Institut Lumière Matière, Université Claude Bernard Lyon 1-CNRS, UMR 5306, Université de Lyon, F-69622 Villeurbanne Cedex, France and School of Aerospace and Mechanical Engineering, Korea Aerospace University, Goyang 412-791, Korea.
Institut Lumière Matière, Université Claude Bernard Lyon 1-CNRS, UMR 5306, Université de Lyon, F-69622 Villeurbanne Cedex, France.
Phys Rev Lett. 2014 Jun 20;112(24):244501. doi: 10.1103/PhysRevLett.112.244501. Epub 2014 Jun 19.
Osmosis across membranes is intrinsically associated with the concept of semipermeability. Here, however, we demonstrate that osmotic flow can be generated by solute gradients across nonselective, fully permeable nanochannels. Using a fluorescence imaging technique, we are able to measure the water flow rate inside single nanochannels to an unprecedented sensitivity of femtoliters per minute flow rates. Our results indicate the onset of a convective liquid motion under salinity gradients, from the higher to lower electrolyte concentration, which is attributed to diffusio-osmotic transport. To our knowledge, this is the first experimental evidence and quantitative investigation of this subtle interfacially driven transport, which need to be accounted for in nanoscale dynamics. Finally, diffusio-osmotic transport under a neutral polymer gradient is also demonstrated. The experiments highlight the entropic depletion of polymers that occurs at the nanochannel surface, resulting in convective flow in the opposite direction to that seen for electrolytes.
跨膜渗透本质上与半透性的概念有关。然而，在这里，我们证明了溶质梯度可以在非选择性的、完全可渗透的纳米通道中产生渗透流。我们使用荧光成像技术，能够以亚飞升每分钟流速的空前灵敏度测量单纳米通道内的水流量。我们的结果表明，在盐度梯度下，从较高的电解质浓度到较低的电解质浓度，会出现对流液体运动，这归因于扩散渗透运输。据我们所知，这是对这种细微的界面驱动输运的首次实验证据和定量研究，在纳米尺度动力学中需要考虑到这种输运。最后，还证明了中性聚合物梯度下的扩散渗透运输。实验突出了聚合物在纳米通道表面发生的熵耗散，导致与电解质相反的对流流动。
