Toward Advanced Superomniphobicity: Hierarchical Insights from Serif-T Nanostructures to Microscale Wrinkles.

Developing a superomniphobic surface that exceeds the static and dynamic repellency observed in nature's springtails for various liquids presents a significant challenge in the realm of surface and interface science. However, progress in this field has been particularly limited when dealing with low-surface-tension liquids. This is because dynamic repellency values are typically at least 2 orders of magnitude lower than those observed with water droplets. Our study introduces an innovative hierarchical topography demonstrating exceptional dynamic repellency to low-surface-tension liquids. Inspired by the structural advantages found in springtails, we achieve a static contact angle of >160° and the complete rebound of droplet impact with a Weber number (We) of ∼104 using ethanol. These results surpass all existing benchmarks that have been reported thus far, including those of natural surfaces. The key insight from our research is the vital role of the microscale air pocket size, governed by wrinkle wavelength, in both static and dynamic repellency. Additionally, nanoscale air pockets within serif-T nanostructures prove to be essential for achieving omniphobicity. Our investigations into the wetting dynamics of ethanol droplets further reveal aspects such as the reduction in contact time and the occurrence of a fragmentation phenomenon beyond We ∼ 350, which has not been previously observed.

Springtail-inspired superomniphobic surface with extreme pressure resistance.

Both high static repellency and pressure resistance are critical to achieving a high-performance omniphobic surface. The cuticles of springtails have both of these features, which result from their hierarchical structure composed of primary doubly reentrant nanostructures on secondary microgrooves. Despite intensive efforts, none of the previous studies that were inspired by the springtail were able to simultaneously achieve both high static repellency and pressure resistance because of a general trade-off between these characteristics. We demonstrate for the first time a springtail-inspired superomniphobic surface displaying both features by fabricating a hierarchical system consisting of serif-T-shaped nanostructures on microscale wrinkles, overcoming previous limitations. Our biomimetic strategy yielded a surface showing high repellency to diverse liquids, from water to ethanol, with a contact angle above 150°. Simultaneously, the surface was able to endure extreme pressure resulting from the impacts of drops of water and of ethylene glycol with We >> 200, and of ethanol with We ~ 53, which is the highest pressure resistance ever reported. Overall, the omniphobicity of our springtail-inspired fabricated system was found to be superior to that of the natural springtail cuticle itself.