A highly fluorinated SiO2 particle assembled, durable superhydrophobic and superoleophobic coating for both hard and soft materials

Robust Superhydrophobic Films Based on an Eco-Friendly Poly(l-lactic acid)/Cellulose Composite with Controllable Water Adhesion

Poly(l-lactic acid) (PLLA) featuring desirable biodegradability and biocompatibility has been recognized as one of the promising eco-friendly biomaterials. However, low crystallization and poor mechanical and chemical performances dramatically hamper its practical application. In this work, we report that functionalized cellulose/PLLA composite superhydrophobic stereocomplex films with controllable water adhesion and protein adsorption can be fabricated by a facile approach for the first time. First, cellulose is surface-modified by means of two silanization modification methods. Then, superhydrophobic cellulose/PLLA composite films are prepared through a solvent-evaporation-induced phase separation method. The two cellulose/PLLA composite films exhibit extreme water repellency but tunable water adhesion from sticky to slippery. The protein adsorption capacity of the cellulose/PLLA composite films can also be regulated. In addition, the stereocomplexation of the composite film provides excellent mechanical properties with an elongation at break of 22.36%, which is 237.8% higher than that of a pure PLLA film, which is more suitable for biomaterials. Furthermore, good biodegradability of the PLLA composite films in nature enables the bio-based composites as alternative materials to replace conventional petroleum-based polymers. The superhydrophobic films have also been demonstrated for many applications, including slippery surfaces, liquid transportation without loss, and antifouling.

Soft touchless sensors and touchless sensing for soft robots

Soft robots are characterized by their mechanical compliance, making them well-suited for various bio-inspired applications. However, the challenge of preserving their flexibility during deployment has necessitated using soft sensors which can enhance their mobility, energy efficiency, and spatial adaptability. Through emulating the structure, strategies, and working principles of human senses, soft robots can detect stimuli without direct contact with soft touchless sensors and tactile stimuli. This has resulted in noteworthy progress within the field of soft robotics. Nevertheless, soft, touchless sensors offer the advantage of non-invasive sensing and gripping without the drawbacks linked to physical contact. Consequently, the popularity of soft touchless sensors has grown in recent years, as they facilitate intuitive and safe interactions with humans, other robots, and the surrounding environment. This review explores the emerging confluence of touchless sensing and soft robotics, outlining a roadmap for deployable soft robots to achieve human-level dexterity.

Enhancing Textile Water Repellency with Octadecyltrichlorosilane (OTS) and Hollow Silica Nanoparticles

Superhydrophobic coatings have attracted substantial attention owing to their potential application in various industries. Conventional textiles used in daily life are prone to staining with water and household liquids, necessitating the development of water-repellent and stain-resistant coatings. In this study, we fabricated a highly water-repellent superhydrophobic PET fabric by using an eco-friendly water-based coating process. Fluorine-free octadecyltrichlorosilane (OTS) solutions with various wt.% of hollow silica (HS) nanoparticles were used to produce a superhydrophobic surface via a facile dip coating method. Our findings revealed that the incorporation of HS nanoparticles substantially increased the water contact angle, with higher concentrations resulting in enhanced water repellency and increased surface roughness. The treated fabrics had a remarkable water contact angle of 152.4° ± 0.8°, demonstrating their superhydrophobic fiber surface. In addition, the durability of these superhydrophobic properties was investigated via a laundry procedure, which showed that the fabrics maintained their water repellency even after 20 laundering cycles. EDX and XRD analyses confirmed that the morphological evaluations did not reveal any substantial structural alterations. Significantly, the fibers maintained their strength and durability throughout the testing, enduring only minor hollow SiO2 nanoparticle loss. This eco-friendly and cost-effective method holds great potential for application in apparel and other industries, offering an effective solution to resist water stains and improve performance in various contexts.

Multifunctional Amphiphobic Coating toward Ultralow Interfacial Adhesion of Hydrates

Hydrate adhesion is a challenging issue in some practical applications. However, most current anti-hydrate coatings fail to maintain their properties when subject to crude oil and corrosive contaminants. In addition, the effect of surface properties on the nucleation of hydrates is still unexplored from a microscopic perspective. In this study, a multifunctional amphiphobic PF/ZSM-5 coating consisting of 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane modified ZSM-5 zeolite (F/ZSM-5) and adhesive polyethersulfone was fabricated by the spraying method. The interfacial nucleation and adhesion of hydrates on substrates were studied from a microscopic perspective. The coating exhibited excellent repellencies to various liquids, including water, edible oil, liquid paraffin, vacuum pump oil, n-hexadecane, and crude oil. The tetrabutylammonium bromide (TBAB) hydrate is readily nucleated on the bare Cu surface. In contrast, the coated substrate effectively inhibited the hydrate nucleation on the surface and even reduced the adhesion force to 0 mN/m. Furthermore, this coating was fouling- and corrosion-resistant and can maintain an ultralow hydrate adhesion force even after immersion in crude oil or TBAB solution for 20 and 300 d, respectively. The durable anti-hydrate performance of the coating was attributed mainly to the unique architecture and excellent amphiphobic properties enabling stable air cushions between the solid-liquid interface.

