Anisotropic hygroscopic hydrogels for high-power, self-sustained passive daytime cooling

Researchers from The Hong Kong Polytechnic University and Jiangnan University, led by Professor Xi Shen, have published a groundbreaking study in Nano-Micro Letters, introducing an innovative anisotropic synergistically performed insulation-radiation-evaporation (ASPIRE) cooler. This cooler leverages a dual-alignment structure within a hygroscopic hydrogel to achieve high-power passive daytime cooling with water self-regeneration.

Why the ASPIRE Cooler Matters

• High Cooling Power: The ASPIRE cooler achieves an impressive cooling power of 311 W m⁻² and an average sub-ambient cooling temperature of ~8.2 °C under direct sunlight.
• Water Self-Regeneration: The cooler can sustain multi-day cooling with water self-regeneration at night, making it self-sustained and suitable for practical applications.
• All-Weather Performance: The ASPIRE cooler maintains effective cooling under both clear and cloudy conditions, demonstrating its robustness and versatility.

Innovative Design and Mechanisms

• Dual-Alignment Structure: The ASPIRE cooler features a dual-alignment structure inspired by human skin, with vertically aligned hydrophilic PVA networks internally for efficient water transport and vertically aligned hydrophobic aerogel externally for thermal insulation and radiative cooling.
• Multiscale Engineering: The coordinated thermal and water transport through multiscale engineering, including molecular crosslinking and nanostructured cell walls, contribute to high radiative and conductive thermal resistance while maintaining low water transport resistance.
• Synergistic Cooling Mechanism: The cooler combines evaporative cooling, radiative cooling, and thermal insulation to reduce heat gains from solar and environmental sources, resulting in a high net cooling power.

Future Outlook

• Scalability and Practical Applications: The scalable synthesis methods and practical configurations of the ASPIRE cooler highlight its potential for real-world applications in high-power, sustainable cooling systems.
• Further Research: Future work may focus on optimizing the materials and structures to enhance the cooling performance and durability of the cooler. Additionally, integrating the ASPIRE cooler with other advanced technologies could expand its applicability.
• Mechanistic Insights: This study provides valuable insights into the mechanisms underlying the synergistic cooling performance of the ASPIRE cooler, offering a promising path for the development of advanced passive cooling technologies.

Stay tuned for more groundbreaking advancements from the research team at The Hong Kong Polytechnic University and Jiangnan University as they continue to explore innovative solutions for high-power, sustainable cooling!