Bio-Inspired Tough Metafiber with Hierarchical Photonic Structures for Durable Passive Radiative Thermal Management

Nanoscience Organic Polymeric Materials Chemistry Materials Science Engineering Optics Energy Engineering Materials Chemistry Life Sciences Physics Bioengineering
bio-inspired fiber photonic structure molecular engineering radiative thermal management multimode thermal regulation

Academic Background

With the intensification of global climate change, energy consumption in buildings, particularly from air conditioning systems, continues to rise. Statistics show that building air conditioning systems account for approximately 10% of global annual electricity consumption, a figure that is increasing alongside carbon emissions, further exacerbating the vicious cycle of global warming. Passive radiative thermal management technologies, especially radiative cooling through selective spectral modulation, are considered a potential solution to this issue. This technology achieves automatic temperature regulation without additional energy input or environmental pollution by scattering sunlight (0.3-2.5 μm) and radiating heat through the atmospheric window (8-14 μm) into outer space (approximately 3 K).

However, existing radiative cooling materials, such as glass, blocks, films, and coatings, often suffer from insufficient flexibility and air permeability, limiting their application to specific object surfaces. Fiber-based materials, due to their excellent flexibility and plasticity, are widely used in various scenarios. Nevertheless, existing fiber materials exhibit significant defects in mechanical strength and durability, particularly in outdoor cooling applications, where the combination of high sunlight reflectivity and mechanical strength remains a major challenge.

Source of the Paper

This paper was authored by Xiaoyan Li, Zhiguang Guo, and other researchers from Donghua University, Sichuan University, and the University of Chicago, among other institutions. The paper was published in 2025 in the journal Advanced Fiber Materials under the title Bio-Inspired Tough Metafiber with Hierarchical Photonic Structures for Durable Passive Radiative Thermal Management.

Research Process and Results

1. Research Design and Fiber Preparation

Inspired by natural silk fibers, the researchers designed a biomimetic fiber (PMABF) with a hierarchical photothermal structure. Silk fibers are renowned for their unique hierarchical morphological structure, which imparts excellent optical and mechanical properties. By constructing a multi-scale structure of nanofiber aggregates and employing molecular interface engineering, the researchers developed a tough meta-fiber resembling silk.

The preparation process involved the following steps: 1. Preparation of Aramid Nanofiber (ANFs) Gel: Kevlar 1000D fibers were sheared, washed, and dried, then mixed with dimethyl sulfoxide (DMSO), potassium hydroxide (KOH), and deionized water, and stirred for 24 hours to form an ANFs gel. 2. Fiber Formation: The ANFs gel was injected into needles of different shapes (e.g., silk-like and circular) and left to stand at room temperature for 24 hours to form ANFs gel fibers. 3. Molecular Interface Engineering: The ANFs gel fibers were immersed in a methyltrimethoxysilane (MTMS) solution, and acetic acid was added for in-situ hydrolysis and condensation, forming a nanofiber network structure. 4. Freeze-Drying: Through solvent displacement and freeze-drying techniques, the final PMABF fibers with a hierarchical photothermal structure were prepared.

2. Optical and Mechanical Performance Testing

The researchers conducted a series of experiments to test the optical and mechanical properties of PMABF fibers: - Optical Performance: PMABF fabrics exhibited a high mid-infrared (MIR) emissivity of 98.6% within the atmospheric window and a solar spectrum reflectivity of 86.7%. This high reflectivity is attributed to its ellipsoidal photonic structure featuring surface micro/nano-particles and numerous internal voids. - Mechanical Performance: Through molecular interface engineering, the tensile strength of PMABF fibers increased by 125%, and compressive stress increased by 261.5%. The strong intermolecular forces effectively distributed external stresses, enhancing the mechanical strength of the fibers. - Thermal Stability and Hydrophobicity: PMABF fibers demonstrated excellent thermal stability and hydrophobicity, maintaining their structure and performance even in extreme environments.

3. Practical Application Testing

The researchers applied PMABF fibers to building roofs and exterior walls to simulate their performance in building thermal management. Using EnergyPlus software, they calculated significant reductions in annual energy consumption for buildings installed with PMABF across 11 different climatic conditions, with a maximum reduction of 85.7%. Additionally, PMABF fibers were used to create dual-mode fabrics, switching between cooling and heating modes by depositing a silver film on one side of the fiber using high-vacuum resistance evaporation coating (HVREC) technology.

Conclusion and Significance

This study successfully developed a tough meta-fiber with a hierarchical photothermal structure through biomimetic design, achieving excellent optical and mechanical properties suitable for passive radiative cooling. PMABF fibers not only exhibit high solar reflectivity and MIR emissivity but also demonstrate outstanding mechanical strength, thermal stability, and hydrophobicity, providing new solutions for building energy management and thermal protection in extreme environments.

Research Highlights

  1. Biomimetic Design: By mimicking the hierarchical structure of silk fibers, a biomimetic fiber with excellent optical and mechanical properties was successfully developed.
  2. Molecular Interface Engineering: Molecular interface regulation enhanced the mechanical strength and optical performance of the fibers, achieving synergistic effects in the hierarchical structure.
  3. Practical Applications: The application of PMABF fibers in building thermal management and dual-mode fabrics demonstrates their significant potential in energy savings and thermal management.

Other Valuable Information

The research also showcased the potential of PMABF fibers in thermal stealth and electrothermal applications, further broadening their application scenarios. Using high-vacuum resistance evaporation coating technology, the researchers successfully prepared silver-coated fibers with high conductivity, offering new possibilities for infrared stealth and electrothermal regulation.

This study not only provides new insights into the design of fiber materials but also offers practical solutions for building energy management and thermal protection in extreme environments, holding significant scientific and application value.