Journal Article atomically thin membranes selective transport sub-nanometer pores CVD graphene Research Support, U.S. Gov't, Non-P.H.S. asymmetric structure dialysis and desalting finite element analysis graphene graphene nanopores graphene wafer ion rectification microsystems modification nanoelectromechanical systems nanomechanical switches nanoporous graphene membranes selectivity single crystalline graphene single‐crystal Cu(111)