Scalable method of fabricating structured polymers for passive daytime radiative cooling and other applications

A method for controlling the transmission of light to a substrate, the method comprising:

• disposing a porous structured polymer layer atop a substrate, the substrate having
• a first surface defining at least part of an enclosed volume;
• providing fluid having a refractive index that is within about 30% of the refractive index of the porous structured polymer layer in fluid communication with the porous structured polymer layer;
• wetting the porous structured polymer layer with the fluid;
• withdrawing the fluid from the enclosed volume to a reservoir separate from the enclosed volume;
• and
• drying the porous structured polymer layer as the fluid is withdrawn from the enclosed volume.

A fluid heating and cooling system comprising:

• a substrate having a first light-permeable surface defining at least part of an enclosed volume;
• an opaque porous structured polymer layer disposed on the first light-permeable surface and in fluid communication with the enclosed volume;
• a reservoir in fluid communication with the enclosed volume and including a first fluid, the first fluid being able to wet but not dissolve the opaque porous structured polymer layer, and dry the porous structured layer when the fluid is withdrawn in the reservoir;
• and
• a source of a second fluid in fluid communication with a cooling conduit and a heating conduit;
• wherein the reservoir being configured to supply the first fluid to the enclosed volume such that the first fluid contacts the opaque porous structured polymer layer, the first fluid has a refractive index that is within about 15% of the refractive index of the opaque porous structured polymer layer, the cooling conduit is proximate to the opaque porous structured polymer layer, and the heating conduit is positioned to receive light transmitted through the substrate.