A Review of Recent Advances in Superhydrophobic Surfaces and Their Applications in Drag Reduction and Heat Transfer

Abstract

Inspired by the superhydrophobic properties of some plants and animals with special structures, such as self-cleaning, water repellent, and drag reduction, the research on the basic theory and practical applications of superhydrophobic surfaces is increasing. In this paper, the characteristics of superhydrophobic surfaces and the preparation methods of superhydrophobic surfaces are briefly reviewed. The mechanisms of drag reduction on superhydrophobic surfaces and the effects of parameters such as flow rate, fluid viscosity, wettability, and surface morphology on drag reduction are discussed, as well as the applications of superhydrophobic surfaces in boiling heat transfer and condensation heat transfer. Finally, the limitations of adapting superhydrophobic surfaces to industrial applications are discussed. The possibility of applying superhydrophobic surfaces to highly viscous fluids for heat transfer to reduce flow resistance and improve heat transfer efficiency is introduced as a topic for further research in the future.

Bionic research on Paramisgurnus dabryanus scales for drag reduction

“…Turbulent kinetic energy can reect the intensity of energy exchange and transformation and is an index to measure the development or decline of turbulence. It can be obtained by eqn (7):…”

“…The current methods of fluid drag reduction mainly include microbubble, 5 polymer additive, 6 superhydrophobic 7 and bionic structure 8 methods. Injecting airflow into the ship surface to form a layer of bubbles can reduce the frictional resistance.…”

PDMS/PVDF Electrospinning Membranes for Water-in-Oil Emulsion Separation and UV Protection

“…Among them, materials with both hydrophobicity and lipophilicity can selectively absorb the oil phase in the oil–water mixture, while materials with hydrophilic and oleophobic properties can separate water from oil [ 14 , 15 , 16 ]. Compared with hydrophilic materials, the theory and preparation basis of hydrophobic materials are more complete [ 17 ]. The microstructure is one of the critical factors affecting hydrophobicity, and constructing a reasonable microstructure is the key to the preparation of hydrophobic materials [ 18 ].…”

Hole-Transporting Self-Assembled Monolayer Enables Efficient Single-Crystal Perovskite Solar Cells with Enhanced Stability

“…A contact angle of ∼50°was observed for PTAA, while MeO-2PACz demonstrated a contact angle of ∼7.2°, indicating superhydrophilic behavior, as surfaces with contact angles below 10°are identified as superhydrophilic surfaces. 48 Previous studies have recommended crystal growth on a hydrophobic layer such as PTAA, 23 which promotes the growth of larger crystals from fewer seeds to yield crystals suitable for solar cell fabrication. However, we discovered that we were able to grow large crystals when the substrates were coated with the hydrophilic self-assembled monolayer MeO-2PACz.…”

“…Figure a,b shows the difference in hydrophobicity between these two HTLs coated on ITO glass, based on the contact angle of our perovskite precursor in γ-butyrolactone (GBL). A contact angle of ∼50° was observed for PTAA, while MeO-2PACz demonstrated a contact angle of ∼7.2°, indicating superhydrophilic behavior, as surfaces with contact angles below 10° are identified as superhydrophilic surfaces …”