Biomimetic thermal regulation in intelligent fruit packaging: A fungal hypothermia-bioinspired hydrogel coating

Ambient temperature constitutes a critical environmental factor in postharvest fruit logistics and retail ecosystems. Here, we presented an design of intelligent fruit packaging incorporating poly(N-isopropyl acrylamide) (pNIPAM)-based hydrogel coating to enable thermoregulation, inspired from the natural thermoregulatory mechanism of fungal hypothermia. The as-prepared coating exhibited tough mechanical properties (tensile strength of 62.62 ± 2.84 kPa, Young’s modulus of 57.46 ± 1.69 kPa) and durable thermal responsiveness. When ambient temperature surpassed the lower critical solution temperature (LCST) of hydrogel coating, the packaging transited from hydrophilic to hydrophobic, and deswelled water to the surface, promoting evaporative cooling. Simultaneously, the coating underwent an optical transition from transparent to opaque state, reducing the solar irradiance transmission, including visible light, infrared light, and ultraviolet light. Notably, the LCST exhibited precise tunability across a food logistics-relevant temperature range (3–32 °C) as required through NaCl concentration modulation. Here, we prepared intelligent packagings for different fruit with various LCST, which effectively achieved the temperature reduction within the packaging, and maintained the fruit quality. This biomimetic application enables autonomous thermal regulation in agri-food logistics, while providing a way for intelligent food packaging systems.