  Electrostatic gating lies in the heart of modern FET-based integrated
circuits. Usually, the gate electrode has to be placed very close to the
conduction channel, typically a few nanometers, in order to achieve efficient
tunability. However, remote control of a FET device through a gate electrode
placed far away is always highly desired, because it not only reduces the
complexity of device fabrication, but also enables designing novel devices with
new functionalities. Here, a non-local gating effect in graphene using both
near-field optical nano-imaging and electrical transport measurement is
reported. With assistance of absorbed water molecules, the charge density of
graphene can be efficiently tuned by a local-gate placed over 30 {\mu}m away.
The observed non-local gating effect is initially driven by an in-plane
electric field established between graphene regions with different charge
densities due to the quantum capacitance near the Dirac point in graphene. The
nonlocality is further amplified and largely enhanced by absorbed water
molecules through screening the in-plane electric field and expending the
transition length. This research reveals novel non-local phenomenon of Dirac
electrons, and paves the way for designing electronic devices with
remote-control using 2D materials with small density of states.
