Droplet Directional Bouncing-Enabled Bent Micropillar Arrays Integrated on Focusing Optical Elements for Anti-fogging, Anti-fouling, and Anti-icing Applications

Focusing optical elements are susceptible to performance degradation in harsh environments caused by fog, ice, and dust. Existing protective solutions struggle to balance high light transmittance with effective anti-icing and self-cleaning properties. Here, taking inspiration from asymmetric structures observed in nature, a focusing optical element with surface-integrated bent micropillar arrays is proposed, which exhibits antifogging, antifouling, and anti-icing capabilities. The focusing element is fabricated through a combination of femtosecond-laser processing, soft lithography, and pneumatic pressure-assisted molding. The bending angle of the micropillar array can be precisely regulated by adjusting the femtosecond-laser parameters. The results demonstrate that the bent micropillar arrays facilitates directional droplet rebound and imparts self-cleaning and antifogging functionalities to the surface. Additionally, it markedly decreases ice adhesion strength. Under simulated conditions characterized by pollution, elevated humidity, and low temperature, the focusing element sustains a high visible light transmittance exceeding 86%, while exhibiting outstanding multifunctional protective capabilities and stability. This work presents a design paradigm for the stable operation of optical devices in challenging environments.