Hydrodynamic metamaterials: Principles, experiments, and applications

Hydrodynamic metamaterials, a nascent research field, possess immense potential for fluid flow manipulation. With engineered structure design, they offer unparalleled control over fluid behavior beyond the capabilities of conventional methods. In this review, we focus on hydrodynamic metamaterials and provide a comprehensive overview of the current state of this research field. We start by introducing basic theories and principles of hydrodynamic metamaterials and then illustrate the different functions of hydrodynamic metamaterials that have been realized in porous medium flow and Hele-Shaw flow. Moreover, we also demonstrate the multifunctional metamaterials that have been developed in hydrodynamics. Some research progresses are highlighted due to their promising applications, including drag reduction, microfluidic manipulation, and biological tissue coculture. The review concludes by identifying major challenges and proposing research directions for the future.