Biological channels display a wide and varied range of properties, including the degree of water permeation and the ability to filter unwanted species. We have used these channels as inspiration for developing our own synthetic channels for specific purposes: desalination and water purification. We have conducted long time scale molecular dynamics simulations on carbon nanotube based membranes (see Figure) to elucidate various properties of these hydrophobic pores. The dependence of pore width, length and functionalisation, as well as the effect of salt (NaCl) concentration and pressure, on water permeability and salt rejection has been determined. We find that:
An array of carbon nanotubes (red) forming a membrane that is highly permeable to water (blue surface), but not sodium (yellow) and chloride (green) ions.