Flexible and Robust Core-Shell PANI/PVDF@PANI Nanofiber Membrane for High-Performance Electromagnetic Interference Shielding.

Developing high-performance electromagnetic interference (EMI) shielding materials that are lightweight and flexible and have excellent mechanical properties is an ideal choice for modern integrated electronic devices and microwave protection. Herein, we report the preparation of core-shell polyaniline (PANI)-based nanofiber membranes for EMI shielding through seed polymerization. Electrospinning a PANI solution leads to homogeneously dispersed PANI on the nanofiber surface, with abundant attachment sites for aniline through electrostatic adsorption and hydrogen bonding interaction, allowing PANI to grow on the nanofiber surfaces. This stable core-shell heterostructure provides more interfaces for reflecting and absorbing microwaves. The PANI/PVDF@PANI membranes achieved a shielding efficiency (SE) of 44.7 dB at a thickness of only 1.2 mm, exhibiting an exceptionally high specific EMI shielding effectiveness (SE/t) of 372.5 dB cm-1. Furthermore, the composite membrane exhibits outstanding mechanical stability, durability, air permeability, and moisture permeability, also making it suitable for applications such as EM shielding clothing.

Single-cell and spatiotemporal transcriptomic analyses reveal the effects of microorganisms on immunity and metabolism in the mouse liver.

The gut-liver axis is a complex bidirectional communication pathway between the intestine and the liver in which microorganisms and their metabolites flow from the intestine through the portal vein to the liver and influence liver function. In a sterile environment, the phenotype or function of the liver is altered, but few studies have investigated the specific cellular and molecular effects of microorganisms on the liver. To this end, we constructed single-cell and spatial transcriptomic (ST) profiles of germ-free (GF) and specific-pathogen-free (SPF) mouse livers. Single-cell RNA sequencing (scRNA-seq) and single-nucleus RNA sequencing (snRNA-seq) revealed that the ratio of most immune cells was altered in the liver of GF mice; in particular, natural killer T (NKT) cells, IgA plasma cells (IgAs) and Kupffer cells (KCs) were significantly reduced in GF mice. Spatial enhanced resolution omics sequencing (Stereo-seq) confirmed that microorganisms mediated the accumulation of Kupffer cells in the periportal zone. Unexpectedly, IgA plasma cells were more numerous and concentrated in the periportal vein in liver sections from SPF mice but less numerous and scattered in GF mice. ST technology also enables the precise zonation of liver lobules into eight layers and three patterns based on the gene expression level in each layer, allowing us to further investigate the effects of microbes on gene zonation patterns and functions. Furthermore, untargeted metabolism experiments of the liver revealed that the propionic acid levels were significantly lower in GF mice, and this reduction may be related to the control of genes involved in bile acid and fatty acid metabolism. In conclusion, the combination of sc/snRNA-seq, Stereo-seq, and untargeted metabolomics revealed immune system defects as well as altered bile acid and lipid metabolic processes at the single-cell and spatial levels in the livers of GF mice. This study will be of great value for understanding host-microbiota interactions.

Electrospinning of Biodegradable, Monolithic Membrane with Distinct Bimodal Micron-Sized Fibers and Nanofibers for High Efficiency PMs Removal.

Atmospheric particulate matter (PMs) pollution has raised increasing public concerns, especially with the outbreak of COVID-19. The preparation of high-performance membranes for air filtration is of great significance. Herein, the biosynthetic polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was adopted to create a hierarchical structure and biodegradable nonwoven membrane for PMs filtration through a facile directly electrospinning method. The as-prepared membranes with hierarchical structure contain abundant nanowires (5-100 nm) and microfibers (2-5 µm) with different diameter (1000-5000 nm). We have achieved realization of formation mechanisms of such bimodal micro- and nanofibers, which stem from the branching of microfiber at early stage of electrospinning. The PHBV membranes exhibit a very high PM0.3 removal efficiency of 99.999% and PM2.5 removal efficiency of 100% with 0.077% standard atmospheric pressure in the air flow speed of 5.3 cm/s. More importantly, the PHBV membranes can be completely disintegrated within 1 week under composted conditions, indicating the great biodegradability of PHBV membranes. Our work provides insights for the development of biodegradable, high performance air filters for pollutants, molds, bacteria, and viruses.

Microbiota-mediated shaping of mouse spleen structure and immune function characterized by scRNA-seq and Stereo-seq.

Gut microbes exhibit complex interactions with their hosts and shape an organism's immune system throughout its lifespan. As the largest secondary lymphoid organ, the spleen has a wide range of immunological functions. To explore the role of microbiota in regulating and shaping the spleen, we employ scRNA-seq and Stereo-seq technologies based on germ-free (GF) mice to detect differences in tissue size, anatomical structure, cell types, functions, and spatial molecular characteristics. We identify 18 cell types, 9 subtypes of T cells, and 7 subtypes of B cells. Gene differential expression analysis reveals that the absence of microorganisms results in alterations in erythropoiesis within the red pulp region and congenital immune deficiency in the white pulp region. Stereo-seq results demonstrate a clear hierarchy of immune cells in the spleen, including marginal zone (MZ) macrophages, MZ B cells, follicular B cells and T cells, distributed in a well-defined pattern from outside to inside. However, this hierarchical structure is disturbed in GF mice. Ccr7 and Cxcl13 chemokines are specifically expressed in the spatial locations of T cells and B cells, respectively. We speculate that the microbiota may mediate the structural composition or partitioning of spleen immune cells by modulating the expression levels of chemokines.

