**1. Introduction**

Water plays a crucial role in most creatures alive in nature, covering requests for organismic daily consumptions, agricultural irrigation, and industrial production. Water shortage is an acute problem in many areas of the world. Collecting water with satisfactory efficiency from a humid/foggy atmosphere is deemed as a fundamental step to release the tough issue, which is also a hot and significant research direction.

In water collection, fog-water capturing and water droplet transport for collection are two main steps. A single superhydrophilic or superhydrophobic surface could not meanwhile accelerate both courses. For example, hydrophilicity can speed up fogwater capturing. However, it may cause water retention, which may slow down water transport and further water harvesting. On a hydrophobic surface, droplets can roll easily for collection while the efficiency of fog-water capturing is very low. To handle the dilemma, researchers have paid attention to the natural superwetting surfaces which have an exciting ability to manipulate liquid behaviours [1, 2]. They possess special wettability designs or/and unique micro/nano-structures.

Creatures surviving in droughty environments usually have a special ability to collect water. For example, some desert plants and animals can capture water from the

#### **Figure 1.**

*Biological surface that can collect water: spider silk with joint and knot, cactus with conical structure, desert beetle with heterogeneous surface.*

humid air during nightfall caused of temperature differences. Creatures living in highly humid environments also have the ability to manipulate water droplets or flow. For example, on spider silk, morning dews are spontaneously collected. This chapter will respectively introduce the water collection ability of spider silks, cactus, and desert beetles (**Figure 1**). The natural surface and bio-inspired model to mimic the surface structure are involved. The strategies to enhance water collecting efficiency by designing special wettability or micro/nano-structure are detailly introduced.
