Mizuki Tenjimbayashi

Asymmetric Superhydrophobic/Superhydrophilic Cotton Fabrics Designed by Spraying Polymer and Nanoparticles

Inspired by the special wettability of certain natural life forms, such as the high water repellency of lotus leaves, many researchers have attempted to impart superhydrophobic properties to fabrics in academic and industrial contexts. Recently, a new switching system of wettability has inspired a strong demand for advanced coatings, even though their fabrication remains complex and costly. Here, cotton fabrics with asymmetric wettability (one face with natural superhydrophilicity and one face with superhydrophobicity) were fabricated by one-step spraying of a mixture of biocompatible commercial materials, hydrophobic SiO2 nanoparticles and ethyl-α-cyanoacrylate superglue. Our approach involves controlling the permeation of the fabric coatings by changing the distance between the fabric and the sprayer, to make one side superhydrophobic and the other side naturally superhydrophilic. As a result, the superhydrophobic side, with its high mechanical durability, exhibited a water contact angle of 154° and sliding angle of 16°, which meets the requirement for self-cleaning ability of surfaces. The opposite side exhibited high water absorption ability owing to the natural superhydrophilic property of the fabric. In addition, the designed cotton fabrics had blood absorption and clotting abilities on the superhydrophilic side, while the superhydrophobic side prevented water and blood permeation without losing the natural breathability of the cotton. These functions may be useful in the design of multifunctional fabrics for medical applications.

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.

Highly durable superhydrophobic coatings with gradient density by movable spray method

Superhydrophobic surface is expected to be applied in anti-fouling, anti-icing, and anti-bacterial. However, practical use is interrupted by low mechanical strength, time-consuming process, and limited coating substrate. Here highly durable superhydrophobic coatings were prepared by simple and novel spraying method, which sprays with changing the “spray distance between substrate and spray” (SD), named “movable spray method.” We prepared the solution that changes wettability and durability with spraying distance by mixing SiO2 nanoparticles and ethyl alpha cyanoacrylate polymer (EAC). Then, we evaluated the chemical components and surface morphologies of each spraying distance coatings (0 ∼ 50 cm) by XPS, SEM, and laser scanning microscope. It revealed that surface roughness and SiO2/EAC ratio increased as the SD increases. Thus, durable superhydrophobic coatings were designed by spraying with increasing SD gradually. Glow discharge-optical emission spectrometry analysis revealed that designed coatings sh...

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.

Determination of blood potassium using a fouling-resistant PVDF–HFP-based optode

Monitoring potassium levels in blood is a significant aspect of clinical analysis. For this reason, polymeric bulk optodes have received much attention for their use in portable and easy-to-use analysis systems in situ determination without additional calibration. However, blood contamination on the detection area of the sensor can hinder accurate sensing and also increases risk of infection from the wounds. In this paper, we report a system for determination of potassium in blood which has the additional advantage of being blood-fouling resistant. We have replaced the generally used poly(vinyl chloride) (PVC) with hydrophobic fluorinated poly(vinylidene fluoride–hexafluoropropylene) (PVDF–HFP) for preparation of a polymeric bulk optode. Sensing ability in the visual range of the polymeric bulk optode was retained despite the variation of the polymer matrix. These polymeric bulk optodes are suitable for potassium determination in blood with the PVDF–HFP-based optode possessing better blood antifouling properties than the PVC-based optode. The blood monitoring system described here represents the basis for functionalization of the optode toward safe and easily implementation in blood and in situ sensing applications.

Electrospun nanofiber SLIPS exhibiting high total transparency and scattering

Antifouling coatings are important in fields such as mobility, architecture, power generation devices, and medical devices, where energy efficiency is required to be maximized. Slippery liquid-infused porous surfaces (SLIPS) are an antifouling approach inspired by nature from the pitcher plant, and have recently received widespread attention in many fields. SLIPS can repel various liquids, including organic solvents with low contact angle hystereses, but require further development to extend their application. We previously reported a fast and straight-forward process for preparing SLIPS called Gel-SLIPS. SLIPS were prepared by the non-solvent-induced phase separation (NIPS) of a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF–HFP)/di-n-butyl phthalate solution. In the current study, SLIPS were prepared by electrospinning to give nanofiber SLIPS. These exhibited high scattering (50%), high total transmittance (93.2%), and a low sliding angle (≤10°). These properties resulted from the nanofiber non-woven structure of the PVDF–HFP. Nanofiber SLIPS provide control over scattering by altering the under layer density, all while maintaining the total transparency. These characteristics are useful for energy efficient optical devices such as solar cells and street lighting.

A Lubricant-Sandwiched Coating with Long-Term Stable Anticorrosion Performance.

Lubricant-infused surface(s) (LIS) bioinspired by the Nepenthes pitcher plant are receiving enormous attention owing to their excellent hydrophobicity as well as their self-healing ability. Thus, they have been applied as anticorrosion coatings. However, the loss of lubricant mediated by vapor or other liquids deteriorates their functions. Herein, we introduce a lubricant-inserted (sandwiched) microporous triple-layered surface (LIMITS) that prevents the sudden loss of lubricant. The sandwiched lubricant gradually self-secretes toward the surface, resulting in long-term stability even under water. The LIMITS prevented the corrosion of the Fe plate for at least 45 days, which is much superior to a conventional LIS coating. This work opens an avenue for the application of slippery coating materials that are stable under water and will also promote the development of anticorrosion coating in various industries.

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.