Fluorine-Free Waterborne Coating for Environmentally Friendly, Robustly Water-Resistant, and Highly Breathable Fibrous Textiles

Biopolymer Nanofibers for Nanogenerator Development

The development of nanogenerators (NGs) with optimal performances and functionalities requires more novel materials. Over the past decade, biopolymer nanofibers (BPNFs) have become critical sustainable building blocks in energy-related fields because they have distinctive nanostructures and properties and can be obtained from abundant and renewable resources. This review summarizes recent advances in the use of BPNFs for NG development. We will begin by introducing various strategies for fabricating BPNFs with diverse structures and performances. Then, we will systematically present the utilization of polysaccharide and protein nanofibers for NGs. We will mainly focus on the use of BPNFs to generate bulk materials with tailored structures and properties for assembling of triboelectric and piezoelectric NGs. The use of BPNFs to construct NGs for the generation of electricity from moisture and osmosis is also discussed. Finally, we illustrate our personal perspectives on several issues that require special attention with regard to future developments in this active field.

Green-Solvent-Processed Fibrous Membranes with Water/Oil/Dust-Resistant and Breathable Performances for Protective Textiles

Waterproof and breathable membranes (WBMs) are highly demanded worldwide due to their promising applications in outdoor protective clothing, medical hygiene, and electronic devices. However, the design of such materials integrated with environmental friendliness and high functionality has been considered a long-standing challenge. Herein, we report the green-solvent-processed polyamide fibrous membranes with amphiphobicity and bonding structure via ethanol-based electrospinning and water-based impregnating techniques, endowing the fibrous membranes with outstanding water/oil/dust-resistant and good breathable properties. The developed green smart fibrous membranes exhibit integrated properties with robust water and oil intrusion pressures of 101.2 and 32.4 kPa, respectively, excellent dust removal efficiency of above 99.9%, good water vapor transmission rate of 11.2 kg m^-2 d^-1, air permeability of 2.6 mm s^-1, tensile strength of 15.6 MPa, and strong toughness of 22.8 MJ m^-3, enabling the membranes to protect human beings and electronic devices effectively. This work may shed light on designing the next generation green smart fibrous WBMs for protective textiles.

Hyperbranched polymer hydrogels with large stimuli-responsive changes in storage moduli and peroxide-induced healing

Hydrogels prepared using hyperbranched polymers with dynamic disulfide bonds show larger changes in moduli upon exposure to chemical stimuli for both softening and stiffening responses compared to linear polymers.

Bioinspired textile with dual-stimuli responsive wettability for body moisture management and signal expression

A smart bioinspired loofah textile with biosafe wettability shows high directional liquid transport capacity and the ability to identify liquids with different pH values.

Sacrifice Template Strategy to the Fabrication of a Self-Cleaning Nanofibrous Membrane for Efficient Crude Oil-in-Water Emulsion Separation with High Flux

The superhydrophilic/underwater superoleophobic membrane materials have attracted considerable attention in oil/water separation. However, most materials are extremely susceptible to pollution during oil-water separation, which drastically restricts their widespread applications. Herein, a momordica-charantia-like nanofibrous membrane (MCNM) with underwater superoleophobic performance was fabricated through a sacrifice template strategy by the electrospinning solution of zeolitic imidazolate framework-8 (ZIF-8) and polyacrylonitrile particles. The opened voids and wrinkles left after removing the template of nanocrystals ZIF-8 not only increased the porosity and roughness of the as-prepared fibrous membrane but also tremendously improved the underwater superoleophobicity. Therefore, the as-prepared MCNM showed excellent self-cleaning performance toward crude oil under water, avoiding the decrease of the separation efficiency and flux caused by membrane fouling during oil-water separation. Meanwhile, the separation efficiency of various surfactant-stabilized oil-in-water emulsions was higher than 99.6% with a flux up to 1580 ± 30 L m^-2 h^-1 solely driven by gravity. Moreover, no obvious wrinkles and cracks were observed on the resulted nanofibrous membrane after the sand impact and bent testing. More importantly, the as-prepared MCNM still maintained exceptional underwater superoleophobicity in harsh environment (3.5 wt % NaCl, 4 M HCl, 50 °C hot water) even after ultrasound for 1 h. The robust mechanical and chemical stability makes the antifouling MCNM exhibit tremendous potential for practical applications in dealing with oily wastewater in the future.

