Bio-inspired sustained entrainment in immiscible liquid-liquid systems for collecting floating oil

Entrainment, where a solid object in a liquid bath moves towards the air phase, is common in industry and daily-life. However, most research on liquid entrainment has only focused on air-liquid interfaces, with little attention given to oil-water systems. Here, we look at a specific scenario where a solid object is immersed downwards from the upper oil phase to the lower water one. We demonstrate a biomimetic object, learned from bumble bees' tongues, with mesoscale structures that can keep the oil film and protect itself from the adhesion of water. By screening structure parameters, we find that the oil film can be sustained by both the propping effect of the structure and the flow and shape evolution. Heating the structure can recover the oil for effective recycling. This approach has the potential for oil spill cleanup by drilling oil spill film by using an unmanned aerial vehicle (UAV). Entrainment, where a solid object in a liquid bath moves towards the air phase, is common in industry and daily-life.