Contact Angle Hysteresis on Superhydrophobic Surfaces: An Ionic Liquid Probe Fluid Offers Mechanistic Insight

Langmuir ◽  
2011 ◽  
Vol 27 (6) ◽  
pp. 2166-2169 ◽  
Author(s):  
Joseph W. Krumpfer ◽  
Pei Bian ◽  
Peiwen Zheng ◽  
Lichao Gao ◽  
Thomas J. McCarthy
Keyword(s):  
Contact Angle ◽  
Ionic Liquid ◽  
Contact Angle Hysteresis ◽  
Superhydrophobic Surfaces ◽  
Mechanistic Insight

Relationship between Work of Adhesion and Contact Angle Hysteresis on Superhydrophobic Surfaces

2008 ◽  
Vol 112 (30) ◽  
pp. 11403-11407 ◽  
Author(s):  
Yonghao Xiu ◽  
Lingbo Zhu ◽  
Dennis W. Hess ◽  
C. P. Wong
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Superhydrophobic Surfaces ◽  
Work Of Adhesion

scholarly journals A Simple Method to Create Superhydrophobic Aluminium Surfaces

2012 ◽  
Vol 706-709 ◽  
pp. 2874-2879 ◽  
Author(s):  
R. Jafari ◽  
Masoud Farzaneh
Keyword(s):  
Contact Angle ◽  
Stearic Acid ◽  
Synergistic Effects ◽  
Low Cost ◽  
Contact Angle Hysteresis ◽  
Spray Coating ◽  
Superhydrophobic Surfaces ◽  
Water Contact ◽  
Simple Method ◽  
Static Contact

Superhydrophobic surfaces were prepared using a very simple and low-cost method by spray coating. A high static water contact angle of about 154° was obtained by deposition of stearic acid on an aluminium alloy. However, this coating demonstrated a high contact angle hysteresis (~ 30º). On the other hand, superhydrophobic surfaces with a static contact angle of about 162º and 158º, and a low contact angle hysteresis of about 3º and 5º were respectively obtained by incorporating nanoparticles of SiO2and CaCO3in stearic acid. The excellent resulting hydrophobicity is attributed to the synergistic effects of micro/nanoroughness and low surface energy. A study of the wettability of these surfaces at temperatures ranging from 20 to-10 °C showed that the superhydrophobic surface becomes rather hydrophobic at supercooled temperatures.

Evaporative Particle Deposition on Superhydrophobic Surfaces

2013 ◽  
Author(s):  
Mercy Dicuangco ◽  
Susmita Dash ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Contact Angle ◽  
Particle Deposition ◽  
Contact Angle Hysteresis ◽  
Droplet Evaporation ◽  
Superhydrophobic Surfaces ◽  
Contact Radius ◽  
Droplet Shape ◽  
Substrate Heating ◽  
Solid Liquid ◽  
Constant Contact Angle

The ability to control the size, shape, and location of particulate deposits is important in patterning, nanowire growth, sorting biological samples, and many other industrial and scientific applications. It is therefore of interest to understand the fundamentals of particle deposition via droplet evaporation. In the present study, we experimentally probe the assembly of particles on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex particles. Superhydrophobic surfaces are known to result in a significant decrease in the solid-liquid contact area of a droplet placed on such a substrate, thereby increasing the droplet contact angle and reducing the contact angle hysteresis. We conduct experiments on superhydrophobic surfaces of different geometric parameters that are maintained at different surface temperatures. The transient droplet shape and wetting behavior during evaporation are analyzed as a function of substrate temperature as well as surface morphology. During the evaporation process, the droplet exhibits a constant contact radius mode, a constant contact angle mode, or a mixed mode in which the contact angle and contact radius change simultaneously. The evaporation time of a droplet can be significantly reduced with substrate heating as compared to room-temperature evaporation. To describe the spatial distribution of the particle residues left on the surfaces, qualitative and quantitative evaluations of the deposits are presented. The results show that droplet evaporation on superhydrophobic surfaces, driven by mass diffusion under isothermal conditions or by substrate heating, suppresses particle deposition at the contact line. This preempts the so-called coffee-ring and allows active control of the location of particle deposition.