Self-Powered, Long-Durable, and Highly Selective Oil-Solid Triboelectric Nanogenerator for Energy Harvesting and Intelligent Monitoring

Triboelectric nanogenerators (TENGs) have potential to achieve energy harvesting and condition monitoring of oils, the "lifeblood" of industry. However, oil absorption on the solid surfaces is a great challenge for oil-solid TENG (O-TENG). Here, oleophobic/superamphiphobic O-TENGs are achieved via engineering of solid surface wetting properties. The designed O-TENG can generate an excellent electricity (with a charge density of 9.1 µC m^-2 and a power density of 1.23 mW m^-2), which is an order of magnitude higher than other O-TENGs made from polytetrafluoroethylene and polyimide. It also has a significant durability (30,000 cycles) and can power a digital thermometer for self-powered sensor applications. Further, a superhigh-sensitivity O-TENG monitoring system is successfully developed for real-time detecting particle/water contaminants in oils. The O-TENG can detect particle contaminants at least down to 0.01 wt% and water contaminants down to 100 ppm, which are much better than previous online monitoring methods (particle > 0.1 wt%; water > 1000 ppm). More interesting, the developed O-TENG can also distinguish water from other contaminants, which means the developed O-TENG has a highly water-selective performance. This work provides an ideal strategy for enhancing the output and durability of TENGs for oil-solid contact and opens new intelligent pathways for oil-solid energy harvesting and oil condition monitoring.

Selective Fabrication of Robust and Multifunctional Super Nonwetting Surfaces by Diverse Modifications of Zirconia-Ceria Nanocomposites

The creation of surfaces with various super nonwetting properties is an ongoing challenge. We report diverse modifications of novel synthesized zirconia-ceria nanocomposites by different low surface energy agents to fabricate nanofluids capable of regulating surface wettability of mineral substrates to achieve selective superhydrophobic, superoleophobic-superhydrophilic, and superamphiphobic conditions. Surfaces treated with these nanofluids offer self-cleaning properties and effortless rolling-off behavior with sliding angles ≤7° for several liquids with surface tensions between 26 and 72.1 mN/m. The superamphiphobic nanofluid coating imparts nonstick properties to a solid surface whereby liquid drops can be effortlessly displaced on the coating with a near-zero tilt and conveniently lifted off using a needle tip, leaving no trace. Further, the superamphiphobic surface demonstrates good oil repellency toward ultralow surface tension liquids such as n-hexane and n-heptane. The superoleophobic-superhydrophilic surface repels oil droplets well regardless of whether it is in the air or underwater conditions. In addition, reaping the benefits of the ZrO₂-CeO₂ nanocomposites' photocatalysis feature, the superoleophobic-superhydrophilic coating exhibits self-cleaning ability by the degradation of color dyes. Modification of the wettability of substrates is carried out by a cost-effective and facile solution-immersion approach, which creates surfaces with hierarchical nano-submicron-scaled structures. The multipurpose coated surfaces have outstanding durability and mechanical stability. They also resist well high-temperature-high-pressure conditions, which will provide various practical applications in different fields, including the condensate banking removal in gas reservoirs or the separation of oil/water mixtures.

A robust surface with superhydrophobicity and underwater superoleophobicity for on-demand oil/water separation

Superhydrophobic and underwater superoleophobic surface combine the superiorities of the two opposite wettabilities. Generally, such a surface is constructed by hydrophilic areas and hydrophobic areas treated with fluorine-containing modifiers. However, the surface energy in a narrow range and poor bonding force between water-loving and water-repelling components make the surface fragile and its wettability unstable. Herein, we present a strategy to fabricate a robust surface with superhydrophobicity and underwater superoleophobicity. Hydrophilic aluminum phosphate as a binder can strongly interact with superhydrophobic titanium dioxide nanoparticles. Mixing the two ingredients to accurately control the surface energy in a narrow range and then spray coating, the superhydrophobic and underwater superoleophobic surfaces are conveniently prepared on diverse substrates. Under acid/base aqueous solution conditions, O₂-plasma etching, and sand impingement, the coatings remain superhydrophobic and underwater superoleophobic. Taking advantage of the wettability and robustness of coatings, the as-prepared membranes realize on-demand and multicycle separation under gravity without continuous external stimulus. Importantly, even after 100 sand impingement cycles, the treated membranes still maintain prominent separation performance.

