Propelling liquids on superhydrophobic surfaces with superhydrophilic diverging grooves

The autonomous locomotion of liquids on free solid surfaces is becoming common in many industrial applications. To propel liquids uphill, superhydrophilic diverging grooves at varying angles of divergence 2, 4, 6, 8, and 10° were fabricated on superhydrophobic aluminum surfaces in this study. Experiments on propelling liquids were performed on specially designed surfaces subject to different angles of inclination, and the correlation between propelling capacity and the angles of divergence is examined. The results show that the propelling capacity can be enhanced by increasing the angle of divergence. To propel more liquids uphill, a superhydrophobic surface with a superhydrophilic diverging groove at an angle of divergence of 10° is recommended. To achieve a greater uphill height, designing a surface with an angle of divergence larger than 6° is sufficient. Superhydrophilic and superhydrophobic properties are discussed, and the mechanism of propelling is described. Furthermore, the key influence factors on the uphill height are theoretically revealed.