Pan Bin, Clarkson Christopher R, Atwa Marwa, Debuhr Chris, Ghanizadeh Amin, Birss Viola I
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB T2N 1N4, Canada.
Department of Geoscience, University of Calgary, Calgary, AB T2N 1N4, Canada.
J Colloid Interface Sci. 2021 May;589:411-423. doi: 10.1016/j.jcis.2020.12.108. Epub 2020 Dec 31.
The Lucas-Washburn (L-W) equation is the classical theory to describe the dynamics of spontaneous imbibition in single micro-channels and micro-scale porous media. However, for nanoliter droplets imbibition in nanoporous media, the L-W equation may not be suitable, due to the nanoscale liquid-solid interactions, e.g., contact line pinning and capillary condensation. In addition, for an intrinsically hydrophobic nanoporous substrate, spontaneous imbibition of a nanoliter droplet is hypothesized to occur if capillary condensation had occurred internally already.
A nanoporous carbon scaffold was synthesized and used as a model nanoporous medium. A recently-developed micro-injection technique was used to generate a series of nanoliter water droplets (2.8-34 nL); the entire wetting dynamics (i.e., apparent contact angle and droplet volume as a function of time) were observed inside an environmental scanning electron microscope.
The L-W equation does not describe the wetting dynamics of nanoliter water droplets in nanoporous media. A new theoretical model is developed to characterize the corresponding dynamics. It is demonstrated that, even for an intrinsically hydrophobic nanoporous substrate, spontaneous imbibition of a nanoliter droplet can occur if capillary condensation had occurred internally already.
卢卡斯-沃什伯恩（L-W）方程是描述单微通道和微尺度多孔介质中自发渗吸动力学的经典理论。然而，对于纳米多孔介质中纳升液滴的渗吸，由于纳米级的液-固相互作用，例如接触线钉扎和毛细凝聚，L-W方程可能并不适用。此外，对于本质上疏水的纳米多孔基底，如果内部已经发生了毛细凝聚，则推测会发生纳升液滴的自发渗吸。
合成了一种纳米多孔碳支架并将其用作模型纳米多孔介质。使用一种最近开发的微注射技术来产生一系列纳升水滴（2.8 - 34纳升）；在环境扫描电子显微镜内观察了整个润湿动力学（即表观接触角和液滴体积随时间的变化）。
L-W方程无法描述纳米多孔介质中纳升水滴的润湿动力学。开发了一种新的理论模型来表征相应的动力学。结果表明，即使对于本质上疏水的纳米多孔基底，如果内部已经发生了毛细凝聚，纳升液滴也会发生自发渗吸。
