Cencha Luisa G, Dittrich Guido, Huber Patrick, Berli Claudio L A, Urteaga Raul
Polymer Reaction Engineering Group, INTEC (Universidad Nacional del Litoral-CONICET), Gemes 3450, Santa Fe 3000, Argentina.
Hamburg University of Technology, Materials Physics and High-Resolution X-Ray Analytics, Hamburg University of Technology, 21073 Hamburg, Germany.
Phys Rev Lett. 2020 Dec 4;125(23):234502. doi: 10.1103/PhysRevLett.125.234502.
When a macroscopic droplet spreads, a thin precursor film of liquid moves ahead of the advancing liquid-solid-vapor contact line. Whereas this phenomenon has been explored extensively for planar solid substrates, its presence in nanostructured geometries has barely been studied so far, despite its importance for many natural and technological fluid transport processes. Here we use porous photonic crystals in silicon to resolve by light interferometry capillarity-driven spreading of liquid fronts in pores of few nanometers in radius. Upon spatiotemporal rescaling the fluid profiles collapse on master curves indicating that all imbibition fronts follow a square-root-of-time broadening dynamics. For the simple liquid (glycerol) a sharp front with a widening typical of Lucas-Washburn capillary-rise dynamics in a medium with pore-size distribution occurs. By contrast, for a polymer (PDMS) a precursor film moving ahead of the main menisci entirely alters the nature of the nanoscale transport, in agreement with predictions of computer simulations.
当宏观液滴扩散时，一层薄薄的液体前驱膜会在前进的液 - 固 - 气接触线之前移动。尽管这种现象已在平面固体基板上得到广泛研究，但到目前为止，尽管它对许多自然和技术流体传输过程很重要，但其在纳米结构几何形状中的存在却几乎未被研究。在这里，我们使用硅基多孔光子晶体，通过光干涉测量法来解析半径为几纳米的孔中毛细作用驱动的液面前沿扩散。在进行时空重标度后，流体轮廓会汇聚到主曲线上，这表明所有的吸渗前沿都遵循时间平方根展宽动力学。对于简单液体（甘油），在具有孔径分布的介质中会出现具有典型卢卡斯 - 沃什伯恩毛细上升动力学展宽特征的尖锐前沿。相比之下，对于聚合物（聚二甲基硅氧烷），在主弯月面之前移动的前驱膜完全改变了纳米级传输的性质，这与计算机模拟的预测结果一致。
