Oozing control and retraction in colloid 3D printing: parametric analysis

Despite the simplicity and wide use of direct ink writing 3D printing of colloidal materials, the oozing problem is a major challenge that affects its printing quality. However, the impact of the printing parameters on oozing control methods is not well studied. This study investigates the effects of the extrusion configurations and printing parameters on oozing when printing colloidal materials. The extrusion configurations examined includes direct and Bowden-extrusion set ups, while the printing parameters considered are nozzle diameter, printing speed, and the Bowden-tube dimensions. The results reveal that smaller nozzle diameters tend to increase oozing, whereas lower printing speeds help reduce it. Direct extrusion consistently results in less oozing compared to Bowden extrusion across all control methods. In turn, reducing the length of the Bowden tube effectively minimizes oozing, and its diameter has a more pronounced impact at higher printing speeds. Furthermore, Bowden extrusion demands greater retraction volumes, longer distances, and more time compared to direct extrusion. Experimental demonstrations were conducted to control oozing using various parameters. This study provides valuable insights for researchers seeking to select the optimal extrusion configuration and printing parameters to minimize oozing when printing colloidal materials that exhibit shear-thinning and yield-stress fluid behavior.