistance of the graphene heating film can be adjusted.After five printings,the conductivity is about9.7×10~4 S/m.The prepared heating film has rapid heating performance.The five-layer graphene heating film is rapidly heated to 111°C at a voltage of only 3.0 V,and can be further increased to 193.4°C at 5.0 V.The graphene heating film also has good flexibility and durability.After 5,000 times of bending and flexing,the resistance of the graphene heating film does not change significantly.(3)Using expanded graphite as the raw material and poly(sodium p-benzenesulfonate)(PSS)as the exfoliating additive,the graphene dispersion was prepared by microfluidization.On this basis,graphene/PEDOT:PSS composite functional ink was prepared by in-situ polymerization with 3,4-ethylenedioxythiophene(EDOT).The results show that the rod-shaped PEDOT and the two-dimensional graphene sheets form a three-dimensional network structure,which is beneficial to conductive pathways;PEDOT:PSS and graphene are combined throughπ-πinteractions.The formulated functional ink can be printed on the fabric.The gel electrolyte was drop coating on the surface to prepare a micro-supercapacitor with high area specific capacitance,excellent cycle performance,and high power density and energy density.Typically,the area specific capacitance of MSCs is 41.0m F/cm~2 for the graphene concentration of 4 mg/m L;after 1000 cycles of charge and discharge tests,the capacitance retention rate is still 90.86%;the area energy density of MSCs is 3.64μWh/cm~2 for the area power density of 131.17μW/cm~2.The fabric-based MSCs has good flexibility.Under different flexing conditions,the capacitance retention rate is>92.73%,and the capacitance retention rate is still high after 5000 cycles of bending.