MECHANISM OF THE FILM FORMATION BY THE INKJET PRINTING METHOD

针对聚合物溶液液滴（d= 30 ~ 100 μm）的喷墨打印，研究了溶剂的物理性质、初始溶质浓度和表面润湿性对喷墨打印的影响。观察了液滴的蒸发过程，并测量了形成的薄膜形状。在高初始溶质浓度和高蒸发速率条件下，在疏水表面形成环状膜。这是由于接触线固定后的内部流动造成的。内部流动取决于黏度，黏度在快速紧固时减小。在高初始溶质浓度下，在亲冷表面形成点状膜。具有不同沸点的二元溶剂是控制喷墨印刷薄膜形状的突破口。3 .双溶剂喷墨印刷增加了钉钉时的液滴粘度，这是双溶剂影响膜形的主要因素。利用流动显示技术观察液滴截面处的循环源流动。由于地表的温差，这种流动不能用马兰戈尼对流来理解。数值模拟表明，可视化流动是由于液滴表面和体积之间的密度差造成的自然对流。这种密度差是由溶质浓度引起的。在高初始溶质浓度下观察到强对流。这与高溶质浓度下的高粘度相冲突。这种意想不到的现象也可以用溶质浓度引起的自然对流来解释。在疏冻/亲冻图案表面喷射的液滴沉积在亲冻部分。研究发现，延迟在冻干部分的钉钉时间对冻干部分的沉积是很重要的。

For the inkjet printings of the polymer solution droplet (d= 30-100 μm), the effects of the physical properties of the solvent, the initial solute concentration and the surface wettability are studied. The evaporation process of the droplet is observed and the resulted film shape is measured.1. Deposited on the lyophobic surface, ring-like films form at the high initial solute concentration and the high evaporation rate. This is due to the internal flow after the pinning of the contact line. The internal flow depends on the viscosity which decreases at the fast pinning.2. On the lyophilic surface, dot-like films form at the high initial solute concentration. The binary solvent with the different boiling points is the breakthrough to control the film shape for the inkjet printings.3. The binary-solvent inkjet printings increase the droplet viscosity at the pinning, which is the primary factor that the binary solvent affects the film shape.4. The circulating source flow at the cross section of the droplet is observed by the flow visualization. This flow cannot be understood by the Marangoni convection due to the temperature difference on the surface.5. The numerical simulation clarified that visualized flow is due to the natural convection by the density difference between the surface and the bulk of the droplet. This density difference is due to the solute concentration.6. The strong convection is observed for the high initial solute concentration. This conflicts the high viscosity at the high solute concentration. This unexpected phenomenon is also understood by the natural convection due to the solute concentration.7. The droplet ejected on the lyophobic/lyophilic patterned surface deposits on the lyophilic part. To delay the pinning time on the lyophilic part is found to be important to deposit on the lyophilic part.