Micro-Nano Hierarchical Dendritic Structures for DropletCurve Manipulation: Implications for Microfluidic Devices

Directional droplet manipulation has wide potential applications in many fields, such as microfluidic devices and liquid transportation. Herein, micro-nano hierarchical dendritic structures were fabricated for droplet curve manipulation, which may have implications for microfluidic devices. The formation of superhydrophobicity was promoted by micro-nano hierarchical dendritic structures and carbon pollutants adsorbed during heating. An S-shaped curve directly drawn on the superhydrophobic surface with the tip of a syringe was used to show the droplet transportation along a curved route. The obtained superhydrophobic area had a water contact angle (WCA) of approximately 165° and a water slide angle (WSA) of almost 0°. The S-shaped curve exhibited high hydrophobicity with a WCA parallel to the curve of approximately 145° and perpendicular to the curve of approximately 138°. The as-fabricated surface exhibited a good curve manipulation property by repelling continuous water droplets from the superhydrophobic area to the S-shaped hydrophobic curve with no residual droplet on the route. In addition, the relationship between the droplet volume and the critical tilting angle was studied, which may play a certain guiding role in droplet manipulation. This method is expected to pave the way for droplet manipulation in microfluidic devices.