Paint That Changes Color Based on Air Temperature

Temperature-Responsive Paint Changes Color With Heat Researchers inspired by a desert-dwelling chameleon are developing an energy-efficient, cost-effective coating. According to research published in ACS Nano Letters, this material can keep buildings cool in summer and warm in winter without requiring additional energy. Many desert organisms possess special adaptations enabling survival in harsh environments with large daily temperature fluctuations. For example, the Namaqua chameleon in southwest Africa changes color to regulate body temperature as conditions shift. These animals appear light gray in hot weather to reflect sunlight and stay cool, then turn dark brown when cold to absorb heat. This unique ability represents a naturally occurring example of passive temperature control—a phenomenon that could be adapted to create more energy-efficient buildings. However, many existing systems such as cooling paints or colored steel tiles are designed only to keep buildings either cool or warm and cannot switch between "modes." Inspired by the Namaqua chameleon, Fuqiang Wang and colleagues wanted to create a color-changing coating that adapts as external temperatures fluctuate. To produce the coating, researchers mixed thermochromic microcapsules, specialized microparticles and binders to create a suspension that they sprayed or brushed onto a metal surface. When heated to 68 degrees Fahrenheit (20°C), the surface began changing from dark gray to light gray. The light-colored coating reflected up to 93 percent of solar radiation when reaching 86 degrees Fahrenheit (30°C). This material showed no signs of damage even when heated above 175 degrees (80°C) throughout an entire day. The team then tested this coating alongside three conventional coatings (standard white paint, passive radiative cooling paint and blue steel tiles) over four seasons in outdoor tests on miniature, doghouse-sized buildings. The new coating was slightly warmer than the passive radiative cooling system during winter. However, both maintained similar temperatures in less cold conditions. In summer, the new coating was considerably cooler than white paint and steel tiles. In spring and autumn, the new coating was the only system capable of adapting to widely fluctuating temperature changes, transitioning from heating to cooling throughout the day. Researchers noted that this color-changing system could provide significant energy savings for regions experiencing multiple seasons and is easy and inexpensive to produce. Source