GT2 - Nigar Namazzade - Self-assembled metamaterial for passive daytime radiative cooling

Описание: Webinar du 18/03/2025, donné par Nigar Namazzade (CRPP, Université de Bordeaux) pour le GDR Ondes et organisé par le groupement thématique :
GT2 : Physique et ingénierie des structures sub-longueur d'onde

Cette vidéo fait partie d'une série de trois:
1 -    • GT2 - Alexandre Baron - Métastructures opt...   par Alexandre Baron
2 -    • GT2 - Joshua Davis - Plasmonic multipod cl...   par Joshua Davis
3 -    • GT2 - Nigar Namazzade - Self-assembled met...   par Nigar Namazzade

Résumé:
Passive daytime radiative cooling (PDRC) is a phenomenon in which a body exposed to solar radiation cools via thermal radiation without requiring an external energy source. For this to occur, two conditions must be met: (1) the body must efficiently backscatter most of the incident solar radiation (0.2–2.5 µm), effectively behaving like a white object, and (2) it must exhibit strong thermal emissivity within the atmospheric transparency window (ATW) in the 7–14 µm range.

According to Kirchhoff’s law of thermal radiation, a body in thermal equilibrium has an emissivity equal to its absorptivity. This implies that designing a perfect absorber in a spectral range corresponding to blackbody radiation is equivalent to designing a perfect emitter in that range. Following this principle, our objective is to design and fabricate a metamaterial that functions as a passive daytime radiative cooler. Ultimately, we aim to develop a material that is easy to fabricate and capable of lowering the temperature of a target object.

In this study, we investigate a potential structure consisting of microballoons or voids embedded in PDMS. PDMS is chosen for its excellent emissivity in the ATW, while the microballoon provides porosity that enhances reflectance in the solar spectrum. The proposed design is numerically characterized, and theoretical predictions are compared with experimental data of fabricated samples. Numerical simulations are performed using the Finite Element Method and effective medium parameter retrieval to accurately model the system’s behavior.