Takeshi Matsubayashi

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.

A facile method of synthesizing size-controlled hollow cyanoacrylate nanoparticles for transparent superhydrophobic/oleophobic surfaces

Hollow nanoparticles have broad technological implications in a wide range of applications. Particularly, they have attracted great attention as functional coatings in applications such as optical devices, which have an optical transparency derived from a low refractive index. However, creating a facile and versatile method that can accurately control the hollow nanoparticle size has proven extremely challenging. Herein, we report a simple, instantly complete, one-pot method, designated the supersaturated gas-cored instant polymerization (SGCIP) method, to synthesize size-controlled hollow cyanoacrylate nanoparticles (HCNPs). The SGCIP method uses supersaturated gas created by mixing two solvents (water and acetone) and the instant polymerization of cyanoacrylate, whereby it demonstrates facile control of the particle diameters ranging from 13 to 1830 nm reproducibly by simply changing the solvent ratio. Moreover, a unique phase transition (from network to particle formation) is observed during the adjustment of the solvent ratio. As a one-concept application, transparent superhydrophobic/oleophobic coatings are achieved by self-assembly of the HCNPs and silanization. The successful synthesis of such fascinating materials may also provide new insights into the design and development of functional hollow nanoparticles for various applications.

Facile design of plant-oil-infused fine surface asperity for transparent blood-repelling endoscope lens

Minimally invasive medical operations, especially endoscope operations, have attracted much attention and play a major role in modern medicine. Endoscope operations are superior to decrease incisions, enabling good post-operation progress. However, during its implementation, blood adheres to the lens of the endoscope, resulting in obstructed vision. This prolongs the operation time and causes the patient to gain weight. Hence, we developed a blood-repelling and transparent material for coating the surface of an endoscope lens. The coating material was produced from plant oil and a rough material for trapping the oil. Edible plant oil was particularly used to enable application to medical devices. A fine surface asperity was achieved by a one-dip treatment, which also enhanced the capillary force and durability of the oil under a water shower. The application of the developed coating material to an endoscope lens in an animal experiment enabled the effective repulsion of blood and other body fluids, the maintenance of a clear vision, and high transmittance. The developed coating material promises to contribute to the achievement of antifouling surfaces in medical 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 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.

A superrepellent coating with dynamic fluorine chains for frosting suppression: effects of polarity, coalescence and ice nucleation free energy barrier

Ice formation on surfaces is a serious issue in many different fields in terms of function, safety, and cost of operation in human life. Hydrophobic coating technology is one of the effective ways to prevent ice formation. Previous studies focused on the effects of surface structure and surface chemical modification on anti-icing ability. However, only a few studies have clarified a method to inhibit the initial formation of ice on surfaces; in addition, an effective mechanism for anti-frosting has not been identified as yet. Here, hydrophobic smooth surface coatings using three coupling agents with low surface energy and different molecular chain dynamics were fabricated. The surface roughnesses were lower than 1 nm. The fluorocarbon-based coatings delayed frost formation compared with the uncoated surface until −6 °C. We explored why the coating surface prevented frost formation and the effects of surface chemical modification on frost resistance from the viewpoint of heat exchange contact area during droplet coalescence, ice nucleation free energy barrier, polarity and polarizability of the coated surface.