Large-area fabrication of superhydrophobic surfaces for practical applications: an overview

Abstract

This review summarizes the key topics in the field of large-area fabrication of superhydrophobic surfaces, concentrating on substrates that have been used in commercial applications. Practical approaches to superhydrophobic surface construction and hydrophobization are discussed. Applications of superhydrophobic surfaces are described and future trends in superhydrophobic surfaces are predicted.

Figure 1

Steps used in the covalent layer-by-layer assembly of functional particles, with C groups and A groups on a substrate activated with A groups, for superhydrophobic surfaces. B groups are formed by the reactions of A groups with C groups.

Figure 2

Preparation of superhydrophobic films based on covalent assembly yielding raspberry-like particles (reprinted with permission from [20], © 2005 American Chemical Society).

Figure 3

Preparation of superhydrophobic surfaces on cotton textiles by complex coating of silica nanoparticles and hydrophobization (reprinted with permission from [15], © 2009 Elsevier B.V.).

Figure 4

SEM images of (a) porous membrane produced by solvent casting of 17.9 mg ml⁻¹ polypropylene solution using methyl ethyl ketone as the nonsolvent (reprinted with permission from [23], © 2008 Elsevier B.V.); (b) superhydrophobic poly(vinyl chloride) film obtained by coating with a mixture of 2 : 1 (v/v) ethanol and H₂O as the nonsolvent (reprinted with permission from [27], © 2006 Elsevier B.V.).

Figure 5

Nanoparticle-polymer composite coating for superhydrophobic surfaces.

Figure 6

SEM images of (a) poly(ethylene terephthalate) textile fabric coated with silicone nanofilaments and (b) coated samples after the abrasion test (Textile Friction Analyzer, 1450 cycles, load: 5 N, corresponding to a contact pressure of 7.8 kPa) and (c) drops of water showing the wetting properties of the sample after the abrasion test. The inset of the SEM image in (a) shows a drop of water deposited on the coated fabric (reprinted with permission from [34], © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim).

Figure 7

Water droplets on the surface of a modified colored cotton fabric (a) and 3D atomic force microscopy image of the modified fiber surface (b) (reprinted with permission from [35], © 2007 Royal Society of Chemistry).

Figure 8

(a) Schematic illustration of the procedure for the preparation of dual-size structure on the surface of woven cotton fibers, combining an in situ Stöber reaction with the subsequent adsorption of silica nanoparticles, and morphology of samples obtained by (b) in situ introduction of silica microparticles on cotton fibers and (c) three-cycle adsorption of silica nanoparticles on sample (a) (reprinted with permission from [42], © 2009 American Chemical Society).

Figure 9

Fabrication of superhydrophobic surfaces by hydrothermal growth of nanostructured surface and hydrophobization.

Figure 10

Scheme showing the structure of dodecyltrimethoxysilane-treated fiber for improved adhesion and stability of ZnO nanorods to a cotton substrate (reprinted with permission from [49], © 2008 Elsevier B.V).

Figure 11

Examples of surface reactive molecules for low-surface-energy modification: (a) long alkyl chain with R₁ groups; (b) long alkyl chain organic silanes with R₂ groups; (c) long alkyl chain fluorinated silanes with R₃ groups, in which R₁ can be –SH, –OH, –COOH, –NH₂, etc, and R₂ and R₃ can be –Cl, –OCH₃, –OCH₂CH₃; the length of these chains can be varied from C8 to C18; and (d) polymers based on polydimethylsiloxane, which can be bis-end-capped or mono-end-capped, where R₄ is usually a 3-aminopropyl or glycidyl ether group.

Figure 12

Water droplets rolling off substrates with a normal hydrophobic surface (left) and a self-cleaning superhydrophobic surface (right) through dust particles.