| Flow drag reduction is of great significance for energy conservation, emission reduction, and enhancing equipment performance. Inspired by the Nepenthes pitcher plant, the bio-inspired Liquid-Infused Surface (LIS) has emerged as a novel technology for reducing interfacial drag. It functions by immobilizing a lubricating liquid, which is immiscible with the working fluid, within a micro-structured substrate to create a stable liquid-liquid slippery interface. This approach effectively addresses the instability issue of the entrapped air layer on traditional superhydrophobic surfaces under high-pressure and shear conditions. This paper provides a systematic review of the research progress in LIS-based drag reduction technology. It begins by elucidating the core drag reduction mechanism based on the Navier slip theory. A key focus is placed on analyzing the influence of the viscosity ratio (M) between the lubricant and the working fluid, as well as the flow Reynolds number, on the slip characteristics and drag reduction efficacy. The review highlights that a viscosity ratio much less than one (M ? 1) is a fundamental prerequisite for achieving drag reduction, and it discusses the significant differences in the drag reduction behavior and stability of LIS between laminar and turbulent flow regimes. The fabrication methods for LIS, including photolithography, spray coating, and anodization, are summarized. The paper also outlines the exploratory applications of LIS in fields such as marine vessels, pipeline transport, microfluidics, and biomedical devices. Finally, the review concludes by summarizing the core challenges for practical engineering applications and prospecting future research directions, including the optimization of substrate structures, in-depth investigation of drag reduction mechanisms in turbulent flows, and the development of multifunctional integrated surfaces. |
