Jin Yiwei, Chen Jiankui, Chen Wei, Yin Zhouping
The State Key Laboratory of Intelligent Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, HuaZhong University of Science and Technology, Wuhan 430074, China.
Micromachines (Basel). 2025 Feb 27;16(3):278. doi: 10.3390/mi16030278.
For a near-eye display, a resolution of over 10,000 pixels per inch (PPI) for the display device is needed to eliminate the "screen door effect" and have better display quality. Electrohydrodynamic (EHD) printing techniques, which have the advantages of a high resolution, wide material applicability and flexibility in patterning, have been widely used in the printing of high-resolution structures. However, due to factors such as the extremely small size of the droplets, the electric charge, the electric field, and the unavoidable positioning error, various deposition defects can occur. For droplets at a nanoscale, the dynamic deposition process is hard to observe. The continuum hypothesis fails and the fluid cannot be described by the traditional Navier-Stokes equation. In this work, the behaviors of charged nanodroplet deposition into a microcavity in an electric field are studied. The many-body dissipative particle dynamics (MDPD) method is used to examine the deformation of the nanodroplet during the impact process at a mesoscale. The dynamic process of charged droplet deposition into a microcavity under an electric field is revealed. Strategies for failure-free printing are proposed by analyzing the influences of the impact speeds, positioning errors, charge levels and electric intensities on the out-of-pixel spread length. The relationship between the internal charge moves and the deformation of the charged droplet in the deposition process is first discussed. The spreading theory of charged droplet deposition into a microcavity with a positioning error is established by analyzing the Coulombic capillary number. Moreover, the printing parameter space that results in successful printing is acquired.
对于近眼显示器，显示设备需要每英寸超过10,000像素（PPI）的分辨率，以消除“纱窗效应”并获得更好的显示质量。电流体动力学（EHD）打印技术具有高分辨率、材料适用性广和图案化灵活性等优点，已广泛应用于高分辨率结构的打印。然而，由于液滴尺寸极小、电荷、电场以及不可避免的定位误差等因素，可能会出现各种沉积缺陷。对于纳米级的液滴，动态沉积过程很难观察到。连续介质假设失效，流体无法用传统的纳维-斯托克斯方程来描述。在这项工作中，研究了带电纳米液滴在电场中沉积到微腔中的行为。采用多体耗散粒子动力学（MDPD）方法在介观尺度上研究纳米液滴在撞击过程中的变形情况。揭示了带电液滴在电场作用下沉积到微腔中的动态过程。通过分析撞击速度、定位误差、电荷水平和电场强度对像素外扩散长度的影响，提出了无故障打印策略。首次讨论了沉积过程中内部电荷移动与带电液滴变形之间的关系。通过分析库仑毛细管数，建立了带电液滴在有定位误差情况下沉积到微腔中的铺展理论。此外，还获得了能够实现成功打印的打印参数空间。
