Tuning SWCNT Length to Optimize the Rate-Efficiency-Stability Triad in Nanofluidic Water Channels.

This work shows that the length of single-walled carbon nanotubes is critical in governing the trade-off among the rate, efficiency, and stability of pressure-driven water transport. A critical length of 1.06 nm marks the transition in the transport mechanism from a thermal-fluctuation-dominated regime to an ordered water-chain mode. This transition is driven by the evolution of the potential of mean force with tube length, which progresses from a flat landscape to a high-barrier profile and ultimately forms a low-resistance tunnel in long nanotubes. Notably, this tunnel endows the water chain with an enhanced ability to restore its continuity, allowing it to bridge fracture gaps as wide as 7 Å even in the absence of an external pressure difference. These insights reveal a length-dependent mechanism that could revolutionize CNT-hydrogel hybrids for biomedical applications.