Dynamic Electrowetting at Nanoporous Surfaces: Switchable Spreading, Imbibition, and Elastocapillarity

导电基底，例如纳米多孔金属和半导体的表面，允许人们通过电势来控制电解质的润湿能。因此，可以调节液滴形状和表面处的液体扩散动力学，然而，经由纳米孔内的液体微滴的电位依赖性曲率，到多孔表面中的吸入也处于外部控制之下。此外，巨大的拉普拉斯压力和流体-固体界面应力，典型的纳米孔限制的液体，引起多孔固体的显著变形，并因此导致在电润湿的情况下，在液体毛细作用与固体弹性的电位依赖性耦合，即电可切换的弹性毛细作用。这些现象（液滴形状动力学，吸液和变形行为）的复杂的相互作用几乎没有探索到今天。在这里，它提出了实验探索的润湿动力学的水性电解质在定制的，单晶硅表面的管状纳米孔沿着与密切相关的固体的弹性变形下的电位控制的固-液界面张力的平行阵列穿过。应研究在纳米孔表面处具有介电氧化物层的直接润湿和电润湿。前体膜的存在，液滴扩散和吸胀动力学，以及变形的微观（原子硅晶格）和宏观（基板）规模将通过随时间变化的液滴形状分析，光流体干涉，光学测量和同步加速器为基础的原位X-射线衍射下的平均孔径和孔隙率的表面。实验应与本优先计划中的项目密切合作进行分析，重点是平面和多孔表面上液体扩散、吸胀和弹性毛细现象的计算建模和介观唯象理论。这个项目的首要目标是一个基本的，预测性的理解电开关静态和动态润湿纳米多孔表面。

Electrically conductive substrates, such as surfaces of nanoporous metals and semiconductors allow one to control the wetting energies of electrolytes by electrical potentials. Thereby, it is possible to tune droplet shape and liquid spreading dynamics at surfaces, however also the imbibition into the porous surface is under external control via electrical potential-dependent curvatures of the liquid menisci within the nanopores. Moreover, the enormous Laplace pressures and fluid-solid interfacial stresses, typical of nanopore-confined liquids, induce noticeable deformations of the porous solids, and thus result in the case of electrowetting in a potential-dependent coupling of liquid capillarity with solid elasticity, i.e. electrically switchable elastocapillarity. The complex interplay of these phenomenologies (droplet shape dynamics, imbibition and deformation behaviour) have been barely explored to date. Here, it is proposed to explore experimentally the wetting dynamics of aqueous electrolytes at tailored, single-crystalline silicon surfaces traversed by a parallel array of tubular nanopores along with the intimately related elastic deformation of the solids under electrical potential control of the solid-liquid interfacial tension. Both direct and electrowetting with dielectric oxide layers at the nanopore surfaces shall be studied. The existence of precursor films, droplet spreading and imbibition dynamics as well as the deformation on the microscopic (atomic silicon lattice) and macroscopic (substrate) scale will be scrutinized by time-dependent droplet shape analysis, opto-fluidic interferometry, dilatometry and synchrotron-based in-situ x-ray diffraction under variation of the mean pore diameter and porosity of the surface. The experiments shall be analysed in close cooperation with projects in this priority program focusing on computational modelling and mesoscopic phenomenological theories for liquid spreading, imbibition and elastocapillarity at planar and porous surfaces. The overarching objective of this project is a fundamental, predictive understanding of electrically switchable static and dynamic wetting at nanoporous surfaces.