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Published online: 7 May 2008 | doi:10.1038/nchina.2008.100

Carbon nanotubes: Tiny hydroelectric power converters

Ai Lin Chun

Introduction

Allowing water molecules to flow inside or outside of carbon nanotubes can form a unique nanofluidic system for various applications such as energy conversion. Previous theoretical and experimental studies have attempted to explain the transport behaviour of water through these channels, but the mechanisms are still far from clear. Sishen Xie at the Chinese Academy of Sciences, Lianfeng Sun at the National Center for Nanoscience and Technology, both in Beijing, and co-workers¹ have shown experimentally that dragging water molecules inside a carbon-nanotube channel using an external electric field can generate an electromotive force along the tube.

Xie and Sun suspended individual nanotubes about 100 nm above a silicon substrate surface and connected them to four electrodes. The carbon-nanotube ends were treated so that they were open and water molecules were free to flow through. When current was applied at one end of the nanotube and the device was exposed to water vapour, a voltage difference was observed. Control experiments showed that the voltage difference depends on the amount of water in the nanotube and that the polar nature of the water molecules is essential for their interaction with the tubes.

It was suggested that the water flow inside the carbon nanotube is driven by the applied current and causes one part of the device to act as a 'motor'. The electrical energy is then partially converted into kinetic energy of the flowing water molecules. This in turn generates an electromotive force along another part of the nanotube, which makes up the 'generator'.

Energy conversion in the generator and motor portions of the device may form unique tunable molecular channels for nanoscale energy-conversion applications in the future.

The authors of this work are from:
National Center for Nanoscience and Technology, Beijing, China; Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China; Graduate University of the Chinese Academy of Sciences, Beijing, China.

Reference

1. Zhao, Y. et al. Individual water-filled single-walled carbon nanotubes as hydroelectric power converters. Adv. Mater. doi: 10.1002/adma.200702956 (2008). | Article |