Flexible surfaces prepared through direct ink writing with drag reduction and antifouling

The riblet structure on the surface of the shark skin provides significant drag reduction and fouling protection. Inspired by the structure of the shark skin, we present a direct ink writing protocol by modifying the rheological properties of polydimethylsiloxane to make it printable, and a series of flexible surfaces have been created with drag reduction and antifouling. The shear stress transport k-omega model was used as a suitable turbulence model for the numerical study to compare with results of drag reduction tests. Simulations and tests proved that printed non-smooth surfaces effectively reduced water drag, where the maximum drag reduction rate reached 18.16 % at 0.06 m/s. Through the analysis of the characteristics of the flow field near the wall, the drag reduction mechanism of the riblet surface was examined. Moreover, the antifouling tests revealed that the printed surface exhibited excellent fouling resistance and inhibited the spread of dirt on the surface. Our findings may provide a new surface skinning strategy for ships, underwater vehicles and wearable devices to reduce drag and contaminant adhesion and improve navigation efficiency and longevity.