Simply Adjusting the Unidirectional Liquid Transport of Scalable Janus Membranes toward Moisture-Wicking Fabric, Rapid Demulsification, and Fast Oil/Water Separation

Inspired by nature, Janus membranes with unidirectional liquid transport (ULT) were developed to be used in the fields of fog collection, moisture-wicking fabrics, demulsification, etc. However, the obtained Janus membranes are often unifunctional, and it is still a great challenge to adjust the ULT of Janus membranes for multifunctional applications. Herein, a scalable, low-cost, and machine-washable Janus membrane was developed by combining the cyclic self-assembly of phytic acid and Fe^III and a one-side spraying coating of poly(dimethylsiloxane) (PDMS), featuring adjustable ULT upon challenge for multifunctional applications. By controlling the amount of PDMS, the Janus membranes exhibit two different performances, ULT and switchable permeation. The prepared Janus membranes achieved an excellent moisture-wicking fabric (1.6× the water evaporation rate of cotton), fast water collection under oil, rapid demulsification, and the efficient separation of an oil/water mixture. The separation efficiency of a light or heavy oil from water was higher than 99.9% even after 10 separation cycles, and the flux of the separation was up to 2.55 × 10⁴ or 2.38 × 10⁴ L m^-2 h^-1, respectively. This study could provide an idea for the development of more Janus membranes with adjustable performances to realize multifunctional applications.

Ultrafine, self-crimp, and electret nano-wool for low-resistance and high-efficiency protective filter media against PM0.3

Frequent outbreaks of emerging infectious diseases (EIDs) make personal protective filter media in high demand. Electrospun nanofibrous materials are proved to be very effective in resisting virus-containing fine particles owing to their small fiber diameters; however, hindered by the intrinsic close-packing character of fine fibers, electrospun filters suffer from a relatively high air resistance, thereby poor breathing comfort. Here, we report a biomimetic and one-step strategy to create ultrafine and curly wool-like nanofibers, named nano-wool, which exhibit fluffy assembly architecture and powerful electret effect. By achieving the online self-crimp and in-situ charging of nanofibers, the curly electret nano-wool shows a small diameter of ~0.6 μm (two orders of magnitude lower than natural wool: ~20 μm) and an ultrahigh porosity of 98.7% simultaneously, together with an ultrahigh surface potential of 13260 V (one order of magnitude higher than previous filters). The structural advantages and powerful electret effect enable nano-wool to show excellent filtration efficacy (>99.995% for PM_0.3) and low air resistance (55 Pa). Additionally, nano-wool can be easily scaled up, not only holding great industrial prospect in personal protective respirators, but also paving the way for developing next-generation wool in a cost-efficient and multifunctional form.

Hot-melt Adhesive Bonding of Polyurethane/Fluorinated Polyurethane/Alkylsilane-Functionalized Graphene Nanofibrous Fabrics with Enhanced Waterproofness, Breathability, and Mechanical Properties

Waterproof-breathable (WB) materials with outstanding waterproofness, breathability, and mechanical performance are critical in diverse consumer applications. Electrospun nanofibrous membranes with thin fiber diameters, small pore sizes, and high porosity have attracted significant attention in the WB fabric field. Hot-press treatment technology can induce the formation of inter-fiber fusion structures and hence improve the waterproofness and mechanical performance. By combining electrospinning and hot-press treatment technology, polyurethane/fluorinated polyurethane/thermoplastic polyurethane/alkylsilane-functionalized graphene (PU/FPU/TPU/FG) nanofiber WB fabric was fabricated. Subsequently, the morphologies, porous structure, hydrostatic pressure, water vapor transmission rate (WVTR), and stress–strain behavior of the nanofiber WB fabric were systematically investigated. The introduction of the hydrophobic FG sheet structure and the formation of the inter-fiber fusion structure greatly improved not only the waterproofness but also the mechanical performance of the nanofiber WB fabric. The optimized PU/FPU/TPU-50/FG-1.5 WB fabric exhibited an excellent comprehensive performance: a high hydrostatic pressure of 80.4 kPa, a modest WVTR of 7.6 kg m⁻² d⁻¹, and a robust tensile stress of 127.59 MPa, which could be used to achieve various applications. This work not only highlights the preparation of materials, but also provides a high-performance nanofiber WB fabric with huge potential application prospects in various fields.

Multifunctional, Waterproof, and Breathable Nanofibrous Textiles Based on Fluorine-Free, All-Water-Based Coatings

Developing environmentally benign, multifunctional waterproof and breathable membranes (WBMs) is of great importance but still faces enormous challenges. Here, an environmentally benign fluorine-free, ultraviolet (UV) blocking, and antibacterial WBM with a high level of waterproofness and breathability is developed on a large scale by combining electrospinning and step-by-step surface coating technology. Fluorine-free water-based alkylacrylates with long hydrocarbon chains were coated onto polyamide 6 fibrous membranes to construct robust hydrophobic surfaces. The subsequent titanium dioxide nanoparticle emulsion coating prominently decreased the maximum pore size, leading to higher water resistance, endowing the membranes with efficient UV-resistant and antibacterial properties. The resulting fibrous membranes possessed excellent waterproofness of 106.2 kPa, exceptional breathability of 10.3 kg m^-2 d^-1, a significant UV protection factor of 430.5, together with a definite bactericidal efficiency of 99.9%. We expect that this methodology for construction of environmentally benign and multifunctional WBMs will shed light on the material design, and the prepared membranes could implement their promising applications in covering materials, outdoor equipment, protective clothing, and high-altitude garments.