Department of Electrical Engineering and Computer Science, York University, Toronto, Ontario M3J 1P3, Canada.
Department of Mechanical Engineering, York University, Toronto, Ontario M3J 1P3, Canada.
J Chem Phys. 2023 Jul 14;159(2). doi: 10.1063/5.0149663.
Inkjet-printed micro-patterns on hydrophobic surfaces have promising applications in the fabrication of microscale devices such as organic thin-film transistors. The low wettability of the surface prevents the inkjet-printed droplets from spreading, connecting to each other, and forming a pattern. Consequently, it is challenging to form micro-patterns on surfaces with low wettability. Here, we propose a sequential printing and drying method to form micro-patterns and control their shape. The first set of droplets is inkjet-printed at a certain spacing and dried. The second set of droplets is printed between these dry anchors on the surface with low wettability. As a result, a stable bridge on the surface with low wettability forms. This printing method is extended to more complicated shapes such as triangles. By implementing an energy minimization technique, a simple model was devised to predict the shape of the inkjet-printed micro-patterns while confirming that their equilibrium shape is mainly governed by surface tension forces. The gradient descent method was utilized with parametric boundaries to emulate droplet pinning and wettability of the anchors and to prevent convergence issues from occurring in the simulations. Finally, the energy minimization based simulations were used to predict the required ink to produce dry lines and triangles with smooth edges.
喷墨打印在疏水性表面上的微图案在制造微尺度器件（如有机薄膜晶体管）方面具有广阔的应用前景。表面的低润湿性阻止了喷墨打印的液滴扩散、相互连接并形成图案。因此，在低润湿性表面上形成微图案具有挑战性。在这里，我们提出了一种顺序打印和干燥的方法来形成微图案并控制其形状。首先在一定的间隔下喷墨打印一组液滴并干燥。第二组液滴在疏水性表面上这些干燥的锚点之间打印。结果，在疏水性表面上形成了稳定的桥。这种打印方法可以扩展到更复杂的形状，如三角形。通过实施能量最小化技术，设计了一个简单的模型来预测喷墨打印微图案的形状，同时确认其平衡形状主要受表面张力的控制。利用梯度下降法和参数边界来模拟液滴的固定和锚点的润湿性，以防止模拟中出现收敛问题。最后，基于能量最小化的模拟用于预测产生干燥线和具有平滑边缘的三角形所需的墨水。