Assembly and analytical validation of a metagenomic reference catalog of human gut microbiota based on co-barcoding sequencing.

Human gut microbiota is associated with human health and disease, and is known to have the second-largest genome in the human body. The microbiota genome is important for their functions and metabolites; however, accurate genomic access to the microbiota of the human gut is hindered due to the difficulty of cultivating and the shortcomings of sequencing technology. Therefore, we applied the stLFR library construction method to assemble the microbiota genomes and demonstrated that assembly property outperformed standard metagenome sequencing. Using the assembled genomes as references, SNP, INDEL, and HGT gene analyses were performed. The results demonstrated significant differences in the number of SNPs and INDELs among different individuals. The individual displayed a unique species variation spectrum, and the similarity of strains within individuals decreased over time. In addition, the coverage depth analysis of the stLFR method shows that a sequencing depth of 60X is sufficient for SNP calling. HGT analysis revealed that the genes involved in replication, recombination and repair, mobilome prophages, and transposons were the most transferred genes among different bacterial species in individuals. A preliminary framework for human gut microbiome studies was established using the stLFR library construction method.

The fabrication and evaluation of silver nanoparticle-based keratin scaffolds.

The biotoxicity caused by focus releasing of Ag, which associated with the Ag loading mode, is a problematic issue that need to be solved for practical utilization of the keratin based wound dressing. In this study, keratin/AgNPs blend scaffolds (Ker/Ag) and keratin scaffolds with AgNPs attached on the scaffold's wall surface (Ag@Ker) were prepared. Structure and physical properties of the scaffolds were tested and investigated. In comparison to the Ag@Ker scaffolds, the Ker/Ag scaffolds with uniform dispersion of AgNPs have larger tensile strength and slower degradation rate. Both kind of scaffolds present excellent antibacterial property with 10 µg mL-1 AgNPs addition, while the Ker/Ag displayed a linear Ag releasing ratio in the first 5-7 days, which is beneficial for obtaining a continuous antibacterial property and avoiding the biotoxicity caused by focus release of Ag. Correspondingly, cytotoxicity assay further reveals that the continuously slow release of Ag of the Ker/Ag scaffolds accelerated the proliferation of cell. Infectious animal models and histological studies showed that the Ker/Ag scaffolds can effectively inhibit the inflammatory response and accelerate epithelialization. Thus, it can be concluded that the Ker/Ag scaffolds with uniform dispersion of AgNPs are more attractive as wound repair materials.

Nanofiber template-induced preparation of ZnO nanocrystal and its application in photocatalysis.

Traditional preparation of ZnO nanocrystal requires heating zinc acetate to a temperature over 350 °C, whereas in this work, zinc acetate was first electrospun with PVDF to form a nanofiber, followed by thermal treatment at only 140 °C to give nanocrystalline ZnO. The much lower temperature required in thermal treatment is attributed to the high reactivity of zinc acetate at nano dimension. The as-prepared ZnO-doped PVDF nanofiber mat shows excellent effect in the photocatalytic degradation of Rhodamine B, comparable to ZnO particle thermally treated at 600 °C. Highly-oriented ZnO nanorods were obtained by further hydrothermal synthesis of the electrospun nanofiber mat, giving nanostructured ZnO of different morphologies well-aligned on the surface of organic nanofiber. Notably, the hydrothermal synthesis of the successful preparation of these nanostructured ZnO requires a processing temperature below 100 °C at atmospheric pressure, showing great potential to be scaled up for vast manufacturing.

Visualization of the interaction of water aerosol and nanofiber mesh.

Face masks play a critical role in reducing the transmission risk of COVID-19 and other respiratory diseases. Masks made with nanofibers have drawn increasingly more attention because of their higher filtration efficiency, better comfort, and lower pressure drop. However, the interactions and consequences of the nanofibers and microwater droplets remain unclear. In this work, the evolution of fibers made of polymers with different contact angles, diameters, and mesh sizes under water aerosol exposure is systematically visualized. The images show that capillarity is very strong compared with the elasticity of the nanofiber. The nanofibers coalesce irreversibly during the droplet capture stage as well as the subsequent liquid evaporation stage. The fiber coalescence significantly reduces the effective fiber length for capturing aerosols. The nanofiber mesh that undergoes multiple droplet capture/evaporation cycles exhibits a fiber coalescing fraction of 40%-58%. The hydrophobic and orthogonally woven fibers can reduce the capillary forces and decrease the fiber coalescing fraction. This finding is expected to assist the proper design, fabrication, and use of face masks with nanofibers. It also provides direct visual evidence on the necessity to replace face masks frequently, especially in cold environments.

