The fountain effect of ice-like water across nanotubes at room temperature.

The well-known fountain effect of superfluid helium can directly convert heat to mechanical work by the transport of the superfluid across narrow channels under a temperature difference. But it is regarded as a unique feature of superfluids, only occurring below the temperature of 2.17 K. Here we report a peculiar fountain effect of ice-like water across nanotubes at room temperature. Based on molecular simulations, we observed fascinating ultrafast fountain flow across nanotubes from the cold side to the hot side under a small temperature difference, due to the near-dissipationless nature of ice-like ordered water inside the nanotubes. Water molecules exhibit collective behavior and spontaneously convert thermal energy from the surrounding into directed motion without dissipation. A surprising pressure difference of up to 256 bar is generated from a temperature difference of 23 K, almost reaching the thermodynamic limit. This finding is anticipated to provide a new protocol for power harvesting devices, heat engines and nanomotors.