Controlling body heat is important in a variety of situations, particularly during heavy physical exertion and when patients have high fevers. Currently there are few methods of lowering one’s temperature, and many of those can be impractical, especially if a power source is required. Now, a team of scientists at the University of Missouri has developed a material that can cool the skin by about 11°F (6°C) and also act as a substrate for flexible body monitoring electronics. The new material may perform a variety of healthcare related tasks while moderating body temperature, something that soldiers, athletes, and others could benefit from. The porous material reflects sunlight and allows body heat to escape at the same time and a prototype device containing it was tested on human skin. “Our device can reflect sunlight away from the human body to minimize heat absorption, while simultaneously allowing the body to dissipate body heat, thereby allowing us to achieve around 11 degrees Fahrenheit of cooling to the human body during the daytime hours,” said Zheng Yan, a corresponding author of the study appearing in the Proceedings of the National Academy of Sciences (PNAS). “We believe this is one of the first demonstrations of this capability in the emerging field of on-skin electronics.” The researchers believe that their material, being strong yet flexible, could function as a part of clothing that covers large areas of the body. They even suspect that this approach could lead to lower usage of air conditioning as spaces won’t need to be cooled as much. From the study in PNAS: This property [passive cooling] is inherited from multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) supporting substrates. The multiscale pores of SEBS substrates, with characteristic sizes ranging from around 0.2 to 7 µm, can effectively backscatter sunlight to minimize heat absorption but are too small to reflect human-body mid-infrared radiation to retain heat dissipation, thereby delivering around 6 °C cooling effects under a solar intensity of 840 W⋅m−2. Other desired properties, rooted in multiscale porous SEBS substrates, include high breathability and outstanding waterproofing. The proof-of-concept bioelectronic devices include electrophysiological sensors, temperature sensors, hydration sensors, pressure sensors, and electrical stimulators, which are made via spray printing of silver nanowires on multiscale porous SEBS substrates. The devices show comparable electrical performances with conventional, rigid, nonporous ones. Also, their applications in cuffless blood pressure measurement, interactive virtual reality, and human–machine interface are demonstrated. Study in Proceedings of the National Academy of Sciences: Multiscale porous elastomer substrates for multifunctional on-skin electronics with passive-cooling capabilities Source
