Fabrication of a lotus leaf-like hierarchical structure to induce an air lubricant for drag reduction

In this study, a lotus leaf-like hierarchical structure featuring microscale and nanoscale dimensions was fabricated through chemical deposition. Wetting and tribological experiments showed that the micro-nano hierarchical structure displays superhydrophobic and drag-reducing attributes. Simulation revealed that the structure with a micro-nano feature surface allows ultra-low friction drag reduction when fluid flows through microchannels by trapping air inside surface cavities. Experimental results proved the feasibility of the model in predicting the friction drag reduction performance of the structure. The model was thus used to investigate the effect of the distribution density of micropapillae on friction coefficient. Optimization results indicated that an interval ratio of 0.75 can improve the air fraction of the liquid/solid interface and thus reduce friction drag. Novelty statement In this work, a novel hierarchical structure has been successfully fabricated to improve the lubrication properties by its superhydrophobicity. The fabricated surfaces are used to test the effects of hierarchical structure on the values of friction coefficient. Results of wettability and lubrication experiments facilitate understand of reducing frication drag. The volume of fluid simulation method is used to explain the friction drag of the surface is reduced by air lubrication, and help optimization design the distribution density of micro roughness. The results are important because that it can provide feasible approach to have a broad prospect for micro/nano hierarchical structure surfaces for many technological applications.