Nature-inspired parylene/SiO2 core-shell micro-nano pillars: Effect of topography and surface chemistry

Abstract

We investigated the synergy of surface topography and chemistry in micro/nanostructured pillars inspired by nature, specifically mimicking tokay gecko (Gekko gecko Linnaeus, 1758) feet and sacred lotus (Nelumbo nucifera Gaertn., 1788) leaves. The aim is to understand and replicate their adhesive and self-cleaning properties for diverse applications. Through a detailed fabrication process and chemical modifications, the surfaces exhibit superhydrophobic characteristics. The research precisely examines the fabrication of surfaces with well-defined micropillars using lithography and deep silicon substrate etching. Diverse surface treatments, including silanization and O2 plasma, are applied to tailor the chemical composition of microstructured surfaces. Utilizing a ≈ 5 nm thin SiO2 interface layer, the study reveals superhydrophobic properties post-silanization and an eightfold increase in adhesion force (FA) between the studied surface and reference surfaces. FA measurements using atomic force microscopy reveal an eightfold increase in adhesion on both flat and microstructured surfaces, emphasizing the transformative effects of microstructures on surface morphology. The findings highlight the potential for multifunctional surface designs, elucidating that superhydrophobic properties correlate with structure topography while FA amplitude is predominantly determined by surface termination. Inspired by nature, this research unveils novel possibilities in functional materials and surface engineering, with broad implications across various applications.