Green Radiative Cooling and Antimicrobial Materials Based on Polylactic Acid Oligomer Hexagonal Microspheres

Thermal management by passive radiative cooling materials can save energy and reduce emission of green-house gas remarkably compared with traditional air-conditioner cooling. However, few of these materials are degradable, thus their disposal may lead to another environmental problem. Meanwhile, the COVID-19 pandemic and other infectious diseases have raised the requirement of hygienic and antimicrobial performance. This work reports a discovery that polylactic acid oligomer (PLAO) material possesses radiative cooling effect, wide-spectrum antimicrobial property and degradability, simultaneously. The radiative cooling effect is attribute to the hexagonal microsphere geometry and nanotexture of polylactic acid oligomer (PLAO) crystals, which enhance the reflectivity in the solar spectrum through multiple scattering effect and exhibit high emissivity in the mid-infrared atmospheric window. Hierarchically porous PLAO coating material realizes an apparent temperature reduction of 6.8 ℃ under irradiation of solar spectrum (AM 1.5). The material also shows wide-spectrum antimicrobial and anti-viral properties against coronaviruses (including COVID-19 virus), gram-positive bacteria, gram-negative bacteria, fungi and multidrug resistant bacteria.