Unidirectional spontaneous motion of water droplets on eggshell pores.

Hypothesis: Birds produce eggs and rely on incubation to produce offspring, with moisture retention playing a critical role in this process. While the role of moisture maintenance within eggshells has been extensively studied, we hypothesize that the unique structure of eggshell pores also contributes to water retention by facilitating the transport of water droplets from the external surface to the inner side.

Experiments: Experiments were conducted to demonstrate the unidirectional, spontaneous motion of water droplets on eggshell pores. Additionally, simulations were employed to explore the transport mechanism of water droplets through eggshell's pore structures. The capillary effect was specifically investigated to explore how it, in combination with the unique structure of eggshell pores, drives the unidirectional spontaneous motion of water droplets from the outer surface to the interior.

Findings: Our research shows that the combination of eggshell's unique pore structures and the capillary effect is the primary mechanism driving the motion of water droplets from the outer surface to the interior of eggs. This discovery not only provides new insights into how bird eggs retain moisture during hatching, but it also holds potential applications in fields such as in vitro embryo development, egg storage, anti-fouling for oil-water separation membranes, and the design of breathable medical protective equipment.