Daytime radiative cooling dressings for accelerating wound healing under sunlight

The process of wound healing is sensitive to various factors of the local environment, including temperature, humidity and sterility. However, due to lack of efficient thermal regulation in existing wound dressings, the perturbed local environment and oxidative stress caused by an increased wound temperature under outdoor sunlight inevitably impacts wound healing. Here we demonstrate a daytime radiative cooling dressing based on a polyamide 6/silk fibroin bilayer that reduces the thermal load for skin wounds under sunlight illumination. The mid-infrared transparent polyamide 6 and the biocompatible silk fibroin together endow a high mid-infrared emissivity (~0.94) and sunlight reflectivity (~0.96), thus achieving a temperature of ~7 °C below ambient under direct sunlight. When used for repairing mouse skin full-thickness injuries under sunlight, we observed an accelerated wound healing rate compared with that of commercial dressings. This work therefore offers a promising strategy for passive temperature regulation to accelerate wound healing under sunlight.