Ink bridge control in the electrohydrodynamic printing with a coaxial nozzle
Ink bridge control in the electrohydrodynamic printing with a coaxial nozzle
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DOI：
10.1016/j.jmapro.2020.10.057
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发表时间：
2020-12
影响因子：
6.2
通讯作者：
Zhen Li;K. N. Al-Milaji;Hong Zhao;Da-Ren Chen
中科院分区：
文献类型：
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作者：
Zhen Li;K. N. Al-Milaji;Hong Zhao;Da-Ren Chen
最近提出了一种用于电流体动力（EHD）打印的同轴喷嘴，该同轴喷嘴由两个同轴对齐的毛细管组成，以通过使内部和外部油墨通道之间的连续油墨循环来最小化喷嘴堵塞（通常在单个毛细管EHD打印中遇到）。然而，通过同轴喷嘴的EHD打印仍然处于早期发展阶段，特别是关于在喷射过程期间墨流和弯月面的控制。连接内、外毛细管两个开口的墨桥在保持油墨循环和影响钉扎在内毛细管尖端的喷射弯月面方面起着重要作用。在这项研究中，一个闭环反馈控制开发自动调节的墨桥在印刷过程中的体积。研究发现，墨桥体积影响喷射弯月面的体积和形状，这与打印的点尺寸直接相关。将同轴打印喷嘴与单个毛细管喷嘴进行比较，添加较大的外喷嘴不会降低打印分辨率。两种印刷配置之间的印刷点直径的差异小于5%。对于给定的印刷设置和特定的油墨，确定最佳的油墨桥体积以产生最小的点尺寸。通过墨桥形状控制，打印分辨率可提高24.5%。墨桥体积、喷射弯月面体积和印刷点尺寸之间的相关性还取决于油墨导电性和内部毛细管的挤出长度。同轴喷嘴EHD打印具有连续的油墨循环和有效的油墨桥控制，为图案生成和微细加工提供了可靠的制造工艺。
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.