Key Takeaways & Executive Findings
- •• The 55 wt% solid content monodispersed latexes were synthesized under the synergistic action of ionic and nonionic surfactants. • The 55 wt% solid content monodispersed latexes open a homogeneous assembly avenue, establishing high-crystallinity photonic metamaterial (crystallinity: 71.5%). • We developed scalable-designed and color-regulating passive daytime radiative cooling coating based on the high-crystallinity photonic metamaterial, showing high solar reflectance (~0.94), high infrared emittance (~0.97), large sub-ambient cooling temperature (average 5.3 °C), and great cooling power (~95.5 W m−2). • The work provides a promising route to reduce carbon emissions and energy consumption for global sustainability.
Abstract
Methods allowing passive daytime radiative cooling (PDRC) to be carried out in an energy-efficient and scalable way are potentially important for various disciplines. Here, we report a sustainable strategy for scalable-designed and color-regulating PDRC coating based on high-crystallinity photonic metamaterial (crystallinity: 71.5%; enhanced assembly efficiency: 72%), that is derived from the as-prepared 55 wt% solid content poly(methyl methacrylate-butyl acrylate-methacrylic acid) P(MMA-BA-MAA) monodispersed latexes (approaching theoretical limit: 59 wt%). Robust meter-scale PDRC coatings are constructed by various industrial modes onto diverse surfaces, addressing bottlenecks like dull appearance, high cost, low efficiency, and hard construction. Notably, the solar reflectance, long-wave infrared emittance, and calculated theoretical cooling power of the designed PDRC coating, respectively, reach ~0.94, ~0.97, and ~95.5 W m−2 under solar radiation, which can achieve an average 5.3 °C sub-ambient daytime temperature drop in the summer in Nanjing. The cooling performance, scale preparation, and cost-effectiveness of the PDRC coating have extended into leading position compared with those of state-of-the-art designs. This work provides promising route to reduce carbon emissions and energy consumption for global sustainability.
1. Introduction
From the perspectives of global total energy consumption, ~51% of residential housing energy in the United States and above 50% in China are consumed for maintaining the desired indoor temperature (~22 °C) [1, 2]. Especially in hot summer, conventional cooling systems that have been prevalently used require substantial amounts of power input and coolant consumption, which pose global threats of greenhouse gas emissions and urban heat island effect [3]. The escalating energy crisis and climate challenges have intensified the urgency for sustainable cooling. Radiative cooling (RC) emerges as a transformative solution enabling sub-ambient cooling, which cools terrestrial objects by dissipating thermal radiation to the ultracold outer space (~3 K) through the atmospheric transparent spectral window (ATSW: 8 to 13 µm) [4, 5]. As a spontaneous, energy-free, and environment-friendly cooling technique, RC addresses critical challenges, including building energy saving, human thermal management, and synergistic cooling applications [6–8]. In this aspect, various promising RC designs have been extensively explored, such as hierarchical porous polymer [9], dielectric particle-embedded coating [10], fiber-structured film [11], and even metamaterials [12]. These designs hold significant influence and support for more sustainable and carbon–neutral development.
In the contemporary era, photonic engineering, which enables synergistic sunlight reflection and thermal emission, has gained considerable attention for efficient daytime cooling [13, 14]. Photonic crystal (PC), a distinctive class of photonic metamaterial, have been developed for passive daytime radiative cooling (PDRC) based on manipulating light-matter interactions at subwavelength scales [15–17], e.g., photonic-structure colored radiative coolers (measured cooling power: ~51.6 W m−2) [18], flexible hybrid photonic films (theoretical cooling power: ~99.8 W m−2) [19], and mesoporous photonic coating (theoretical cooling power: ~72 W m−2) [20]. However, these studies are largely grounded in theoretical perspectives, and the associated materials are high cost, low yield, along with hardly scale-up generation, which limits their manufacturability. Consequently, it remains a challenge to develop PDRC design with photonic structures for desired real-world applications.
We present here an easy-to-perform and scalable approach to enable a versatile color-regulating PDRC coating based on the high-crystallinity photonic metamaterial, colloidal photonic crystal (CPC), self-assembled from as-prepared monodispersed colloidal latexes with solid content (SC) up to 55 wt%. The structural color of
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Xiao-Qing Yu, Fucheng Li, Jiawei Wang, Nianxiang Zhang, Guo-Xing Li, Yan Song, Qing Li, Su Chen (2026). Scalable-Designed Photonic Metamaterial for Color-Regulating Passive Daytime Radiative Cooling. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01975-y
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Frequently Asked Questions
What is the main achievement of this research?
The research develops a scalable-designed and color-regulating passive daytime radiative cooling (PDRC) coating based on high-crystallinity photonic metamaterial, achieving high solar reflectance (~0.94), high infrared emittance (~0.97), and large sub-ambient cooling temperature (average 5.3 °C) with great cooling power (~95.5 W m−2).
How is the photonic metamaterial synthesized?
The photonic metamaterial is derived from 55 wt% solid content poly(methyl methacrylate-butyl acrylate-methacrylic acid) P(MMA-BA-MAA) monodispersed latexes, synthesized under the synergistic action of ionic and nonionic surfactants, approaching the theoretical limit of 59 wt%.
What are the key performance metrics of the PDRC coating?
The PDRC coating exhibits a solar reflectance of ~0.94, long-wave infrared emittance of ~0.97, and a calculated theoretical cooling power of ~95.5 W m−2, achieving an average 5.3 °C sub-ambient daytime temperature drop in summer in Nanjing.
What are the advantages of this PDRC coating compared to existing designs?
The PDRC coating offers scalable production via various industrial modes, cost-effectiveness, and addresses bottlenecks like dull appearance, high cost, low efficiency, and hard construction, positioning it as a leading design in cooling performance and manufacturability.
What is the significance of this work for sustainability?
This work provides a promising route to reduce carbon emissions and energy consumption by enabling energy-efficient, scalable, and color-regulating passive daytime radiative cooling, contributing to global sustainability.
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