Molecular dynamic simulations on wetting transition of nanofluid on a single grooved structure

• Three types of intrinsic wettability for smooth surfaces and various groove sizes were simulated. • A revised formula was presented to calculate the wetting state on the nanoscale . • The density distribution of ethanol solution in nano-grooves was explored. • Influence of intrinsic wettability and size of structure on wetting states was investigated. Wettability played a crucial role in surface science, and one of the most widely used methods for adjusting wettability was constructing surface structures. The fifty percent mole fraction ethanol solution wetting on a single grooved structure was studied with molecular dynamic simulation. Three types of intrinsic wettability for smooth surfaces (hydrophilic, moderate, and hydrophobic) and various groove sizes of structures were simulated. A revised formula was presented to calculate the wetting state on the nanoscale, and the density distribution of ethanol solution in nano-grooves was explored. The influence of intrinsic wettability and the size of nano-structure on wetting states was investigated, and molecular concentration distribution and the free energy in wetting transition was analyzed quantitatively. Results showed the revised formula demonstrated the accuracy in differentiating the wetting state at the nanoscale. The density of ethanol solution in the nano-groove was proportional to the spacing (from 0.5 g/cm 3 to 0.627 g/cm 3 ) and inversely proportional to the height (from 0.645 g/cm 3 to 0.56 g/cm 3 ). It was related not only to the potential field of the nano-groove, but also to the mole fraction of ethanol molecules in the groove. The wetting transition from Cassie state to Wenzel state was triggered with the increase of the groove’s spacing and the decrease of the height. The corresponding free energy was changed from high level dropping to lower. This article was helpful to the standardization and normalization of wetting state at the nanoscale.