Article
Chemistry, Multidisciplinary
Linsheng Zhang, Yasmin A. . Mehanna, Colin R. Crick, Robert J. Poole
Summary: This study systematically evaluated the slip length on an irregularly structured superhydrophobic surface and found that decreasing surface tension leads to a decrease in slip length while increasing viscosity results in an increase in slip length when the surface tension of the liquids is matched to isolate effects.
Article
Chemistry, Multidisciplinary
Hamed Esmaeilzadeh, Keqin Zheng, Carol Barry, Joey Mead, Majid Charmchi, Hongwei Sun
Summary: This study evaluated the performance of hydrophobic surfaces under external hydrostatic pressures using an acoustic wave device (QCM), finding that the wetting state of hydrophobic surfaces transitions at a critical hydrostatic pressure and the drag reduction induced by the surfaces decreases with increasing pressure.
Article
Mechanics
Liuzhen Ren, Haibao Hu, Luyao Bao, Mengzhuo Zhang, Jun Wen, Luo Xie
Summary: The gas-liquid interface (GLI) over superhydrophobic surfaces (SHSs), where the flow slips, is crucial for reducing frictional drag in underwater applications. A new hybrid slip boundary condition has been proposed to explain inconsistent slip conditions reported in the literature under different groove length scales and unify existing exclusive slip assumptions.
Article
Nanoscience & Nanotechnology
Bin Liu, Yongming Zhang
Summary: This study investigates the natural transition in flat-plate boundary layers on superhydrophobic surfaces, considering the influence of the leading edge region. A computational method is proposed to accurately obtain the flow field from the leading edge region to the downstream region, taking into account the influence of the leading edge region. The results show that the leading edge region decreases the thickness of the laminar boundary layers and increases the slip velocity on the wall. The influence of the leading edge region also delays the critical location of flow instability and narrows the unstable zone. Additionally, a method for predicting the spectrum of wall fluctuating pressure in the laminar flow region over underwater vehicles is presented.
Article
Automation & Control Systems
Daniel Gortat, Alejandro Ortega Ancel, Andre Farinha, Raphael Zufferey, Mirko Kovac
Summary: Aerial-aquatic robotic vehicles have great potential in disaster response and environmental monitoring, but they face challenges in power requirements for takeoff and transitioning between air and water. The use of superhydrophobic surfaces can address these challenges by reducing the wetted surface area. This article analyzes various superhydrophobic surfaces to assess their benefits in drag reduction for aerial-aquatic robotic vehicles.
ADVANCED INTELLIGENT SYSTEMS
(2023)
Article
Mechanics
Hyungyu Sung, Hongseok Choi, Chiwook Ha, Choongyeop Lee, Hyungmin Park
Summary: The combination of bubble injection and superhydrophobic surfaces provides a solution to the challenges of air flow and depletion on the surface. By introducing bubbles over superhydrophobic surfaces with longitudinal grooves, the plastron can be replenished with a small amount of air even after the surface is fully wetted. The effective plastron thickness is related to surface light intensity, which serves as a criterion for successful replenishment.
Article
Physics, Fluids & Plasmas
Noura Bettaieb, Marco Castagna, Pierre-Yves Passaggia, Azeddine Kourta, Nicolas Mazellier
Summary: In this study, a mechanism is proposed to explain the loss of performance of superhydrophobic (SH) surfaces in laminar flow regimes, considering the flow of air inside the plastron and the associated momentum loss induced by roughness elements with different geometric characteristics. Numerical simulations and experiments show that high roughness and low porosity lead to a loss of drag reduction.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Multidisciplinary Sciences
Christopher Vega-Sanchez, Sam Peppou-Chapman, Liwen Zhu, Chiara Neto
Summary: This study reveals that lubricant-infused surfaces can effectively reduce drag in microfluidic flow. The spontaneous nucleation of surface nanobubbles leads to a significant increase in interfacial slip, a mechanism that is likely to occur on most infused surfaces.
