Flexible and Superhydrophobic Composites with Dual Polymer Nanofiber and Carbon Nanofiber Network for High-Performance Chemical Vapor Sensing and Oil/Water Separation

Durable superhydrophobic surface in wearable sensors: From nature to application

The current generation of wearable sensors often experiences signal interference and external corrosion, leading to device degradation and failure. To address these challenges, the biomimetic superhydrophobic approach has been developed, which offers self-cleaning, low adhesion, corrosion resistance, anti-interference, and other properties. Such surfaces possess hierarchical nanostructures and low surface energy, resulting in a smaller contact area with the skin or external environment. Liquid droplets can even become suspended outside the flexible electronics, reducing the risk of pollution and signal interference, which contributes to the long-term stability of the device in complex environments. Additionally, the coupling of superhydrophobic surfaces and flexible electronics can potentially enhance the device performance due to their large specific surface area and low surface energy. However, the fragility of layered textures in various scenarios and the lack of standardized evaluation and testing methods limit the industrial production of superhydrophobic wearable sensors. This review provides an overview of recent research on superhydrophobic flexible wearable sensors, including the fabrication methodology, evaluation, and specific application targets. The processing, performance, and characteristics of superhydrophobic surfaces are discussed, as well as the working mechanisms and potential challenges of superhydrophobic flexible electronics. Moreover, evaluation strategies for application-oriented superhydrophobic surfaces are presented.

Nanomaterial grafted polymorphous activated carbon cloth surface for antibacterial, capacitive deionization and oil spill cleaning applications

This work reports the development of multifunctional or polymorphous surfaces using zinc oxide (ZnO) nanorods, silica (SiO2), and fluoropolymer functionalization in a sequential process. Firstly, zinc oxide nanorods were grown on activated carbon cloth (ACC) using a simple low-temperature synthesis process. ZnO nanorods-coated ACC substrate was applied to investigate the antimicrobial properties, and the results showed inhibition of 50% for Escherichia coli (E.coli) and 55% for Bacillus subtilis (B.subtilis) over 48 h of incubation time. Subsequent in-situ modification of silica nanoparticles like layer on ZnO nanorods-coated ACC surface was developed and used as an electrode for brackish water desalination in a capacitive deionization system. ZnO-SiO2 modified ACC surface enhanced the desalination efficiency by 1.6 times, the salt removal rate (SRR) by threefold, and the durability (fouling prevention) for long-term usage compared to pristine ACC. Further modification of the ZnO-SiO2-ACC surface using fluoropolymer rendered the surface superhydrophobic and oleophilic. Vegetable (1.4 g/g) and crude oil (1.6 g/g) adsorption capacities were achieved for modified surface which was 70% enhancement compared with pristine ACC. The dynamic oil spill adsorption test exhibited the complete removal of oil spills on water surfaces within a few seconds, suggesting a potential application in oil spill cleaning.

Biomass poplar catkin fiber-based superhydrophobic aerogel with tubular-lamellar interweaved neurons-like structure

Superhydrophobic aerogels are attractive candidates in controlling oil spills. The major challenges for existing aerogels are the construction of mechanical endurance as well as accessible of building materials. Herein, a newfangled biomass superhydrophobic aerogel (M-PCF/CS) with both superior compressibility and oil caption speed is fabricated by assembling poplar catkin fiber (PCF) hollowed-out shell of 330 nm and chitosan (CS) into tubular-lamellar interweaved neurons-like structure. The resultant aerogels (porosity ~ 96.12%), with flexuous PCF as the elastic buffer and second-pore capillaries, exhibit large longitudinal and transverse compressibility, endurable fatigue tolerance, fast oil sorption rate with a capacity of 28.8-78.1 g/g at 5-25 s. In parallel, the aerogels are tolerant of NaCl, UV radiation, and organic solvents without superhydrophobic variation and a case of oil spill remediation via pump-supported experiment shows that the aerogels facilely achieve continuous oil recycling from seawater by 23052-43956 L·m^-2·h^-1. Furthermore, the resultant M-PCF/CS, with assistance of an oscillator, can be applied to separate oil/water emulsions with efficiency of 98.07-99.11%. The successful fabrication of this material provides a new design strategy for the construction of mechanically robust aerogels for speedy and economical cleanup of oil pollutants from water.

