A fabric that can be switched between two different states to stabilize radiative heat loss and keep the wearer comfortable across temperature ranges is the subject of a study that was published in PNAS Nexus.
Po-Chun Hsu, Jie Yin, and partners planned a texture made of a layered, semi-strong electrochemical cell sent on a nylon slice in a kirigami example to permit it to stretch and move with the wearer’s body. Although a variety of breathable or insulating fabrics are used in modern clothing, each one only offers one thermal mode, which is determined by the emissivity of the fabric—the rate at which it releases heat.
The fabric’s active material can switch between two states by electrical means: a transmissive dielectric state and a lossy metallic state, each with a different emissivity. By adjusting how much of the wearer’s body heat is retained and radiated away, the fabric can thus maintain the wearer’s comfort. Regardless of whether the outside temperature was 17.1°C (62.8°F) or 22.0°C (71.6°F), a user would feel the same temperature on their skin. This fabric has been set up to be controlled by a smartphone app, and the authors refer to it as a “wearable variable-emittance device,” or WeaVE.
Although they require a lot of energy, some active thermoregulatory fabrics make use of technologies like electric heating or recirculating water. The minuscule amount of energy required to alter the fabric’s state is all that the WeaVE system needs. The authors estimate that the energy contained in a typical smartphone battery could be used to switch the fabric approximately 1,000 times.
More information: Po-Chun Hsu, A Kirigami-enabled Electrochromic Wearable Variable Emittance (WeaVE) Device for Energy-Efficient Adaptive Personal Thermoregulation, PNAS Nexus (2023). DOI: 10.1093/pnasnexus/pgad165
