A Hydrophobic Self-Repairing Power Textile for Effective Water Droplet Energy Harvesting

Triboelectric nanogenerators (TENGs) are useful for harvesting clean and widely distributed water droplet energy with high efficiency. However, the commonly used polymer films in TENGs for water droplet energy harvesting have the disadvantages of poor breathability, poor skin affinity, and irreparable hydrophobicity, which greatly hinder their wearable uses. Here, we report an all-fabric TENG (F-TENG), which not only has good air permeability and hydrophobic self-repairing properties but also shows effective energy conversion efficiency. The hydrophobic surface composed of SiO₂ nanoparticles and poly(vinylidenefluoride-co-hexafluoropropylene)/perfluorodecyltrichlorosilane (PVDF-HFP/FDTS) exhibits a static contact angle of 157° and displays excellent acid and alkali resistance. Because of its low glass transition temperature, PVDF-HFP can facilitate the movement of FDTS molecules to the surface layer under heating conditions, realizing hydrophobic self-repairing performance. Furthermore, with the optimized compositions and structure, the water droplet F-TENG shows 7-fold enhancement of output voltage compared with the conventional single-electrode mode TENG, and a total energy conversion efficiency of 2.9% is achieved. Therefore, the proposed F-TENG can be used in multifunctional wearable devices for raindrop energy harvesting.

Highly Hydrophobic Cotton Fabrics Modified by Poly(methylhydrogen)siloxane and Fluorinated Olefin: Characterization and Applications

Highly hydrophobic cotton fabrics were obtained with poly(methylhydrogen)siloxane (PMHS) and a further fluorinated olefin modification. The chemical structures and microstructures of PMHS-modified cotton fabrics were characterized, and application of the resultant cotton fabrics in stain resistance and oil–water separation was demonstrated. PMHS chains with very low surface energy were grafted onto cotton fabric by the dehydrogenation reaction between –Si–H of PMHS and –OH groups of cotton fabric at room temperature. The water contact angle of PMHS-modified cotton fabric was 141.7°, which provided the modified cotton fabric with good stain resistance to waterborne pollutants. The separation efficiency of diesel from water was higher than 92% for 20 repeatable separation cycles. A further improvement in stain resistance to oil was also demonstrated by a further addition reaction of 1H,1H,2H-perfluoro-1-decene with PMHS-modified cotton fabric.

Environmentally benign non-wettable textile treatments: A review of recent state-of-the-art

Among superhydrophobic materials, non-wettable textiles are probably the ones that come in contact or interact with the human body most frequently. Hence, textile treatments for water or oil repellency should be non-toxic, biocompatible, and comply with stringent health standards. Moreover, considering the volume of the worldwide textile industry, these treatments should be scalable, sustainable, and eco-friendly. Due to this awareness, more and more non-wettable textile treatments with eco-friendly processes and green or non-toxic chemicals are being adopted and reported. Although fluorinated alkylsilanes or fluorinated polymers with C8 chemistry (with ≥ 8 fluorinated carbon atoms) are the best performing materials to render textiles water or oil repellent, they pose substantial health and environmental problems and are being banned. For this reason, water/solvent-borne, C8-free vehicles for non-wettable treatment formulations are probably the only ones that can have commercialization prospects. Hence, researchers have come up with a variety of new, non-toxic, green formulations and materials to render fabrics liquid repellent that constitute the focus of this review paper. As such, this review article discusses and summarizes recent developments and techniques on various sustainable superhydrophobic treatments for textiles, with comparable performance and durability to formulations based on fluorinated C8 compounds. The current state-of-the-art technologies, potential commercialization prospects, and relevant limitations are discussed and summarized with examples. The review also attempts to indicate promising future strategies and new materials that can transform the process for non-wettable textiles into an all-sustainable technology.

Fabrication of superhydrophobic coatings with self-cleaning properties on cotton fabric based on Octa vinyl polyhedral oligomeric silsesquioxane/polydimethylsiloxane (OV-POSS/PDMS) nanocomposite

HYPOTHESIS

Wetting behavior of solid surfaces plays an important role in various industrials and even daily life applications. Controlling the surface wettability through fabricating strongly hydrophilic or hydrophobic properties is achieved by tailoring surface topography and chemical composition. Polyhedral oligomeric silsesquioxanes (POSSs) are a class of hybrid materials with the possibility of hydrophobicity enhancement through simultaneous increase in surface roughness and reduction of surface energy.

