Guo Lei, Duan Yongqing, Deng Weiwei, Guan Yin, Huang YongAn, Yin Zhouping
State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
Micromachines (Basel). 2019 Mar 1;10(3):172. doi: 10.3390/mi10030172.
The quality of electrohydrodynamic jet (e-jet) printing is crucially influenced by the satellite drop formed when the primary drop detaches from the meniscus. If the satellite drop falls onto the substrate, the patterns on the substrate will be contaminated. The electric charge carried by the satellite drop leads to more complex satellite/meniscus interaction than that in traditional inkjet printing. Here, we numerically study the formation and flight behavior of the charged satellite drop. This paper discovered that the charge relaxation time (CRT) of the liquid determines the electric repulsion force between the satellite drop and meniscus. The satellite drop will merge with the meniscus at long CRT, and fail to merge and deteriorate the printing quality at short CRT. The simulations are adopted to discover the mechanism of generation and flight behavior of charged satellite drops. The results show that the critical CRT decreases with the dielectric constant of the liquid and the supplied flow rate. Namely, for small dielectric constant and fixed CRT, the satellite drop is less likely to merge with the meniscus, and for high flow rate, the satellite drop is prone to merge with the meniscus due to the delay of necking thread breakup. These results will help to choose appropriate parameters to avoid the satellite drop from falling onto the substrate.
电流体动力喷射（e-jet）打印的质量受到主液滴从弯月面分离时形成的卫星液滴的显著影响。如果卫星液滴落到基板上，基板上的图案将会被污染。卫星液滴携带的电荷导致其与弯月面之间的相互作用比传统喷墨打印中的情况更为复杂。在此，我们对带电卫星液滴的形成和飞行行为进行了数值研究。本文发现液体的电荷弛豫时间（CRT）决定了卫星液滴与弯月面之间的电斥力。在长电荷弛豫时间下，卫星液滴会与弯月面合并，而在短电荷弛豫时间下则无法合并并降低打印质量。通过模拟来揭示带电卫星液滴的产生和飞行行为机制。结果表明，临界电荷弛豫时间随液体的介电常数和供应流速的减小而降低。也就是说，对于小介电常数和固定的电荷弛豫时间，卫星液滴与弯月面合并的可能性较小，而对于高流速，由于缩颈细丝破裂的延迟，卫星液滴易于与弯月面合并。这些结果将有助于选择合适的参数以避免卫星液滴落到基板上。