Large-area fabrication of superhydrophobic micro-conical pillar arrays on various metallic substrates

Superhydrophobic micro-conical pillar arrays have huge application prospects, from anti-icing to oil/water separation, corrosion resistance, and water droplet manipulation. However, there is still a lack of versatile methods with high processing efficiency to fabricate superhydrophobic micro-conical pillar arrays on various metallic substrates. Herein, a nanosecond laser ablation technology with versatility and high processing efficiency was developed to fabricate large-area superhydrophobic micro-conical pillar arrays. The simulation and experiments indicated that the height and the pillar inclination angle of micro-conical pillars could be easily controlled by adjusting the nanosecond laser parameters or the tilted angles of metallic substrates. The fabricated superhydrophobic micro-conical pillar arrays not only showed good mechanical robustness and chemical stability but also easily reduced the contact time for an impinging water droplet, showing potential application prospects in anti-icing from freezing rain. This kind of method with versatility and high processing efficiency will promote the practical applications of superhydrophobic micro-conical arrays.

Effect of Silica Size and Content on Superamphiphobic Properties of Silica-Fluoropolymer Core-Shell Coatings

We present a facile approach to fabricate superamphiphobic surfaces by spray coating silica-fluoropolymer core-shell particles without substrate pretreatment with an additional binder resin. A series of SiO2@poly(1H,1H,2H,2H-heptadecafluorodecyl methacrylate) (SiO2@PFMA) core-shell particles with core particles of different sizes were prepared via thiol-lactam initiated radical polymerization (TLIRP). The surface of each SiO2 particle with an average particle size of 12, 80, 150, and 350 nm was modified with (3-mercaptopropyl) trimethoxysilane and used as a seed for TLIRP. The SiO2@PFMA particles with various SiO2 sizes and contents were coated on aluminum substrates by a spray gun and then thermally treated to form a stable, rough composite layer. During the spray coating, the core-shell particles were aggregated by rapid evaporation of the solvent and then irregularly adhered to the substrate resulting in hierarchical structures. In the case of SiO2@PFMAs with low SiO2 contents, the roughness created mainly by the polymer shell disappeared during heat treatment. However, the substrates coated with SiO2@PFMAs with high SiO2 contents maintained the roughness even after heat treatment. The core-shell particles prepared with 12 nm SiO2 formed a stable superamphiphobic surface. The water/hexadecane contact and sliding angles on an aluminum plate coated with SiO2@PFMA, prepared using 12 nm silica at 46 wt% silica content (12 nm-SiO2(46)@PFMA), were 178.5°/159.2° and 1°/7°, respectively. The cross-cut tape test showed that adhesion between the 12nm-SiO2(46)@PFMA and the aluminum substrate was classified as 5B. A glass surface spray-coated with the core-shell composite particles exhibited transparent superhydrophobicity and translucent superamphiphobicity by controlling the concentration of the coating solution.

Bionic smart recycled paper endowed with amphiphobic, photochromic, and UV rewritable properties

The single-use of large volumes of paper has become a serious issue which is depleting our resources and damaging the environment. It is of great significance and challenging to adopt simple, reasonable and practical methods to prepare functional recyclable paper. In this article, inspired by pleochromatic creatures and plant leaves' special wettability, a series of photochromic amphiphobic recycled paper (PAR _i ) products was successfully prepared by adding gourd-like modified tungsten trioxide (MTT) to waste paper pulp. The results show that PAR_2-7 has excellent lyophobic performance and amazing photochromic properties. It is worth noting that PAR₇ has an impressive amphiphobic behavior, and its surface water contact angle (WCA) and oil contact angle (OCA) are 146 ± 1° and 137 ± 1°, respectively. It can withstand continuous ultraviolet light irradiation for 60 h, indicating excellent resistance to ultraviolet radiation. Most importantly, the reversible photochromic properties of PAR₇ make it possible to write repeatedly on the surface by using ultraviolet light. In short, the performance of the prepared PAR is stable and superior, which can not only alleviate paper waste, but also means it has great potential in the fields of decoration, packaging, and banknote anti-counterfeiting technology.

Robust Superamphiphobic Coatings Based on Raspberry-like Hollow SnO2 Composites

Good mechanical and chemical stabilities are the key factors for the wide application of superhydrophobic surfaces. In this work, we first prepared raspberry-like hollow structured SnO₂ nanoparticles using a simple hydrothermal method, followed by an annealing step. Then, the intrinsic raspberry-like hollow SnO₂ nanoparticles were combined with hydrophilic SiO₂ nanoparticles to construct rough surfaces with suitable hierarchical structures, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS-17) was used as a hydrophobic modifier of SnO₂, while epoxy resin was used as an adhesive to prepare a superamphiphobic coating with good stability and durability. Such a coating can be applied on various substrates using a simple spray-coating or drop-coating method. The water contact angle and diiodomethane contact angle of the coating could reach up to ∼165 and ∼151°, respectively. After various chemical and mechanical stability tests including hot water treatment, salt water corrosion, strong adhesive tape peeling, and kneading, the coatings still remained amphiphobic. The facile fabrication of the robust superhydrophobic coating has great potential for applications in real life and industrial production.

Robust superhydrophobic polyurea@cellulose nanocrystal coating

A multifunctional superhydrophobic PU@CNC composite coating with self-cleaning properties and mechanical durability was fabricated using a facile spraying method.