Although the traditional tapered structure can realize the directional movement of underwater oil droplets, the continuous adaptive self-transport of oil droplets in complex environments remains a challenge. Therefore, the subject aims to develop a new groove tapered structure surface to achieve efficient self-transport of oil droplets in various environments. Inspired by the anisotropic groove structure of rice leaves and the asymmetric tapered structure of cactus spines, we obtained the micro groove structure on the upper and reverse surfaces of polytetrafluoroethylene by 100 mW femtosecond laser processing. The groove tapered structure with different angels was gotten followed 220 mW. The wettability of the structure surface was characterized by the contact angle test platform and the surface micro groove morphology was analyzed by a scanning electron microscope. The self-transport capacity of oil droplets in various environments was analyzed and studied with a high-speed camera to record the transport process of oil droplets under water, air-water interface and in air. Firstly, the sample was placed vertically in water and dichloroethane was placed on the surface of the super-oleophobic aluminum sheet. By moving the base of the aluminum sheet, the oil droplets approached the top of the tapered structure and were then transported by the tapered structure from its top to bottom. The comparative experiment of underwater transport of groove and grooveless tapered structures was carried out. Then as the above method, 2 μL dichloroethane oil drops on samples with different tapered angles were transported, the relations between tapered angle and oil drops transport rate on the groove tapered structure were revealed. Furthermore, the transport capacity of the groove tapered structure under different oil drop volumes, different tilt angles and the maximum volume of its underwater oil drop transport were explored. Finally, the oil drop transport capacity of the structure was tested in the air and air-water interface. The research results showed that the spacing of micro grooves on the structure surface was about 13 μm, the water droplets on the surface of the structure showed super-hydrophobicity with a contact angle of 161.9° in air. Micro grooves played a decisive role in the oil droplet transport capacity of the tapered structure. The grooveless tapered structures cannot complete the transport, while the groove tapered structure completed the transport quickly. When the tapered angle is 16°, the transport rate of oil droplets reached the maximum speed up of 112.17 mm/s. In addition, the speed of 16° groove tapered structure transport 2 μL volume oil drop was relatively the fastest and its maximum volume of dichloroethane transport underwater was up to 16 μL. Moreover, with the increase of the tilt angle of the samples, the transport speed gradually decreased and tended to be stable. When the tilt angel increased to 90°, the transport could still be completed against gravity. The groove tapered structure could achieve the continuous self-transport of oil droplets in various environments such as under water, air and air-water interface, which demonstrated a more efficiency self-transport ability of oil droplets under water compared with the traditional tapered structure. Finally, an underwater self-driving oil collecting device is prepared by taking advantage of the groove tapered structure's good structural expansibility, the operation mode without energy consumption or external force driving and the excellent self-transport ability of oil droplets, showing the possible potential applications of this structure. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.
