Electrospinning Machine | Thermally insulating mats based on electrospun fibers with bioinspired nano-groove surface structure

Heating and insulation of buildings account for more than 50% of total energy costs, highlighting the urgent need not only for advanced insulation materials but also for nature-inspired design strategies to improve energy efficiency and address the global energy crisis.

In this study, the authors propose a one-step fabrication method that enhances the thermal insulation efficiency and mechanical properties of polymer fiber mats. By leveraging bioinspired design, the researchers successfully fabricated nano-grooved fibers through precise humidity control during in-situ electrospinning. This approach mimics the nano-grooved structure of Old Man Cactus hairs, offering a simple yet effective method to regulate the nanoscale morphology of the fibers. When applied to hot water pipes, the nano-grooved fibers reduced the surface temperature by 10% compared to traditional insulation coatings. Notably, the nano-grooved fiber coating saves 25% energy per unit area and is approximately 29 times more efficient per gram of material mass than commercial rubber insulation. This research highlights the critical role of nanoscale surface morphology engineering, particularly in the facile fabrication of nano-grooved structures, for mitigating energy and heat loss during thermal transmission. Capitalizing on the unique advantages of humidity-controlled polymer fiber structuring, this method enables the development of flexible high-performance thermal insulation materials, opening new pathways for versatile applications across various fields. The related research, entitled "Thermally insulating mats based on electrospun fibers with bioinspired nano-groove surface structure," was published in the journal Chemical Engineering Journal.

Chemical Engineering Journal. Highlights of this article:
• Fiber design inspired by the nano-groove structure of Cephalocereus senilis cactus hairs.
• Nano-grooved fibers reduce surface temperature by about 10% compared to traditional insulation coatings.
• The coating saves 25% energy per area and has 29 times higher weight efficiency compared to rubber insulation.
• Nanoscale surface morphology significantly improves thermal insulation performance.
• This method enables scalable production of next-generation energy-efficient insulation materials.

This study achieved the one-step preparation of polymer fiber mats with nano-groove structures (ngF) by precisely controlling the relative humidity (RH) during electrospinning, with the specific mechanism as follows: 

1. Differentiated setting of humidity parameters: Specific humidity conditions were set for two fiber morphologies (smooth fiber sF and nano-grooved fiber ngF). Smooth fibers were prepared at 60% RH, while nano-grooved fibers were prepared at 30% RH. This humidity difference is key to controlling the fiber surface morphology. 

2. Regulation of solvent evaporation kinetics: Humidity determines the microstructure of the fiber surface by affecting the evaporation rate and manner of the solvent in the polymer solution. In a low humidity environment of 30%, the solvent (a mixture of dimethylacetamide and tetrahydrofuran) evaporates faster, leading to the formation of significant nanoscale groove structures on the fiber surface. The formation of these grooves originates from interfacial disturbances caused by uneven surface tension in the polymer solution during rapid solvent evaporation, ultimately solidifying into a stable nano-grooved morphology. 

3. Biomimetic matching with biological structures: Through the aforementioned humidity control, the surface roughness (Ra≈119 nm) of the prepared nano-grooved fibers is close to that of cactus hairs (Ra≈131 nm), successfully mimicking the thermal insulation characteristics of the natural structure. Meanwhile, parameters such as fiber diameter (ngF approx. 5.17 μm) and cross-sectional morphology (circularity 0.64) were also precisely controlled through humidity regulation, ensuring the overall performance of the fiber mat. 

This one-step electrospinning process based on humidity control allows for precise regulation of nanoscale surface morphology without additional post-processing steps, providing a simple and scalable technical path for the efficient preparation of biomimetic thermal insulation materials.

Figure 1 Strategy for preparing biomimetic hairy fiber mats by electrospinning inspired by cactus hairs and their functional application in thermal insulation.

Figure 2 Study on the morphology, cross-section, and surface of single cactus hair-inspired polymer fibers.

Figure 3 Thermal insulation performance of polymer fibers and cactus hair mats.

Figure 4 Comparison of thermal conductivity between commercial and electrospun materials.

Figure 5 Schematic explanation of the effect of nano-grooves on the heat flow behavior of ngF mats.

Figure 6 Heat transfer simulation and energy saving analysis of cactus hair-inspired fibers.

Conclusion
The new method adopted in this study facilitated the development of recyclable polymer mats as alternatives to existing insulation materials. The study successfully prepared thermal insulation mats based on nano-grooved fibers, which showed a 65% higher temperature difference (ΔT) at all temperatures compared to fibers without nano-grooves. This indicates that biomimicking the nano-groove structure of cactus hairs helps develop fiber mats with wide applicability, good flexibility, high mechanical strength, and thermal insulation properties. All these fiber mats can be easily prepared via one-step electrospinning under controlled humidity conditions. 

This study clearly shows that the thermal insulation performance of these materials is largely influenced by the roughness and morphology of individual fibers in the mat. Importantly, the properties of single fibers were verified using scanning thermal microscopy and theoretically confirmed through numerical simulations. The random arrangement of fibers in the mats and coatings enhances thermal insulation by trapping air within the nano-grooves of the electrospun non-woven fibers. 

Inspired by cactus hair mats, the thermal insulation efficiency of nano-grooved fibers (ngF) for water pipes is about 30% higher than that of smooth fibers (sF) and about 10% higher than that of commercial rubber coatings under the same experimental conditions. In addition to excellent thermal insulation performance, these mats also exhibit outstanding mechanical properties, with significant improvements in the toughness and strain of the nano-grooved fiber mats. Compared to commercial insulation materials, the nano-grooved fiber coating is 25% more energy-efficient per unit area and about 29 times more energy-efficient per gram of material. 

In summary, this research demonstrates a practical and simple one-step strategy to enhance the applicability and effectiveness of biomimetic nano-grooved fiber mats as thermal insulation materials.

Original link: https://doi.org/10.1016/j.cej.2025.166441