Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
Laboratoire Photonique Numérique et Nanosciences, Université de Bordeaux, LP2N, F-33405 Talence, France.
Soft Matter. 2022 Jul 27;18(29):5509-5517. doi: 10.1039/d2sm00305h.
Studying the Brownian motion of fibers and semi-flexible filaments in porous media is the key to understanding the transport and mechanical properties in a variety of systems. The motion of semi-flexible filaments in gel-like porous media including polymer networks and cell cytoskeleton has been studied theoretically and experimentally, whereas the motion of these materials in packed-colloid porous media, advanced foams, and rock-like systems has not been thoroughly studied. Here we use video microscopy to directly visualize the reptation and transport of intrinsically fluorescent, semiflexible, semiconducting single-walled carbon nanotubes (SWCNTs) in the sub-micron pores of packed colloids as fixed obstacles of packed-colloid porous media. By visualizing the filament motion and Brownian diffusion at different locations in the pore structures, we study how the properties of the environment, like the pore shape and pore structure of the porous media, affect SWCNT mobility. These results show that the porous media structure controls SWCNT reorientation during Brownian diffusion. In packed-colloid pores, SWCNTs diffuse along straight pores and bend across pores; conversely, in gel pores, SWCNTs consistently diffuse into curved pores, displaying a faster parallel motion. In both gel and packed-colloid porous media, SWCNT finite stiffness enhances SWCNT rotational diffusion and prevents jamming, allowing for inter-pore diffusion.
研究纤维和半柔性细丝在多孔介质中的布朗运动是理解多种体系中输运和力学性质的关键。半柔性细丝在凝胶状多孔介质中的运动（包括聚合物网络和细胞细胞骨架）已经在理论和实验上进行了研究，而这些材料在填充胶体多孔介质、先进泡沫和类岩石系统中的运动尚未得到充分研究。在这里，我们使用视频显微镜直接可视化在填充胶体的亚微米孔中作为固定障碍物的本征荧光、半柔性、半导体单壁碳纳米管 (SWCNT) 的蠕动和输运。通过在孔结构的不同位置可视化细丝运动和布朗扩散，我们研究了环境特性（如多孔介质的孔形状和孔结构）如何影响 SWCNT 的迁移率。这些结果表明，多孔介质结构控制 SWCNT 在布朗扩散过程中的重定向。在填充胶体孔中，SWCNT 沿直孔扩散并在孔中弯曲；相反，在凝胶孔中，SWCNT 始终扩散到弯曲的孔中，表现出更快的平行运动。在凝胶和填充胶体多孔介质中，SWCNT 的有限刚度增强了 SWCNT 的旋转扩散并防止了堵塞，从而允许在孔之间扩散。
