Electrospinning Machine| Hierarchical infrared spectral engineered super fabric for mitigating urban heat island

With accelerated global urbanization, urban heat island (UHI) effects and global warming pose severe challenges to public health and energy consumption. Urban construction materials (e.g., bricks, concrete, glass) exacerbate heat accumulation due to low specific heat capacity and poor solar reflectivity, increasing risks of heat-related illnesses and surging air-conditioning energy use. Thus, developing low-carbon, efficient, and sustainable cooling technologies is critical.

Recently, Prof. Wei Wang and Assoc. Prof. Dan Yu from Donghua University pioneered an asymmetric electrospinning technique to design a hierarchical infrared spectral-engineered super fabric (SEBA) integrating spectral selectivity and broadband properties for wearable applications. Its exceptional optical and thermal performance also suits building envelope retrofits, enhancing human comfort and mitigating UHI. The study, titled "Hierarchical infrared spectral engineered super fabric for mitigating urban heat island," was published in Chemical Engineering Journal.

SEBA Structure & Material Design

Outer layer: Polyacrylonitrile/silica/alumina (PAN/SiO₂/Al₂O₃) composite membrane suppresses solar absorption via 93.76% solar reflectivity, with high atmospheric transparency window (ATW, 8–13 μm) spectral selectivity ratio (1.20) and emissivity (0.91) for efficient radiative cooling.Middle layer: Copper-nickel electroplated polyester conductive fabric (CF) enhances infrared reflection and structural support.

Inner layer: Poly(vinylidene fluoride-co-hexafluoropropylene)/polyvinylpyrrolidone/silicon carbide (PVDF-HFP/PVP/SiC) composite membrane boasts 99% broadband infrared emissivity, efficiently absorbing body heat to prevent accumulation.

Material Properties

The outer layer’s Mie scattering by SiO₂/Al₂O₃ nanoparticles boosts near-infrared reflectivity, with optimized 0.108 mm thickness for maximal solar reflection.

The inner layer’s PVDF-HFP and SiC nanoparticles enhance body heat absorption, with 0.107 mm thickness shielding the middle layer’s spectral interference.

Performance Test Results

Passive Daytime Radiative Cooling (Horizontal Placement): Under average solar irradiance of 504.77 W/m², SEBA maintained an average temperature 3.67°C below ambient, with a maximum temperature difference of 6.80°C, significantly outperforming commercial white cotton fabric (above ambient temperature) and the control group without SiO₂/Al₂O₃ (markedly higher than ambient).

Vertical Placement: Even when exposed to surrounding thermal radiation, SEBA remained 0.54°C cooler than traditional broadband radiative cooling fabrics, demonstrating its adaptability in complex urban environments.

Human Thermal Management Performance
The inner layer's 99% broadband infrared emissivity efficiently absorbs body radiative heat (peak wavelength at 9.5μm at 33°C, with 44% energy in the ATW band), preventing heat accumulation between clothing and skin while optimizing the local microenvironment.

Practical Performance

Thermal Insulation: Low thermal conductivity (~23 mW·(m·K)⁻¹) effectively blocks environmental heat transfer.

Breathability & Moisture Permeability: Reduced air permeability minimizes convective heat gain, while high moisture permeability (6.829 mg·(cm²·h)⁻¹) ensures wearer comfort.

Durability: Maintains stable spectral performance after washing, aging, and abrasion tests. Outer layer solar reflectivity slightly declines, but infrared emissivity remains unchanged; inner layer broadband emissivity stays consistent.

Architectural Energy Savings
EnergyPlus simulations across 14 Chinese cities showed SEBA reduced summer cooling energy by 5.10% (Hangzhou) and 5.46% (Shanghai), validating its scalability for sustainable UHI mitigation.

Figure 1. Hierarchical infrared spectral-engineered SEBA super fabric for urban heat island mitigation.(a) Application of SEBA fabric on building facades alleviates urban heat island (UHI) effect and reduces indoor cooling demand.(b) SEBA fabric protects wearers by blocking thermal radiation from ground and surrounding buildings while enabling passive cooling through atmospheric transparency window (ATW) radiation.(c) Fabrication process of SEBA super fabric.

