The paper: https://advances.sciencemag.org/content/3/11/e1700895 https://advances.sciencemag.org/content/3/11/e1700895 And the paper for nanoPE: https://scienc

The paper: https://advances.sciencemag.org/content/3/11/e1700895 https://advances.sciencemag.org/content/3/11/e1700895 And the paper for nanoPE: https://science.sciencemag.org/content/353/6303/1019 https://science.sciencemag.org/content/353/6303/1019 ... TLDR, they sandwiched a reflective and emissive surface inside of a thermally transparent material. Body heat convects to the surface (so it needs to be tight fitting), and the surface is radiatively coupled to the environment (emissive surface), but not to the body (reflective surface). You lose out on directly radiating body heat through the nanoPE, but that doesn't work well anyway. Anyway... it probably wouldn't work very well if the ambient temperature was high since it is absorbing LWIR from the environment. The article does mention MIR (MWIR) a few times, though. There isn't anything MWIR specific with this fabric, but the atmosphere is generally very cold in that band, so maybe LWIR can be reradiated in the MWIR by the fabric even when the ground temperature is at/above body temperature. The blackbody power in the MWIR at 98.6F is pretty poor, so it can't be much. They used an ambient temperature of 22.0C in the paper, which is kind of cheating (why bother with a cooling shirt at that temperature?). The LWIR coupling will help a lot at that temperature. Once the ambient gets close to human body temp, though, it'll not work nearly as well. One could run the numbers to see, the thermal model is pretty simple.