Electrospinning Device for Nanofibers| High-Performance Radiative Cooling Using a Si0,/PHBV FiberMembrane with a Micronano-Multistage Structure

With the intensification of global warming and urban heat island effect, traditional cooling methods consume high energy and pollute the environment. As a passive heat dissipation technology, radiative cooling requires no additional energy input, and is sustainable and environmentally friendly, thus becoming a research hotspot. 

Based on this, Professor Chen Dazhu and others from Shenzhen University introduced an advanced radiative cooling fiber membrane containing 10 wt% SiO₂/PHBV with a micro-nano multistage structure. The membrane uses PHBV as a biodegradable matrix, is prepared by electrospinning technology, and has multiple absorption peaks in the atmospheric window. The SiO₂ nanoparticles embedded in the membrane enhance Mie scattering and act as a selective emitting material in this window. 

This fiber membrane achieves an impressive solar reflectance of 0.95 and an emissivity of 0.89 within the atmospheric window. When exposed to direct sunlight with an average radiation intensity of 537.06 W/m², the cooling temperature of the membrane is 4.85°C, producing a temperature difference of about 12.8°C relative to human skin. The average cooling power of the membrane is 64.05 W/m², and the peak cooling power of the membrane reaches 91.75 W/m² when the average solar radiation intensity is 751.83 W/m². In addition, the fiber membrane has an elongation at break of 151% and a water contact angle of 124.5°, highlighting its applicability in personal wearable cooling fabrics.

The relevant research results were published in the journal ACS Applied Materials & Interfaces under the title "High-Performance Radiative Cooling Using a SiO₂/PHBV Fiber Membrane with a Micronano-Multistage Structure".

Figure 1. Schematic diagram of the preparation process of PHBV and SiO₂/PHBV fiber membranes

Figure 2. Structure and morphology of the fiber membranes: (a) Pore size distribution curves of PHBV and SiO₂/PHBV fiber membranes. (b) FTIR spectra of SiO₂ nanoparticles, PHBV powder, PHBV fiber membrane, and SiO₂/PHBV fiber membrane. (c−g) SEM images of PHBV fiber membranes at concentrations of 2, 3, 4, 5, and 6 wt%. (h) SEM image of SiO₂ nanoparticles. (i−l) SiO₂/PHBV fiber membranes at SiO₂ concentrations of 5, 10, 15, and 20 wt%

Figure 3. Optical and cooling properties of the fiber membranes: (a) Reflection spectra of PHBV and (b) SiO₂/PHBV fiber membranes, with the red shaded area representing the distribution of solar radiation intensity. (c) Mid-infrared emission spectra of PHBV and SiO₂/PHBV fiber membranes, with the blue shaded area representing the transmission range within the atmospheric window. (d) Reflectance fitting curves of fiber membranes with different thicknesses.

Figure 5. Theoretical net radiative cooling power of the fiber membranes: Theoretical net radiative cooling power of 3 wt% PHBV and 10 wt% SiO₂/PHBV fiber membranes at (a) 25°C and (b) 35°C ambient temperatures with a non-radiative heat coefficient hc = 6 W/(m²·K); Theoretical net radiative cooling power of 3 wt% PHBV fiber membranes at (c) 25°C and (d) 35°C ambient temperatures under different non-radiative heat coefficients hc; Theoretical net radiative cooling power of 10 wt% SiO₂/PHBV fiber membranes at (e) 25°C and (f) 35°C ambient temperatures under different non-radiative heat coefficients.

Figure 6. Mechanical properties, hydrophobicity, and thermal stability of the fiber membranes: (a) Stress-strain curves; (b) Average tensile strength and average elongation at break of the fiber membranes; (c) Contact angle between the fiber membranes and water; (d) Thermogravimetric analysis (TGA) curves of PHBV and SiO₂/PHBV fiber membranes.

Conclusion

In summary, this study successfully developed a radiative cooling fiber membrane with PHBV as the substrate and SiO₂ nanoparticles as the selective emitter through electrospinning technology, which has excellent solar reflectance and atmospheric window emissivity. The 3 wt% PHBV fiber membrane has a reflectance of 0.95 in the solar wavelength range (0.3-2.5 μm) and an emissivity of 0.80 in the atmospheric window band (8-13 μm). When SiO₂ nanoparticles (average diameter: 482 nm) are incorporated into the PHBV matrix at a concentration of 10 wt%, the emissivity of the fiber membrane is increased to 0.89 while maintaining the solar reflectance. Theoretical calculations show that the net radiative cooling power of the SiO₂/PHBV fiber membrane is significantly improved, increasing from 64.70 W/m² to 78.62 W/m² at 25°C, and from 84.67 W/m² to 101.04 W/m² at 35°C. Further increasing the SiO₂ content beyond 10 wt% no longer significantly improves the atmospheric window emissivity or cooling power. Outdoor tests show that the cooling temperatures of 3 wt% PHBV and 10 wt% SiO₂/PHBV membranes at night are 1.08°C and 1.91°C, respectively; under solar radiation of 537.06 W/m², the daytime cooling temperatures are 4.1°C and 4.85°C, respectively. The average cooling power of the 10 wt% SiO₂/PHBV membrane is 64.05 W/m², and the peak cooling power reaches 91.75 W/m² under radiation of 751.83 W/m². In addition, the 10 wt% SiO₂/PHBV fiber membrane has an elongation at break of 151% and a water contact angle of 124.5°, showing great application potential in the field of personal wearable cooling fabrics and providing innovative solutions for thermal management in different environments.