Superhydrophobic Surfaces Generated from Water-Borne Dispersions of Hierarchically Assembled Nanoparticles Coated with a Reversibly Switchable Shell (original) (raw)
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Recent Progress in Preparation of Superhydrophobic Surfaces: A Review
In nature, water-repellency (superhydrophobicity) is found, besides in plants, in insects and bird feathers. The booming field of biomimetics allows one to mimic nature to develop nanomaterials, nanodevices, and processes which offer de- sirable properties. Biomimetics means mimicking biology or nature. Inspired from nature, which reveals excellent su- perhydrophobicity, researchers have recently developed and implemented biomimetic superhydrophobic surfaces in a variety of smart and simple ways. Superhydrophobicity is an effect where surface roughness and chemical composition combine to generate unusual water repellent surface, causing water to bounce and roll off the surface. This review arti- cle provides the overview of the recent progress (within the last four years) in the synthesis, characterization, theoretical modelling, and applications of superhydrophobic surfaces, with focus on the different techniques used and how they have developed over the years. At last, the difficulties related to implementation of superhydrophobic surfaces in day to day life are discussed. This review can find interesting for students, scientists and industrial companies working espe- cially on superhydrophobic surfaces.
Recent advances in designing superhydrophobic surfaces
Journal of Colloid and Interface Science, 2013
The interest in superhydrophobic surfaces has grown exponentially over recent decades. Since the lotus leaf dual hierarchical structure was discovered, researchers have investigated the foundations of selfcleaning behavior. Generally, surface micro/nanostructuring combined with low surface energy of materials leads to extreme anti-wetting properties. The great number of papers on this subject attests the efforts of scientists in mimicking nature to generate superhydrophobicity. Besides the thirst for knowledge, scientists have been driven by the many possible industrial applications of superhydrophobic materials in several fields. Many methods and techniques have been developed to fabricate superhydrophobic surfaces, and the aim of this paper is to review the recent progresses in preparing manmade superhydrophobic surfaces.
Assembly Mechanism and the Morphological Analysis of the Robust Superhydrophobic Surface
Coatings
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. Addi...
Superhydrophobic surfaces review: Functional application, fabrication techniques and limitations
Journal of Micromanufacturing
Over the years, researchers have been working to mimic the nature by inducing superhydrophobic properties into a variety of material surfaces so that they exhibit non-wetting properties. Many diverse applications have been found in the fields, such as space and aerospace, defence, automotive, biomedical applications and engineering, sensors, apparels, and so on. Superhydrophobic surfaces repel water generally due to their surface texture or chemical properties. In this article, we focus on the functional applications of the superhydrophobic surfaces, and state-of-the-art fabrication technologies and processes, and the limitations of these processes to generate the superhydrophobic surfaces have been developed over the years.
Superhydrophobic Surfaces: Insights from Theory and Experiment
The Journal of Physical Chemistry B, 2020
Biomimetic nanosurfaces with distinct wettability and versatility have found special enthusiasm in both fundamental research and industrial applications. With the advent of nanotechnology, it is doable to acclimate surface architecture and surface chemistry to attain superhydrophobicity. The uniqueness of superhydrophobic surfaces arises from various phenomenal advances, and its progress is expected to continue for decades in the future. In this Review Article, we discuss recent progress made in defining physical aspects of numerical modeling, experimental practices adopted, and applications of superhydrophobic surfaces. First, we revisit various classical models of superhydrophobicity and recent theoretical advances achieved related to the wetting phenomena. Subsequently, we emphasize various precursors and advance fabrication strategies adopted to fabricate superhydrophobic surfaces. In the following section, we take up various potential applications and appropriate working principles to explain wettability phenomena. Finally, some general conclusions are drawn along with proposed guidelines for designing robust superhydrophobic coatings.