Figure 2. Digital images and morphological characteristics of SEBA super fabric.(a) Digital image of SEBA super fabric.(b) Schematic model illustrating its layered structure.(c) SEM image of SEBA outer layer and (d) fiber diameter distribution.(e) SEM image of SEBA middle layer and (f) fiber diameter distribution.(g) SEM image of SEBA inner layer and (h) fiber diameter distribution.

Figure 3. Structural and spectral properties of SEBA super fabric.(a) Schematic of hierarchical structure.(b) Spectral characteristics of outer layer.(c) Spectral characteristics of inner layer.

Figure 4. Outdoor passive daytime radiative cooling performance of SEBA super fabric under isolated thermal input.(a) Schematic of horizontally placed custom testing device.(b) Structural diagram of the device.(c) Real-time solar irradiance during testing on January 13, 2025 afternoon.(d) Real-time relative humidity and wind speed during testing.(e) Temperature curves with inset showing sky conditions in the afternoon.(f) Temperature difference curves.

Figure 5. Outdoor passive daytime radiative cooling performance of SEBA super fabric under ambient thermal influence.(a) Schematic of vertically placed custom testing device.(b) Structural diagram of the device.(c) Real-time solar irradiance during testing on January 15, 2025 afternoon.(d) Temperature curves.(e) Temperature difference curves.(f) Schematic of SEBA's infrared absorption from human skin.(g) Comparative temperature curves of SEBA vs. commercial cotton fabric in absorbing skin radiation.

Figure 6. Practical performance of SEBA super fabric.(a) Thermal conductivity.(b) Infrared images of outer/inner layers on 60°C hotplate at different times.(c) Surface temperature curves on 60°C hotplate over time.(d) Thermogravimetric curve.(e) Air permeability.(f) Air permeability of SEBA without SiO₂/Al₂O₃.(g) Air permeability comparison: polyester, nylon, commercial cotton, and CF fabric.(h) Moisture permeability.(i) Outer layer durability (washing/aging/abrasion resistance).(j) Inner layer durability (washing/aging/abrasion resistance).

Figure 7. Energy-saving effects of SEBA super fabric applied to building walls/roofs.(a) Total summer cooling energy consumption in 14 Chinese cities.(b) Regional cooling energy savings.(c) Energy savings in Hangzhou and Shanghai.(d) Geographical distribution of summer cooling energy savings across China.

Conclusion
In summary, this study successfully fabricated a hierarchical infrared spectral-engineered super fabric using asymmetric electrospinning technology. This fabric combines selective and broadband infrared spectral characteristics to enhance thermal comfort for both human wearers and buildings while mitigating urban heat island effects.

The SEBA fabric's outer layer exhibits high solar reflectivity (93.76%), effectively suppressing solar radiation absorption, along with a high atmospheric transparency window (ATW) spectral selectivity ratio (1.20) and emissivity (0.91) for efficient radiative heat dissipation. The inner layer features approximately 99% broadband infrared emissivity, efficiently absorbing human body radiation to prevent heat accumulation.

Through rational spectral design, the fabric demonstrates exceptional cooling performance:

When placed horizontally, it maintains an average temperature 3.67°C below ambient

In vertical orientation, it outperforms traditional broadband radiative cooling fabrics by 0.54°C

Its outstanding thermal insulation (~23 mW·(m·K)⁻¹) and airtightness ensure sub-ambient temperature comfort, while maintaining practical moisture permeability (6.829 mg·(cm²·h)⁻¹) for wearability. EnergyPlus simulations confirm SEBA's excellent energy efficiency and sustainability when applied to building facades and roofs.

This solution-processable, high-performance, and scalable hierarchical infrared spectral-engineered super fabric provides an expandable and sustainable strategy for maintaining personal thermal comfort and alleviating urban heat island effects.