1. T. Qiu and J. P. Huang Department of Physics, Fudan University, Shanghai 200433, China Water Nanowheel: Unprecedentedly Fast Transport of Rolling Water Molecules ♠ ABSTRACT ——————————————————— How to achieve a fast flow of water molecules across nanochannels is always a challenge in the fields ranging from water purification or seawater desalination to the understanding of water transport through nanochannels within biological membranes. By developing a Debye double-relaxation theory for water molecules, we propose, for the first time, that the translational THz electric field can pump water molecules across nanochannels at high speeds. The results predicted by our full-atom molecular dynamics simulations agree very well with the theoretical results, and show an unprecedented high speed of 1080 m/s. Meanwhile, the water molecules undergo a wheel-like motion, a combination of both linear transport and regular rotation, which originates from the relaxation dynamics of hydrogen and oxygen atoms in the presence of translational THz fields. This work has a great potential in water purification technology and paves a new way for designing smaller nano-cars. ♦ CONCLUSION —————————————————— By developing the theoretical model and performing independent molecular dynamics simulations, we have revealed an unprecedentedly fast unidirectional flow of single-file water molecules within a nano-channel in the model system that was designed by taking into account both biological implication (the function of charge groups in biological membrane proteins is vital to water permeation through aquaporins) and physical implication (environmental oscillations arising from thermal motion always exist when water molecules transport through nanochannels). Interestingly, we have found that the water molecules undergo a wheel-like motion, namely, a combination of both translational and rotational motions, thus called water nano-wheels. The underlying mechanism originates from the resonant relaxation dynamics of hydrogen and oxygen atoms.  Reference ——————————————————————————————— T, Qiu, X. W. Meng, J. P. Huang. Nonstraight Nanochannels Transfer Water Faster Than Straight Nanochannels. Journal of Physical Chemistry B, 2015, 119(4): 1496-1502. ♥ RESULTS AND DISCUSSION _____________________________ ♣ MODEL _________________________________ The nanochannel, a z−directed (10, 0) single-walled carbon nanotube, is 0.386 nm in radius and 9.590 nm in length; we keep all the carbon atoms immobilized. The fixed ions as the nanoelectrodes line up on both sides of the nanochannel, and their charges vary according to a periodic arrangement with four-time intervals (t1 → t2 → t3 → t4 →...). We perform the simulations in the canonical ensemble at 300K (room temperature) with time step 2 femtosecond. In the simulations, wheel-like motion of the water molecules were observed at frequency from 0.625 THz to 25 THz, other than the random flip-flop reorientation which usually happens to the water molecules in the carbon nanotubes. Meanwhile, the rolling water molecules often rotates in synchrony with the applied field.