Self‐Assembling Cracks to Fabricate Antireflective Antifogging Metasurfaces

Abstract Transparent components often face key visibility issues such as reflection and fogging formation. Antireflective strategies are developed to enhance transparency and reduce reflection. More recently, active antifogging metasurfaces are introduced to harness external light for efficient fog removal via photothermal heating but they are made of optical absorbers that compromise visibility. Here, these limitations are addressed by taking advantage of a seemingly disadvantageous phenomenon, crack formation, to develop a multifunctional optical device combining plasmonic photothermal heating with an antireflective function. This process creates linear arrays of plasmonic nanoparticles, generating localized heating under illumination, while a mesoporous sol‐gel hybrid silica coating provides antireflection and water repellency. The device, characterized by environmental ellipsometry and hyperspectral microscopy, effectively reduces reflections and accelerates fog removal under external light, including smartphone Light Emitting Diodes (LEDs). Its scalable, solution‐based fabrication makes it suitable for applications such as windows, eyewear, and cryogenic microscopy. More broadly, this work demonstrates how structural defects can be transformed into functional advantages for optical applications.