Pneumatic Conveying Printing Based on Super Hydrophobic Surface

In today's era, the inkjet printing (IJP) technique plays important roles in the fabrication of mechanical, electronical, and even biological devices. However, the current IJP techniques are incapable of handling viscous inks, which greatly hinder the extensive industrial application. Here, it is found that utilizing the superhydrophobic materials on the end surface of a nozzle combined with the dragging and shearing effects of an airflow, micrometer-sized droplets can be generated under a quite low ejection/extrusion pressure. This variation of the traditional IJP technique is called pneumatic conveying printing (PCP) and is capable of handling viscous inks. Two PCP prototypes using micropump and micropiezo as the ink extruder, respectively, are homemade to demonstrate the printing performance. For the PCP using micropump inks with viscosities as high as several thousand mPa s can be printed. For the PCP using a micropiezo, the maximum allowed viscosity is about 700 mPa s. Furthermore, the pressure within the pipeline or ink chamber and the shear rate at the orifice during PCP are much smaller than those of the traditional IJP due to the slower ink extrusion rate. Both experiment and simulation are carried out to reveal the mechanisms of the proposed PCP technique.