Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, USA.
Small. 2010 Mar 22;6(6):768-75. doi: 10.1002/smll.200901843.
By exploiting the thermoplastic and photosensitive nature of SU-8 photoresists, different types of hierarchical pillar arrays with variable aspect ratios are fabricated through capillary force lithography (CFL), followed by photopatterning. The thermoplastic nature of SU-8 enables the imprinting of micropillar arrays with variable aspect ratios by CFL using a single poly(dimethylsiloxane) mold, simply by tuning the initial film thickness of SU-8 on a substrate. The pillar array is subsequently photopatterned through a photomask, followed by post-exposure baking above the glass transition temperature (T(g)) of SU-8. The pillars in the exposed region become highly crosslinked and, therefore, neither soluble nor able to reflow above T(g), whereas the pillars in the unexposed regions can reflow and flatten out. Two developing strategies are investigated after UV exposure of the SU-8 pillar arrays including i) solvent development and drying and ii) thermal reflow to create bilevel hierarchical structures with short pillars and single-level, dual-scaled, high-aspect-ratio (up to 7.7) pillars in a microdot array, respectively.
通过利用 SU-8 光致抗蚀剂的热塑性和光敏性，通过毛细作用力光刻（CFL）和随后的光图案化，可以制造出具有不同纵横比的不同类型的分级柱阵列。SU-8 的热塑性使得可以通过 CFL 使用单个聚二甲基硅氧烷（PDMS）模具来压印具有可变纵横比的微柱阵列，只需调整 SU-8 在基底上的初始膜厚度即可。然后通过光掩模对柱阵列进行光图案化，然后在 SU-8 的玻璃化转变温度（Tg）以上进行后曝光烘烤。在曝光区域中的柱子变得高度交联，因此既不溶于也不能在 Tg 以上再流，而在未曝光区域中的柱子可以再流和平整。在 SU-8 柱阵列的 UV 曝光后，研究了两种显影策略，包括 i）溶剂显影和干燥以及 ii）热回流，以分别在微点阵列中创建具有短柱和单级、双尺度、高纵横比（高达 7.7）柱的双层分级结构。
