Ultrafast self-transportation and efficient separation of organic droplets on semi-conical asymmetric structure

Manipulating oil droplets in an aqueous solution is highly desirable for organic multiphase liquid separation. Despite substantial works in the realm of organic multiphase liquid manipulation and separation, the ultrafast transportation and efficient and precise separation of these liquids, especially those with varied surface tensions, encounters significant challenges due to little driving forces. To address this issue, a semi-conical structure with pine-needlelike features and incorporated wedge-shaped grooves is fabricated, which could support the ultrafast transport and separation of organic droplets. For pre-wetted superhydrophobic surfaces, organic liquids with lower surface tension can be transported at a speed of 305.6 mm/s. The Laplace pressure difference caused by the conical structure determines the direction of transport of organic liquids, and the capillary force caused by flat wedge-shaped grooves increases the transport speed of organic droplets on the surface. Based on the characteristics of “differential” transportation and directional transportation, the separation of mixed organic liquids is realized. This biomimetic design concept will pave a path for microfluidics, liquid manipulation, and the separation of various organic liquids.