A coaxial nozzle, consisting of two coaxially aligned capillaries to minimize the nozzle clogging (often encountered in a single capillary EHD printing) by enabling continuous ink circulation between the inner and outer ink channels, had been recently proposed for the electrohydrodynamic (EHD) printing. The EHD printing by the coaxial nozzle, however, remains in the early development stage, particularly with respect to the control of ink flow and meniscus during the jetting process. The ink bridge, which connects both openings of the inner and outer capillaries, plays an important role in keeping the ink circulating and influencing the jetting meniscus pinned at the inner capillary tip. In this study, a closed-loop feedback control was developed to automatically regulate the volume of the ink bridge during the printing. It was found that the ink bridge volume affects the volume and shape of the jetting meniscus, which is directly correlated to the printed dot size. Comparing the coaxial printing nozzle to the single capillary nozzle, the addition of the larger outer nozzle does not decrease the printing resolution. The difference in the printed dot diameter between the two printing configurations is less than 5 %. For a given print setting and a specific ink, an optimal ink bridge volume was identified to produce the smallest dot size. With the ink-bridge shape control, the print resolution can be improved by 24.5 %. The correlation between the ink bridge volume, jetting meniscus volume, and the printed dot size also depends on the ink conductivity and the extrusion length of the inner capillary. The coaxial nozzle EHD printing, featuring the continuous ink circulation and effective ink bridge control, provides a reliable manufacturing process in the pattern generation and microfabrication.

最近已经提出了一种同轴喷嘴，该同轴喷嘴由两个同轴排列的毛细管组成，以通过在内部和外部墨水通道之间进行连续的墨水循环来最大程度地减少喷嘴的堵塞（在单毛细管EHD打印中经常遇到），该喷嘴已被提出用于电动流体力学（EHD）打印。但是，通过同轴喷嘴进行的EHD打印仍处于早期开发阶段，特别是在喷射过程中控制墨水流量和弯液面方面。连接内部和外部毛细管的两个开口的墨水桥在保持墨水循环并影响固定在内部毛细管尖端的喷射弯液面方面起着重要作用。在这项研究中，开发了一种闭环反馈控制，可在打印过程中自动调节墨桥的体积。已经发现，墨桥的体积影响喷射弯月面的体积和形状，其与印刷的点的尺寸直接相关。将同轴打印喷嘴与单个毛细管喷嘴进行比较，增加较大的外部喷嘴不会降低打印分辨率。两种打印配置之间的打印点直径差异小于5％。对于给定的打印设置和特定的墨水，确定了最佳的墨水桥体积以产生最小的点尺寸。通过墨桥形状控制，可以将打印分辨率提高24.5％。墨桥体积，喷射弯月面体积和打印的点大小之间的相关性还取决于墨水的电导率和内部毛细管的挤出长度。同轴喷头EHD打印