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Center for Nonlinear Studies |
Ion transport through porous systems permeates through many areas of science and technology, from cell behavior to sensing and separation to catalysis and batteries. Two-dimensional materials, such as graphene molybdenum disulfide, and hexagonal boron nitride, present new opportunities to develop filtration and sensing technologies, encompassing ion exclusion membranes, DNA sequencing, single molecule detection, and beyond. Moreover, the physics of ionic transport through pores and constrictions within these materials is a distinct realm of competing many-particle interactions (e.g., solvation/dehydration, electrostatic blockade, hydrogen bond dynamics) and confinement. We show how sub-nanoscale pores in graphene membranes display selectivity even when the graphene pores do not have charge or functional groups and how such selectivity can be tuned by adjusting the pore radius and number of graphene layers. This will enable the optimization of water flow and ion rejection for applications such as filtration and desalination. We also examine a scaling theory for the access/convergence/contact resistance that predicts a special simulation cell aspect ratio – the golden aspect ratio – where finite size effects are eliminated. We employ this approach to resolve the experimental and theoretical discrepancies in the radius dependence of graphene nanopore resistance. These results will enable the use of all-atom molecular dynamics simulations to study contextual properties of access resistance – its dependence on irregular pore geometries, protein and molecular-scale fluctuations, the presence of charges, and other functional groups.
Host: David Metiver