Humans lose body heat in many ways, such as through direct contact with cold surfaces or via convection in windy weather, but most commonly due to infrared electromagnetic waves that radiate energy away.
Bulky winter coats defend their wearer from the elements using air pockets to retain warmth and insulate from the cold. However, the days of puffy down jackets may be numbered, thanks to photonic crystal textiles that block body heat from radiating away. Çetin et al. proposed one such material and numerically evaluated its theoretical performance.
“Photonic crystals are artificially formed structures with periodic alternating arrangements of high and low dielectric constant materials,” said author Zebih Çetin. “Electromagnetic waves scattered from different points of the structure cause interference, and depending on whether this interference is damping (destructive) or strengthening (constructive), waves with frequencies in a certain range would be prohibited from propagating inside the crystal, giving rise to what are called photonic bandgaps.”
The bandgaps can be arranged to reflect desired frequencies, retaining body heat or keeping the body cool by blocking heat from the environment.
Instead of mounting photonic crystals onto fabric, the desired effect can be achieved simply by using a fiber that meets the required geometrical, electrical, and optical properties. By weaving the fabric into a periodic pattern, the textile itself becomes the photonic crystal.
Based on the authors’ calculations, such a fabric could block up to 53% of radiated electromagnetic energy.
“The pattern we propose is a proof-of-concept model of a class of textiles with intricate weaving patterns using a wide range of available materials,” said Çetin. “This shows that fundamental physics can still be a fashionable subject!”
Source: “Photonic crystal textiles for heat insulation,” by Zebih Çetin, Yiğit Tunçtürk, and Hüseyin Sami Sözüer, Journal of Applied Physics (2023). The article can be accessed at https://doi.org/10.1063/5.0157736.