Chakraborty Anirban, Liu Xinchuan, Luo Cheng
Mechanical and Aerospace Engineering, University of Texas at Arlington, TX, USA.
J Vis Exp. 2012 Jul 2(65):3725. doi: 10.3791/3725.
Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 1977(1). They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications(2,3). Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials(4). For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form(5,6). One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes. A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers(4), polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures(7). The fabricated microstructures of conducting polymers have been used as humidity(8), chemical(8), and glucose sensors(9). Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions(9,10,11). The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems(12,13,14), and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel(15).
自1977年在掺杂聚乙炔中发现高电导率以来，导电聚合物就备受关注(1)。它们具有重量轻、性能易于定制以及应用范围广泛等优点(2,3)。由于导电聚合物对环境条件（如空气、氧气、湿气、高温和化学溶液）敏感，光刻技术在处理这些材料时面临重大技术挑战(4)。例如，当前的光刻方法，如紫外线（UV）光刻，由于这些方法涉及湿法和/或干法蚀刻工艺，不适用于对导电聚合物进行图案化。此外，当前的微纳系统主要呈平面形式(5,6)。一层结构构建在另一层制造特征的顶表面上。这些结构的多层堆叠在一起，在共同的基板上形成众多器件。微结构的侧壁表面尚未用于构建器件。另一方面，侧壁图案可用于，例如，构建三维电路、修改流体通道以及引导纳米线和纳米管的水平生长。一种大冲孔方法已在制造业中应用了一百多年，用于在金属薄板上创建大图案。受此方法启发，我们开发了一种微冲孔光刻方法（MPL），以克服对导电聚合物进行图案化和生成侧壁图案的障碍。与大冲孔方法一样，MPL也包括两个操作（图1）：（i）切割；和（ii）拉伸。“切割”操作被用于对三种导电聚合物进行图案化(4)，聚吡咯（PPy）、聚（3,4 - 乙撑二氧噻吩） - 聚（4 - 苯乙烯磺酸盐）（PEDOT）和聚苯胺（PANI）。它还被用于创建铝微结构(7)。所制备的导电聚合物微结构已被用作湿度传感器(8)、化学传感器(8)和葡萄糖传感器(9)。铝和导电聚合物的组合微结构已被用于制造电容器和各种异质结(9,10,11)。“切割”操作还被用于生成亚微米图案，如100纳米和500纳米宽的聚吡咯线以及100纳米宽的金线。“拉伸”操作有两个应用：（i）在高密度聚乙烯（HDPE）通道上制作金侧壁图案，可用于构建三维微系统(12,13,14)，以及（ii）在HDPE基板上制造聚二甲基硅氧烷（PDMS）微柱，以增加通道的接触角(15)。
