Exploration of the Electrical Conductivity of Double-Network Silver Nanowires/Polyimide Porous Low-Density Compressible Sponges

Abstract

Stress-responsive, highly flexible, and breathable nanocomposite sponges show an electrical conductivity from 1.7 to 166.6 S/cm depending on the applied stress. Key for the responsive electrical conductivity of the sponges is the change of percolation of the silver nanowires. These sponges made of short electrospun fibers and silver nanowires could be applied without any amplifier for the operation of automobile bulbs and as an efficient Joule heater. The time required for electric heating (current on) and cooling is very short. Interestingly, the maximum temperature reached by electric heating depends on the compression status. The higher the compression status, the lower is the maximum temperature, which is in accordance with the understanding of Joule heaters. It is noteworthy that these sponges are thermally, chemically, and mechanically very stable. These conductive sponges will open a new area for novel conductive devices with relevance for real-world applications.

Low Density, Thermally Stable, and Intrinsic Flame Retardant Poly(bis(benzimidazo)Benzophenanthroline‐dione) Sponge

“…It has been shown in the past that large aspect ratio electrospun polymer short fibers can form ultralow density 3D porous sponges by percolation and self‐assembly of short fibers in the suspension during freeze‐drying . The present work aimed at making high temperature stable and intrinsic flame retardant sponges.…”

“…Large specific surface area, controllable aspect ratio and morphology, versatility and easy modification endow electrospun fiber unique advantages to fabricate 3D sponge materials, which not only broaden the applications of electrospun nanofibers but also provide varying properties to the sponges. Series of electrospun polymer nanofibers including polyacrylonitrile, polyimide (PI), and polyacrylate‐based polymer has been used to assemble mechanical stable 3D sponges with numerous applications. Biodegradable polymer sponges, poly(lactic acid), polycaprolactone, and poly(vinyl alcohol) (PVA), were also prepared using similar approach, which showed applications in tissue engineering.…”

“…However, these polymer‐based sponges have the common drawback of poor thermal properties which limits their application in high temperature areas. Therefore, aromatic PI sponges were developed which exhibited superior thermal resistance and showed initial degradation temperature above 400 and 500 °C in air and nitrogen, respectively . In spite of good thermal stability and thermal insulation, the PI sponges are flammable and lose their sponge morphology immediately under flame.…”

Carbon Nanofibrous Sponge Made from Hydrothermally Generated Biochar and Electrospun Polymer Nanofibers

“…The resulting 3D structures/sponges are morphologically stable/robust, and they possess hierarchically structured pores with sizes in the range from sub-micrometers to hundreds of micrometers; consequently, they have low densities (i.e., less than 100 mg cm − 3 ) and high porosities (i.e., larger than 90 vol%). Furthermore, these structures/sponges can be made to contain various functional materials such as carbon nanofibers [10], carbon nanoparticles [11], SiO 2 nanoparticles [12], Au nanoparticles [13], Ag nanowires [14], and halloysite nanotubes [15].…”

Impact of the Fiber Length Distribution on Porous Sponges Originating from Short Electrospun Fibers Made from Polymer Yarn

“…Recently, the potential of electrospun fibers was reported for the fabrication of novel electrospun fibrous sponges by the use of short electrospun fibers . Owing to flexible fabrication conditions and diversified electrospun fibers, the sponges displayed tunable densities, multifunctionality, and applicability for various applications, for instance, reversible manual compression, hydrophilic or super hydrophobic, electrics, respirable open cells, or scaffolds for tissue engineering . Thus, these sponges could perfectly overcome the mechanical brittleness of traditional inorganic aerogel and high cost of carbon aerogel problems, making them a perfect candidate for broad applications due to their high potential for functionalization.…”