A secondary composite bionic microstructure inspired by bottle grass to enhance the directional movement properties of droplets

Directional self-driven movement of liquid droplets has potential applications in microfluidic chips, self-cleaning surfaces, liquid delivery systems, biomedical engineering, and other fields. Inspired by the bottlebrush trichome structure, a novel bionic functional surface structure that can realize the directional movement of droplets without external energy is designed and prepared in this study. The structure consists of a primary hierarchical microgroove structure and a secondary capillary reinforcement structure. The primary hierarchical microgroove structure forms a liquid film in the low-rib region by capillary force, which guides the liquid in the high-rib region to slide rapidly, transforming the solid-liquid contact into a liquid-liquid contact, and significantly reduces the droplet movement resistance. The secondary capillary reinforced structure upgrades the single capillary drive to a double capillary drive through the design of the manifold ribs, which further reduces the resistance and increases the droplet movement speed. The structure compensates for the high viscous resistance of the microstructure due to fabrication, and improves and increases the droplet moving speed and distance, respectively, which provides a theoretical basis and technical support for microfluidic chips and other fields.