Combining a flexible solar cell with an electrocaloric device, researchers have created solar-powered clothing that allows the body to adapt dynamically to changes in ambient temperature, according to a new study. The new device could help guarantee the safety and comfort of the human body amid fluctuating environmental temperatures and even extend survivability in extreme environments, like those in outer space or other planets. Clothing is the most common way humans regulate their body temperature relative to the environment. However, it is normally focused on keeping an individual either warm or cool. The ability of clothing to adapt to fast-changing environmental temperatures, particularly in harsh environments like polar regions, deserts, or space, where temperatures can quickly fluctuate between very hot and very cold, remains challenging for current approaches to thermoregulatory clothing. Current thermoregulatory clothing technologies can be separated into two categories. Passive systems encompass radiative cooling, phase change, and adsorption systems. Although these systems have the advantage of not requiring external energy, many only provide one-way thermoregulation (warming up or cooling down). Active thermoregulatory systems allow for rapid cooling or warming but often have large power demands and/or require large and complex mechanical equipment, limiting their use in more conventional clothing types.
Here, Ziyuan Wang and colleagues present an all-day, solar-powered bidirectional thermoregulatory clothing system capable of rapidly responding to various complex or quick environmental temperature changes. Wang et al.'s system combines an organic photovoltaic module with a bidirectional electrocaloric unit into a single flexible device, which can be integrated into conventional clothing. No additional power sources are required since the device is self-powered from sunlight. According to the authors, the device could provide 10.1 Kelvin (K) of cooling to the skin during hot days but also keep the body 3.2 K warmer than bare skin in the dark or at night. As a result, the device maintains human skin temperature within a thermal comfort zone between 32.0 °C and 36.0 °C, even though the environmental temperature varies between 12.5 °C and 37.6 °C. The high efficiency of the device allows for 24 hours of controllable thermoregulation with just 12 hours of sunlight energy input. "The integrated device of Wang et al. opens many possibilities for developing actively controlled, self-powered and wearable localized thermal-management systems and expanding human adaptation to harsh environments," write Xingyi Huang and Pengli Li in a related Perspective. "It is possible to imagine a future of all-weather thermal management that is not limited by an energy supply and where extra collected energy might even power electronic devices under special conditions."
For reporters interested in trends, an August 2021 Science Report described an approach for developing metafabric that could provide passive daytime radiative cooling.
