The "anti-pee paint" concept is a real-world application of superhydrophobic technology used to combat the widespread problem of public urination.
The paint is actually a clear, specialized nano-coating that creates an extremely water-repellent (hydrophobic) surface, often mimicking the natural structure of a lotus leaf. When applied to walls, this coating dramatically reduces the surface tension between the wall and any liquid that touches it, preventing the liquid from adhering or soaking in.

The entire principle is based on instant, poetic justice: when a person attempts to urinate on a wall treated with this coating, the liquid stream is violently repelled. Instead of draining down the wall, the urine bounces off with the same force it hit, splashing back onto the shoes, trousers, and feet of the person relieving themselves.

This technique was popularized in 2015 by the residents of the St. Pauli district in Hamburg, Germany, and has since been trialed in other cities, including London and San Francisco. While expensive to apply, it is viewed by proponents as a highly effective, non-confrontational deterrent that saves local governments money on cleanup and steam-washing, by teaching offenders an unforgettable, splash-back lesson.

The approach has proven more effective than just relying on fines, as the immediate, self-inflicted consequence creates a powerful, memorable disincentive for repeat offenses.

Source: Engineering & schience