Department of Science and Technology, Soft Matter, Fluidics and Interfaces (SFI), University of Twente, Enschede, The Netherlands.
Department of Science and Technology, Physics of Fluids (POF), Max Planck - University of Twente Center for Complex Fluid Dynamics, University of Twente, Enschede, The Netherlands.
Soft Matter. 2018 Mar 7;14(10):1780-1788. doi: 10.1039/c7sm02337e.
Liquid-infused membranes inspired by slippery liquid-infused porous surfaces (SLIPS) have been recently introduced to membrane technology. The gating mechanism of these membranes is expected to give rise to anti-fouling properties and multi-phase transport capabilities. However, the long-term retention of the infusion liquid has not yet been explored. To address this issue, we investigate the retention of the infusion liquid in slippery liquid-infused membranes (SLIMs) via liquid-liquid displacement porometry (LLDP) experiments combined with microscopic observations of the displacement mechanism. Our results reveal that pores will be opened corresponding to the capillary pressure, leading to preferential flow pathways for water transport. The LLDP results further suggest the presence of liquid-lined pores in SLIM. This hypothesis is analyzed theoretically using an interfacial pore flow model. We find that the displacement patterns correspond to capillary fingering in immiscible displacement in porous media. The related physics regarding two-phase flow in porous media is used to confirm the permeation mechanism appearing in SLIMs. In order to experimentally observe liquid-liquid displacement, a microfluidic chip mimicking a porous medium is designed and a highly ramified structure with trapped infusion liquid is observed. The remaining infusion liquid is retained as pools, bridges and thin films around pillar structures in the chip, which further confirms liquid-lining. Fractal dimension analysis, along with evaluation of the fluid (non-wetting phase) saturation, further confirms that the fractal patterns correspond to capillary fingering, which is consistent with an invasion percolation with trapping (IPT) model.
受超滑液浸润多孔表面 (SLIPS)启发的液浸膜最近被引入到膜技术中。这些膜的闸门机制有望产生抗污染性能和多相传输能力。然而，浸润液的长期保留尚未得到探索。为了解决这个问题，我们通过液-液置换压孔法 (LLDP) 实验结合对置换机制的微观观察来研究超滑液浸润膜 (SLIM) 中浸润液的保留情况。我们的结果表明，孔隙将在毛细压力的作用下打开，从而形成水传输的优先流道。LLDP 结果进一步表明 SLIM 中存在液体衬里的孔隙。该假设通过界面孔隙流动模型进行了理论分析。我们发现，置换模式与多孔介质中非混相置换中的毛细指进相对应。使用多孔介质中两相流的相关物理知识来确认出现在 SLIM 中的渗透机制。为了实验观察液-液置换，设计了一个模拟多孔介质的微流控芯片，并观察到具有被困浸润液的高度分支结构。芯片中支柱结构周围的剩余浸润液保留为液池、液桥和薄膜，进一步证实了液体衬里的存在。分形维数分析以及对流体（非润湿相）饱和度的评估进一步证实，分形模式与毛细指进相对应，这与具有捕获的侵入渗流 (IPT) 模型一致。
