Atomistic Simulations of Electrowetting in Carbon Nanotubes

Electrowetting of carbon nanotubes by mercury was studied using classical molecular dynamics simulations in conjunction with a macroscopic electrocapillarity model. A scaled ab initio mercury dimer potential, optimized to reproduce the mercury liquid density (at 300 K), melting point, and wetting angle on graphite, was selected for the simulations. Wetting of (20,20) single-walled carbon nanotubes by mercury occurs above a threshold voltage of 2.5 V applied across the interface. Both the electrocapillary pressure and imbibition velocity increase quadratically with voltage and can acquire large values, for example, 2.4 kbar and 28 m/s at 4 V, indicating a notable driving force. The observed voltage scaling can be captured by the Lucas−Washburn equation modified to include a wetting-line friction term.