scholarly journals Adhesion Mechanism of Water Droplets on Hierarchically Rough Superhydrophobic Rose Petal Surface

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Hannu Teisala ◽  
Mikko Tuominen ◽  
Jurkka Kuusipalo
Keyword(s):  
Fine Structure ◽  
Water Droplet ◽  
Spherical Shape ◽  
High Water ◽  
Superhydrophobic Surfaces ◽  
Natural Phenomenon ◽  
Water Droplets ◽  
Adhesion Mechanism ◽  
Submicron Scale ◽  
Rose Petal

Extremely hydrophobic surfaces, on which water droplets sit in a spherical shape leaving air entrapped into the roughness of the solid, are often called superhydrophobic. Hierarchically rough superhydrophobic surfaces that possess submicron scale fine structures combined with micron scale structures are generally more hydrophobic, and water droplet adhesion to those surfaces is lower in comparison with surfaces possessing purely micrometric structures. In other words, usually a fine structure on a superhydrophobic surface reduces liquid-solid contact area and water droplet adhesion. Here we show that this does not apply to a high-adhesive superhydrophobic rose petal surface. Contrary to the present knowledge, the function of the fine structure on the petal surface is to build up the high adhesion to water droplets. Understanding of the specific adhesion mechanism on the rose petal gives insight into an interesting natural phenomenon of simultaneous superhydrophobicity and high water droplet adhesion, but, in addition, it contributes to more precise comprehension of wetting and adhesion mechanisms of superhydrophobic surfaces overall.

scholarly journals Water droplet friction and rolling dynamics on superhydrophobic surfaces

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Matilda Backholm ◽  
Daniel Molpeceres ◽  
Maja Vuckovac ◽  
Heikki Nurmi ◽  
Matti J. Hokkanen ◽  
...  
Keyword(s):  
Contact Angle ◽  
Friction Force ◽  
Water Droplet ◽  
Superhydrophobic Surfaces ◽  
Silicon Surfaces ◽  
Force Sensors ◽  
Water Droplets ◽  
Indirect Contact ◽  
Gold Standard Method ◽  
Superhydrophobic Coatings

Abstract Superhydrophobicity is a remarkable surface property found in nature and mimicked in many engineering applications, including anti-wetting, anti-fogging, and anti-fouling coatings. As synthetic superhydrophobic coatings approach the extreme non-wetting limit, quantification of their slipperiness becomes increasingly challenging: although contact angle goniometry remains widely used as the gold standard method, it has proven insufficient. Here, micropipette force sensors are used to directly measure the friction force of water droplets moving on super-slippery superhydrophobic surfaces that cannot be quantified with contact angle goniometry. Superhydrophobic etched silicon surfaces with tunable slipperiness are investigated as model samples. Micropipette force sensors render up to three orders of magnitude better force sensitivity than using the indirect contact angle goniometry approach. We directly measure a friction force as low as 7 ± 4 nN for a millimetric water droplet moving on the most slippery surface. Finally, we combine micropipette force sensors with particle image velocimetry and reveal purely rolling water droplets on superhydrophobic surfaces.

Initial-Position-Driven Opposite Directional Transport of Water Droplet on Wedge-Shaped Groove

Nanoscale ◽  
2021 ◽  
Author(s):  
Shaoqian Hao ◽  
Xie Zhang ◽  
Zheng Li ◽  
Jianlong Kou ◽  
Fengmin Wu
Keyword(s):  
Water Droplet ◽  
Initial Position ◽  
Water Droplets ◽  
Transport Direction ◽  
Directional Transport ◽  
Prevailing View ◽  
Functionalized Surface

Transport direction of water droplets on a functionalized surface is of great significance due to its wide applications in microfluidics technology. The prevailing view is that a water droplet on...

scholarly journals Influence of Substrate Material on Flow in Freezing Water Droplets—An Experimental Study

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1628
Author(s):  
Erik Fagerström ◽  
Anna-Lena Ljung ◽  
Linn Karlsson ◽  
Henrik Lycksam
Keyword(s):  
Turbine Blades ◽  
Maximum Velocity ◽  
Substrate Material ◽  
The Arctic ◽  
Natural Phenomenon ◽  
Contact Radius ◽  
Freezing Process ◽  
Water Droplets ◽  
Symmetry Line ◽  
Influence Of Substrate

Freezing water droplets are a natural phenomenon that occurs regularly in the Arctic climate. It affects areas such as aircrafts, wind turbine blades and roads, where it can be a safety issue. To further scrutinize the freezing process, the main objective of this paper is to experimentally examine the influence of substrate material on the internal flow of a water droplet. The secondary goal is to reduce uncertainties in the freezing process by decreasing the randomness of the droplet size and form by introducing a groove in the substrate material. Copper, aluminium and steel was chosen due to their differences in thermal conductivities. Measurements were performed with Particle Image Velociometry (PIV) to be able to analyse the velocity field inside the droplet during the freezing process. During the investigation for the secondary goal, it could be seen that by introducing a groove in the substrate material, the contact radius could be controlled with a standard deviation of 0.85%. For the main objective, the velocity profile was investigated during different stages of the freezing process. Five points along the symmetry line of the droplet were compared and copper, which also has the highest thermal conductivity, showed the highest internal velocity. The difference between aluminium and steel was in their turn more difficult to distinguish, since the maximum velocity switched between the two materials along the symmetry line.

scholarly journals One-step fabrication of soft calcium superhydrophobic surfaces by a simple electrodeposition process

RSC Advances ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 297-308
Author(s):  
Zhi Chen ◽  
Yongbo Hu ◽  
Xu He ◽  
Yihao Xu ◽  
Xuesong Liu ◽  
...  
Keyword(s):  
Formation Process ◽  
Superhydrophobic Surface ◽  
Surface Preparation ◽  
Superhydrophobic Surfaces ◽  
Water Droplets ◽  
Step Method ◽  
Electrodeposition Process ◽  
Pressing Force ◽  
One Step

We investigated a one-step method for calcium superhydrophobic surface preparation and researched the formation process of loose, flower-like microstructures. Also, we found that the pressing force strongly impacts the dynamics of water droplets.

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