Superhydrophobic Surfaces analyzes the fundamental concepts of superhydrophobicity and gives insight into the design of superhydrophobic surfaces. The book serves as a reference for the manufacturing of materials with superior water-repellency, self-cleaning, anti-icing and corrosion resistance. It thoroughly discusses many types of hydrophobic surfaces such as natural superhydrophobic surfaces, superhydrophobic polymers, metallic superhydrophobic surfaces, biological interfaces, and advanced/hybrid superhydrophobic surfaces. - Provides an adequate blend of complex engineering concepts with in-depth explanations of biological principles guiding the advancement of these technologies - Describes complex ideas in simple scientific language, avoiding overcomplicated equations and discipline-specific jargon - Includes practical information for manufacturing superhydrophobic surfaces - Written by experts with complementary skills and diverse scientific backgrounds in engineering, microbiology and surface sciences

This book introduces the fabrication of superhydrophobic surfaces and some unique droplet behaviors during condensation and melting phase change on superhydrophobic surfaces, and discusses the relationship between droplet behavior and surface wettability. The contents in this book, which are all research hotspots currently, shall not only bring new insights into the physics of condensation and icing/frosting phenomena, but also provide theoretical support to solve the heat transfer deterioration, the ice/frost accretion and other related engineering problems. This book is for the majority of graduate students and researchers in related scientific areas.

In-flight icing is a serious meteorological hazard caused by supercooled cloud particles (with an average size of 20-50 æm) that turn into ice as an immediate consequence of impact with an aircraft, and it poses a serious risk to the safety of the aircraft and its passengers. Anti-icing surface treatment is a potential solution to mitigate ice accretion and maintain optimal flying conditions. Superhydrophobic coatings inspired by nature (e.g., lotus leaf) have attracted much attention in recent years due to their excellent water repellent properties. These coatings have been extensively applied on various substrates for self-cleaning, anti-fogging, and anti-corrosive applications. The performance of these coatings depends on the chemical composition and their rough hierarchical surface morphology composed of micron and sub-micron-sized structures. Recently, there has been an increased interest to fabricate superhydrophobic coatings that can repel droplets of cloud-relevant sizes (20-50 æm) before they freeze to the surface in practical flight conditions (i.e., icephobic surfaces). The main goal of this work was to numerically model the hydrodynamic and thermal behaviour of cloud-sized droplets on superhydrophobic surfaces when interacting with micron-sized surface features. Consequently, by correlating the hydrophobicity and the icephobicity of the surface, we found viable solutions to counteract icing and to prevent ice accumulation on critical aerodynamic surfaces. For this purpose, we developed a computational model to analyze the hydrodynamics of the impact of the micro-droplet on a micro-structured superhydrophobic surface under room temperature and freezing (including rapid-cooling and supercooling) conditions. All coding and implementations were carried out in the OpenFOAM platform, which is a collection of open-source C++ libraries for computational continuum mechanics and CFD analysis. Superhydrophobic surfaces were directly modelled as a series of fine, micro-structured arrays with defined cross sections and patterns. Surface chemistry was included in the simulations using a dynamic contact angle model that describes well the hydrodynamics of a micro-droplet on rough surfaces. A multi-region transient solver for incompressible, laminar, multi-phase flow of non-isothermal, non-Newtonian fluids with conjugate heat transfer boundary conditions between solid and fluid regions was developed to simulate both the dynamics of the micro-droplet impact on the substrate and the associated heat transfer inside the droplet and the solid bulk simultaneously. In addition, a phase change (freezing) model was added to capture the onset of ice formation and freezing front of the liquid micro-droplet. The computational model was validated using experimental data reported in the literature. In addition, an analytical model was derived using the balance of energy before impact and at the maximum spreading stage, which we found to be in good agreement with the data obtained from simulations. Since aluminum (Al) is the base material used in aerospace industries, the thermo-physical properties of aluminum were extensively used in our simulations. Comparing laser-patterned aluminum substrates with a ceramic base composite material that has a low thermal diffusivity (such as titanium-dioxide), we showed that the onset of icing was significantly delayed on the ceramic-based substrate, as the droplet detached before freezing to the surface. Finally, a freezing model for the supercooled water droplet based on classical nucleation theory was developed. The model is an approximation for a supercooled droplet of the recalescence step, which was assumed to be initiated by heterogeneous nucleation from the substrate. This research extended our knowledge about the hydrodynamic and freezing mechanisms of a micro-droplet on superhydrophobic surfaces. The developed solvers can serve as a design tool to engineer the roughness and thermo-physical properties of superhydrophobic coatings to prevent the freezing of cloud-sized droplets in practical flight conditions.

This unique book presents ways to mitigate the disastrous effects of snow/ice accumulation and discusses the mechanisms of new coatings deicing technologies. The strategies currently used to combat ice accumulation problems involve chemical, mechanical or electrical approaches. These are expensive and labor intensive, and the use of chemicals raises serious environmental concerns. The availability of truly icephobic surfaces or coatings will be a big boon in preventing the devastating effects of ice accumulation. Currently, there is tremendous interest in harnessing nanotechnology in rendering surfaces icephobic or in devising icephobic surface materials and coatings, and all signals indicate that such interest will continue unabated in the future. As the key issue regarding icephobic materials or coatings is their durability, much effort is being spent in developing surface materials or coatings which can be effective over a long period. With the tremendous activity in this arena, there is strong hope that in the not too distant future, durable surface materials or coatings will come to fruition. This book contains 20 chapters by subject matter experts and is divided into three parts— Part 1: Fundamentals of Ice Formation and Characterization; Part 2: Ice Adhesion and Its Measurement; and Part 3: Methods to Mitigate Ice Adhesion. The topics covered include: factors influencing the formation, adhesion and friction of ice; ice nucleation on solid surfaces; physics of ice nucleation and growth on a surface; condensation frosting; defrosting properties of structured surfaces; relationship between surface free energy and ice adhesion to surfaces; metrology of ice adhesion; test methods for quantifying ice adhesion strength to surfaces; interlaboratory studies of ice adhesion strength; mechanisms of surface icing and deicing technologies; icephobicities of superhydrophobic surfaces; anti-icing using microstructured surfaces; icephobic surfaces: features and challenges; bio-inspired anti-icing surface materials; durability of anti-icing coatings; durability of icephobic coatings; bio-inspired icephobic coatings; protection from ice accretion on aircraft; and numerical modeling and its application to inflight icing.

Various states of hydrophobic wetting and hysteresis are observed when water droplets are deposited on micro-post surfaces of different post densities. Hysteresis is commonly defined as the difference between the advancing and receding contact angle and after many decades of research, the mechanisms governing hysteresis are still not fully understood. Particularly, stick-slip behavior of the three-phase contact line has been observed and qualitatively attributed to surface or chemical heterogeneities, but the behavior has yet to be quantified. In this thesis, contact line motion particularly focused on stick-slip behavior and its influence on drop width and contact angle was examined as a new approach to understanding hysteresis as pertaining to micro-textured surfaces. This work focuses on developing a fundamental understanding and physical model of the stick-slip behavior of the contact line and preliminarily explores the influence of contact line velocity on this stick-slip behavior and contact angle. By characterizing stick-slip behavior and hysteresis on micro-post surfaces, models can be developed that in the future can aid in surface design for optimal wetting behavior in industrial and power plant applications. Additionally, the pinning parameter has been used to predict roll off angle on micro-post surfaces for a variety of post densities and these predictions have been experimentally verified. With further definition of the pinning parameter to include surface roughness and impact phenomena, the pinning parameter can be used in surface design for droplet shedding in industrial applications.