Modulating graphene's optical conductivity with an electrolyte nanopatterning technique reduces or eliminates scattering loss caused by rough edges from etching. This technique uses a resist mask patterned with features as small as 30 nm to shield graphene from ions in an electrolyte. It can provide a carrier density variation of about 1014 cm−2 across a length of just 15 nm. And it can be combined with a technique of growing or transferring graphene on atomically smooth hexagonal boron nitride (hBN) to increase graphene's carrier mobility, e.g., to 10,000 cm2/(V·s) or more. The resulting graphene metamaterials can be used to make voltage-tunable electro-optical devices, such as beam-steering devices, electro-optical switch and modulators, and reconfigurable holograms.