The self-cleaning effect of a lotus leaf is caused by contamination being attracted to a rolling drop of water on the leaf’s surface. Due to an extremely low surface energy of a lotus leaf, any contaminants are attracted to a water drop and are being removed from the leaf surface upon drop movement across the leaf. In order for this effect to happen, water should roll freely on the leaf surface driven by just gravity forces. The ability of a water drop to move this way can be characterized by the so-called “sliding angle” or “contact angle hysteresis”, and for “Lotus Effect” to happen, this angle should be