Preparing superhydrophobic surfaces with very low contact angle hysteresis

2013 ◽  
Vol 29 (8) ◽  
pp. 633-636 ◽  
Author(s):  
Y F Huang ◽  
C Huang ◽  
Y L Zhong ◽  
S P Yi
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Superhydrophobic Surfaces

Effects of contact angle hysteresis on ice adhesion and growth on superhydrophobic surfaces under dynamic flow conditions

2012 ◽  
Vol 291 (2) ◽  
pp. 427-435 ◽  
Author(s):  
Mohammad Amin Sarshar ◽  
Christopher Swarctz ◽  
Scott Hunter ◽  
John Simpson ◽  
Chang-Hwan Choi
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Superhydrophobic Surfaces ◽  
Flow Conditions ◽  
Dynamic Flow ◽  
Ice Adhesion

High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects

2009 ◽  
Vol 95 (6) ◽  
pp. 064102 ◽  
Author(s):  
Feng-Ming Chang ◽  
Siang-Jie Hong ◽  
Yu-Jane Sheng ◽  
Heng-Kwong Tsao
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Superhydrophobic Surfaces ◽  
High Contact Angle

Dropwise Condensation on Superhydrophobic Microporous Wick Structures

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Sean H. Hoenig ◽  
Richard W. Bonner
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Contact Angle ◽  
Droplet Size ◽  
Copper Powder ◽  
Contact Angle Hysteresis ◽  
High Heat ◽  
Superhydrophobic Surfaces ◽  
High Heat Flux ◽  
Sintered Copper

Previous research in dropwise condensation (DWC) on rough microtextured superhydrophobic surfaces has demonstrated evidence of high heat transfer enhancement compared to smooth hydrophobic surfaces. In this study, we experimentally investigate the use of microporous sintered copper powder on copper substrates coated with a thiol-based self-assembled monolayer to attain enhanced DWC for steam in a custom condensation chamber. Although microtextured superhydrophobic surfaces have shown advantageous droplet growth dynamics, precise heat transfer measurements are underdeveloped at high heat flux. Sintered copper powder diameters from 4 μm to 119 μm were used to investigate particle size effects on heat transfer. As powder diameter decreased, competing physical factors led to improved thermal performance. At consistent operating conditions, we experimentally demonstrated a 23% improvement in the local condensation heat transfer coefficient for a superhydrophobic 4 μm diameter microporous copper powder surface compared to a smooth hydrophobic copper surface. For the smallest powders observed, this improvement is primarily attributed to the reduction in contact angle hysteresis as evidenced by the decrease in departing droplet size. Interestingly, the contact angle hysteresis of sessile water droplets measured in air is in contradiction with the departing droplet size observations made during condensation of saturated steam. It is evident that the specific design of textured superhydrophobic surfaces has profound implications for enhanced condensation in high heat flux applications.

Superhydrophobic Surfaces Properties for Anti-Icing

2011 ◽  
Author(s):  
Mohammad Amin Sarshar ◽  
Christopher Swarctz ◽  
Scott Hunter ◽  
John Simpson ◽  
Chang-Hwan Choi
Keyword(s):  
Contact Angle ◽  
Wind Tunnel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Superhydrophobic Surfaces ◽  
Ice Formation ◽  
Flow Conditions ◽  
Water Droplets ◽  
Dynamic Flow ◽  
Static Contact

In this paper, the iceophobic properties of superhydrophobic surfaces are compared to those of uncoated aluminum and steel plate surfaces as investigated under dynamic flow conditions by using a closed loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared at the Oak Ridge National Laboratory by coating aluminum and steel plates with nano-structured hydrophobic particles. The contact angle and contact angle hysteresis measured for these surfaces ranged from 165–170° and 1–8°, respectively. The superhydrophobic plates along with uncoated control ones were exposed to an air flow of 12 m/s and 20°F with micron-sized water droplets in the icing wind tunnel and the ice formation and accretion were probed by using high speed cameras for 90 seconds. Results show that the developed superhydrophobic coatings significantly delay the ice formation and accretion even with the impingement of accelerated super-cooled water droplets, but there is a time scale for this phenomenon which has a clear relation with contact angle hysteresis of the samples. Among the different superhydrophobic coating samples, the plate having the lowest contact angle hysteresis showed the most pronounced iceophobic effects, while the correlation between static contact angles and the iceophobic effects was not evident. The results suggest that the key parameter for designing iceophobic surfaces is to retain a low contact angle hysteresis, rather than to have only a low contact angle, which can result in more efficient anti-icing properties in dynamic flow conditions.

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