Jettability and printability of customized gold nanoparticles-based ink on flexible substrate through inkjet printing process

Among the different metal nanoparticles for formulating inkjet-based conductive inks, gold remains the best choice for fabricating different patterns on economical and bio-degradable substrates such as commercial photo papers for developing low-cost sensing devices. Formulating customized gold nanoparticle (AuNPs) inks remains challenging as the ink must meet specific physical, chemical and rheological properties to achieve appropriate jettable behaviour and printable characteristics. It should exhibit well-controlled viscoelastic response for the smooth and optimized flow through the nozzles and then cure immediately to facilitate the shape retention of deposited feature. In this work, the jettability window definition framework using dimensionless numbers such as Re, We, Ca, and Z are defined for the aqueous-based AuNPs inks synthesized via ultrasonic spray pyrolysis technique and formulated into three concentration levels of 300, 600, and 1200 ppm. A theoretical CFD based simulation study is conducted to observe the ink droplet formation behaviour at different droplet velocities through inkjet nozzle. Among these formulated inks, 1200 ppm shows the most favourable behaviour as obtained through the simulation and jettability window results. It is tested further to see how different printing settings, like pulse voltage and number of repetitions, affected the continuity and density of the ink, affecting the quality of the printed AuNPs. This work demonstrates the process capabilities of inkjet printing technology by testing the formulated AuNPs ink.