NATURE COMMUNICATIONS
(2022)
Article
Mechanics
Henry Rodriguez-Broadbent, Darren G. Crowdy
Summary: At high surface Peclet numbers, the presence of surfactants can lead to surface immobilization, but a different mechanism is proposed for longitudinal shear flow along a unidirectional trench at high Marangoni numbers, where the meniscus becomes a constant-shear-stress surface due to contamination by surfactant. Experimental observations support the presence of recirculating interfacial flows on the meniscus. By calculating slip lengths, it is shown that the effective immobilization of the surfaces with vortical flows on the meniscus highlights the caution needed when comparing theory and experiments based on effective slip properties alone.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Y. Xu, C. Ruan
Summary: This study numerically investigated the drag reduction effects of superhydrophobic surfaces with continuous V-shaped microstructures. The results showed that the width of the microstructures had a major influence on the drag reduction effects, while the height had minimal influence. Compared to V-shaped and rectangular microstructures, superhydrophobic surfaces with continuous V-shaped microstructures exhibited better drag reduction effects.
JOURNAL OF APPLIED FLUID MECHANICS
(2022)
Article
Engineering, Chemical
Taiba Kouser, Yongliang Xiong, Dan Yang
Summary: Drag reduction is crucial in fluid transportation and vehicle industries, with polymer additives and superhydrophobic surfaces playing key roles in reducing drag force. Decreasing resistance can enhance performance of immersed vehicles and save energy consumption.
CHEMBIOENG REVIEWS
(2021)
Article
Physics, Fluids & Plasmas
Xin Zhao, Andreas Best, Wendong Liu, Kaloian Koynov, Hans-Jurgen Butt, Clarissa Schonecker
Summary: The study investigated the wetting and flow characteristics of superhydrophobic surfaces with irregular nanostructures, specifically fluorinated silicon nanofilaments. It was found that velocity profiles near the surface are still nonlinear at distances below 1 μm. The presence of regions with homogeneous wetting and air inclusions with different slip lengths contribute to the understanding of drag reduction and surface optimization in applications.
PHYSICAL REVIEW FLUIDS
(2021)
Article
Chemistry, Physical
Chongyang Mai, Chengcheng Lv, Li Yang, Lielun Zhao, Yawen Guo, Yan Jiang, Hongwen Zhang
Summary: In this article, a raspberry-like particle-assisted breath figures method was introduced to fabricate superhydrophobic surfaces. SiO2 particles were generated on the surface of microspheres and then separated according to their structures. The superhydrophobic surface was prepared using the breath figures method. The adhesion of the surface could be transformed by changing the amount of microspheres added. The contact mode and the height to width ratio of the pores were also found to be key factors affecting the surface adhesion.
SURFACES AND INTERFACES
(2023)
Article
Chemistry, Physical
Eunsang Lee, Florian Mueller-Plathe
Summary: The Cassie-Baxter state of wetting can explain the behavior of water droplets on superhydrophobic rough surfaces, including the equilibrium contact angle and the slippery dynamics. This study provides a deeper understanding of the contact line dynamics on rough surfaces using the molecular kinetic theory. The findings demonstrate the importance of additional friction forces and shed light on the origin of contact angle hysteresis.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Multidisciplinary Sciences
Jubair A. A. Shamim, Yukinari Takahashi, Anjan Goswami, Nadeem Shaukat, Wei-Lun Hsu, Junho Choi, Hirofumi Daiguji
Summary: This study investigated the evaporation and wetting transition behavior of fakir droplets on different microstructured surfaces. The substrate used was diamond-like carbon, and the effect of varying the micro pillar dimensions was analyzed. The results showed that the interfacial properties of the surfaces influenced the evaporation behavior and wetting transition. An important finding was the demonstration of a slippery superhydrophobic surface that suppresses the transition to a wetted state for small droplets, without the need for large pillar height or multiscale roughness. The study also assessed the accuracy of theoretical models and developed a numerical model to compute droplet penetration within the micropillars.
SCIENTIFIC REPORTS
(2023)
