Quantification of Marangoni flows and film morphology during solid film formation by inkjet printing
Quantification of Marangoni flows and film morphology during solid film formation by inkjet printing
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喷墨印刷固体成膜过程中马兰戈尼流动和薄膜形态的量化
DOI：
10.1007/s00348-017-2460-5
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发表时间：
2017
影响因子：
2.4
通讯作者：
Fukai Jun
中科院分区：
文献类型：
--
作者：
Ishizuka Hirotaka;Fukai Jun
我们可视化实验内部流动的聚苯乙烯-苯甲醚溶液的喷墨液滴在基板上在室温下形成固体膜。定量研究了接触角和蒸发速率对膜内流动和膜形貌的影响。通过测量内部流动和膜形态之间的关系，研究了膜形成过程中的传输过程，这提供了三个显着的发现。首先，自钉扎和2.3Pa s下自由表面向外流动的强度决定了薄膜的形态。溶质分布，对应于边缘区域的环状膜和凸槽的点状膜，已经开发了自钉扎。第二，在自钉扎接近接触线的质量分数收敛到1，无论膜的形态。这意味着自钉扎与接触角和蒸发速率等参数无关。第三，在室温下，溶质的Marangoni数比热的大20-30倍。因此，由溶质Marangoni效应引起的自由表面上的向外流动在自钉扎之前的液滴中占主导地位。对于不同接触角和蒸发速率的液滴，自钉扎时的溶液Marangoni数和膜中心的厚度变化表现出良好的关系。这表明，薄膜的形态可以在技术上控制的溶质Marangoni数在室温下。
We visualized experimentally the internal flow inside inkjet droplets of polystyrene–anisole solution during solid film formation on substrates at room temperature. The effects of contact angle and evaporation rate on the internal flow and film morphology were quantitatively investigated. The transport process during film formation was examined by measuring the relationship between internal flow and film morphology, which provided three remarkable findings. First, self-pinning and the strength of outward flow on the free surface under 2.3 Pa s determined film morphology. The solute distribution, corresponding to rim areas in ring-like films and a convex trough in dot-like films, had already developed at self-pinning. Second, the mass fraction at self-pinning close to the contact line converged to one, regardless of the film morphology. This implies that self-pinning is independent of parameters such as the contact angle and evaporation rate. Third, at room temperature, the solutal Marangoni numbers were 20–30 times larger than the thermal ones. Thus, the outward flow on the free surface caused by the solutal Marangoni effect dominates in droplets before self-pinning. The solutal Marangoni number at self-pinning and thickness variation at the center of the film displayed a good relationship for droplets with different contact angles and evaporation rates. This suggests that film morphology can be technically controlled by solutal Marangoni number at room temperature.