A Fluorine-free Slippery Surface with Hot Water Repellency and Improved Stability against Boiling.

Inspired by natural living things such as lotus leaves and pitcher plants, researchers have developed many excellent antifouling coatings. In particular, hot-water-repellent surfaces have received much attention in recent years because of their wide range of applications. However, coatings with stability against boiling in hot water have not been achieved yet. Long-chain perfluorinated materials, which are often used for liquid-repellent coatings owing to their low surface energy, hinder the potential application of antifouling coatings in food containers. Herein, we design a fluorine-free slippery surface that immobilizes a biocompatible lubricant layer on a phenyl-group-modified smooth solid surface through OH-π interactions. The smooth base layer was fabricated by modification of phenyltriethoxysilane through a sol-gel method. The π-electrons of the phenyl groups interact with the carboxyl group of the oleic acid used as a lubricant, which facilitates immobilization on the base layer. Water droplets slid off the surface in the temperature range from 20 to 80 °C at very low sliding angles (<2°). Furthermore, we increased the π-electron density in the base layer to strengthen the OH-π interactions, which improved long-term boiling stability under hot water. We believe that this surface will be applied in fields in which the practical use of antifouling coatings is desirable, such as food containers, drink cans, and glassware.

Bioinspired Hand-Operated Smart-Wetting Systems Using Smooth Liquid Coatings.

Manually controllable "hand-operated" smart systems have been developed in many fields, including smart wetting materials, electronic devices, molecular machines, and drug delivery systems. Because complex morphological or chemical control are generally required, versatile strategies for constructing the system are technologically important. Inspired by the natural phenomenon of raindrops rarely bouncing and usually spreading on a puddle, we introduce a droplet-impact-triggering smart-wetting system using "non-smart" smooth liquid coating materials. Changing the droplet impact energy by changing the volume or casting height causes the droplet to completely bounce or spread on the liquid surface, regardless of the miscibility between the two liquids, owing to the stability of air layer. As the bouncing of a droplet on a liquid interface is not usually observed during wetting, we first analyze how the droplet bounces, then prove that the wettability is triggered by the droplet's impact energy, and finally introduce some applications using this system.

Droplet Motion Control on Dynamically Hydrophobic Patterned Surfaces as Multifunctional Liquid Manipulators.

In this letter, we introduce a novel liquid manipulation strategy to design dynamically hydrophobic and statically hydrophobic/hydrophilic patterned surfaces using an "omniphobicity"-based technique. The surfaces guide the sliding direction of a droplet in the presence of a statically hydrophilic area where the droplet does not stick on the transport path significantly enhancing the fluidic system transport efficiency. The concept of dynamically hydrophobic and statically hydrophobic/hydrophilic patterned surfaces in conjunction with omniphobic patterning techniques having surface multifunctionality, we believe, has potential not only for fluidic applications but also for future material engineering development.

Chitin Nanofibers Extracted from Crab Shells in Broadband Visible Antireflection Coatings with Controlling Layer-by-Layer Deposition and the Application for Durable Antifog Surfaces.

Reflection from various surfaces of many optical systems, such as photovoltaics and displays, is a critical issue for their performance, and antireflection coatings play a pivotal role in a wide variety of optical technologies, reducing light reflectance loss and hence maximizing light transmission. With the current movement toward optically transparent polymeric media and coatings for antireflection technology, the need for economical and environmentally friendly materials and methods without dependence on shape or size has clearly been apparent. Herein, we demonstrate novel antireflection coatings composed of chitin nanofibers (CHINFs), extracted from crab shell as a biomass material through an aqueous-based layer-by-layer self-assembly process to control the porosity. Increasing the number of air spaces inside the membrane led low refractive index, and precise control of refractive index derived from the stacking of the CHINFs achieved the highest transmittance with investigating the surface structure and the refractive index depending on the solution pH. At a wavelength of 550 nm, the transmittance of the coatings was 96.4%, which was 4.8% higher than that of a glass substrate, and their refractive index was 1.30. Further critical properties of the films were the durability and the antifogging performance derived from the mechanical stability and hydrophilicity of CHINFs, respectively. The present study may contribute to a development of systematically designed nanofibrous films which are suitable for optical applications operating at a broadband visible wavelength with durability and antifog surfaces.

