During the process of electrohydrodynamic printing, ink is ejected and deposited onto the substrate surface driven by electric field force. The strength and stability of the electric field play a decisive role in the printing effect. Due to its dielectric properties, insulating materials weaken the electric field. The accumulation of surface charges and residual charges in droplets generated by the electrohydrodynamic printing electric field will further weaken the electric field and cause electric field distortion, which seriously affects the stability of electrohydrodynamic printing. Therefore, how to enhance the electric field and eliminate electric field distortion is the key to improving printing performance.

Principle of plasma assisted current body printing process

Experiments have found that when conducting electric current jet printing on the original insulation surface, the ink jet is extremely unstable and deposits in the form of explosions or burrs. However, after treating the insulation surface with plasma, under the same printing conditions, the ink can achieve stable jet deposition and print lines uniformly without burrs.

Figure 1-1 (a) Nozzle state during PI surface current body printing before and after plasma treatment; (b) Comparison of PI surface printing patterns before and after processing; (c) Comparison of printed patterns on ceramic surfaces before and after processing.

Figures 1-1 (a) and (b) show the comparison of nozzle spray states and snowflake patterns printed on PI surfaces under the same printing parameters before and after plasma surface treatment. Figure 1-1 (c) shows the comparison of silver paste flower patterns printed on ceramic surfaces under the same printing parameters before and after plasma surface treatment.

In summary, plasma treatment of insulation surfaces changes the surface microstructure and modifies a large number of oxygen-containing functional groups, leading to an increase in surface hydrophilicity; At the same time, plasma surface modification also significantly increases surface conductivity, reduces deep charge traps, increases shallow charge traps, and reduces the ability of the insulating surface to bind charges, suppressing the accumulation of charges on the insulating surface and causing the residual charges of the deposited droplets to dissipate rapidly; The increase in conductivity and the injection of oxygen-containing functional groups enhance surface polarization, thereby stabilizing and strengthening the spatial electric field, ultimately greatly improving the stability of current body printing.