The research on nozzles for microscale printing of high viscosity pastes containing micron-sized particles

Direct extrusion of high viscosity pastes containing micron-sized particles at the microscale is a major challenge in the field of additive manufacturing. The nozzle, as a crucial component, has a profound impact on the printing performance through its material composition and structural design. In this study, we have taken into account the influence of Coulomb friction and developed a hydrodynamic model to analyze the flow behavior of high-viscosity pastes within various nozzles. It should be noted that the paste is a composite material with non-Newtonian fluid properties, and its behavior is described by the Herschel-Bulkley constitutive equation. This model provides a clear representation of how the Coulomb friction and structure of the nozzle affect the pressure and velocity distribution during paste extrusion. In addition, experimental studies on the printing performance of various nozzles have shown that the glass nozzle, due to the wall slip phenomenon resulting from its smooth inner surface, can significantly improve the flow velocity and flow rate of the paste. As a result, it enables stable, continuous and high-speed printing. In our experiment, the glass nozzle showed a 100-fold increase in printing speed compared to the dispensing nozzles commonly used in industry, with a printing resolution as fine as 43 mu m. This result highlights the immense potential of glass nozzles in printing high-viscosity pastes containing micrometer-sized particles.