Patterning of Thin Polymer Film by Surface-pattern-directed Dewetting

本论文通过具有不同拓扑结构和化学性质的基底，诱导聚合物薄膜的去润湿行为，控制去润湿的发生过程，达到了制备有序图案的目的。同时探讨了有序图案形成机理以及图案的潜在应用。在物理改性的条纹图案的硅基底上，薄膜以条纹的边界为成核因子破裂而发生去润湿，最终形成了规则排列的聚合物条纹图案。研究还发现基底条纹的宽度必须小于一定的临界值时才能形成规则去润湿图案。其次，在化学改性的条纹和方块图案的硅基底上，由于基底与化学图案微观上高度差别和润湿性差别造成薄膜在图案边界破裂而发生去润湿，最终我们得到了比原来改性模板更小、更复杂的聚合物条纹和面心结构的图案。另外控制实验条件，我们在硅基底上得到了与模板图案不同的化学图案，聚合物薄膜在这种图案化的基底上按成核机理发生去润湿而得到了薄膜微图案。利用薄膜方程理论解释了薄膜在这种改性基底上的去润湿行为。最后我们将聚合物薄膜的微图案通过图案转移的方法传递到其他材料上。研究结果表明通过改性基底来控制去润湿不但是制备聚合物薄膜微图案化的新方法，与原来改性的模板相比，还可以大大减小薄膜微图案的尺寸和改变图案的形状，这为软物质在微米及纳米水平上图案化提供了不需传统刻蚀技术的简单易行的方法。In this thesis, the dewetting behavior of thin polymer film on the physically and chemically modified substrates were investigated by the use of optical microscopy and atomic force microscopy. It indicated that ordered pattern could form by the substrate directed dewetting. The mechanisms and the optimal condition on pattern formation were discussed. The ordered pattern has been transferred to form PDMS stamp and this demonstrated the potential applications of the obtained pattern. On physically modified substrate, dewetting of polymer film was initiated at the boundaries of the stripe pattern, and the polymer stripe pattern was obtained. The result indicated that the order pattern could be achieved only when the substrate pattern was smaller then a critical value. On chemically modified substrate, due to the microscale wettability contrast and the height contrast between the chemical pattern and silicon substrate, dewetting of polymer film was initiated at the boundaries of the chemical pattern. Smaller and more complex polymer stripe and face center cubic pattern compared to the mold could be obtained. In addition, ordered OTS dot pattern could be realized by controlled microcontact printing. Dewetting of thin polymer film on this substrate was initiated at the ordered OTS, which acted as nucleation sites and finally ordered polymer microstructures formed. Theses thin polymer raicrostructures have been transferred onto other materials for future use. The obtained result was discussed by employing the thin film equation. The substrate-pattern-directed dewetting is a new way to pattern thin polymer film with reduced the pattern size as well as pattern morphology by contrast with the original mold pattern. Our research provided a simple and non-lithography method to pattern soft material at micrometer scale