Efficient Anti-Fog and Anti-Reflection Functions of the Bio-Inspired, Hierarchically-Architectured Surfaces of Multiscale Columnar Structures

Today, in the fields of optical precision instruments, medical devices, and automotive engineering, the demand for anti-reflection and anti-fog surfaces is growing rapidly. However, the anti-fog function often compromises the efficiency of the anti-reflection function. Therefore, optical precision instruments are always restricted by the inability to combine high anti-reflection efficiency and excellent anti-fog performance into one material. In addition, the synergistic mechanism of harmonizing anti-fogging and anti-reflection is currently unclear, which has a negative impact on the development and optimization of multifunctional surfaces. Herein, bio-inspired anti-fogging and anti-reflection surfaces (BFRSs) possessing multiscale hierarchical columnar structures (MHCS) were obtained using a brief and effective preparation technique, combining the biotemplating method and sol-gel method. Specifically, condensed fog droplets distributed on the BFRS can be absolutely removed within 6 s. In addition, the BFRSs endow the glass substrate with a relatively higher reflectance (17%) than flat glass surfaces (41%). Furthermore, we demonstrated the synergistic mechanism of the anti-fogging and anti-reflection functions of BFRSs. On the one hand, the high transparency benefits from the multiple refraction and scattering of light in the MHCS array. On the other hand, the excellent anti-fogging performance is attributed to the imbalance of the capillary force of the MHCS acting on the liquid film. The explanation for these two mechanisms provides more possibilities for the subsequent preparation of multifunctional surfaces. At the same time, the bionic research concept provides new solutions for the researcher to conquer the combination of high transmission and anti-fog properties for precision optical surfaces.