Water jumps over a nanogap between two disjoint carbon nanotubes assisted by terahertz electric field

Abstract

Controlling the water permeation through carbon nanotubes (CNTs) with more complex structures holds great promise for many practical applications, such as nanometer water gates, energy collection, and biosensors. In this work, upon using extensive molecular dynamics simulations, we find a fascinating phenomenon that terahertz electric fields can more significantly stimulate the transport of a single-file water chain across two disjoint CNTs with a nanogap, where the water flow is several times to an order greater than that of static electric fields. This is because the static electric field promotes the formation of a water bridge in the nanogap region, which connects the two single-file water chains. Thus, the water molecules have to move collectively through the two CNTs, resulting in a relatively low water flow. However, under the terahertz electric field, the single-file water chain can be interrupted because of the resonant effect, and the water phase becomes vapor-like. In this case, some water molecules are partially or not hydrogen bonded and will have more freedom to move quickly through the disjoint CNTs. Consequently, the terahertz electric field is a more efficient external stimulus to promote the water permeation across the nanogap between two disjoint CNTs, which should have great implications for the design of controllable nanofluidic devices.