Super-hydrophilic track for rapid directional transport of water droplets on the superhydrophobic surface

Directional transport of water droplet on curved track attracts considerable research interest in microfluidics. In this work, we first study the directional transport of water droplet on super-hydrophilic curved track. The water droplet can quickly move along the whole super-hydrophilic track without deviation. The speed of the water droplet on the super-hydrophilic track is 0.075 m/s. In theory, the van der Waals’ force existing in the super-hydrophilic track keeps the water droplet from deviating during rapid movement. In addition, we further study the influence of track geometry and water droplet size on the transport capacity of the super-hydrophilic track. Compared with track depth, the track width has a great effect. The water droplet deviates from the track with a width of 50 μm. But the water droplet can directionally move along the super-hydrophilic track with a width of 100 μm and 150 μm without deviation. In addition, for the same super-hydrophilic track, the larger the water droplet volume, the easier it is to deviate from the track. Finally, to demonstrate the application of super-hydrophilic track on superhydrophobic surface, we performed the rapid mixing and directional collection of water droplets. This strategy is of great significance for extending it to applications such as microchannels in microfluidics, water collection systems, and others.