Self-junctioned copper nanofiber transparent flexible films are produced using electrospinning and electroplating processes that provide high performances of T = 97% and Rs = 0.42 Ω sq(-1) by eliminating junction resistance at wire intersections. The film remains conductive after being stretched by up to 770% (films with T = 76%) and after 1000 cycles of bending to a 5 mm radius.

A highly transparent, flexible, stretchable and patternable copper fiber heater was successfully fabricated for potential use in smart windows and other applications. The thickness of the electrospun polymer nanofibers was controlled during subsequent copper plating by adjusting the electroplating time, with minimal sacrifice in transparency. Self-fused junctions, formed via electroplating, significantly reduced the contact resistance between the intersecting copper-plated fibers. The heater temperature remained constant up to 300% sheet stretching. De-icing tests confirmed the potential applicability of such heaters in smart windows or vehicle defrosters. The copper-plated fibers may be transferred onto any surface with a complex 3D structure, as demonstrated by fabricating a heat-radiating Venus statue covered with the copper-plated fibers. The highest temperature of 328°C was achieved by using a transparent fibrous film having 90% transparency and 0.058 Ω sq − 1 sheet resistance.

The present work aims at development of self-healing materials capable of partially restoring their mechanical properties under the conditions of prolonged periodic loading and unloading, which is characteristic, for example, of aerospace applications. Composite materials used in these and many other applications frequently reveal multiple defects stemming from their original inhomogeneity, which facilitates microcracking and delamination at ply interfaces. Self-healing nanofiber mats may effectively prevent such damage without compromising material integrity. Two types of core-shell nanofibers were simultaneously electrospun onto the same substrate in order to form a mutually entangled mat. The first type of core-shell fibers consisted of resin monomer (dimethylsiloxane) within the core and polyacrylonitrile within the shell. The second type of core-shell nanofibers consisted of cure (dimethyl-methyl hydrogen-siloxane) within the core and polyacrylonitrile within the shell. These mutually entangled nanofiber mats were used for tensile testing, and they were also encased in polydimethylsiloxane to form composites that were also subsequently subjected to tensile testing. During tensile tests, the nanofibers can be damaged in stretching up to the plastic regime of deformation. Then, the resin monomer and cure was released from the cores and the polydimethylsiloxane resin was polymerized, which might be expected to result in the self-healing properties of these materials. To reveal and evaluate the self-healing properties of the polyacrylonitrile-resin-cure nanofiber mats and their composites, the results were compared to the tensile test results of the monolithic polyacrylonitrile nanofiber mats or composites formed by encasing polyacrylonitrile nanofibers in a polydimethylsiloxane matrix. The latter do not possess self-healing properties, and indeed, do not recover their mechanical characteristics, in contrast to the polyacrylonitrile-resin-cure nanofiber mats and the composites reinforced by such mats. This is the first work, to the best of our knowledge, where self-healing nanofibers and composites based on them were developed, tested, and revealed restoration of mechanical properties (stiffness) in a 24 h rest period at room temperature.

Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

The capacity for core-shell nanofiber mats containing healing agents (resin monomer and cure) in their cores to adhere to a substrate was studied using blister testing. After extended periodic bending, the adhesion energy was measured, and the effect of self-healing on the composite's delamination from the substrate was considered. In addition, the cohesion of two layers of the self-healing nanofibers was examined using blister testing and compared to that of ordinary nanofiber mats. The damage inflicted by prolonged periodic bending to the interface of the two nanofiber mats was demonstrated to have self-healed, and the cohesion energy was measured.

The demand for wearable, stretchable soft electronics for human–machine interface applications continues to grow given the potential of these devices in humanoid robotics, prosthetics, and health-monitoring devices. We demonstrate fabrication of multifunctional sensors with simultaneous temperature-, pressure-, proximity-, and strain (or bending)-sensing capabilities, combined with heating and UV-protection features. These multifunctional sensors are flexible, light, and transparent and are thus body-attachable. Silver nanowires are supersonically sprayed on a large-scale transparent and flexible roll-to-roll substrate. The junctions between nanowires are physically fused by a strong impact resulting from supersonic spraying, which promotes adhesion and efficient deposition of the nanowire network. Accordingly, nanowires are strongly interconnected, facilitating efficient propagation of electric signals through the fused nanowire network, which allows simultaneous operation of such sensors while maintaining significant transparency. These multifunctional sensors are mechanically durable and retain long-term stability. A theoretical discussion is provided to explain the respective mechanisms of heating and proximity, pressure, and strain sensing.

Here, we demonstrate the production of electrospun SnO(x)-ZnO polyacrylonitrile (PAN) nanofibers (NFs) that are flexible, freestanding, and binder-free. This NF fabric is flexible and thus can be readily tailored into a coin for further cell fabrication. These properties allow volume expansion of the oxide materials and provide shortened diffusion pathways for Li ions than those achieved using the nanoparticle approach. Amorphous SnO(x)-ZnO particles were uniformly dispersed in the carbon NF (CNF). The SnO(x)-ZnO CNFs with a Sn:Zn ratio of 3:1 exhibited a superior reversible capacity of 963 mA·h·g(-1) after 55 cycles at a current density of 100 mA·g(-1), which is three times higher than the capacity of graphite-based anodes. The amorphous NFs facilitated Li2O decomposition, thereby enhancing the reversible capacity. ZnO prevented the aggregation of Sn, which, in turn, conferred stable and high discharge capacity to the cell. Overall, the SnO(x)-ZnO CNFs were shown to exhibit remarkably high capacity retention and high reversible and rate capacities as Li ion battery anodes.

Here, ultrathin, flexible, and sustainable nanofiber‐based piezoelectric nanogenerators (NF‐PENGs) are fabricated and applied as wave energy harvesters. The NF‐PENGs are composed of poly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)) nanofibers with embedded barium strontium titanate (BaSrTiO3) nanoparticles, which are fabricated by using facile, scalable, and cost‐effective fiber‐forming methods, including electrospinning and solution blowing. The inclusion of ferroelectric BaSrTiO3 nanoparticles inside the electrospun P(VDF‐TrFE) nanofibers enhances the sustainability of the NF‐PENGs and results in unique flexoelectricity‐enhanced piezoelectric nanofibers. Not only do these NF‐PENGs yield a superior performance compared to the previously reported NF‐PENGs, but they also exhibit an outstanding durability in terms of mechanical properties and cyclability. Furthermore, a new theoretical estimate of the energy harvesting efficiency from the water waves is introduced here, which can also be employed in future studies associated with various nanogenerators, including PENGs and triboelectric nanogenerators.