Heo S G, Jang D, Koo H-J, Yoon H
Opt Express. 2019 Feb 4;27(3):3439-3447. doi: 10.1364/OE.27.003439.
Generally, the fabrication of curved structures such as microlens arrays has been regarded as an expensive and complicated process. Here, we propose a facile method to form a microlens array with controlled lens curvature by combining residue-free nanoimprint lithography (NIL) with V-shaped molds and the successive thermal reflow procedure of the printed polymeric structures. The V-shaped molds used in this study enable the bottom substrate to be exposed after the NIL process when the initial thickness is controlled. Then, we use the thermal reflow to realize hemi-cylindrical curved lenses by applying heat. The polymers are self-pinned on the exposed substrate, which is strong enough to fix the boundary to not dewet or be flattened in the broad temperature range of the reflow process, which is essential for a large-area fabrication. Furthermore, we demonstrate the modulation of the focal lengths of the lenses by controlling the initial polymer thickness coated on a substrate.
一般来说，诸如微透镜阵列等弯曲结构的制造一直被视为一个昂贵且复杂的过程。在此，我们提出一种简便的方法，通过将无残留纳米压印光刻（NIL）与V形模具以及印刷聚合物结构的连续热回流工艺相结合，来形成具有可控透镜曲率的微透镜阵列。本研究中使用的V形模具在控制初始厚度时，能使底部基板在纳米压印光刻工艺后暴露出来。然后，我们通过加热利用热回流实现半圆柱形曲面透镜。聚合物自固定在暴露的基板上，其强度足以在回流过程的宽温度范围内固定边界，使其不会去湿或变平，这对于大面积制造至关重要。此外，我们通过控制涂覆在基板上的初始聚合物厚度来展示透镜焦距的调制。
