Preparation and Characterisation of Super‐Hydrophobic Surfaces

The interest in highly water‐repellent surfaces has grown in recent years due to the desire for self‐cleaning surfaces. A super‐hydrophobic surface is one that achieves a water contact angle of 150° or greater. This article explores the different approaches used to construct super‐hydrophobic surfaces and identifies the key properties of each surface that contribute to its hydrophobicity. The models used to describe surface interaction with water are considered, with attention directed to the methods of contact angle analysis. A summary describing the different routes to hydrophobicity is also given.     

New approach to fabricate an extremely super‐amphiphobic surface based on fluorinated silica nanoparticles

Superoleophobic surfaces possessing static contact angles greater than 140° with organic liquids are extremely rare. A simple approach has been developed to fabricate an extremely superamphiphobic coating material based on fluorinated silica nanoparticles resulting contact angles of water and diiodomethane at 167.5° and 158.6°, respectively. The contact angle of diiodomethane at 158.6° is substantially higher than the highest literature reported value we know of at 110°. In addition, this developed film also possesses extremely high contact angles with other organic liquids such as soybean oil (146.6°), decahysronaphthalene (142.5°), diesel fuel (140.4°), and xylene (140.5°). This developed superamphiphobic organic–inorganic hybrid film possesses unique liquid repellency for both water and organic liquids that can be used as functional coatings on numerous substrates by a simple coating process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1984–1990, 2008     

Fabricating Super‐Hydrophobic Lotus‐Leaf‐Like Surfaces through Soft‐Lithographic Imprinting

Summary: A soft‐lithographic imprinting approach to fabricate super‐hydrophobic surfaces has been developed in this work. In this process, fresh lotus leaves were used as masters and PDMS stamps were prepared by replica molding against the lotus‐leaf surfaces. By using the stamps and an epoxy‐based azo polymer solution as “ink”, the mimicked lotus‐leaf surfaces made of the polymer were fabricated by pressing the featured faces of the stamps against “inked” substrates and drying under a proper condition after peeling off the stamps. The lotus‐leaf‐like surfaces show super‐hydrophobic characteristics with the water contact angle higher than 150° and contact angle hysteresis less than 3°.

SEM images of lotus‐leaf‐like papillary structures on the imprinted surface.     

Super‐Resolution Imaging of Plasma Membrane Glycans

Much of the physiology of cells is controlled by the spatial organization of the plasma membrane and the glycosylation patterns of its components, however, studying the distribution, size, and composition of these components remains challenging. A bioorthogonal chemical reporter strategy was used for the efficient and specific labeling of membrane‐associated glycoconjugates with modified monosaccharide precursors and organic fluorophores. Super‐resolution fluorescence imaging was used to visualize plasma membrane glycans with single‐molecule sensitivity. Our results demonstrate a homogeneous distribution of N‐acetylmannosamine (ManNAc)‐, N‐acetylgalactosamine (GalNAc)‐, and O‐linked N‐acetylglucosamine (O‐GlcNAc)‐modified plasma membrane proteins in different cell lines with densities of several million glycans on each cell surface.     

Fabrication of Biomimetic Superhydrophobic Coating with a Micro‐Nano‐Binary Structure

Summary: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor‐induced phase separation occurred during the solidifying process and a rough surface with a micro‐nano‐binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed.

SEM image of a single micro‐flower.     

Super‐Hydrophobic PDMS Surface with Ultra‐Low Adhesive Force

Summary: Rough polydimethylsiloxane (PDMS) surface containing micro‐, submicro‐ and nano‐composite structures was fabricated using a facile one‐step laser etching method. Such surface shows a super‐hydrophobic character with contact angle higher than 160° and sliding angle lower than 5°, i.e. self‐cleaning effect like lotus leaf. The wettabilities of the rough PDMS surfaces can be tunable by simply controlling the size of etched microstructures. The adhesive force between etched PDMS surface and water droplet is evaluated, and the structure effect is deduced by comparing it with those own a single nano‐ or micro‐scale structures. This super‐hydrophobic PDMS surface can be widely applied to many areas such as liquid transportation without loss, and micro‐pump (creating pushing‐force) needless micro‐fluidic devices.

Etched PDMS surface containing micro‐, submicro‐, and nano‐composite structures shows a self‐cleaning effect with water CA as high as 162° and SA lower than 5°.     

Shear‐Controlled Micro/Nanometer‐Scaled Super‐Hydrophobic Surfaces with Tunable Sliding Angles from Single Component Isotactic Poly(propylene)

Summary: With the proper selection of shear and thermal conditions, super‐hydrophobic polymeric surfaces (contact angle > 150°) with tunable sliding angles (from less than 1° to higher than 90°) can be prepared from pure isotactic poly(propylene) (iPP) without any further modification with low‐surface‐energy components under ambient atmosphere. The formed surfaces have naturally good thermal properties, chemical and moisture resistance, low density, and potentially low manufacturing cost.

SEM images of formed super‐hydrophobic surfaces and related two extreme sliding angles (contact angles of these surfaces are higher than 150°).     

“Click & Seed” Approach to the Biomimetic Modification of Material Surfaces

A simple, versatile, protein‐repulsive, substrate‐independent biomimetic surface modification is presented that is based on the creation of a PEO brush on a polydopamine anchoring layer and its capacity for selective follow‐up modifications with various ligands using a copper‐catalyzed alkyne‐azide cycloaddition reaction. The desired surface concentration of peptide biomimetic ligands can be controlled by adjusting the peptide concentration in the reaction mixture, then measuring the activity of ¹²⁵I‐radiolabeled peptides that are immobilized on the substrates. The performance of the prepared substrates is tested in cell cultures with MEF cells and a human ECC line.

