Purdue workforce develops thin-layer light-weight and ultrawhite paints for daytime radiative cooling


The Purdue College researchers who created the world’s whitest paint (earlier submit) have developed a brand new formulation that’s thinner and lighter—superb for radiating warmth away from vehicles, trains and airplanes.

The unique world’s whitest paint used nanoparticles of barium sulfate to mirror 98.1% of daylight, cooling out of doors surfaces greater than 4.5°C under ambient temperature.

To realize this degree of radiative cooling under the ambient temperature, we needed to apply a layer of paint at the very least 400 microns thick. That’s high quality in the event you’re portray a strong stationary construction, just like the roof of a constructing. However in functions which have exact measurement and weight necessities, the paint must be thinner and lighter.

—Xiulin Ruan, a Purdue professor of mechanical engineering and developer of the paint

Ruan’s workforce started experimenting with different supplies, pushing the restrict of supplies’ functionality to scatter daylight. Their newest formulation is a nanoporous paint incorporating hexagonal boron nitride (hBN) because the pigment, a substance principally utilized in lubricants. This new paint achieves practically the identical benchmark of photo voltaic reflectance (97.9%) with only a single 150-micron layer of paint.

Thin ultrawhite paint formulation

Purdue College researchers have created a brand new system for the world’s whitest paint, making it thinner and lighter. The earlier iteration (left) required a layer 0.4 millimeters thick to attain sub-ambient radiant cooling. The brand new formulation (proper) can obtain comparable cooling with a layer simply 0.15 millimeters thick. That is skinny and light-weight sufficient for its radiant cooling results to be utilized to autos corresponding to vehicles, trains and airplanes. (Purdue College picture/Andrea Felicelli)

An open-access paper on the analysis is revealed in Cell Stories Bodily Science.

Skinny and light-weight radiative cooling paints are wanted for a lot of weight-sensitive functions. Nevertheless, it’s troublesome to attain excessive photo voltaic reflectance with skinny layers. This work develops ultrawhite hBN-acrylic paints that obtain photo voltaic reflectance of 97.9% and sky window emissivity of 0.83 with solely 150 μm thickness and 0.029 g/cm2 weight, representing important reductions from earlier radiative cooling paints.

The excessive refractive index and nanoplatelet morphology of hBN allow a novel mixture of Mie scattering-like excessive scattering coefficient and Rayleigh scattering-like sturdy backscattering, and a porosity of 44.3% presents excessive refractive index distinction between hBN and air; all contribute to attain excessive photo voltaic reflectance with a skinny coating.

Area exams present full daytime cooling beneath direct daylight, reaching 5–6°C under ambient temperature on common throughout sunlight hours. Our hBN-acrylic paint demonstrates comparable cooling efficiency with latest greatest applied sciences, and the thinness and light-weight weight scale back obstacles towards many sensible functions.

—Felicelli et al.


Felicelli et al.

Laptop simulations confirmed that the nanoplatelets are simpler in bouncing again the photo voltaic radiation than spherical nanoparticles utilized in earlier cooling paints.

The paint additionally incorporates voids of air, which make it extremely porous on a nanoscale. This decrease density, along with the thinness, reduces weight. The newer paint weighs 80% lower than barium sulfate paint but achieves practically similar photo voltaic reflectance.

This mild weight opens the doorways to every kind of functions. Now this paint has the potential to chill the exteriors of airplanes, vehicles or trains. An airplane sitting on the tarmac on a scorching summer season day received’t need to run its air con as onerous to chill the within, saving giant quantities of power. Spacecraft additionally need to be as mild as potential, and this paint will be part of that.

—George Chiu, a Purdue professor of mechanical engineering and an professional in inkjet printing

Patent functions for this paint formulation have been filed by way of the Purdue Analysis Basis Workplace of Expertise Commercialization.

This analysis was supported by the Nationwide Science Basis with Award No. 2102645, and lead writer Andrea Felicelli was supported by a Nationwide Science Basis Graduate Analysis Fellowship. The analysis was carried out at Purdue’s FLEX Lab and Ray W. Herrick Laboratories and the Birck Nanotechnology Middle of Discovery Park District at Purdue.


  • Andrea Felicelli, Ioanna Katsamba, Fernando Barrios, Yun Zhang, Ziqi Guo, Joseph Peoples, George Chiu, Xiulin Ruan (2022) “Skinny layer light-weight and ultrawhite hexagonal boron nitride nanoporous paints for daytime radiative cooling,” Cell Stories Bodily Science, doi: 10.1016/j.xcrp.2022.101058


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