Exploring water transport in fractured nanotubes

Single-walled carbon nanotubes (SWCNTs) are atomically smooth, enabling them to transport water very efficiently at the nanoscale. This, plus advantageous electronic properties, makes SWCNTs suitable for next-generation nanofluidic devices in seawater desalination, energy storage, drug delivery, and osmotic energy conversion.

However, stresses and environmental changes can form sub-nanometer fractures in SWCNTs that decrease water transport efficiency, limiting their application. Wang et al. used molecular dynamics simulations to systematically explore how structural defects and external stimuli affect nanoscale water transport in SWCNTs.

While previous work has studied fractures, external electric fields, and nanotube geometry separately, the authors considered the interplay of these factors. They found that fractured nanotubes can remain functional: In shorter nanotubes, 1.34 nanometers long, the water flux was stable despite fractures up to 3 angstroms. Longer nanotubes, between 3 and 5 nanometers, maintained stable flux with fractures up to 8 angstroms — about three times the diameter of a water molecule.

“Our results suggest that this physical threshold in the longer nanotubes is likely tied to the correlation length of the hydrogen bond network 1D water chains,” said author Rong-Yao Yang. “This implies that the structural stability of confined water is not infinitely compensable by nanotube length, a nuance that is crucial for understanding the fundamental limits of nanoscale fluid transport.”

In addition, the simulations showed that an electric field at a frequency of 14 terahertz — selected for its optimal coupling with water molecule vibrations — substantially increases water flux, but also disrupts the hydrogen bond network, making the flux more sensitive to fractures.

These findings could guide the design of robust, high-performance nanofluidic systems. Next, the authors plan to investigate how modifying the nanotube surface at fracture sites affects water transport.

Source: “Modulating water transport in fractured carbon nanotubes: The role of terahertz electric fields and nanotube geometry,” by Shu-Peng Wang, Qi-Lin Zhang, Zhen-Yan Lu, Zhi-Jun Ma, and Rong-Yao Yang, Journal of Applied Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0312964 .