Scalable Superhydrophobic Flexible Nanofiber Film for Passive Daytime Radiative Cooling

Abstract

Passive daytime radiative cooling technology can cool objects without any energy consumption. Although some progress has been made, there are still challenges in manufacturing low-cost, anticontaminant, and weathering-resistant radiative coolers for long-term cooling. Herein, a superhydrophobic flexible cooling radiator (SFCR) as a film is fabricated by a facile, inexpensive, and scalable electrospinning and electrospraying method. The SFCR film consists of poly­(vinylidene fluoride-co-hexafluoropropylene) fiber frameworks adhered to by numerous microaggregates from SiO2 nanoparticles. The SFCR film exhibited a strong solar reflectivity of 98.5% and an average emissivity of more than 95%. It also showed superior superhydrophobicity and wettability with a static water contact angle of 156° and sliding angle of 2.2°. The average temperature drop of the film was 11.6 °C compared to the air around the film under sunlight. Importantly, the self-cleaning effect of the SFCR film robustly protects its surface against outdoor contamination and is conducive to sustainable cooling. This SFCR film integrating radiative cooling with self-cleaning characteristics is promising for scalable production and can be utilized on buildings, vehicles, and other terrestrial objects.

Superhydrophobic SiO2–Glass Bubbles Composite Coating for Stable and Highly Efficient Daytime Radiative Cooling

“…For further investigation of the outdoor radiative cooling capability of the SDRC coating, field experiments were carried out from 4 May 2022 to 18 June 2022 on the roof of the School of Materials Science and Engineering, Hubei University, Wuhan, China (30°35′1″N, 114°19′44″E, 70 m altitude), under direct sunlight for radiative cooling performance (Figure a,b), experimental setup with reference to previous studies. ,, The radiative cooling effect of the different coatings was first tested using a 5 cm × 5 cm aluminum sheet as a substrate. Experiments were carried out using pristine aluminum sheets and a commercial superhydrophobic silica as the control group, and real-time temperatures were recorded for all samples and PE-shielded air (Figure a).…”

Recent progress in organic-based radiative cooling materials: fabrication methods and thermal management properties

“…102 Moreover, hydrophobic SiO 2 nanoparticles were selected to enhance the superhydrophobicity of a P(VdF-HFP) film obtained by electrospraying method. 103 Researchers often use Al 2 O 3 and SiO 2 as fillers of polymer radiatve cooling matrix at the same time, which can improve the high reflectivity and show dual selectivity and broadband optical properties in IR region. 104 What's more, the composite radiative cooling membranes with gradient moisture absorption ability are more comfortable to wear.…”

Electrospun polymer nanocomposites for thermal management: a review

“…So far, two methods for preparing PVDF/SiO 2 composites applied in PDRC have been addressed, namely, e-spinning/emulsion deposition 66 and e-spinning/e-spraying. 70 Then the direct e-spinning method would be supplemented. In 2022, Li et al obtained a spinning solution by adding SiO 2 microspheres (3–7 μm) to the N , N -dimethylformamide solution of PVDF and stirring at 60 °C and ultrasonic vibration.…”

“…A superhydrophobic PDRC was fabricated by Hu et al via first e-spinning a PVDF-HFP solution to obtain fiber frameworks and then e-spraying SiO 2 nanoparticles on the as-prepared fiber frameworks. 70 In the process, the ethanol- N , N -dimethylformamide–acetone mixture for producing a homogeneous SiO 2 colloidal dispersion being similar to the solvent for PVDF, acted as a binder to make the SiO 2 spheres closely adhere to the fiber frameworks. The membrane prepared by the two technologies successively possesses more 3D micro/nanoscale structures.…”