ORIGINAL PAPER Modeling water purification by an aquaporin-inspired graphene-based nano-channel A. Lohrasebi 1,2 & T. Koslowski 3 Received: 3 April 2019 /Accepted: 14 August 2019 /Published online: 28 August 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Understanding the mechanism of water and particle transport through thin-film membranes is essential to improve the water permeability and the salt rejection rate of the purification progress. In this research, mimicking from the structure and operation of the aquaporin channel, graphene-based nano-channels were designed to be used as a water filter. The effects of variation of the channel’ s main elements, such as the width of the bottleneck and charges attached to the channel on its efficiency, were investigated via molecular dynamics simulations. We observe that the water flow through the channel decreases by increasing the charge, while the ion rejection rate of the channel is enhanced. Moreover, we find that the geometry and shape of the bottleneck part of the channel can affect the channel water flow and its selectivity. Finally, the pressure and the flow velocity in the channel were considered by using finite element models, and the results indicate that they are high at the entrance of the channel. The outcomes of this study can be used to improve the molecular knowledge of water desalination, which might be helpful in designing more efficient membranes. Keywords Water desalination . Aquaporin . Graphene-based channel . Molecular dynamics simulation Introduction According to the lack of fresh water resources, there is a crucial need for improvement of low-cost technologies for water distillation enabling access to safe drinking water for people especially in the developing countries. As a practical approach, water-filtering processes can be used to overcome this challenge, and since most of the biolog- ical cells have the ability of water filtering, water desali- nation could be performed with the aid of nano-filters designed to mimic the biological filters of cells, such as aquaporins. Aquaporins are integral membrane proteins that form channels in the biological cell membrane , through which water can flow rapidly into and out the cell , without the passage of any ions [ 1, 2]. Hence, mimicking their structure and function could be very helpful in designing high-performance micro- or nano-fil- ters. So far, their structural dynamics and the mechanism of water molecule transport have been investigated in sev- eral studies [3–6]. It was reported that the hourglass shape of the aquaporin channels facilitates fast water transport through the cell membrane with no leakage of ions . Furthermore, it was found that the aquaporins act as a two-stage filter. The first stage of the filter is located in the central part of the channel (NPA); and the second one is placed on the external cellular face of the channel (ar/ R) [3, 7]. Moreover, the electric field created by the spe- cial arrangement of amino acids within the NPA region is supposed to be a main factor in proton rejection and water permittivity through aquaporin [3, 6, 7]. The structure of these kinds of channels is shown schematically in panels of Fig. 1. Inspired by the operation and function of the protein channels, such as aquaporins and ion channels, artificial nano-scale filters can be proposed to use in various Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00894-019-4160-y) contains supplementary material, which is available to authorized users. * A. Lohrasebi lohrasebi@nano.ipm.ac.ir 1 Department of Physics, University of Isfahan, Isfahan 8174673441, Iran 2 School of Nano-Science, Institute for Research in Fundamental Sciences (IPM), Tehran 193955531, Iran 3 Institute for Physical Chemistry, University of Freiburg, Albertstrasse 23a, D-79104 Freiburg, Germany Journal of Molecular Modeling (2019) 25: 280 https://doi.org/10.1007/s00894-019-4160-y