Superhydrophobic, electrically conductive and multifunctional polymer foam composite for chemical vapor detection and crude oil cleanup

The leakage of chemicals (either vapors or liquids) severely threatens the environment and even people's health. It remains a great challenge to develop multifunctional and durable materials that can not only detect the chemical vapors but also clean up the liquid chemicals especially high viscous crude oil. Here, a superhydrophobic and conductive foam composite (SCFC) is prepared by decorating carbon black nanoparticles (CBNPs) onto the skeleton of the pre-swollen polymer foam under the assistance of ultrasonication. The CBNPs are firmly embedded onto the skeleton surface, exhibiting a strong interfacial adhesion and hence excellent surface stability and durability. The SCFC possesses stable vapor sensing behavior and can detect various chemical vapors with a low detection limit and good cycling performance. When used for oil/water separation, the SCFC has large oil adsorption capacity for different oils with excellent reusability. Also, the outstanding photo-thermal conversion performance of the SCFC can be used to significantly reduce the oil viscosity and hence realize efficient cleanup of the crude oil. The multifunctional SCFC has promising applications in the field of environment protection, flexible electronics, etc.

Biomass-derived oriented neurovascular network-like superhydrophobic aerogel as robust and recyclable oil droplets captor for versatile oil/water separation

Using tubular kapok fibers (KF) and sodium alginate (SA) as the natural building block, we put forward a novel oriented neurovascular network-like superhydrophobic aerogel with robust dry and wet compression resilience by directional freeze-drying and chemical vapor deposition. In the block, SA forms aligned channel structures providing space for rapid oil transmission, while KF serves as vascular-like capillaries acting as instant "tentacle" to capture the tiny oil droplets in water, facilitating fascinating oil capture efficiency for versatile oil/water separation, The aerogel after dry and wet compression (under a strain of 60%) can recover 96.0% and 97.3% its original, respectively, facilitating stable oil recovery (81.1-89.8%) by squeezing, high separation efficiency (99.04-99.64%) and permeation flux separating oil contaminants from water. A pump-supported experiment shows the aerogel efficiently collecting oil contaminants from the water's surface and bottom by 11503-25611 L·m^-2·h^-1. Particularly, the aerogel as robust oil droplets captor facilely achieves isolation of 99.39-99.68% emulsified oils from oil/water emulsions by novel oil trapping mechanism which simply involves exerting kinetic energy on emulsified oils through repeated oscillation, potentially indicating a simple and efficient alternative to membrane-based oily wastewater remediation via filtration.

3D MXene Sponge: Facile Synthesis, Excellent Hydrophobicity, and High Photothermal Efficiency for Waste Oil Collection and Purification

Photothermally assisted superhydrophobic sponges play a vital role in the fields of waste oil collection, oil purification, and solar desalination. However, the widely reported superhydrophobic sponges with photothermal efficiency usually suffer from a post-/premodification process of harmful materials, high loading content of photothermal agents, and low photothermal efficiency. Herein, an MXene-based melamine sponge (MS) was facilely fabricated by hydrogen bonding interaction between the amino groups on the skeleton of the MS and the polar groups on the surface of the as-exfoliated 2D MXene Ti₃C₂T_x nanosheets. Interestingly, the as-fabricated MXene sponge exhibits excellent hydrophobicity and high photothermal efficiency under an extremely low loading of MXene Ti₃C₂T_x nanosheets (0.1 wt %). Moreover, the highly hydrophobic sponge also possesses a high oil absorption capacity as high as 176 times of its own weight and keeps stable under multiple absorption/desorption cycling tests. Surprisingly, the surface temperature of the MXene sponge can quickly reach 47 °C under illumination and has good reproducibility during multiple light on/off cycles. The excellent photothermal performance and large oil absorption capacity of the MXene sponge endow the highly hydrophobic sponge with fast solvent evaporation speed and high-purity waste oil collection (99.7 wt % dichloromethane) under illumination, which holds great promise for oil/water separation, leaked oil collection, and photo-driven waste oil collection and purification applications. It is envisioned that this work can open a new strategy for new designs of 3D multifunctional sponges for high-performance waste oil collection and purification.

Recent Progress of Nanostructured Sensing Materials from 0D to 3D: Overview of Structure-Property-Application Relationship for Gas Sensors

Along with the progress of nanoscience and nanotechnology, nanomaterials with attractive structural and functional properties have gained more attention than ever before, especially in the field of electronic sensors. In recent years, the gas sensing devices have made great achievement and also created wide application prospects, which leads to a new wave of research for designing advanced sensing materials. There is no doubt that the characteristics are highly governed by the sensitive layers. For this reason, important advances for the outstanding, novel sensing materials with different dimensional structures including 0D, 1D, 2D, and 3D are reported and summarized systematically. The sensing materials cover noble metals, metal oxide semiconductors, carbon nanomaterials, metal dichalcogenides, g-C₃ N₄ , MXenes, and complex composites. Discussion is also extended to the relation between sensing performances and their structure, electronic properties, and surface chemistry. In addition, some gas sensing related applications are also highlighted, including environment monitoring, breath analysis, food quality and safety, and flexible wearable electronics, from current situation and the facing challenges to the future research perspectives.