Recently, Weiping Wu's team in the Department of High Power Laser Element Technology and Engineering at the Shanghai Institute of Optics and Precision Machinery (SIPM) of the Chinese Academy of Sciences (CAS), in collaboration with Fudan University, has made progress in antifouling treatment of the surface of ultrathin nano-optical elements. The team proposed a new type of "liquid-like" ultra-smooth film with anti-fouling effect by in situ grafting a flexible bottle-brush shaped organosilicon polymer monolayer onto the surface of an optical substrate. The transparent ultra-smooth anti-fouling film has no significant decrease in transmittance in the visible region, and only a 3% decrease in transmittance in the infrared region, making it a rare high-transmittance solution for hydrophobic surfaces across the entire spectrum. The related research results were published in the Journal of Materials Chemistry A under the title of A fluffy all-siloxane bottlebrush architecture for liquid-like slippery surfaces. Materials Chemistry A.
Optical components (optical lenses, windows, photovoltaic panels, etc.) are used in optical instrumentation, microelectronics, aerospace, energy and biomedical devices. Optical components are highly susceptible to external contamination in the actual service environment, which reduces the optical transmittance of windows and affects optical signal sensitivity, imaging quality and reliability. Through the formation of environmental pollutants and has excellent durability of the protective layer, the surface of the optical components for protective treatment, can make the surface of the optical components long-term resistance to external pollution. However, different optical windows require high transmittance in different wavelength bands. Therefore, it is necessary to ensure that the optical performance of the optical element itself is not lost while the surface protective layer achieves the protective effect.
This work designs a new liquid-like super-smooth film. A flexible bottle-brush molecular structure with "silicone backbone and side chains" was gradually constructed on the surface of the substrate by a simple two-step process, i.e., in-situ hydrolytic polycondensation on the surface of the substrate and the subsequent silica hydrogenation reaction. Unlike conventional special wettable surfaces (superhydrophobic, superoleophobic, etc.), the ultra-smooth films do not require the preparation of surface micro-nano-structures and have a thickness of less than 5 nm, so that they have almost no effect on the optical properties of the substrate itself. In addition, the liquid-like super-slick films have excellent dynamic sliding properties, such as very low contact angle hysteresis of the liquid on the surface, higher molecular grafting surface density, contact angle hysteresis as low as 9.4°, and ultra-high broad-spectrum transparency. The work verifies the effectiveness and durability of the surface in practical application scenarios of optical components through oil droplet, icing, dust, and abrasion resistance tests, which are quite promising for applications.
The research work is supported by the National Natural Science Foundation of China and the National Key Research and Development Program of China.
▲Fig. 1 (a) Schematic structure of the super-slip thin film; (b) AFM photo; (c) Transmission spectra of quartz substrate before and after treatment.
▲Fig. 2 (a) Physical photographs of quartz sheet after surface treatment and comparison of antifouling performance before and after treatment; before and after treatment (b) sliding effect of oil droplets (n-hexane) on the surface and (c) comparison of antifouling effect.
