Modeling of self-driven directional movement of underwater oil droplets on bio-inspired nano-coated 3D-printed conical models

The contamination of water with oil from industrial processes has become a worldwide problem that requires the development of efficient, reliable and economical separation methods. Inspired by droplet movements on spider silk, we present in this contribution a model of the separation of oil and water that is based on the effect that liquid droplets move on cone-shaped structures, driven by capillary forces. We extend existing models to barrel-shaped oil droplets that move, completely surrounded by water, along suitably shaped filaments and derive the forces acting on the droplets from first principles of physics. By bringing together the results of the theoretical model and the corresponding experiments, the underlying mechanism of the directional movement of droplets in another liquid medium is thoroughly investigated and modeled. The resulting model predicts the dependence of the droplet motion on time and on system definingparameters, such as droplet size, viscosity, and dynamic contact angles formed between droplet and filament surface. We expect this work to pave the road for the design and preparation of bionic structures in the field of droplet transport phenomena, which is of great interest in various applications.

Automated summary

In this contribution, we present a model of oil-water separation based on the movement of liquid droplets on cone-shaped structures inspired by spider silk. The forces acting on the droplets are derived from first principles of physics, and their directional movement in another liquid medium is thoroughly investigated and modeled. The resulting model predicts the droplet motion dependence on time and system defining parameters, which provides a possibility for the design and preparation of bionic structures in droplet transport phenomena.