EXPERIMENTS

In this study, octavinyl-POSS (OV-POSS) structures were utilized in fabrication of superhydrophobic cotton fabric. Coating was successfully performed through creating a two-layer topography via spraying method. In brief, surface roughness was enhanced by spraying a base layer of TiO₂ sol over the surface followed by applying a nanocomposite layer composed of 0.02 wt% of POSS in polydimethylsiloxane (PDMS).

FINDINGS

It was observed that, water contact angle (WCA) of pristine and TiO₂ coated fabric was enhanced from 0° up to ∼168° using 0.02 wt% OV-POSS/PDMS nanocomposite with a water sliding angle (WSA) of <10°. According to the results, environmentally friendly nature of precursors, high thermal, mechanical and chemical stability, self-cleaning and anti-adhesion propertiesof the as-prepared coating and simple preparation method with no special post-treatment requirement, confirm that the as-prepared coating is perfect candidate for large-scaled applications.

One-pot fabrication of durable antibacterial cotton fabric coated with silver nanoparticles via carboxymethyl chitosan as a binder and stabilizer

In this article, durable antimicrobial cotton fabric was prepared by a one-pot modification process using a colloidal solution of silver nanoparticles (Ag NPs) stabilized by carboxymethyl chitosan (CMC). Due to coordination bonds between the amine groups of CMC and the Ag NPs and the ester bonds present between the carboxyl groups of CMC and the hydroxyl groups of cellulose, the Ag NPs were tightly immobilized onto the cotton fiber surface. As a result, the Ag NPs that were adhered on the cotton fabrics have uniform dispersion and small size, ranging from 10 nm to 80 nm. This provides the cotton fabric with remarkable and durable antibacterial activity against both S. aureus and E. coli. After 50 laundering cycles, the bacterial reduction rate (BR) for the modified cotton fabric remained over 94%. This method is simple, and it is particularly suitable for the industrial finishing process.

Excellent binding effect of l-methionine for immobilizing silver nanoparticles onto cotton fabrics to improve the antibacterial durability against washing

Silver nanoparticles (Ag NPs) have outstanding antimicrobial effects, but their weak adhesive force onto cotton fiber surfaces often causes undesired silver loss from antibacterial fabrics, diminishing antibacterial durability, and even leading to environmental and health risks. To improve adhesion of the Ag NPs, various strategies have been tried, but achieving long-term antibacterial effectiveness still remains challenging. Here, l-methionine is proposed as a binder reagent because it has low toxicity towards mammalian cells and has a methyl group to enhance its coordination ability. The antibacterial cotton fabric was fabricated via a very simple pad-dry-cure process: after dipping a cotton fabric in an l-methionine solution followed with heating for esterification, Ag NPs are formed via the reaction of silver nitrate with sodium borohydride. The resulting cotton fabric exhibits an excellent antibacterial property and laundering durability. Its bacterial reduction rates (BR) against both S. aureus and E. coli remained over 97% even after 90 consecutive laundering cycles. Moreover, the modification causes insignificant damage to cotton's characteristics, such as tensile breaking strength, water absorptivity, and vapor permeability.

Single-faced flame resistance of cotton fabrics modified via mist copolymerization

Mist copolymerization for fabricating single-sided flame retardant cotton fabrics.

Recent Progress in Fabrication and Applications of Superhydrophobic Coating on Cellulose-Based Substrates

Multifuntional fabrics with special wettability have attracted a lot of interest in both fundamental research and industry applications over the last two decades. In this review, recent progress of various kinds of approaches and strategies to construct super-antiwetting coating on cellulose-based substrates (fabrics and paper) has been discussed in detail. We focus on the significant applications related to artificial superhydrophobic fabrics with special wettability and controllable adhesion, e.g., oil-water separation, self-cleaning, asymmetric/anisotropic wetting for microfluidic manipulation, air/liquid directional gating, and micro-template for patterning. In addition to the anti-wetting properties and promising applications, particular attention is paid to coating durability and other incorporated functionalities, e.g., air permeability, UV-shielding, photocatalytic self-cleaning, self-healing and patterned antiwetting properties. Finally, the existing difficulties and future prospects of this traditional and developing field are briefly proposed and discussed.

Water-based, heat-assisted preparation of water-repellent cotton fabrics using graft copolymers

A simple, practical, environmentally-friendly method to prepare repellent coated cotton fabrics.