Integrated Analysis on Transport Phenomena during Thin Film Formation Using Inkjet method

从实验和理论上讨论了一种利用喷墨方法使薄膜变平的方法。首先对液滴在衬底上蒸发的流体动力学进行了分析。在本系统中，溶质衍生和热衍生的Marangoni力影响流体动力学。它们在自由面上以相反的方向发展流动。随着衬底温度的升高，热导出力增大。然而，随着蒸发时间的推移，溶质衍生力最终主导了流体动力学。二元溶剂之所以经常形成平坦的薄膜，一直被认为是因为液滴中的流体流动可以由溶剂的表面张力之间的差异来控制。然而，由于溶剂导向力大于溶剂导向力，因此膜的形状与溶剂表面张力差所产生的流体流量无关，因此膜的形状受自钉扎位置的影响，自钉扎位置可由粘度、接触角和挥发速率控制。Marangoni部队被用来控制微妙的平整度。根据这一结果，提出了一种形成平坦薄膜的新方法。

A way how to flatten a thin film using inkjet method is discussed experimentally and theoretically. Firstly the fluid dynamics in solution droplets evaporating on a substrate are analyzed. On the present system, the solutal-derived and thermal-derived Marangoni forces affect the fluid dynamics. They develop the flow in the opposite direction on the free surface. The thermal-derived forces increase with increasing the temperature of substrate. However, after evaporation is advanced in time, the solutal-derived forces finally dominates the fluid dynamics.The reason why binary solvent often forms a flat thin film has been thought to be that the fluid flow in the droplet can be controlled by the difference between the surface tensions of the solvents. However, the film configuration is not correlated to the fluid flow expected from the difference between the surface tension of the solvents, because the solutal-derived forces are larger than solvent-derived one.Consequently, the film shape is influenced by self-pinning position, which can be controlled by viscosity , contact angle and evaporation rate. The Marangoni forces are used to control delicate flatness. According to this result, a new method is proposed to form flat thin films.