Focusing Effect for Sliding Drops Induced by Adaptive Surfaces

自适应表面引起的滑动水滴的聚焦效应

• 批准号: 505838917
• 负责人: Dr. Rüdiger Berger
• 金额: --
• 依托单位: Max-Planck-Institut für Polymerforschung
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/505838917?language=en
• 关键词: Focusing; Effect; Sliding; Drops; Induced

Surface adaptation has been put forward to be one cause for the velocity dependence of advancing and receding contact angles, even at low slide velocity. By considering a dry-to-wet and a wet-to-dry relaxation process, we had proposed a model, which is able to explain these dynamic contact angles (Langmuir 2018, 34, 11292). The aim of our project is to experimentally verify the model and explore, how applicable it is. In the first funding period, we built an inclined plane setup to measure advancing and receding contact angles versus velocity for water drops up to 1 m/s. We synthesized a random poly(styrene/acrylic acid) copolymer PS/AA and demonstrated that for water drops on PS/AA films, advancing-contact-angle-versus-velocity-curves can indeed be fitted with the model. The fit revealed relaxation times < 2 ms of the polymer at the surface. However, we are still missing independent measurements of the dry-to-wet relaxation times, which would be required for full validation of the model. The aim for the second funding period is to investigate polymer surfaces, where we can independently measure the relaxation time of the dry-to-wet and the wet-to-dry transitions. Then, recorded advancing-contact-angle-versus-velocity-dependencies can be validated independently using our model. Therefore, we plan to synthesize three types of polymer brushes: (1) PS and poly(2-vinylpyridine) (PVP) binary brush films, (2) pH-responsive poly(N,N-dimethyl aminoethyl meth¬acrylate) (PDMAEMA) brushes and (3) different block copolymer layers. For series of drops sliding on an adaptive surface we predicted a focusing effect. It is induced by partial adaptation caused by the first drop sliding along the surface. This drop leaves behind a lane of increased surface energy and we expect that subsequent drops will then slide along the same lane. Our aim is to verify this hypothesis.

表面自适应被认为是前进和后退接触角依赖于速度的原因之一，即使在低滑动速度下也是如此。通过考虑干到湿和湿到干的松弛过程，我们提出了一个能够解释这些动态接触角的模型（Langmuir 2018, 34,11292）。我们项目的目的是通过实验验证该模型并探索其适用性。在第一个资助阶段，我们建立了一个斜面装置，用于测量水滴前进和后退的接触角与速度的关系，水滴速度最高可达1m /s。我们合成了一种随机聚苯乙烯/丙烯酸共聚物PS/AA，并证明了水滴在PS/AA薄膜上的推进接触角-速度曲线确实可以与该模型相拟合。拟合显示聚合物表面的弛豫时间< 2 ms。然而，我们仍然缺少干湿弛豫时间的独立测量，这将是模型完全验证所必需的。第二个资助期的目标是研究聚合物表面，在那里我们可以独立测量从干到湿和从湿到干转变的松弛时间。然后，记录的推进接触角与速度的依赖关系可以使用我们的模型独立验证。因此，我们计划合成三种类型的聚合物刷：(1)PS和聚（2-乙烯基吡啶）（PVP）二元刷膜，(2)ph响应型聚（N，N-二甲基氨基乙基甲基丙烯酸酯）（PDMAEMA）刷和(3)不同的嵌段共聚物层。对于在自适应表面上滑动的一系列液滴，我们预测了聚焦效应。它是由第一滴水沿表面滑动引起的部分适应引起的。这个水滴留下了一条增加表面能量的通道，我们预计随后的水滴会沿着同一通道滑动。我们的目的是验证这一假设。