Electrospinning Device for Nanofibers| Lightweight and Mechanically Robust Ambient-ElectrospunNanofibrous Sponges Combined with Solar-Driven Active Heatingand Low-Temperature Superinsulation

ACS Applied Materials & Interfaces: Ambient-Electrospun Nanofibrous Sponges Combining Solar-Driven Active Heating and Low-Temperature Superinsulation

Prolonged exposure to cold environments can cause varying degrees of damage to human cardiovascular and immune systems, even endangering life. Natural thermal insulation materials like cotton and down face issues of moisture absorption and insect susceptibility, while synthetic fiber materials, though moisture- and insect-resistant, have micron-scale fiber diameters that limit further improvement in thermal performance. Nanofibrous sponge materials with high porosity and low bulk density have emerged as promising new thermal insulation materials. However, developing lightweight, highly elastic nanofibrous sponges combining efficient cold insulation and active heating functions remains challenging due to poor mechanical stability and passive thermal management approaches.

Recently, Associate Professor Wu Hongyan from Zhejiang Sci-Tech University published new research in ACS Applied Materials & Interfaces titled "Lightweight, and Mechanically Robust Ambient-Electrospun Nanofibrous Sponges Combined with Solar-Driven Active Heating and Low-Temperature Superinsulation". Addressing current challenges in electrospun bulk material preparation (complex equipment and stringent environmental conditions), the researchers developed a method by controlling phase separation characteristics of spinning solutions. By introducing highly hygroscopic urea to induce rapid solidification of jets under ambient conditions and incorporating photothermal nanoparticles in situ, they fabricated lightweight, highly elastic polyacrylonitrile nanofibrous sponges (PNFS) with both low-temperature superinsulation and solar-driven active heating capabilities.

Fig. 1: PNFS fabrication design and morphology

Fig. 2: Mechanical properties

The PNFS can stand on foxtail grass without bending its bristles, demonstrating ultralight properties (bulk density ~3.8 mg cm-3). Thanks to enhanced single-fiber mechanical properties from crosslinking and its layered network structure, PNFS maintains over 80% of its initial Young's modulus and maximum compressive strength after 500 compression cycles, showing excellent elastic recovery and microstructural stability. Compression stress-strain curves at different temperatures (0°C, 20°C, -50°C, -100°C) show small hysteresis loops with minimal plastic deformation, indicating good low-temperature elastic recovery.

Fig. 3: Passive insulation and hydrophobic properties

The PNFS exhibits ultrahigh porosity (~99.7%), storing substantial air to reduce solid-phase heat transfer, while random nanofiber arrangement creates numerous micropores to minimize gas-phase heat transfer, resulting in low thermal conductivity (~27 mW m-1 K-1) - outperforming commercial high-end polyester insulation. The material also shows excellent hydrophobicity (water contact angle 128°) and stain resistance, with stable thermal conductivity (~27 mW m-1 K-1) even after 8 hours at 95% RH, ensuring reliable performance in rain/snow.

Fig. 4: Solar-driven active heating

Remarkably, PNFS demonstrates unique solar-driven active heating. Under simulated sunlight, surface temperature rapidly rises to 50°C. PNFS with 15wt% SiC shows over double the average solar absorption (300-2500 nm) compared to unmodified samples, with significantly enhanced absorption peaks in the 10.6-13.2 μm range (human infrared window), indicating effective conversion of both solar and body radiation into stored heat. This feature provides new possibilities for developing cold-weather gear in high-altitude, sunny regions.

DOI: https://doi.org/10.1021/acsami.5c04605