Robust multistage thermochromic superhydrophobic coating prepared by a facile one-step spray coating method

Emerging smart thermochromic coating technologies have demonstrated significant potential in applications such as temperature indication, safety warning, and energy efficiency management. Inspired by the thermoregulation mechanism of chameleon skin, this study presents a reversible thermochromic superhydrophobic coating featuring multilevel temperature responsiveness and multicolor transitions based on ambient temperature. Three types of thermochromic microcapsules (TCMs) were combined with nano-silica (SiO₂) to construct dual-scale particles, which were further modified with long-chain silanes. A fluorine-free, environmentally friendly superhydrophobic coating with a hierarchical micro/nanostructure was subsequently fabricated via a simple one-step spraying method. The coating exhibits a distinct and reversible tricolor transition (“green–yellow–red”) within the temperature range of 15–35 °C, closely aligning with human thermal perception. It demonstrates excellent superhydrophobicity, with a water contact angle (WCA) exceeding 150° and a sliding angle below 3°. Notably, the WCA increases to over 160° after mild sand abrasion. The coating maintains remarkable stability after sandpaper abrasion, mechanical impact, chemical corrosion, and prolonged UV exposure, showcasing exceptional durability. Electrochemical impedance spectroscopy (EIS) further verifies its outstanding barrier performance. Additionally, the coating shows strong liquid repellency against various common liquids (tea, cola, milk, juice), along with excellent self-cleaning capabilities and broad substrate applicability. This innovative, green, and robust thermochromic superhydrophobic coating offers strong potential for practical applications in smart surfaces, thermal warning systems, and multifunctional protective materials.