Controllable Water Adhesion and Anisotropic Sliding on Patterned Superhydrophobic Surface for Droplet Manipulation

Abstract

Superhydrophobic surfaces with hydrophilic patterns have wide applications in biomedical and chemical analysis domains. In this work, a rapid, simple, and top-down micromilling method was proposed for fabricating hydrophilic patterns such as micro dots, line, and circle grooves on superhydrophobic surfaces. This method could be extended to construct various linear patterns on diverse substrates on account of its mechanical material-removal mechanism. Hydrophilic micro dots, line, and circle grooves were milled on the superhydrophobic Al alloy surface. The milled micro dots demonstrate great adhesion toward water droplets without changing the contact angles, whereas the prewetted line grooves exhibit strong anisotropic water adhesion; that is, the resistance force that restricts the droplet from detaching in directions parallel and perpendicular to the grooves is significantly different due to the different stress state of the droplet on the grooves. The adhesion force perpendicular to the groove, together...