Artificial (Biomimetic) Superhydrophobic Surfaces
Artificial (biomimetic) superhydrophobic surfaces utilizing the Lotus effect are reviewed in this chapter. First, modern ways of production of superhydrophobic surfaces are discussed, including lithography, deposition, stretching, itching, evaporation, so
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Abstract Artificial (biomimetic) superhydrophobic surfaces utilizing the Lotus effect are reviewed in this chapter. First, modern ways of production of superhydrophobic surfaces are discussed, including lithography, deposition, stretching, itching, evaporation, sol-gel, and others. The variety of materials used to make superhydrophobic surfaces (metals, polymers, semiconductors, nanotubes, nanoparticles) is discussed. Then wetting and self-cleaning properties of micro- and nanopatterned silicon and polymer biomimetic surfaces are presented on the basis of experimental measurements. After that, commercially available superhydrophobic products (paints, textiles, glasses) are reviewed as well as future applications in industry, bio- and nanotechnology.
In the preceding chapter, we discussed biological superhydrophobic and self-cleaning surfaces and experimental methods of their study. In this chapter, we will review artificial (biomimetic) superhydrophobic surfaces. First we will discuss various ways to produce rough superhydrophobic surfaces (Table 11.1). Second, we will review properties of these surfaces and present some applications that are coming to the market. In recent years, fabrication of superhydrophobic surfaces has become an area of active fundamental research. This chapter will discuss a number of new approaches, and there is no doubt that in the near future new technological concepts will emerge. In general, the same techniques that are used for micro- and nanostructure manufacturing, such as lithography, etching, and deposition, have been used for producing superhydrophobic surfaces. Advantages and shortcomings of these techniques are summarized in Table 11.2. One especially interesting development is the creation of reversible surfaces that can be turned from hydrophobic to hydrophilic by applying electric potential, heat, or ultraviolet (UV) irradiation [112, 198, 207, 308, 342]. Another important task is to create transparent superhydrophobic surfaces, which may have numerous potential applications for optics and self-cleaning glasses. In order for the surface to be transparent, roughness details should be smaller than the wavelength of the visible light (about 400–700 nm) [226]. While the fundamental research is very active, a number of attempts to produce commercial products using the lotus effect have been made [118, 308]. This includes glasses, textile, paints, aerosols, etc.
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11 Artificial (Biomimetic) Superhydrophobic Surfaces
Table 11.1. Typical materials and corresponding techniques to produce micro/nanoroughness [54] Material Teflon
Technique Plasma
Fluorinated block polymer solution PFOS
Casting under humid environment Electro- and chemical polymerization Laser treatment
PDMS PS-PDMS Block copolymer PS, PC, PMMA
Contact angle Notes 168
160
Transparent
152
Reversible (electric potential)
166
Electrospinning
>150
Evaporation
>150
Nanoimprint Oxygen plasma etching Sol-gel
156 >150
Al
Chemical etching
>150
Copper
Electrodeposition
160
Si
Photolithography
170
Si
164
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