MEMS analogous micro-patterning of thermotropic nematic liquid crystalline elastomer films using a fluorinated photoresist and a hard mask process
MEMS analogous micro-patterning of thermotropic nematic liquid crystalline elastomer films using a fluorinated photoresist and a hard mask process
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DOI：
10.1039/c7tc03958a
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发表时间：
2017-12
影响因子：
6.4
通讯作者：
David Ditter;Wei‐Liang Chen;A. Best;H. Zappe;K. Koynov;C. Ober;R. Zentel
中科院分区：
文献类型：
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作者：
David Ditter;Wei‐Liang Chen;A. Best;H. Zappe;K. Koynov;C. Ober;R. Zentel
在这项工作中，我们提出了一种方法来图案液晶弹性体（LCEs）在微米范围内，而不使用任何机械加工步骤，以制备微米尺寸的LCE致动器兼容的微机电系统（MEMS）技术。开发了多层旋涂工艺以合成和结构化300-3500 nm厚的LCE膜。将水溶性牺牲层、光配向层和在其液晶相中聚合和交联的LCE制剂依次旋涂到基板上。氟化光致抗蚀剂层用于在光刻和蚀刻工艺中结构化厚度高达700 nm的LCE膜。对于较厚的LCE膜，使用氢倍半硅氧烷（HSQ）作为硬掩模的硬掩模工艺被使用。薄膜厚度和均匀性分析与轮廓。LCE层的致动运动之前和之后的图案化和LCE图案进行了研究，通过（偏光）显微镜（POM），扫描电子显微镜（SEM）和轮廓。利用所描述的技术实现了1.5-2.0微米的分辨率，这使得可变形状和指向矢取向的可变形微米尺寸的LCE致动器可接近。所呈现的结果展示了LCE在MEMS器件中的潜力。
In this work, we present a method to pattern liquid crystal elastomers (LCEs) in the micrometer range without using any mechanical processing steps to prepare micron sized LCE actuators compatible with microelectromechanical system (MEMS) technology. Multi-layer spin-coating processes are developed to synthesise and structure 300–3500 nm thick LCE films. A water soluble sacrificial layer, a photoalignment layer and a LCE formulation, which is polymerised and crosslinked in its liquid crystal phase, are spin-coated successively onto a substrate. A fluorinated photoresist layer is used to structure LCE films with thicknesses up to 700 nm in a photolithographic and etching process. For thicker LCE films a hard mask process, using hydrogen silsesquioxane (HSQ) as hard mask, is used. Film thicknesses and homogeneities are analysed with profilometry. Actuation motions of LCE layers are investigated before and after patterning and LCE patterns are investigated via (polarised optical) microscopy (POM), scanning electron microscopy (SEM) and profilometry. A resolution of 1.5–2.0 microns is achieved with the described techniques, which make deformable micron sized LCE actuators of variable shape and director orientation accessible. The presented results demonstrate the potential of LCEs in MEMS devices.