High-Transparency, Self-Standable Gel-SLIPS Fabricated by a Facile Nanoscale Phase Separation

Slippery liquid-infused porous surfaces (SLIPSs) that were both highly transparent and free-standing (self-standability) were fabricated by an extremely simple process using non-solvent-induced phase separation (NIPS) of a poly­(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (PVDF-HFP)/di-<i>n</i>-butyl phthalate solution. We call these “Gel-SLIPS” because the porous PVDF-HFP film fabricated using the NIPS process has been used as a gel electrolyte in a lithium-ion battery. In previous reports, SLIPS fabrication required complex processes, high annealing temperatures, and drying. Gel-SLIPS can be fabricated from the adjusted solution and the lubricant at room temperature and pressure in 5 min by squeegee, cast, or dip methods. NIPS is based on a quick phase separation process in situ, and reduction of the surface energy is not required because of the considerable fluorine in PVDF-HFP. Moreover, because of the flexible nanonetwork structure of PVDF-HFP, Gel-SLIPS exhibited self-standability and high transmittance (>87% at 600 nm). Gel-SLIPS is thus highly versatile in terms of the fabrication process and film characteristics

Gradient Functional Characteristic of Polymer/Nanoparticle Stacks on a Polyethylene Naphthalate Film

Gradient refractive index layered antireflection (GRIL-AR) films were fabricated using a layer-by-layer (LbL) self-assembly method. As a substrate, we chose indium tin oxide–polyethylene naphthalate (ITO–PEN; the refractive index of PEN is 1.77). We deposited the GRIL-AR films on the PEN side of ITO–PEN, and the refractive index was gradually decreased from 1.59 to 1.35 by alternating deposition cycles of SiO₂ as a low-refractive-index material and TiO₂ as a high-refractive-index material. In the LbL process, each material was movable because it was coated in wet conditions; this may have led to fabrication of the gradient refractive index. When poly­(ethylene imine) (PEI) was compared with poly­(diallyldimethylammonium chloride), antireflection (AR) using PEI showed high abrasion durability because of the loopy structure of the polymer and a high polymer ratio in the film. With the drying process, the prepared film showed enhanced abrasion durability. GRIL-AR on ITO–PEN showed broad-band AR properties

Performance of a time domain reflectometer in the detection of soil moisture variations.

O objetivo do trabalho foi avaliar o desempenho do reflectômetro no domínio do tempo (TDR) comparativamente ao tensiômetro com manômetro de mercúrio (considerado como instrumento padrão), dando-se ênfase na sensibilidade de detecção de variações na umidade do solo sob condições de molhamento e secagem. Foi instalado um experimento em um solo classificado como Nitossolo Vermelho distrófico latossólico de textura muito argilosa, localizado próximo ao Posto Meteorológico do Departamento de Ciências Exatas, ESALQ/USP, Piracicaba (SP), Brasil, 22 o 42’ 30’’ de latitude sul e 47 o 38’ 00’’ de longitude oeste. Com dados de um ensaio de determinação da condutividade hidráulica do solo pelo Método do Perfil Instantâneo, de um período de secagem e de inundações intermitentes do solo, analisou-se a concordância entre a constante dielétrica obtido pelo TDR e o potencial matricial da água no solo obtido pelo tensiômetro, além dos valores de umidade volumétrica obtidos pelas mesmas técnicas. Concluiu-se que o desempenho do TDR foi superior ao do tensiômetro sob condições de secagem do solo e na detecção de variações de umidade.The performance of a time domain-reflectometer (TDR) was compared with a mercury tensiometer (considered to be the norm), emphasizing the detection of variations in soil water content under wetting and drying conditions (as in instantaneous profile method to determine soil hydraulic conductivity). An experiment was performed in a Nitossolo Vermelho distrófico latossólico argiloso (Brazilian classification system), close to the meteorological observatory of the ESALQ/USP, Piracicaba (SP), Brazil, latitude 22 o 42’30’’ S, longitude 47 o 38’00’’ W. Data of matric potential, dieletric constant and water content during a dry period and water application were analyzed. The TDR cable tester was better than the tensiometer to detect the soil moisture variation

A Biocompatible Slippery Surface Based on a Boehmite Nanostructure with Omniphobicity for Hot Liquids and Boiling Stability

Omniphobic surfaces have attracted much attention and have a lot of applications in various fields. In particular, the application of omniphobicity to containers of prepackaged foods such as curry is extremely important for reducing food waste because they are especially liable to remain in the container owing to their high viscosity. To realize such application, the surface must be biocompatible to prevent health damage to the human body. However, few omniphobic surfaces with biocompatibility have been developed. Here, we present a silicone oil-immobilized biocompatible slippery surface with omniphobicity. A biocompatible base layer to immobilize the silicone oil as a lubricant was fabricated by combining a boehmite nanostructure and silicone oil grafting through thermal treatment. The slippery surface demonstrated omniphobicity not only for room-temperature liquids but also for high-temperature liquids including hot liquid foods. In addition, the surface exhibited long-term stability against boiling in hot water. Moreover, the surface could be fabricated within an hour. We believe that because of its excellent biocompatibility and omniphobicity, this surface will be applied to not only food containers but also various other applications