Single Step Fabrication of Nano-Structured Superhydrophobic Surfaces Showing Angle Dependent Colours
Superhydrophobic surfaces show extraordinary water-repellent properties with low drag for fluid flow due to reduced liquid-solid contact area. Due to high contact angle and low contact angle hysteresis these surfaces also show self-cleaning effect. In nature different plants and leaves, such as Lotus leaf and Rose petals show superhydrophobic behaviour due to wax coated micro/nano hierarchical structures on their surfaces. In this work, we report fabrication of superhydrophobic surfaces on silicon substrate using a one step process. This is a wafer scale large area fabrication technique for superhydrophobic surfaces. DRIE (Deep Reactive Ion Etching) technique was used to fabricate the nano structured extremely water repellent surfaces. Two different fabrication approaches have been followed in this work. In one approach the DRIE was carried out directly on silicon surface and in the second approach DRIE was done after spin coating alumina nanoparticles dissolved in ethanol on silicon surface. In both the processes, DRIE was done for a different number of etch cycles. The width of the nano-structures formed after DRIE process varies in the range of 300 nm to 500 nm. Contact angle has been measured and compared for the superhydrophobic surfaces fabricated using the above two approaches. Contact angle as high as 170 0 ±1 0 was measured and less than 2 0 contact angle hysteresis was observed for water droplet. Also an angle dependent colour change phenomena, which was observed for the nano structured silicon substrates obtained using the second approach at different viewing angles is reported.
Microstructure Design for Artificial Superhydrophobic Surfaces
International Journal of Engineering and Advanced Technology, 2020
Superhydrophobic surfaces are the surfaces that do not allow the droplets of liquid to spread and wet it. Ideally, the droplets remain almost spherical in shape and with a very small angle of tilt, slide away from the surface. This occurs due to very high contact angle. A perfectly spherical droplet would make 1800 angle of contact, but practically this high contact angle is never possible for a stable droplet. The surfaces that make contact angle (CA)>90o are said to be hydrophobic surfaces. If CA is greater than 150o , the surface is known as superhydrphobic surface. This property of the surface is termed as superhydrophobicity. In this paper, the surface morphology to be engineered is studied, which is governed by certain principles. Theories of Thomas Young [1], Wenzel [2] and Cassie-Baxter [3] are reviewed and effect of micro and nano level of roughness, producing hierarchical structures is analyzed. Subsequently, the designing of such super hydrophobic surfaces is attempted.
Advanced Functional Materials, 2015
in order to facilitate the unique function of the "lotus effect" on various substrates. [ 2 ] Moreover, upon mimicking the micro-to nanoscale structural roughness of the natural plants and insects, engineered superhydrophobic surfaces with tunable contact angle (CA) and hysteresis have also been fabricated by carbon nanotubes, polymers, and metal oxides, using the techniques such as chemical deposition, sol-gel, etching, or nanoprinting. [ 3 ] Directional surfaces with controllable liquid transportation properties, i.e., water condensation and collection, are also achieved on the poly(methyl methacrylate)-nylon fi bers, patterned poly(acrylic acid)/ poly(allylamine hydrochloride)/SiO 2 /semifl uorosilane superhydrophobic surface and conical copper wire by mimicking the special hydrophilic/hydrophobic region distribution of spider silk, Namib beetle's back, and cactus spines, respectively. [ 4 ] Furthermore, antiicing, dry adhesion, and drag reduction superhydrophobic surfaces are obtained by mimicking the Nepenthes pitcher plants, gecko appendage, and water strider legs. [ 5 ] The antifouling effect of the superhydrophobic turkey egg surface has also been discovered recently, which can serve as a cost-effective model for the development of artifi cial antibacteria surfaces. [ 6 ] Compared to the natural biological surfaces, the functions of the artifi cial superhydrophobic surfaces are generally determined by their intrinsic compositions and structures, which make them relatively stationary to the external stimuli. However, natural surface and interface are generally stimuli-responsive. The examples include the self-healing of the living organism tissue surface and the snapping motion of the Venus fl ytrap originated from the elastic instability at the air-solid interface, or the switchable adhesion force of gecko toe pad and butterfl y wings. The stimuli-responsive features of the natural surfaces make them extremely adaptable and durable to the surrounding environment, so that the overall bioecology performance can be promoted to the optimal level. [ 7 ] With emerging demands of functionality and adaptability, it is obvious that the structural design of static superhydrophobic surface (SHS) cannot provide a reasonable solution to overcome the functional and performance challenges. Bioinspired,