Probing Mechanistic Insights into Highly Efficient Lithium Storage of C60 Fullerene Enabled via Three-Electron-Redox Chemistry.

Renewable organic cathodes with abundant elements show promise for sustainable rechargeable batteries. Herein, for the first time, utilizing C60 fullerene as organic cathode for room-temperature lithium-ion battery is reported. The C60  cathode shows robust electrochemical performance preferably in ether-based electrolyte. It delivers discharge capacity up to 120 mAh g-1 and specific energy exceeding 200 Wh kg-1 with high initial Coulombic efficiency of 91%. The as-fabricated battery holds a capacity of 90 mAh g-1 after 50 cycles and showcases remarkable rate performance with 77 mAh g-1 retained at 500 mA g-1 . Noteworthily, three couples of unusual flat voltage plateaus recur at ≈2.4, 1.7, and 1.5 V, respectively. Diffusion-dominated three-electron-redox reactions are revealed by cyclic voltammogram and plateau capacities. Intriguingly, it is for the first time unveiled by in situ X-ray diffraction (XRD) that the C60 cathode underwent three reversible phase transitions during lithiation/delithiation process, except for the initial discharge when irreversible polymerization in between C60 nanoclusters existed as suggested by the characteristic irreversible peak shifts in both in situ XRD pattern and in situ Raman spectra. Cs-corrected transmission electron microscope corroborated these phase evolutions. Importantly, delithiation potentials derived from density-functional-theory simulation based on proposed phase structures qualitatively consists with experimental ones.

Wearable Flexible Strain Sensor Based on Three-Dimensional Wavy Laser-Induced Graphene and Silicone Rubber.

Laser-induced graphene (LIG) has the advantages of one-step fabrication, prominent mechanical performance, as well as high conductivity; it acts as the ideal material to fabricate flexible strain sensors. In this study, a wearable flexible strain sensor consisting of three-dimensional (3D) wavy LIG and silicone rubber was reported. With a laser to scan on a polyimide film, 3D wavy LIG could be synthesized on the wavy surface of a mold. The wavy-LIG strain sensor was developed by transferring LIG to silicone rubber substrate and then packaging. For stress concentration, the ultimate strain primarily took place in the troughs of wavy LIG, resulting in higher sensitivity and less damage to LIG during stretching. As a result, the wavy-LIG strain sensor achieved high sensitivity (gauge factor was 37.8 in a range from 0% to 31.8%, better than the planar-LIG sensor), low hysteresis (1.39%) and wide working range (from 0% to 47.7%). The wavy-LIG strain sensor had a stable and rapid dynamic response; its reversibility and repeatability were demonstrated. After 5000 cycles, the signal peak varied by only 2.32%, demonstrating the long-term durability. Besides, its applications in detecting facial skin expansion, muscle movement, and joint movement, were discussed. It is considered a simple, efficient, and low-cost method to fabricate a flexible strain sensor with high sensitivity and structural robustness. Furthermore, the wavy-LIG strain senor can be developed into wearable sensing devices for virtual/augmented reality or electronic skin.

Transparent PAN:TiO2 and PAN-co-PMA:TiO2 Nanofiber Composite Membranes with High Efficiency in Particulate Matter Pollutants Filtration.

Particulate matter is one of the main pollutants, causing hazy days, and it has been serious concern for public health worldwide, particularly in China recently. Quality of outdoor atmosphere with a pollutant emission of PM2.5 is hard to be controlled; but the quality of indoor air could be achieved by using fibrous membrane-based air-filtering devices. Herein, we introduce nanofiber membranes for both indoor and outdoor air protection by electrospun synthesized polyacrylonitrile:TiO2 and developed polyacrylonitrile-co-polyacrylate:TiO2 composite nanofiber membranes. In this study, we design both polyacrylonitrile:TiO2 and polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membranes with controlling the nanofiber diameter and membrane thickness and enable strong particulate matter adhesion to increase the absorptive performance and by synthesizing the specific microstructure of different layers of nanofiber membranes. Our study shows that the developed polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membrane achieves highly effective (99.95% removal of PM2.5) under extreme hazy air-quality conditions (PM2.5 mass concentration 1 mg/m3). Moreover, the experimental simulation of the test in 1 cm3 air storehouse shows that the polyacrylonitrile-co-polyacrylate:TiO2 nanofiber membrane (1 g/m2) has the excellent PM 2.5 removal efficiency of 99.99% in 30 min.

Variational iteration method for Bratu-like equation arising in electrospinning.

This paper points out that the so called enhanced variational iteration method (Colantoni & Boubaker, 2014) for a nonlinear equation arising in electrospinning and vibration-electrospinning process is the standard variational iteration method. An effective algorithm using the variational iteration algorithm-II is suggested for Bratu-like equation arising in electrospinning. A suitable choice of initial guess results in a relatively accurate solution by one or few iteration.