     

Layer‐by‐Layer Assembled Nanotubes as Biomimetic Nanoreactors for Calcium Carbonate Deposition

Enzyme‐loaded magnetic polyelectrolyte multilayer nanotubes prepared by layer‐by‐layer assembly combined with the porous template could be used as biomimetic nanoreactors. It is demonstrated that calcium carbonate can be biomimetically synthesized inside the cavities of the polyelectrolyte nanotubes by the catalysis of urease, and the size of the calcium carbonate precipitates was controlled by the cavity dimensions. The metastable structure of the calcium carbonate precipitates inside the nanotubes was protected by the outer shell of the polyelectrolyte multilayers. These features may allow polyelectrolyte nanotubes to be applied in the fields of nanomaterials synthesis, controlled release, and drug delivery.

     

Preparation of Nanostructured Polyaniline and its Super‐Amphiphilic Behavior

PANI nanofibers are prepared electrochemically by template‐free method on a stainless steel electrode. Both the hydrophilicity and the lipophilicity of the modified SS surface are enhanced by the nanostructured PANI, and a super‐amphiphilic surface is obtained in this way. The influence of polymerization conditions, such as polymerization potentials, polymerization time, the acidity, and the dopants on the super‐amphiphilic property, has been systematically investigated. In addition, the mechanisms of obtaining a super‐amphiphilic surface are briefly discussed.

     

SLAP: Small Labeling Pair for Single‐Molecule Super‐Resolution Imaging

Protein labeling with synthetic fluorescent probes is a key technology in chemical biology and biomedical research. A sensitive and efficient modular labeling approach (SLAP) was developed on the basis of a synthetic small‐molecule recognition unit (Ni‐trisNTA) and the genetically encoded minimal protein His_6‐10‐tag. High‐density protein tracing by SLAP was demonstrated. This technique allows super‐resolution fluorescence imaging and fulfills the necessary sampling criteria for single‐molecule localization‐based imaging techniques. It avoids masking by large probes, for example, antibodies, and supplies sensitive, precise, and robust size analysis of protein clusters (nanodomains).     

Make them Blink: Probes for Super‐Resolution Microscopy

In recent years, a number of approaches have emerged that enable far‐field fluorescence imaging beyond the diffraction limit of light, namely super‐resolution microscopy. These techniques are beginning to profoundly alter our abilities to look at biological structures and dynamics and are bound to spread into conventional biological laboratories. Nowadays these approaches can be divided into two categories, one based on targeted switching and readout, and the other based on stochastic switching and readout of the fluorescence information. The main prerequisite for a successful implementation of both categories is the ability to prepare the fluorescent emitters in two distinct states, a bright and a dark state. Herein, we provide an overview of recent developments in super‐resolution microscopy techniques and outline the special requirements for the fluorescent probes used. In combination with the advances in understanding the photophysics and photochemistry of single fluorophores, we demonstrate how essentially any single‐molecule compatible fluorophore can be used for super‐resolution microscopy. We present examples for super‐resolution microscopy with standard organic fluorophores, discuss factors that influence resolution and present approaches for calibration samples for super‐resolution microscopes including AFM‐based single‐molecule assembly and DNA origami.     

Synthesis of Novel Biomimetic Zwitterionic Phosphorylcholine‐Bound Chitosan Derivative

Summary: Water‐soluble biomimetic chitosan derivative conjugating zwitterionic phosphorylcholine was efficiently prepared through Atherton‐Todd reaction under the mild conditions, and the possible formation mechanism of zwitterionic product was related to the nucleophilic attack of adjacent 3‐hydroxyl on the D ‐glucosamine residue to phosphorus with the help of base. UV absorption and melting behaviors of DNA/phosphorylcholine‐bound chitosan derivative showed that the phosphorylcholine‐bound chitosan derivative could be a new carrier for long‐circulating macromolecular drug delivery.

Structure of zwitterionic PC‐chitosan.     

Minimal Tags for Rapid Dual‐Color Live‐Cell Labeling and Super‐Resolution Microscopy

The growing demands of advanced fluorescence and super‐resolution microscopy benefit from the development of small and highly photostable fluorescent probes. Techniques developed to expand the genetic code permit the residue‐specific encoding of unnatural amino acids (UAAs) armed with novel clickable chemical handles into proteins in living cells. Here we present the design of new UAAs bearing strained alkene side chains that have improved biocompatibility and stability for the attachment of tetrazine‐functionalized organic dyes by the inverse‐electron‐demand Diels–Alder cycloaddition (SPIEDAC). Furthermore, we fine‐tuned the SPIEDAC click reaction to obtain an orthogonal variant for rapid protein labeling which we termed selectivity enhanced (se) SPIEDAC. seSPIEDAC and SPIEDAC were combined for the rapid labeling of live mammalian cells with two different fluorescent probes. We demonstrate the strength of our method by visualizing insulin receptors (IRs) and virus‐like particles (VLPs) with dual‐color super‐resolution microscopy.     

Bio‐Inspired Silicification on Patterned Surfaces Generated by Microcontact Printing and Layer‐by‐Layer Self‐Assembly

Micropatterns of silica were generated under biocompatible conditions by a combination of microcontact printing (μCP), layer‐by‐layer (LbL) self‐assembly, and biomimetic silicification. Quaternary amine‐containing poly(diallyl dimethyl ammonium chloride) induced polycondensation of silicic acid, resulting in spatioselective formation of silica micropatterns. Scale bar: 10 μm.