Research On Carbon Based Resistance Jet Printing On Flexible Substrate

With the rapid development of nozzle design and functional composite conductive ink,ink-jet printing technology is gradually popularized in many frontier disciplines and industries,such as flexible electronic manufacturing,additive manufacturing,biological tissue engineering and so on.In this paper,a carbon based conductive ink was prepared.In order to obtain the driving parameters and ink viscosity range suitable for ink-jet printing,the formation of ink-jet droplets,spray process and droplet spreading on the flexible substrate surface were studied by numerical simulation.According to the working principle of piezoelectric ink-jet printing,the physical model of the nozzle is simplified,and the simulation model of droplet injection process is established by using the computational fluid dynamics software(ICEM-CFD).VOF algorithm built in fluent 15.0 is used to solve the formation and flight process of droplets.In fluent software,the standard k–? model is selected,the material parameters are defined,the boundary conditions are set,and the driving pressure is set to sinusoidal wave pressure.This paper mainly studies the influence of sine wave pressure amplitude,working time,nozzle diameter and ink characteristics on droplet injection characteristics.By analyzing the forming conditions of droplets,it is found that when the nozzle diameter or ink viscosity is too large,the droplets may not be produced.When the driving pressure amplitude or working time increases,the number and size of droplets increase.In addition,the spreading process of spray droplets on the flat flexible substrate surface is simulated,and the influence of ink characteristics and surface substrate on the spreading process is analyzed.The maximum length of the main droplet spreading on the substrate surface and the height of arching during shrinkage decrease with the increase of ink viscosity.Through the numerical simulation,the driving parameters and the viscosity of the ink,which can obtain good ink-jet morphology and ink spreading morphology,are determined,which will be helpful for the preparation of conductive ink and the study of jet printing process.In order to verify the conductivity and aging of carbon based conductive materials,carbon nanotube/paraffin composites were prepared.The effects of carbon nanotube mass fraction and temperature on the resistance of the composites were analyzed.It is found that the electrical resistance of the composites decreases with the increase of carbon nanotube mass fraction or temperature.A new type of carbon based conductive ink was prepared by using carbon nanotubes as conductive filler and ink for ink jet printing.The effects of the mass fraction of carbon nanotubes in carbon based conductive ink,the number of printing layers,the standing time after printing,the contact area between electrode copper and ink resistance,and the surface substrate material on the conductivity of carbon based conductive ink were studied.It is found that the higher the mass fraction of carbon nanotubes in the carbon based conductive ink,the lower the resistance of the finished product.For a certain carbon nanotube mass fraction of carbon conductive ink,the more the number of spray printing layers,the smaller the resistance of the finished product.When the number of layers is more than 6,the resistance has no obvious change.Under certain temperature and humidity conditions,when the number of layers is more than 3,the ink resistance is not sensitive to the standing time effect after the completion of spray printing.Generally,the resistance value can be basically stable after standing for more than 1 hour.For the carbon based conductive ink coating with high content of carbon nanotubes,the larger the contact area between the coating and the bipolar copper sheet is,the smaller the contact resistance is,and there is a linear relationship between the total resistance and the reciprocal value of the contact area.Using the experimental method proposed in this paper,the total resistance and contact area can be measured,and the coating resistance and contact coefficient can be obtained indirectly by using the linear relationship.Using Xuan paper as the base material of carbon based conductive ink coating,the conductivity of the coating is better than that of ordinary office printing paper,which indicates that the base material has an impact on the conductivity of the conductive coating.