Bio-inspired drag reduction: From nature organisms to artificial functional surfaces

Nature organisms, after billions of years of evolution, have evolved elegant morphologies, structures, patterns, or surface wettabilities with unique functionalities. Among all the intriguing characteristics observed in nature organisms, their drag reduction abilities with low energy consumption have always attracted wide attentions of human beings, because of its great potentiality in various fields, e.g., marine vehicles, aircraft, pipeline transportation, microfluidics, etc. Recently, in-depth studies have been carried out to uncover various biological structures with distinguished drag reduction performance including shark skins, penguin feathers, dolphin skins, lotus leaves, and Nepenthes pitcher. In this review, we will give a succinct account of their drag-reduction mechanisms as well as introduce the recent biomimetic processes to create artificial drag-reduction surfaces. Meanwhile, the remaining challenges and future prospective of bio-inspired drag reduction are also briefly proposed. We hope this review can help people to learn about the natural wisdoms to reduce fluid resistance and stimulate people to develop efficient drag reduction approaches, which are essential for submarine and cargo ship navigation, air vehicles, pipeline transportation, microfluidic system, and so forth.