Porous Transition of Polyelectrolyte Film through Reaction-Induced Phase Separation Caused by Interaction with Specific Metal Ions

We describe a novel method for the simple and eco-friendly fabrication of porous polyelectrolyte films. A polyelectrolyte with many amine groups undergoes structural transformation from a dense to a porous structure upon immersion in a specific metal ion solution. The porous transition was the result of a reaction-induced phase separation, which was caused by the formation of new bonds between the polyelectrolyte and metal ions. This method enables control of the pore size of the porous structure in the nanoscale (54 nm) to microscale (1.63 μm) range through variation of the concentration or type of metal ions in the solution. To the best of our knowledge, this is the first report illustrating wide-range control of the pore size of a porous polyelectrolyte structure achieved by metal ions. These porous polyelectrolyte films with adjustable pore size and metastable metal ions can be employed in applications such as adsorption and catalysis

Electrothermally Triggered Broadband Optical Switch Films with Extremely Low Power Consumption

Smart films with transmittance switching capabilities based on thermal stimuli are widely used in many optoelectronic applications. Despite the development of stably switchable materials, transition temperature control and broadband stepwise transmittance switching remain challenging topics. Additionally, reduction of the energy consumption during switching is also required. Here, we introduce an electrothermally driven film with switchable transmittance produced by stacking paraffin-immobilized polydimethylsiloxane gel on a transparent heater based on an aligned Cu/Ni network. The film shows stepwise transmittance switching capability with extremely low power consumption because of the controlled melting point of paraffin and the high-efficiency transparent heater

Porous Surface Structure Fabricated by Breath Figures that Suppresses <i>Pseudomonas aeruginosa</i> Biofilm Formation

As colonizers of medical-device surfaces, Pseudomonas aeruginosa strains present a serious source of infection and are of major concern. In this study, we fabricated films with porous surfaces by breath figures that disturb mergence by bacterial attachment, thereby impeding biofilm development. Previous studies have shown that microtopography prevents the development of P. aeruginosa biofilms. Accordingly we indented surfaces with patterns of micrometer-sized pores using breath figures at ordinary temperatures and pressures. The antimicrobial effect of surface figures was experimentally investigated by controlling the surface structure. The results suggested that pores of 5–11 μm in diameter effectively inhibit bacterial activity. It appears that biofilm development is precluded by the decreased contact area between the films and bacteria

Trace Material Capture by Controlled Liquid Droplets on a Superhydrophobic/Hydrophilic Surface

A liquid droplet in contact with a superhydrophobic surface can be used to collect dissolved trace materials after evaporating the solvent. This process effect enhances detection limits, but a liquid droplet easily rolls off a superhydrophobic surface. Keeping it at a specific collecting spot area is challenging. Here the means for controlling and capturing a liquid droplet on a superhydrophobic surface is demonstrated. To induce a liquid droplet to a collecting spot, its rolling direction was controlled by two superhydrophobic fabric guides. The liquid droplet was then captured by hydrophilic polymer and hydrophilic nanoparticles at the measuring spot. After removing the solvent, the trace compounds were evaluated with a colorimetric analysis visible to the naked eye

Biocompatible Slippery Fluid-Infused Films Composed of Chitosan and Alginate via Layer-by-Layer Self-Assembly and Their Antithrombogenicity

Antifouling super-repellent surfaces inspired by Nepenthes, the pitcher plant, were designed and named slippery liquid-infused porous surfaces (SLIPS). These surfaces repel various simple and complex liquids including water and blood by maintaining a low sliding angle. Previous studies have reported the development of fluorinated SLIPS that are not biocompatible. Here, we fabricated fluid-infused films composed of biodegradable materials and a biocompatible lubricant liquid. The film was constructed using a combination of electrostatic interactions between chitosan and alginate and hydrogen-bonding between alginate and polyvinylpyrrolidone (PVPON) via the layer-by-layer self-assembly method. After chitosan and alginate were cross-linked, the PVPON was removed by increasing the pH to generate porosity from the deconstruction of the hydrogen-bonding. The porous underlayer was hydrophobized and covered by biocompatible almond oil. Blood easily flowed over this biodegradable and biocompatible SLIPS without leaving stains on the surface, and the material is environmentally durable, has a high transmittance of about 90%, and is antithrombogenic. The results of this study suggest that this SLIPS may facilitate the creation of nonfouling medical devices through a low-cost, eco-friendly, and simple process

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