scholarly journals Trapping a Hot Drop on a Superhydrophobic Surface with Rapid Condensation or Microtexture Melting

Micromachines ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 566 ◽  
Author(s):  
Samira Shiri ◽  
Armela Murrizi ◽  
James Bird
Keyword(s):  
Critical Temperature ◽  
Superhydrophobic Surface ◽  
Water Drop ◽  
Superhydrophobic Surfaces ◽  
Temperature Threshold ◽  
New Class ◽  
Condensation Growth ◽  
Thermal Fuse ◽  
Impact Experiments ◽  
Insight Into

A water drop can bounce upon impacting a superhydrophobic surface. However, on certain superhydrophobic surfaces, a water drop will stick rather than bounce if it is sufficiently hot. Here, we aim to better understand the mechanisms that can lead to this bouncing-sticking transition. Specifically, we model two potential mechanisms in which a superhydrophobic surface could trap a sufficiently hot drop within milliseconds: melting of microtextured wax and condensation of the vapor within the superhydrophobic texture. We then test these mechanisms through systematic drop impact experiments in which we independently vary the substrate and drop temperatures on a waxy superhydrophobic Nasturtium leaf. We find that, whenever the surface or the drop is above a microtexture-melting temperature, the drop sticks. Below this temperature, a critical temperature threshold for bouncing can be predicted and controlled by considering the relative timescales between condensation growth and drop residence time. We envision that these results can provide insight into the design of a new class of superhydrophobic surfaces to act as a rapid thermal fuse to prevent drops that exceed a critical temperature from bouncing onto a thermally sensitive target.

scholarly journals Research of freezing kinetics of water drop on superhydrophobic coating surfaces

Vestnik MGSU ◽  
2019 ◽  
pp. 435-441
Author(s):  
About the author: Valentina I. Loganina
Keyword(s):  
Temperature Distribution ◽  
Superhydrophobic Surface ◽  
Water Drop ◽  
Initial Period ◽  
Technical Problem ◽  
Superhydrophobic Surfaces ◽  
Silicone Resin ◽  
Thermal Imager ◽  
Upward Movement ◽  
Kinetics Of

Introduction. Anti-icing coatings are used to prevent icing of the building roofs and power transmission line poles. One of the characteristics of anti-icing properties of superhydrophobic surfaces is the delay in the crystallization of drops on such surfaces. A significant delay in the crystallization of water drops on superhydrophobic substrates is noted in the scientific and technical literature. However, it is recorded in a number of papers that the delay time of crystallization on hydrophilic substrates is longer than the corresponding values on superhydrophobic surfaces. In connection with the foregoing, the study of the freezing kinetics of a water drop on a superhydrophobic surface in order to assess its efficiency is a relevant scientific and technical problem. Materials and methods. To evaluate the kinetics of freezing a of water drop on a superhydrophobic surface, the following experiment is conducted. A drop of water is placed on the superhydrophobic surface of the mortar substrate, which is placed in a freezer at a temperature of –18 °C. Studies of the drop freezing dynamics on the surface are performed using a Testo 875-1 thermal imager. To create a superhydrophobic surface, an aerosil R 972 with density ρ = 2360 kg/m3, particle size of 16 nm and specific surface area Ssp = 12 000 m2/kg is used as a filler. A silicone resin SILRES® MSE 100 of 10 % concentration is used as a binder. The obtained solutions are deposited on the mortar substrates. The degree of hydrophobicity is assessed by the magnitude of the wetting angle (θ°). Results. Results of the studies of temperature distribution on the water drop surface indicate that the distribution is uneven. The process of drop freezing is multistage. In the initial period, there is a transfer of heat from the surface into the water drop. This stage is followed by the process of drop freezing which is manifested in the upward movement of the freezing front from the substrate. Conclusions. It is revealed that the temperature distribution on the surface of a water drop is uneven. When freezing, a water drop has a pointed top.

Two-Pronged Jet Formation Caused by Droplet Impact on Anisotropic Superhydrophobic Surfaces

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
J. T. Pearson ◽  
D. Bilodeau ◽  
D. Maynes
Keyword(s):  
Superhydrophobic Surface ◽  
Liquid Droplet ◽  
Droplet Impact ◽  
Surface Patterning ◽  
Superhydrophobic Surfaces ◽  
Ohnesorge Number ◽  
Jet Formation ◽  
Anisotropic Surface ◽  
Impact Experiments ◽  
Droplet Impacts

When a liquid droplet impacts a superhydrophobic surface with anisotropic surface patterning in the form of alternating ribs and cavities, the rebounding droplet may exhibit a unique two-pronged jet emission. Droplet impact experiments with 11 different fluids of viscosity that varied by more than three orders of magnitude were conducted, and this paper quantifies the Capillary number, Ca, and Ohnesorge number, Oh, ranges over which the two-pronged phenomenon occurs. For Oh > 0.0154, the behavior was never observed, while at lower values of Oh, the behavior occurs for an intermediate range of Ca that depends on Oh.

Dynamic Impact Behavior of Water Droplet on a Superhydrophobic Surface in the Presence of Stagnation Flow

2012 ◽  
Vol 232 ◽  
pp. 267-272 ◽  
Author(s):  
Morteza Mohammadi ◽  
Sara Moghtadernejad ◽  
Percival J. Graham ◽  
Ali Dolatabadi
Keyword(s):  
Water Droplet ◽  
Weber Number ◽  
Contact Time ◽  
Superhydrophobic Surface ◽  
Superhydrophobic Surfaces ◽  
Impact Behavior ◽  
Stagnation Flow ◽  
Dynamic Impact ◽  
Air Flow Velocity ◽  
Impact Experiments

The following study investigates splashing of impinging water droplets on superhydrophobic surfaces with and without the presence of a stagnation flow. Droplets were accelerated by either gravity or gravity and co-flow. By changing the height and the air flow velocity different combinations of stagnation flow and droplet velocity were created. The spreading diameter, spreading velocity and contact time were studied for different air and droplet speeds. It was clearly observed that for a fixed impact velocity (i.e. constant Weber number), the presence of the stagnation flow promotes splashing and formation of satellite droplets. Consequently, for the co-flow droplet impact experiments, the mass of the recoiled droplet is significantly smaller than that of the impinging droplet in still air.

