Electronic fabrics necessitate both electrical conductivity and, like any textile, elastic recovery. Achieving both requirements on the scale of a single fiber remains an unmet need. Here, two approaches for achieving conductive fibers (107 S m−1) reaching 50% elongation while maintaining minimal change in resistance (<0.5%) in embedded metallic electrodes are introduced. The first approach involves inducing a buckling instability in a metal microwire within a cavity of a thermally drawn elastomer fiber. The second approach relies on twisting an elastomer fiber to yield helical metal electrodes embedded in a stretchable yarn. The scalability of both approaches is illustrated in apparatuses for continuous buckling and twisting that yield tens of meters of elastic conducting fibers. Through experimental and analytical methods, it is elucidated how geometric parameters, such as buckling pre‐strain and helical angle, as well as materials choice, control not only the fiber's elasticity but also its Young's modulus. Links between mechanical and electrical properties are exposed. The resulting fibers are used to construct elastic fabrics that contain diodes, by weaving and knitting, thus demonstrating the scalable fabrication of conformable and stretchable antennas that support optical data transmission.

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Thermally Drawn Highly Conductive Fibers with Controlled Elasticity

Antimicrobial and antiviral nanocomposites based on polylactic acid (PLA) and chitosan were synthesized by a thermochemical reduction method of Ag+ ions in the PLA-Ag+-chitosan polymer films. Features of the structural, morphological, thermophysical, antimicrobial, antiviral, and cytotoxic properties of PLA-Ag-chitosan nanocomposites were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and antiviral, antimicrobial, and cytotoxic studies. The effects of temperature and the duration of reduction of Ag+ ions on the structure of PLA-Ag-chitosan nanocomposites were established. During the thermochemical reduction (T = 160 °C, t = 5 min) of silver palmitate ions in PLA-Ag+-chitosan polymer films, Ag nanoparticles with an average size of 4.2 nm were formed. PLA-Ag-chitosan polymer nanocomposites have strong antimicrobial activity against S. aureus and E. coli strains. In particular, for PLA-chitosan samples containing 4% Ag, the diameters of the S. aureus and E. coli growth inhibition zones were 25.8 and 25.0 mm, respectively. The antiviral activity of the nanocomposites against influenza A virus, herpes simplex virus type 1, and adenovirus serotype 2 was also revealed. The PLA-4%Ag-chitosan nanocomposites completely inhibited the cytopathic effect (CPE) of herpes virus type 1 by 5.12 log10TCID50/mL (high antiviral activity) and the development of the CPE of influenza virus and adenovirus by 0.60 and 1.07 log10TCID50/mL (relative antiviral activity). The obtained nanocomposites were not cytotoxic; they did not inhibit the viability of MDCK, BHK-21, and Hep-2 cell cultures.

Preparation, Characterization, and Antimicrobial and Antiviral Properties of Silver-Containing Nanocomposites Based on Polylactic Acid-Chitosan.

https://doi.org/10.1016/j.cobme.2022.100395

Antimicrobial polymeric composites for high-touch surfaces in healthcare applications

Naked-eye sensing and target-guiding treatment of bacterial infection using pH-tunable multicolor luminescent lanthanide-based hydrogel.

Nanochitin and nanochitosan (with random‐copolymer‐based multiscale architectures of glucosamine and N‐acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod‐shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular‐ and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale‐dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adma.202203325

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications

In recent years, the textile industry has been seeking to develop innovative products. It is a good choice to organically combine materials with superior functional characteristics and commercial t...

Chitosan Natural Polymer Material for Improving Antibacterial Properties of Textiles

As kinds of unique textiles with high extensibility and elasticity, elastic fabrics are widely used for sportswear, medical textiles and electronic textiles. The tensile behavior of fabric is very important for post-processing and usage of fabric. However, there are very few studies on the resultant yarn strain subjected to the applied fabric extension, which is crucial for understanding the tensile behavior of elastic fabric and expanding its potential applications. In order to address the tensile behavior of elastic fabric, a mechanical model of fabric was built for the analysis of local yarn strain within the fabric through finite element method (FEM). The FEM models with full consideration of the tensile property of elastic yarns were built to predict the relationship between the applied fabric strain and the resultant yarn strain. An experimental study was conducted to characterize the yarn deformation behavior during the fabric stretching and compare with the FEM prediction. The FEM simulations show a good agreement with the experimental results. Based on the FEM models, the effects of fabric structural parameters on such a relationship were investigated for understanding the deformation mechanism and thus optimizing the tensile properties of fabrics. A yarn strain of 27.5% could be achieved under 60% fabric strain by adopting an optimized warp yarn spacing of 0.8 mm. The results not only shed light on the origin of high extensibility and elasticity of fabrics but are of great value to the design and development of elastic materials for various applications such as textile-based electronics.

Exploring the relationship between applied fabric strain and resultant local yarn strain within the elastic fabric based on finite element method

Chitin-based bio-composites in nature such as the exoskeleton of crustaceans and squid pen usually exhibit hierarchical structures, where the chitin crystal is the most fundamental structural hierarchy as the load-bearing scaffold. Previous studies have unveiled the mechanical design of the structures at high hierarchies in these biomaterials, while the structure–property relationship remains unclear for the chitin crystal at the bottom hierarchy. In this paper, we investigate the mechanical properties of chitin crystals with $$\alpha$$
 - and $$\beta$$
 -polymorphic structures that mainly exist over the animal kingdom using the reactive force field molecular dynamics simulations. We first validate the force field parameters adopted from literature then study the mechanical behaviors of chitin polymorphs in response to the tensile and shear deformation. It is found that the mechanical performance of $$\alpha$$
 -chitin crystal is comprehensively superior to that of $$\beta$$
 -chitin crystal, such as the elastic modulus, work of fracture, shear modulus and strength. Different from the $$\beta$$
 -chitin, yielding caused by the transformation of crystalline structure is observed in the $$\alpha$$
 -chitin during uniaxial tension. Based on the mechanical properties obtained from simulations and theoretical analysis, we can deduce that the $$\alpha$$
 -chitin shows higher wear resistance than the $$\beta$$
 -chitin, implying better protection against the surface scratch that is one of the environmental threats to organisms. Our results shed light on the structure–property relationship of chitin crystals at the molecular level. The fundamental understanding of mechanical properties of chitin polymorphs is of great significance for the bottom-up modeling and design of chitin-based bio-composites.

Jimin Fu

Papers

Chitosan Natural Polymer Material for Improving Antibacterial Properties of Textiles

Exploring the relationship between applied fabric strain and resultant local yarn strain within the elastic fabric based on finite element method

Mechanical properties of chitin polymorphs: A computational study