Controllable Broadband Optical Transparency and Wettability Switching of Temperature-Activated Solid/Liquid-Infused Nanofibrous Membranes.

Inspired by biointerfaces, such as the surfaces of lotus leaves and pitcher plants, researchers have developed innovative strategies for controlling surface wettability and transparency. In particular, great success has been achieved in obtaining low adhesion and high transmittance via the introduction of a liquid layer to form liquid-infused surfaces. Furthermore, smart surfaces that can change their surface properties according to external stimuli have recently attracted substantial interest. As some of the best-performing smart surface materials, slippery liquid-infused porous surfaces (SLIPSs), which are super-repellent, demonstrate the successful achievement of switchable adhesion and tunable transparency that can be controlled by a graded mechanical stimulus. However, despite considerable efforts, producing temperature-responsive, super-repellent surfaces at ambient temperature and pressure remains difficult because of the use of nonreactive lubricant oil as a building block in previously investigated repellent surfaces. Therefore, the present study focused on developing multifunctional materials that dynamically adapt to temperature changes. Here, we demonstrate temperature-activated solidifiable/liquid paraffin-infused porous surfaces (TA-SLIPSs) whose transparency and control of water droplet movement at room temperature can be simultaneously controlled. The solidification of the paraffin changes the surface morphology and the size of the light-transmission inhibitor in the lubricant layer; as a result, the control over the droplet movement and the light transmittance at different temperatures is dependent on the solidifiable/liquid paraffin mixing ratio. Further study of such temperature-responsive, multifunctional systems would be valuable for antifouling applications and the development of surfaces with tunable optical transparency for innovative medical applications, intelligent windows, and other devices.

Integrated Anti-Icing Property of Super-Repellency and Electrothermogenesis Exhibited by PEDOT:PSS/Cyanoacrylate Composite Nanoparticles.

Ice formation causes numerous problems in many industrial fields as well as in our daily life. Various functional anti-ice coatings have been extensively studied during the past several decades; however, the development of feasible ice-repellent surfaces with long-term stability has been found to be extremely difficult. Here, we report the conductive superhydrophobic coatings with freezing rain repellency that simultaneously possess electrothermogenic ability to rapidly melt newly formed frosts due to the Joule heat. The obtained films have high mechanical flexibility and abrasion resistance produced by composite nanoparticles of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) embedded in ethyl cyanoacrylate. In addition, excellent water repellency (corresponding contact angle >160°) and efficient heating ability (with an estimated energy consumption as low as 260.8 °C cm(2)/W) generated by applying voltage through the conductive film surface have been demonstrated. The proposed concept of combining super-repellency with electrothermal heating may provide a new strategy of addressing problems related to ice formation.

A biologically inspired attachable, self-standing nanofibrous membrane for versatile use in oil-water separation.

Uloborus walckenaerius spider webs provided the inspiration for attachable, self-standing nanofibre sheets. The developed product adds selective wettability against oil-water mixtures to both 2D and 3D materials by attaching or covering them, leading to successful separation through a facile, scalable and low-cost process.

A novel small protein of Bacillus subtilis involved in spore germination and spore coat assembly.

Two small genes named sscA (previously yhzE) and orf-62, located in the prsA-yhaK intergenic region of the Bacillus subtilis genome, were transcribed by SigK and GerE in the mother cells during the later stages of sporulation. The SscA-FLAG fusion protein was produced from T(5) of sporulation and incorporated into mature spores. sscA mutant spores exhibited poor germination, and Tricine-SDS-PAGE analysis showed that the coat protein profile of the mutant differed from that of the wild type. Bands corresponding to proteins at 59, 36, 5, and 3 kDa were reduced in the sscA null mutant. Western blot analysis of anti-CotB and anti-CotG antibodies showed reductions of the proteins at 59 kDa and 36 kDa in the sscA mutant spores. These proteins correspond to CotB and CotG. By immunoblot analysis of an anti-CotH antibody, we also observed that CotH was markedly reduced in the sscA mutant spores. It appears that SscA is a novel spore protein involved in the assembly of several components of the spore coat, including CotB, CotG, and CotH, and is associated with spore germination.