毛细力辅助飞秒激光直写制备各向异性及多级结构

Fabrication of anisotropic and hierarchical structures using femtosecond laser printing capillary force assisted self-assembly

将飞秒激光双光子聚合加工技术和毛细力诱导自组装技术相结合实现了各向异性结构和多级结构的制备。首先,使用飞秒激光双光子加工技术加工出微柱阵列,将微柱置于显影液中显影,然后放置在空气中。在显影液蒸发的过程中,微柱结构单元受到毛细力的作用而弯曲实现自组装。通过控制微柱的高度和直径的不一致性实现了两种各向异性结构制备方法,并成功制备了底层微柱直径分别为2μm和6μm双层结构。由于毛细力的大小和微柱高度无关,且同样端部变形量下较高微柱的弹性回复力小于较低微柱的弹性回复力,更易发生弯曲;直径较大的微柱具有更强的抗弯曲能力,从而引导直径较小的微柱向较大的微柱倾斜,藉此制备了各向异性结构。使用毛细力自组装辅助飞秒激光微纳加工可以实现灵活可控的复杂3D结构的加工,并将在生物医药、化学分析、微流体等领域发挥重要作用。

A method for preparation of designable anisotropic and hierarchical structures using femto- second laser printing and capillary force assisted self-assembly was proposed. First, a periodic micro- pillar arrays template was fabricated by localized femtosecond laser polymerization. The micro-pillars were immersed in developed solution for about 40 min and subsequently exposed in the air. During the evaporation of developed solution, micro-pillars was self-assembled into periodic anisotropic architec-tures with the assistance of capillary force. Two methods to fabricate anisotropic structures were pro- posed. One was realized via controlling heights of pillars in a cell, the other was achieved via control ling pillar diameters. Furthermore, double-layer structures with underlayer pillar diameters of 2 μm and 6 μm were fabricated respectively. The results indicate that the capillary force is irrespective to the height of pillars, and the elastic restoring force of the higher pillars is stronger than the lower pil lars, thus higher pillars are prone to bend and the pillars with larger diameter are more likely to re main upright. Complex 3D structures can be achieved flexibly by combing femtosecond laser fabrica tion with capillary force self-assembly technology, which will play essential roles in biomedicine, chemistry and microfluidic engineering.