Wetting on Patterned Adaptive Conducting Polymer Surfaces for Microfluidic Applications (PolySurf)

“用于微流体应用的图案化自适应导电聚合物表面的润湿(PolySurf)”项目应落实到SPP 2171关于“柔性、自适应和可切换表面的动态润湿”的当前活动中。PolySurf基于Sabine Ludwigs(聚合物材料科学、电化学)和Holger Steeb(微流体、材料建模)的交叉学科专业知识，旨在研究能够使其润湿特性适应外部电场的分层图案化软表面。除了测量水接触角外，还应研究微流控应用中的流体动力学。对于自适应表面制备，已经确定了导电聚合物(CP)的类别。CP在柔性驱动器和传感器方面的应用越来越受到人们的关注，CP聚合物表面与液体的界面在这方面非常重要。导电聚合物的光学和电学性质不仅随掺杂度的变化而变化，而且其润湿性也受到很大的影响。在文献中，中性薄膜和掺杂薄膜之间的表面性质发生了从超疏水到超亲水的极端变化。在PolySurf中，需要系统地了解导电聚合物表面的动态润湿行为。在材料科学方面，既要制备可溶液处理的poly(ethylenedioxythiophene)：poly(styrenesulfonate)薄膜(PEDOT：PSS)，也要制备支化单体的电聚合薄膜。表面图案化技术涉及结构电极上的压印光刻和电聚合，目标是分层图案化以增加表面粗糙度。导电聚合物表面的表征将包括在水溶液中进行系统的电化学研究，以及通过吸收光谱和电导率测量进行形态和功能特性分析，以确定掺杂程度。在润湿表征方面，首先将进行系统的接触角测量(固着液滴、前进/后退接触角)。重点放在水和水/离子电解质上。无电位和施加电位的表面(在现场电化学测量期间)应根据其润湿行为进行监测。作为补充方法，椭圆偏振光谱将同时用于识别表面的变化，例如，当表面与水和含水的电解质接触时，通过膨胀来识别表面变化。这还应提供有关曲面自适应性的信息。除了研究表面三相接触线的动力学外，还应探索微流体应用中对多相流体动力学的润湿特性演变的影响。最终，电化学可切换的微流控器件被设想出来。

The project “Wetting on Patterned Adaptive Conducting Polymer Surfaces for Microfluidic Applications (PolySurf)”, shall be implemented into current activities of the SPP 2171 on “Dynamic Wetting of Flexible, Adaptive and Switchable Surfaces”. PolySurf is based on the coupled interdisciplinary expertise of Sabine Ludwigs (polymer materials science, electrochemistry) and Holger Steeb (microfluidics, material modelling) and aims at hierarchically patterned soft surfaces which can adapt their wetting properties to externally applied electric fields. In addition to water contact angle measurements the fluid dynamics within microfluidic applications shall be explored. For adaptive surface preparation the class of conducting polymers (CPs) has been identified. CPs are gaining increasing interest for flexible actuator and sensor applications, and the interfaces of the CP polymer surfaces with liquids are extremely relevant in this context. Conducting polymers cannot only change their optical and electronic properties as function of the degree of doping, but also the wetting properties are highly influenced. In the literature extreme changes of the surface properties from superhydrophobic to superhydrophilic are reported between neutral and doped films.Within PolySurf a systematic understanding of the dynamic wetting behavior of the conducting polymer surfaces shall be established. On the materials science side both solution-processable films of poly(ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as well as electropolymerized films from branched monomers shall be prepared. Surface patterning techniques involve imprint lithography and electropolymerisation on structured electrodes and are targeted at hierarchical patterning to increase the surface roughness.Characterization of the conducting polymer surfaces will involve systematic electrochemical studies in aqueous electrolytes alongside morphological and functional property analysis by absorption spectroscopy and conductivity measurements to determine the degree of doping.In terms of wetting characterization first systematic contact angle measurements (sessile droplet, advancing/ receding contact angles) will be performed. The focus lies on water and water/ion electrolytes. Surfaces with no potential and with potential applied (during in-situ electrochemical measurements) shall be monitored in terms of their wetting behavior. As complementary method spectroscopic ellipsometry will be used alongside to identify surface variations, e.g. by swelling, when the surfaces are brought in contact with the water and the aqueous electrolytes. This shall also give information about the adaptivity of the surfaces. Beyond the study of the dynamics of three phase contact lines on surfaces, the effect on evolving wetting properties on multi-phase fluid dynamics within microfluidic applications shall be explored. Ultimately, electrochemically-switchable microfluidic devices are envisioned.