Two-Pronged Jet Formation Caused by Droplet Impact on Anisotropic Superhydrophobic Surfaces

2013 ◽  
Author(s):  
John T. Pearson ◽  
Daniel Maynes ◽  
David Bilodeau ◽  
Brent W. Webb
Keyword(s):  
Superhydrophobic Surface ◽  
Liquid Droplet ◽  
Droplet Impact ◽  
Surface Patterning ◽  
Superhydrophobic Surfaces ◽  
Ohnesorge Number ◽  
Jet Formation ◽  
Anisotropic Surface ◽  
Impact Experiments ◽  
Droplet Impacts

When a liquid droplet impacts a superhydrophobic surface with anisotropic surface patterning in the form of alternating ribs and cavities, the rebounding droplet may exhibit a unique two-pronged jet emission. Droplet impact experiments with eleven different fluids of viscosity that varied by more than three orders of magnitude were conducted, and this paper quantifies the Capillary number, Ca, and Ohnesorge number, Oh, ranges over which the two-pronged phenomenon occurs. For Oh > 0.0154, the behavior was never observed, while at lower values of Oh, the behavior occurs for an intermediate range of Ca that depends on Oh.

Fabrication of Superhydrophobic Surface by Modulating Morphology of the Organogel

Soft Matter ◽  
2021 ◽  
Author(s):  
Jianchen Zhu ◽  
Tian ren Zhang ◽  
Yajie Liu ◽  
Daoyi Lu ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Superhydrophobic Surface ◽  
Superhydrophobic Surfaces ◽  
Low Molecular Weight

A kind of low-molecular weight organic gelator (LMOG) bearing hydrazine linkage and end-capped by alkoxy-substituted phenyl, namely 1, 4-bis[(3, 4-bisoctyloxyphenyl)hydrozide]phenylene (BPH-8), was used to facilely fabricate superhydrophobic surfaces by drop-casting...

Stretchable dual cross-linked silicon elastomer with superhydrophobic surface and fast triple self-healing ability at room temperature

Soft Matter ◽  
2021 ◽  
Author(s):  
Yuxing Shan ◽  
shuai liang ◽  
Xiangkai Mao ◽  
Jie Lu ◽  
Lili Liu ◽  
...  
Keyword(s):  
Superhydrophobic Surface ◽  
Room Temperature ◽  
Superhydrophobic Surfaces ◽  
Self Healing ◽  
Wearable Electronics ◽  
Actual Application ◽  
Potential Applications

Abstract. Stretchable elastomers with superhydrophobic surfaces have potential applications in wearable electronics. However, various types of damage inevitably occur on these elastomers in actual application, resulting in deterioration of the...

A critical temperature threshold for coal hydropyrolysis

1987 ◽  
Vol 15 ◽  
pp. 91-100 ◽  
Author(s):  
Martin L. Gorbaty ◽  
Peter S. Maa
Keyword(s):  
Critical Temperature ◽  
Temperature Threshold

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.

scholarly journals Assembly Mechanism and the Morphological Analysis of the Robust Superhydrophobic Surface

Coatings ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 472 ◽  
Author(s):  
Doeun Kim ◽  
Arun Sasidharanpillai ◽  
Ki Hoon Yun ◽  
Younki Lee ◽  
Dong-Jin Yun ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Superhydrophobic Surface ◽  
Spray Coating ◽  
Silica Nanoparticle ◽  
Contact Angle Measurement ◽  
Angle Measurement ◽  
Thin Layers ◽  
Superhydrophobic Surfaces ◽  
Assembly Mechanism ◽  
Developed Surface

Robust superhydrophobic surfaces are fabricated on different substrates by a scalable spray coating process. The developed superhydrophobic surface consists of thin layers of surface functionalized silica nanoparticle (SiO2) bound to the substrate by acrylate-polyurethane (PU) binder. The influence of the SiO2/PU ratio on the superhydrophobicity, and the robustness of the developed surface, is systematically analyzed. The optimized SiO2/PU ratio for prepared superhydrophobic surfaces is obtained between 0.9 and 1.2. The mechanism which yields superhydrophobicity to the surface is deduced for the first time with the help of scanning electron microscopy and profilometer. The effect of mechanical abrasion on the surface roughness and superhydrophobicity are analyzed by using profilometer and contact angle measurement, respectively. Finally, it is concluded that the binder plays a key role in controlling the surface roughness and superhydrophobicity through the capillary mechanism. Additionally, the reason for the reduction in performance is also discussed with respect to the morphology variation.

scholarly journals Preparation of superhydrophobic surfaces with micro/nano alumina molds

RSC Advances ◽  
2018 ◽  
Vol 8 (64) ◽  
pp. 36697-36704 ◽  
Author(s):  
Takashi Yanagishita ◽  
Kaito Murakoshi ◽  
Toshiaki Kondo ◽  
Hideki Masuda
Keyword(s):  
Superhydrophobic Surface ◽  
Porous Alumina ◽  
Hierarchical Structures ◽  
Superhydrophobic Surfaces ◽  
Anodic Porous Alumina ◽  
Nano Alumina

Superhydrophobic surface with hierarchical structures prepared by nanoimprinting using anodic porous alumina molds.

Sign in / Sign up

Export Citation Format

Share Document