Metamorphic Superomniphobic Surfaces

Superomniphobic surfaces are extremely repellent to virtually all liquids. By combining superomniphobicity and shape memory effect, metamorphic superomniphobic (MorphS) surfaces that transform their morphology in response to heat are developed. Utilizing the MorphS surfaces, the distinctly different wetting transitions of liquids with different surface tensions are demonstrated and the underlying physics is elucidated. Both ex situ and in situ wetting transitions on the MorphS surfaces are solely due to transformations in morphology of the surface texture. It is envisioned that the robust MorphS surfaces with reversible wetting transition will have a wide range of applications including rewritable liquid patterns, controlled drug release systems, lab‐on‐a‐chip devices, and biosensors.     

Adaptable and Reprogrammable Surfaces

Establishing control over chemical reactions on interfaces is a key challenge in contemporary surface and materials science, in particular when introducing well‐defined functionalities in a reversible fashion. Reprogrammable, adaptable and functional interfaces require sophisticated chemistries to precisely equip them with specific functionalities having tailored properties. In the last decade, reversible chemistries—both covalent and noncovalent—have paved the way to precision functionalize 2 or 3D structures that provide both spatial and temporal control. A critical literature assessment reveals that methodologies for writing and erasing substrates exist, yet are still far from reaching their full potential. It is thus critical to assess the current status and to identify avenues to overcome the existing limitations. Herein, the current state‐of‐the‐art in the field of reversible chemistry on surfaces is surveyed, while concomitantly identifying the challenges—not only synthetic but also in current surface characterization methods. The potential within reversible chemistry on surfaces to function as true writeable memories devices is identified, and the latest developments in readout technologies are discussed. Finally, we explore how spatial and temporal control over reversible, light‐induced chemistries has the potential to drive the future of functional interface design, especially when combined with powerful laser lithographic applications.     

Scattering from Gamma-distributed Surfaces

Abstract

We present a theoretical and experimental study of the scattering of light from diffusers with gamma-distributed surface height profiles. The theory is developed using a thin-phase screen model: it is shown that, following a steepest-descent method, the mean scattered intensity as a function of the scattering angle follows a modified Bessel K-function. The theory is compared with experimental data in the two extreme cases of the gamma distribution, namely the negative exponential and Gaussian cases. The surfaces used were made by exposing photoresist-coated plates with laser speckle patterns. For the case of a negative-exponential surface it is shown that it is not possible, in practice at least, to extinguish the specular component.     

Nanoengineering of Particle Surfaces

The creation of core–shell particles is attracting a great deal of interest because of the diverse applicability of these colloidal particles; e.g., as building blocks for photonic crystals, in multi‐enzyme biocatalysis, and in drug delivery. This review presents the state‐of‐the‐art in strategies for engineering particle surfaces, such as the layer‐by‐layer deposition process (see Figure), which allows fine control over shell thickness and composition.     

Radiometry of Rough Surfaces

This paper discusses the radiometric properties of perfectly conductive, slightly rough random surfaces. The Kirchhoff approximation, so far used in this kind of study, is analysed. In particular, its inability to construct models of lambertian rough surfaces is pointed out. The small perturbation method, recently put forward, allows the scope and limitations of this approximation to be established. This method also yields exact expressions for the radiant intensity, for either polarized or unpolarized incident radiation and allows the construction of surfaces which produce a lambertian distribution of intensity.     

Surfaces that resist bioadhesion

The search for surfaces that resist bioadhesion has continued with the pursuit of a number of avenues. A large part of the studies has investigated PEG coatings. Nevertheless, there is still controversy about what exactly the properties and modes of action of an ‘ideal’ PEG coating should be. While some studies have reported no irreversible protein adsorption, other, very similar coatings appear less able to resist bioadhesion. Of great interest are results showing that PEG surfaces with very short chains are capable of rejecting proteins. As it is very difficult to obtain direct information about the microstructure of the coatings, studies typically employ plausible models to interpret observations. New analytical techniques and the direct measurement of interfacial forces between proteins and surfaces open up the possibility of improved, guided design and feedback in the optimization of surfaces intended to resist bioadhesion.     

Fluorination of Polymer Surfaces

Polyethylene greenhouse foils show an extraordinary prolonged lifetime at exposure to natural and artificial weathering if a gas‐phase fluorination under low‐pressure conditions was applied. The fluorination was performed by F₂/N₂ mixtures and provided ca. 50 F/100 C (fluorination degree ≈ 25%). The lifetime of PE greenhouse foils at exposure to artificial or natural weathering were increased by at least the factor 2–4 measured in terms of tensile strength and break at elongation.     

Peanut Leaf Inspired Multifunctional Surfaces

Nature has long served as a source of inspiration for scientists and engineers to design and construct multifunctional artificial materials. The lotus and the peanut are two typical plants living in the aquatic and the arid (or semiarid) habitats, respectively, which have evolved different optimized solutions to survive. For the lotus leaf, an air layer is formed between its surface and water, exhibiting a discontinuous three‐phase contact line, which resulted in the low adhesive superhydrophobic self‐cleaning effect to avoid the leaf decomposition. In contrast to the lotus leaf, the peanut leaf shows high‐adhesive superhydrophobicity, arising from the formation of the quasi‐continuous and discontinuous three‐phase contact line at the microscale and nanoscale, respectively, which provides a new avenue for the fabrication of high adhesive superhydrophobic materials. Further, this high adhesive and superhydrophobic peanut leaf is proved to be efficient in fog capture. Inspired by the peanut leaf, multifunctional surfaces with structural similarity to the natural peanut leaf are prepared, exhibiting simultaneous superhydrophobicity and high adhesion towards water.     

Superhydrophobic Surfaces by Electrochemical Processes

This review is an exhaustive representation of the electrochemical processes reported in the literature to produce superhydrophobic surfaces. Due to the intensive demand in the elaboration of superhydrophobic materials using low‐cost, reproducible and fast methods, the use of strategies based on electrochemical processes have exponentially grown these last five years. These strategies are separated in two parts: the oxidation processes, such as oxidation of metals in solution, the anodization of metals or the electrodeposition of conducting polymers, and the reduction processed such as the electrodeposition of metals or the galvanic deposition. One of the main advantages of the electrochemical processes is the relative easiness to produce various surface morphologies and a precise control of the structures at a micro‐ or a nanoscale.