Ultrafast, Reversible Transition of Superwettability of Graphene Network and Controllable Underwater Oil Adhesion for Oil Microdroplet Transportation

Abstract Recently, reversible surface superwettability has attracted enormous interest, and methods to shorten the cycle time of transition have also garnered the attention of researchers. Herein, a superhydrophobic, open‐cell graphene network (OCGN) is fabricated via self‐assembly of graphene oxide and vapor ejection. Owing to the special open‐cell microstructure, the OCGNs can be transformed to be superhydrophilic rapidly within only 1 s by air plasma treatment. Moreover, the OCGNs with pure graphene composition have a high conductivity and show an ultrafast Joule heating rate of up to 20 °C s⁻¹ at a voltage of 20 V. By means of this property, for the first time an ultrafast recovery of the superhydrophobicity for OCGNs by self‐induced Joule heating with the shortest time of 1 min is reported. The mechanism of ultrafast, reversible transition is also explored specifically in this study. In addition, the superhydrophilic OCGNs show superoleophobicity in water and their underwater adhesion for oil droplets can be controlled by plasma treatment. Finally, the OCGNs with different oil adhesion properties are fabricated and the underwater oil microdroplet transportation is realized using OCGNs. Therefore, the OCGNs with smart surface can be an excellent candidate for achieving multifunctional superwettability of surfaces.