A superhydrophobic surface is a surface with a water contact angle close to or higher than 150°. In this feature article, we review the historical and present research on superhydrophobic surfaces, including the characterization of superhydrophobicity, different ways to fabricate rough surfaces, and low-surface-energy modifications on inorganic and organic rough surfaces. It is the combination of surface roughness and low-surface-energy modification that leads to superhydrophobicity. Notably, research on superhydrophobic surfaces has not only fundamental interest but various possible functional applications in micro- and nano-materials and devices.

Superhydrophobic surfaces: from structural control to functional application

Keywords: Fragmentation Chain-Transfer ; Self-Assembled Monolayers ; Walled Carbon Nanotubes ; Well-Defined Polymer ; Nitroxide-Mediated Polymerization ; Block-Copolymer Brushes ; Poly(Methyl Methacrylate) Brushes ; Transfer Raft Polymerization ; Quartz-Crystal Microbalance ; Poly(Acrylic Acid) Brushes Reference EPFL-REVIEW-148464doi:10.1021/cr900045aView record in Web of Science Record created on 2010-04-23, modified on 2017-05-10

Polymer Brushes via Surface-Initiated Controlled Radical Polymerization: Synthesis, Characterization, Properties, and Applications

Design, and Applications Shutao Wang,†,‡ Kesong Liu, Xi Yao, and Lei Jiang*,†,‡,§ †Laboratory of Bio-inspired Smart Interface Science, Technical Institute of Physics and Chemistry, and ‡Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education, School of Chemistry and Environment, BeiHang University, Beijing 100191, People’s Republic of China Department of Biomedical Sciences, City University of Hong Kong, Hong Kong P6903, People’s Republic of China

Bioinspired Surfaces with Superwettability: New Insight on Theory, Design, and Applications

In this review we focus on recent developments in applications of bio-inspired special wettable surfaces. We highlight surface materials that in recent years have shown to be the most promising in their respective fields for use in future applications. The selected topics are divided into three groups, applications of superhydrophobic surfaces, surfaces of patterned wettability and integrated multifunctional surfaces and devices. We will present how the bio-inspired wettability has been integrated into traditional materials or devices to improve their performances and to extend their practical applications by developing new functionalities.

Applications of Bio‐Inspired Special Wettable Surfaces

Nature is a school for scientists and engineers. After four and a half billion years of stringent evolution, some creatures in nature exhibit fascinating surface wettability. Biomimetics, mimicking nature for engineering solutions, provides a model for the development of functional surfaces with special wettability. Recently, bio-inspired special wetting surfaces have attracted wide scientific attention for both fundamental research and practical applications, which has become an increasingly hot research topic. This Critical Review summarizes the recent work in bio-inspired special wettability, with a focus on lotus leaf inspired self-cleaning surfaces, plants and insects inspired anisotropic superhydrophobic surfaces, mosquito eyes inspired superhydrophobic antifogging coatings, insects inspired superhydrophobic antireflection coatings, rose petals and gecko feet inspired high adhesive superhydrophobic surfaces, bio-inspired water collecting surfaces, and superlyophobic surfaces, with particular focus on the last two years. The research prospects and directions of this rapidly developing field are also briefly addressed (159 references).

Recent developments in bio-inspired special wettability

A simple two-step plasmachemical methodology is outlined for the fabrication of microcondensor surfaces. This comprises the creation of a superhydrophobic background followed by pulsed plasma deposition of a hydrophilic polymer array. Microcondensation efficiency has been explored in terms of the chemical nature of the hydrophilic pixels and their dimensions. These results are compared to the hydrophilic-hydrophobic pattern present on the Stenocara beetle's back, which is used by the insect to collect water in the desert. Potential applications include fog harvesting, microfluidics, and biomolecule immobilization.

Mimicking a Stenocara Beetle's Back for Microcondensation Using Plasmachemical Patterned Superhydrophobic−Superhydrophilic Surfaces

Ultrasonic atomization of acrylic acid monomer into an atmospheric pressure glow discharge (APGD) leads to the deposition of structurally well-defined polymeric films. High retention of the carboxylic acid group has been verified by XPS and FT-IR spectroscopy. These films are found to exhibit low water contact angle values and display good adhesive and gas barrier performance.

Atmospheric Pressure Plasma Deposition of Structurally Well-Defined Polyacrylic Acid Films

Hydrophobic polysiloxane-like thin films have been deposited onto polyethylene by introducing octamethylcyclotetrasiloxane and tetramethylcyclotetrasiloxane precursors through an ultrasonic atomizer into an atmospheric pressure glow discharge. Enrichment of the gas feed with oxygen gives rise to the formation of hydrophilic SiOx coatings which exhibit an improvement in gas barrier.

Atmospheric pressure glow discharge deposition of polysiloxane and SiOx films

A simple method for growing polymer brushes by atom transfer radical polymerization (ATRP) off solid surfaces has been devised. This entails pulsed plasmachemical deposition of a halogen-containing initiator layer, followed by either organic or aqueous phase controlled surface polymerization. The wide-scale applicability of this approach is exemplified by functionalizing flat substrates, microbeads, and nonwoven textiles.

Substrate-independent approach for polymer brush growth by surface atom transfer radical polymerization.

Amine-terminated polyamidoamine (PAMAM) dendrimers can be immobilized onto anhydride-functionalized pulsed plasma polymer surfaces via amide linkage formation. The packing density of dendrimers at the surface can be tailored by programming the pulse duty cycle parameters during plasma polymerization. These PAMAM dendrimer layers are shown to be useful for a variety of surface-related phenomena, for example, fluorination, adhesion, and gas barrier enhancement.

L. J. Ward

Papers

Mimicking a Stenocara Beetle's Back for Microcondensation Using Plasmachemical Patterned Superhydrophobic−Superhydrophilic Surfaces

Atmospheric Pressure Plasma Deposition of Structurally Well-Defined Polyacrylic Acid Films

Atmospheric pressure glow discharge deposition of polysiloxane and SiOx films

Substrate-independent approach for polymer brush growth by surface atom transfer radical polymerization.

Controlled attachment of PAMAM dendrimers to solid surfaces